Document 9937pN20Bz2wR224mgzrab233

ETC 02683 1 3 - :i I :! if #T ethyl corporation DEVElOP^r,T PFCTION LIBRARY baton u::U3:, Louisiana etc 02684 ETC 02685 ETC 02686 Handbook of Rigging BY W.. E. ROSSNAGEL Safety Engineer Consolidated Edison Company of New York, Inc. First Edition McGRAW-HILL BOOK COMPANY, INC. NEW YORK TORONTO 1950 LONDON ETC 02687 HANDBOOK OF RIGGING Copyright, 1950, by the McGraw-Hill Book Company, Inc. Printed in the United States of America. All rights reserved. This book, or parts thereof, may not be reproduced in any form without permission of the publishers. PREFACE This handbook is intended for the professional rigger who is engaged full time in rigging operations, for the maintenance mechanic in an industrial or power plant who has less frequent hoisting and rigging jobs to perform, for the operator of cranes, derricks, and hoists, for the painter who has scaffolding to rig up, and for the foreman and the superintendent who are supervising rigging operations. For the practical worker's benefit this book is written in plain, not-too-technical language. For any who are mathematically in clined, some simple formulas and sample problems are included, so that the strength of hoisting tackle, beams, and posts for sup porting heavy loads can be calculated more accurately than by the rule-of-thumb or hit-or-miss methods. Enough technical data is included to make this book of value to design engineers, construction engineers, plant superintendents, inspectors in the purchasing departments of large corporations, as well as to safety engineers and inspectors. Photographs of special scaffolds and other equipment are of in terest to the reader. But if he finds that any pictured device is applicable to his particular problem, he may be at a loss as to construction methods. Hence, in a number of instances, detail shop drawings are included for his use. Techniques and methods have been suggested to accomplish the rigger's tasks with the greatest safety for all workmen employed on a project, as well as for passers-by and the public in general. Since a safely performed job is the most efficient, the cost may be kept at a minimum by taking necessary precautions. Most of the chapters in this handbook are based upon data ac cumulated by the author and incorporated in articles published in such technical magazines as Power, Construction Methods, Engineer ing News-Record, Factory Management and Maintenance, Southern Power and Industry, Power Plant Engineering, Ingenieria e Indus- tria, Supervision, Safety, Safety Engineering, National Safety News, and others. v VI PREFACE The author's sincere thanks are extended to the following gentlemen: Captain Hatch of the Columbia Rope Company; G. L. Griffin of the American Chain and Cable Company, Cable Division; A. J. Gugliotta of the American Chain and Cable Com pany, Chain Division; W. W. Weber of the Forest Products Laboratory of the U.S. Department of Agriculture; H. S. Gehr of the Patent Scaffolding Co.; L. H. Davidson of Chesebro-Whitman Company; W. E. Clapp of the Yale and Towne Manufacturing Company; W. J. Goetz, A. Nacht, T. J. Shaughnessy, and Dr. N. E. Eckelberry of the Consolidated Edison Company of New York, Inc.; and last, but not least, Prof. Lionel S. Marks of Harvard University who has so kindly granted permission to use certain tables from his Mechanical Engineers' Handbook. Among the companies and organizations that furnished drawings, photographs and photo engravings to help make this book more interesting and instructive are National Production Company, American Chain and Cable Company, Inc., American Steel and Wire Company, John A. Roebling's Sons Co., The Thomas Laughlin Company, Columbia Rope Company, Encyclopaedia Britannica, Inc., Yale and Towne Manufacturing Company, Macwhyte Company, Safeway Steel Scaffolds Supply Corporation, ChesebroWhitman Company, Inc., American Standards Association, Silent Hoist & Crane Company, Inc., National Safety Council, Forest Products Laboratory, Hameschfeger Corporation, and Dravo Corporation. New York, N.Y. December, 1949 W. E. Rossnagel Preface ......................................................................................... v I. Fundamentals......................................................... 1 II. Fiber Rope..................................................................... 11 III. Wire Rope.......................................................................... 34 _ IV. Hoisting Chains and Hooks......................................64 V. Slings............................................................................... 72 VI. Wood for Structural Purposes................................ 84 VII. Planks for Scaffolds.............................................. 128 VIII. Testing Scaffold Planks......................................... 134 IX. Swinging andSuspendedScaffolds .... 138 X. Scaffolding...................................................................151 XI. Painting and Repairing Steel Stacks . . . 172 XII. Life Belts, Boatswain's Chairs, and Life Nets 189 XIII. Ladders............................................................................. 204 XIV. Strength Calculations for Timbers .... 218 XV. Strength Calculations for Metal Beams . . 224 XVI. Cranes, Hoists, and Derricks...............................233 -XVII. Chain Hoists................................................................... 257 XVIII. Jacks, Rollers, and Skids.........................................263 XIX. Hoist Signals................................................................... 267 XX. Accident Prevention................................................... 270 XXI. Caring for the Injured.............................................. 280 XXII. Reference Codes, Laws, and Standards . . 288 Appendix. HandyReferenceTables................................. 297 Index..................................................................................................315 ETC 02691 CHAPTER I FUNDAMENTALS The art of rigging may be traced back to prehistoric times. Levers were used then, as now, to pry stones, roll logs, and move objects that were too heavy to be moved by hand. The inclined plane, or a natural ramp, has been used since time immemorial to help move heavy objects up to higher elevations. The first major rigging job of which there is a record was the construction of pyramids in Egypt. All riggers of today should be interested in the building particularly of the Great Pyramid at Giza near Cairo. This was a gigantic undertaking, even by to day's standards. Built about 2700 b.c., this pyramid was 764 ft square at the base and 480 ft high. About 2,300,000 stones, weigh ing from 2 to 30 tons each, had to be transported from the quarry to the Nile River at the flood season when it was at its widest, ferried across the river on rafts, and again dragged from the riv er's edge to the site of the pyramid. Then these stones had to be piled up on each other to a height of a 40-story building. The masonry alone in this one pyramid weighed nearly twenty times as much as that in the 102-story Empire State Building in New York. The accomplishments of the Egyptians in a period of about twenty years are almost unbelievable when we realize that they had no automobile trucks, no railroad cars, no cranes of any de scription, no rope falls, no chain hoists, no jacks, or other mechan ical equipment. Some historians believe that a ramp was built up one side of the pyramid and that the stones were dragged up the slope by perhaps 100,000 slaves working in teams of 50 men each. This temporary ramp was no mean undertaking, as it required nearly a million tons of sand. It seems almost incredible, but the pyramids remain today as undisputable evidence of the skill and ingenuity of the Egyptians. As a point of interest, let us consider what it means to transport and raise (they did not "hoist") nearly six million tons of stone, plus a million tons of sand for the ramp, plus several million tons of sand for backfilling in the pyramid. The average height of lift 1 2 HANDBOOK OF RIGGING may be assumed to be about 150 ft. The Edison Electric Institute Bulletin of June, 1939, gives the following interesting facts relative to the work that can be performed by man power alone: Lifting 86 tons from the ground to a height of 4 ft in an 8-hr workday, a man performs 0.26 kw-hr, or averages 33 watts. (And electricity costs about j to 5 cents per kilowatt-hour.) Carrying 22.3 tons upstairs or up a ramp to a height of 12 ft in 8 hr, he performs 0.20 kw-hr, or averages 25 watts. Pushing a wheelbarrow, he can move 40.7 tons up a ramp to a height of 3 ft in 8 hr and performs 0.093 kw-hr, or averages 12 watts. Shoveling loose earth, a man can raise 20 tons to shoulder height in an 8-hr day. The work performed is 0.084 kw-hr, and the av erage power exerted is 11 watts. Thus, it will be noted that man is a very inefficient machine, and it is easy to understand why 100,000 men were required to trans port the material for the Great Pyramid. The art of rigging has developed to the degree that today we think nothing of building 250-ton traveling cranes for power plants and hammer-head cranes of 300 tons or greater capacity for Navy yards. Trusses and girders weighing up to 50 or 100 tons or more are handled by derricks when erecting modem office buildings or bridges. During the Second World War hundreds of steam loco motives weighing over 100 tons each were hoisted onto the decks or into the holds of steamships for transportation to Allied coun tries. The author does not intend that this book should deal with rig ging operations of this magnitude, but rather with everyday main tenance operations in industrial plants, in factories, in power plants, in the transportation and handling of heavy machinery, and in the erection and demolition of smaller size structures. Rigging includes a multitude of subdivisions, which are included in subsequent chapters. Let us imagine that a heavy piece of machinery is to be hoisted up the outside of a building and in through a window opening. Dependent upon the weight of the load, either a fiber rope or a wire rope tackle will be needed. This may be suspended from a timber gin pole or from a wood or steel outrigger temporarily projected out from a window above or from the roof. To attach the load to the hook on the lower pulley block, a sling is required. Then to support the load as it is swung in through the opening in the wall, a chain hoist may be suspended from a beam of the floor above. When the load is landed, it will FUNDAMENTALS ' 3 CIRCLE IRREGULAR Flo. 1. Formulas (or calculating the areas of plane figures. Rigging also includes erecting temporary scaffolds for painting, repairing, or demolishing structures as well as for supporting heavy * . r loads. In the rigging trade there is no substitute for years of prac tical experience. But when working by rule of thumb alone, many times ropes and other load-bearing parts are stressed to a point B dangerously close to the breaking point without the rigger realiz ing it. The author has no intention of attempting to make pro- ETC 02694 4 HANDBOOK OF RIGGING fessional engineers out of riggers, but owing to the fact that moat riggers today have had better educational advantages than in years gone by, they should be able to make simple calculations to check their loads and the strength of their equipment. The element of chance should be thus reduced to a minimum. The first and the most important step in any rigging operation is to determine the actual weight of the load to be supported or hoisted. If this information cannot be obtained from shipping papers, from catalogue data, or from other dependable sources, it may be necessary to calculate the weight roughly. If the object is of very complex construction, it may be necessary by observing it to estimate the size of a solid chunk of metal it could be melted Fio. 2. Calculating the area of a complex plane figure. into and multiplying by the weight per cubic foot of that metal. Such estimate will be very inaccurate but probably will be some what better than a pure guess. If the object is of more simple shape, imagine it cut up into a number of regular geometric figures, the cubic contents (and the weight) of which can be calculated with a fair degree of accuracy. The sum of these figures will give the total weight. Figure 1 gives the formulas for calculating the area of a few plane figures frequently encountered. For example, to find the area of a flat plate of irregular shape (Fig. 2a), draw chalk lines on the plate from any comers desired so as to subdivide it into a number of triangles. Take the necessary measurements and apply the formula for triangles given in Fig. 1. The sum of the triangles equals the area of the plate. In this example Fig. 2b shows the shape cut into three triangles A, B, and C. Triangle A has a base of 30 in. and a height of 9 in., and its area = --= 135 sq in. Triangle B thus has an area of-2-8--xX--S*i = 119 sq in., and triangle C has an area of FUNDAMENTALS 5 -** ^5 ^ = 26| sq in. Thus, the area of the plate is 135 plus 119 u plus 26^ sq in., or a total of 280j sq in. This area multiplied by the thickness of the plate, say f in., gives 210 cu in. volume. From Table I we learn that steel has a weight of 0.28 lb per cu in. The weight of the plate is found to be 210 cu in. times 0.28 lb, or 59 lb. Figure 3 illustrates the method of calculating the volume of a few elementary solid figures. Like the plane figures, it may be FRUSTUM OF PYRAMID or CONE SPHERE RING 1 V* VOLUME OF PTRAMD or CONE OF WIGHT H.MINUS VOLUME OF PVRAMDorCOWOF WIGHT h. V*.53d*dd V2.d7xDd* COMPOUW FIGURE fwrrsV* SUM OF VOLUMES OF COMPONENT Flo. 3. Formulas for calculating the volumes of solid figures. 6 HANDBOOK OF RIGGING necessary to subdivide the object into smaller geometric shapes and find the volumes of the individual parts. As an example, let us estimate the weight of a concrete mass shown in Fig. 4. First, we divide it into a rectangular block A and a frustum of a pyramid B. The volume of part A is 4 X 5 X 3? ft = 70 cu ft. To get the volume of part B, it is necessary to figure the volume of a pyramid having a height of 6 ft and subtract the volume of a pyramid of height of 3 ft. The volume of the large pyramid is the area of the base times one-third the height, or 4X5X6 3 = 40 cu ft. From this must be subtracted the volume of the small pyramid 2---x----2-----X----3-= 5 cu ft, thus giving the frustum a volume of 40 cu ft -- 5 cu ft = 35 cu ft. The total volume of the concrete block is 70 + 35 cu ft = 105 cu ft. Concrete weighs about 144 lb per cu ft (from Table I) or 144 lb X 105 cu ft = 15,120 lb, or about 75 tons. This could have been calculated on a cubic inch basis rather than cubic foot, and the result would have been the same. A few words about elementary physics may also be helpful to the modem rigger. The elemental machines from which all ma chinery is constructed are the inclined plane, the lever, the wheel and axle (gear or pulley and shaft), and the block and fall. Riggers frequently make use of the inclined plane when hauling a load on rollers up a ramp or up the skids onto a truck. To estimate roughly the pull required to haul the load, draw a diagram ABC (Fig. 5) to scale to represent the incline of, say, 4 ft in 20 ft. A FUNDAMENTALS 7 Material Lb per cu in. Lb per cu ft Wood (spruce).......................................................... Wood (longleaf pine)............................................... Coal (bituminous).................................................... Water.......................................................................... Earth............................................................................ Sand............................................................................. Concrete..................................................................... Cast iron..................................................................... Steel............................................................................. Brass............................................................................ Lead............................................................................. 0.016 0.025 0.029 0.036 0.058 0.070 0.083 0.24 0.28 0.31 0.44 27 44 50 62? 100 120 144 442 487 534 710 load of 15,000 lb is to be pulled up on rollers. Draw to any suit able scale a vertical line DE to represent the weight of the load. For instance, assume a scale of 1 in. = 10,000 lb; then a line 1 in. long represents 1 j X 10,000 lb, or 15,0001b. From D draw a line DF at right angle to the slope of the incline AB. Using the same scale of 1 in. = 10,000 lb, measure the distance EF, which will be the theoretical pull required. This scales about 0.3 in. or 3,000 lb, which is the pull if frictionless rollers are used. The screw jack is an adaptation of the inclined plane, and more will be said about it in a subsequent chapter. Fia. 5. Calculating the force required to move an object up an inclined plane or ramp. The crowbar is a typical lever. As commonly used, there are two arrangements of the fulcrum (see Fig. 6). In Fig. 6a the up ward pull P on the handle lifts the weight W, which owing to grav ity is acting as a downward force. The toe of the crowbar pivots about the fulcrum F, and in effect, the floor or ground exerts an r ETC 02698 8 HANDBOOK OF RIGGING upward force to resist the downward pressure. Let us assume a weight of 1,000 lb acting at a distance of 3 in. from the fulcrum F and a man lifting up on the lever at a distance of 30 in. from the fulcrum. The force P times the force distance (30 in.) always equals the weight ('W = 1,000 lb) times the weight distance (3 in.). Thus P X 30 in. = 1,000 lb X 3 in., or P = 100 lb force required. In other words, if the force distance is ten times the weight dis tance, then the force is one-tenth of the weight, and this rule holds true for other ratios of distances. If the crowbar is used as indicated in Fig. 66, the fulcrum is be tween the force and the load, and the former is then a push P in a downward direction. If the same 30-in. lever is used, we find that the force P times the force distance (27 in.) equals the weight (W = 1,000 lb) times the weight distance (3 in.). Thus P X 27 in. = 1,000 lb X 3 in., or P = 111 lb force required. It will be observed that the crowbar is most efficient, or less work is required, when Fio. 7. Calculating the force required to lift a load by means of the wheels and shaft. used as shown in Fig. 6o. Sometimes it may be necessary to limit the pressure on the fulcrum P, and in Fig. 66 this pressure is always the sum of the weight W and the force P. The wheel and axle is in reality only an adaptation of the lever, but whereas the movement of the lever is limited, the motion of FUNDAMENTALS 9 the wheel may continue indefinitely (see Fig. 7). In this example force P is exerted on the radius (R = 12 in.) of the large pulley while the weight (W = 1,000 lb) is supported on radius (r = 3 in.) of the small pulley. Thus P X 12 in. = 1,000 lb X 3, or P = 250 lb. In making use of the wheel and axle (which in practice is demon strated by belts and pulleys and by gears), the belt pulls or ten sions are inversely proportional to the pulley diameters, or in other words, if one pulley is four times as large as the other, the belt pull on the large pulley is one-fourth of the belt pull on the small pulley. Flo. 8. Calculating the force required to lift a load by means of a train of gears. If there is a train of gears such as on a hand hoist (or power hoist) consisting of several gear reductions, the theoretical force on the crank handle can be readily estimated (see Fig. 8). WX EX AX B r~ LXCXD where P = force on lever or crank, lb W = weight to be lifted, lb E = radius of drum, to center of rope, in. A = radius of pinion A to pitch line of teeth B = radius of pinion B to pitch line of teeth L = length of hand crank or lever, in. C = radius of gear C to pitch line of teeth D = radius of gear D to pitch line of teeth For a discussion of the forces concerned in a block and fall ar rangement, refer to the chapter on Fiber Rope. In each of these mechanical movements friction consumes a portion of the energy ETC 02701 CHAPTER II FIBER ROPE For thousands of years man has made use of vegetable materials for hauling and lifting loads. At first, vine stems were twisted to gether to form a crude strand that had sufficient strength for his requirements, yet was flexible and could be tied into knots. Use had been made at various times of such materials as the fibrous bark of the palm tree, the hair of the coconut, camel hair, horse hair, thongs cut from hides, cotton, jute, sisal, flax, and wild and cultivated hemp, until today we have the modem manila rope. Evolution has passed even the manila rope and produced the wire rope or steel cable as it is commonly known. While wire rope may properly be considered an improvement over manila rope, it has not entirely superseded manila rope, for each has its own field of use. Wire rope is used for permanent installations and where heavy loads are to be lifted. Manila rope, on the other hand, is generally used on temporary work such as construction and paint ing jobs and in marine work. There is a great difference between wire rope and manila rope, not only in strength but in the very nature of the material itself. Steel wire is produced synthetically to meet the exacting specifica tions of the metallurgist. Since it has a known composition, the strength, modulus of elasticity, and other properties are all defi nitely known even before the rope is manufactured, and all wire ropes of the same grade of steel and of the same type of construc tion have the same physical properties. Manila fibers, on the other hand, are a product of Nature, being obtained from the abaca, or wild banana plant, grown in the Phil ippines, and, as such, vary in quality, their strength being depend ent upon climatic conditions, fertility of the soil, cultivation, and curing. The fibers taken from the outer portion of the stalk of the abaca plant are somewhat darker than those taken from nearer the center, and are slightly lower in strength and less durable. They are care fully sorted into grades before being imported by the rope manu facturer. The individual fibers as received are from 6 to 15 ft long, 11 ETC 02702 12 HANDBOOK OF RIGGING but the hanks must be cut to about 7 ft in length in order to pass through the drawing frames, which comb out the fibers parallel to each other. To lubricate and preserve the rope, cordage or special oils are applied to the fibers during the combing process. The fibers, or slivers, come out in a fluffy stream and are then re combed six or seven times. During this process combed fibers from other shipments of the same grade are blended with it to ensure a uniform quality. Each time the fibers are combed, their number becomes less, until the sliver is reduced to the proper size to be spun into a yam or thread, which is the unit of rope construc tion. A number of yams are then twisted left-handed into a strand, and three or four strands are laid right-handed into the finished rope. Material. Manila rope is recommended for all hoisting opera tions calling for the use of fiber rope. When manila is not procur able, substitutes such as sisal (pronounced "sy-sal"), jute, hemp, and cotton may have to be used. The materials and grades most commonly encountered are as follows: 1. Yacht rope--The highest quality manila of very fine appear ance. Costly, but used on special jobs where appearance is an important factor. 2. Bolt rope--High-grade manila rope, about 10 to 15 per cent stronger than No. 1 grade manila. 3. No. 1 manila rope--The standard high-grade hoisting rope used for important rigging jobs. Usually identified by a trade marker. 4. No. 2 manila rope--Has about the same initial strength as No. 1 grade, but loses its strength more rapidly in service. 5. No. 3 manila rope--Has about the same initial strength as No. 1 grade, but loses its strength very rapidly in service. 6. Hardware-store rope--A very poor grade of manila rope, of low strength and short life. 7. American hemp rope (tarred)--Has about 80 per cent of the strength of No. 1 manila rope. 8. Java sisal rope--Has about 75 per cent of the strength of No. 1 manila rope. 9. Henequen sisal rope--From Mexico and Cuba. Has about 60 per cent of the strength of No. 1 manila rope. 10. Jute rope--Has about 50 per cent of the strength of No. 1 manila rope. Manila rope should be light yellow with a silvery or pearly luster and should have a smooth, waxy surface. No. 1 grade rope is very light in color, No. 2 grade is slightly darker, and No. 3 grade is considerably darker. Hardware-store rope is still darker, and the short fibers cause many protruding ends to project from the strands. Yacht and bolt rope, as might be expected, are very light in color but are distinguished from sisal, which feels harsh and dry to the touch. Jute is rather dark brown and feels soft and flexible. Cotton, of course, is white and soft and should be readily recognized. Within a few years nylon rope will probably be on the market. This is nearly white in color, has the wellknown silky appearance, and is laid up quite hard. Its strength is much greater than manila rope, but it is quite elastic. Purchasing. In purchasing manila rope for hoisting purposes, the specifications should require that it be made of first-grade manila fibers, and the order should be placed with a reputable manufacturer. Most rope manufacturers proudly place a marker of some kind in their first-grade rope for identification. Some have one or more yams colored, or they may have a colored string in one strand, or they may have a tightly twisted paper ribbon with their trade-mark on it in one of the strands (Fig. 1). Rope without such a marker should not be used for hoisting purposes, as either it is not first-grade rope or it is made by a manufacturer who does not wish to be identified with it. In ordering new rope the purchaser should specify the type of construction best suited to his requirements. Manila rope is usu- ETC 02704 14 HANDBOOK OF RIGGING ally made up with three strands. But for work where abrasion is a factor, a rope having four strands laid around a small rope core is recommended. This rope is more nearly round in cross section and is used quite extensively for power hoisting. Its strength, however, is very slightly less than three-strand rope. In making a rope, the yarns can be formed into the strands and the strands can be laid into the rope either tightly or loosely, mak ing what is known, respectively, as "hard-laid" or "soft-laid" rope. Hard-laid rope is stiller and more resistant to abrasion, whereas soft-laid rope is limp but stronger. A medium lay is gen erally recommended. The method of measuring manila rope causes confusion at times. Up to 1 in. diameter a rope is called by the diameter, but larger ropes are called by the circumference, which is assumed to be three (not Tf) times the diameter. Storage. Assuming that good manila rope has been procured, it is necessary to store it properly, both before using and between periods of use. If properly stored, it may remain in good condition for 3 or 4 years. Rope should never be kept on the floor or in a box, closet, or small room where air circulation is restricted. Instead, it should be stored on a wood grating platform about 6 in. above the floor or hung up in loose coils on large-diameter wooden pegs. (A dis carded 12-qt pail nailed to the wall makes a good bracket for hang ing rope.) Rope should be protected from the weather and from dampness from any cause. A wet rope should be thoroughly dried and cleaned before being stored away; otherwise it will lose its strength very rapidly. On the other hand, it should be kept away from boilers, radiators, steam pipes, and other sources of heat. In fact, the ultraviolet in the sun's rays is detrimental to manila rope. A temperature of 50 to 70F and a humidity of 40 to 60 per cent are recommended. Exposure to stack gases or to carbon monoxide or carbon diox ide will cause rapid deterioration of a rope. Opening Up a New Coil. In opening up a coil of new rope, the instructions printed on the tag should be carefully followed. After the burlap wrapping has been opened or removed, look inside the coil for the end of the rope. This should be at the bottom of the core, or eye. If it is not, turn the coil over so that the end will be at the bottom. Cut the lashings that bind the coil together, and FIBER ROPE " 15 pull the end of the rope up through the core. As the rope comes out of the coil, it will then unwind in a counterclockwise direction (Fig. 2). Even though the rope is unwound properly, loops or hockles may form in it, and these should be carefully removed. If the rope is unwound improperly, you will be well aware of the fact, as the hockles will develop into numerous kinks, which, if pulled out, will cause severe damage to the rope. Should circumstances require the uncoiling from the outside of the coil, place the coil so that, as the rope pays off, it will unwind in a counterclockwise direction. If a rope should have a large number of kinks, coil it on the floor counter clockwise, then pass the end through the coil, and proceed to uncoil. This should remove the kinks. Fig. 2. The rope unwinds counter clockwise as it comes out of the coil. (Columbian Rope Co.) When a rope is cut to the required length, whippings of yam should be applied at once to the ends to prevent the strands from becoming unlayed. Otherwise, the strands may slip in relation to each other, causing one of them to assume more or less than its share of the load, which wall result in a shortened life of the rope. Strength of Rope. Table I gives the working strength of a three-strand rope of various materials when subjected to direct pull. A factor of safety of 10 has been used. (The "factor of safety" is the breaking strength divided by the safe working load.) If fiber rope is used for high-speed power hoisting, a higher factor of safety should be used. Handling Rope. When a rope is attached to a hook, ring, or pulley block, a thimble should be placed in the loop or eye to re duce the wear on the rope and to decrease the stresses developed in the rope when it is bent around a very small diameter. When a rope is used as a sling, it should not pass over the sharp edges of castings, boxes, or beams unless a padding is used. Also consid eration should be given to the angle between the legs of a sling when placed in position to pick up a load. If the ropes make an angle to the horizontal of 60 deg, they have only 86 per cent of their strength when vertical. At 45 deg their strength is 71 per 16 HANDBOOK OF RIGGING Table I. Sate Working Loads fob Three-strand Fiber Rope Diam Circum Hene- eter, in. lbference, Manila, Java quen in. sisal, lb sisal, lb Jute, lb Nylon Cotton, lb (thy). lb P If 135 110 80 65 65 540 P If 265 210 160 130 130 974 P2 440 350 265 220 220 1,478 P 2f 540 430 325 270 270 2,080 P 2f 1* 3 770 615 465 385 385 900 720 540 450 450 3,660 3PIf 1,200 960 720 600 600 if 3f* 1,350 1,080 810 675 675 1* *P 1,850 1,480 1,110 925 925 if 5P 2,650 2,120 1,590 1,325 1,325 2 6* 3,100 2,480 1,860 1,550 1,550 7P2* 4,650 3,720 2,790 2,325 2,325 Indicates nominal size. Nylon rope, when wet, has S3 per cent of strengths in table. Four-strand rope has about 95 per cent of values in table. ' cent, and at 30 deg it is only 50 per cent, this not including the loss of strength due to sharp bending. Rope should not be dragged over concrete pavement or through sand or cinders, as the outside surface of the rope will be worn and cut by the abrasive action. Also, small particles of gritty material may get between the component parts of the rope and cause in ternal damage. Moisture. As far as is practicable, rope should not be allowed to become wet, as this not only hastens decay but also causes the rope to kink very readily. Fiber ropes used between fixed objects, such as in the case of guys on a gin pole, should be slackened when it begins to rain; otherwise shrinkage may overstrain the wet rope and damage it. Should a wet rope become frozen, it must not be disturbed until completely thawed; otherwise the frozen fibers will be broken as they resist bending. Although every effort should be made to prevent rope from freezing, little harm will be done if the above instruction is followed. While not recommended for general practice, it should be borne in mind that a rope splice which has been soaked in water will be stronger than the dry body of the rope. Likewise, a wet rope is about 10 per cent stronger than a dry rope. ETC 02707 FIBER ROPE 17 Chemicals. Rope should be kept away from acids and other destructive chemicals, as exposure to even the fumes will materially weaken it. Reeving. Each time a rope passes over a sheave, friction is produced, and the pull exerted on the object is proportionately less than the pull exerted by the source of power. When the load is at rest, the tension on the rope is equal to the load divided by the number of parts of the rope actually supporting it. For in stance, if the lower block has two sheaves, there are four parts of rope. If it has two sheaves and the rope is deadened at the lower block, then there are five parts of rope supporting the load. As soon as hoisting is begun, friction causes an additional load on the rope of about 10 per cent for each sheave passed over. This is illustrated in Table II. Table II. Safe Loads for Manila-rope Falls (Using factor of safety of 10.) Rope diameter, in. 1 part Parts of rope supporting load, lb 2 parts 3 parts 4 parts 5 parts 6 parts * 240 440 600 725 490 890 1,200 1,480 1,680 1,830 l 820 1,490 2,030 2,460 2,800 3,050 n 1,230 2,230 3,050 3,700 4,200 4,580 1,680 3,060 4,180 5,070 5,750 6,280 Factor of Safety. One of the principal advantages of rope of any description is the ability to lift heavy loads with a reasonable pull on the hauling line. This is accomplished by means of pulley blocks. In general, the load to be lifted is divided by the number of parts of rope supporting the lower pulley block to obtain the pull on the hauling line. This, however, is true only with the load in a static or stationary condition. The actual strain on the hauling line, when hoisting, is somewhat greater than this figure owing to fric tion of the pulleys, as shown in Table II. A new manila rope f in. in diameter has a nominal breaking ` strength of about 5,400 lb, according to the rope manufacturers, but this does not mean that 5,400 lb can be lifted on it. For [ ordinary slow-speed hoisting where men's lives or valuable equip- 1 j ETC 02708 n 18 HANDBOOK OF RIGGING ment are involved, many safety engineers believe that the safe load should not exceed one-tenth of the breaking strength, or 540 lb. In other words, a factor of safety of 10 should be maintained. This wide margin of 540 to 5,400 lb may r i appear to be excessive. However, there are many indeterminate factors that must be taken into consideration. Let us emphasize the fact that errors in judgment are not always cumulative, al though it is very possible for this to happen. We shall consider a hypothetical case. Let us assume that it is desired to lift a weight thought to be about 2,500 lb on a five-part f-in. manila rope fall, that is, using a double and triple pulley block as shown in Fig. 3. In order to obtain the static tension on the rope, the weight (2,500 lb) is divided by the number of parts of rope supporting that weight (five), which gives a load of 500 lb. This is 8 per cent less than the allowable '4 ROPE safe load of 540 lb and will be considered good practice. However, the load to be lifted has only been estimated, to weigh 2,500 lb; it may be more or it may be less. Very few men can estimate the weight of an object within 25 per cent unless they calculate it mathe matically, SO' we shall assume that the actual weight happens to be 10 per cent LOAD 2,500 LBS. heavier than estimated, or 2,750 lb. This means that the actual static rope tension Flo. 3. A five-part rope fall. is also 10 per cent higher than our first figure, or 550 lb. Now, each time a rope passes over a sheave in a pulley block, friction is developed. For ordinary cal culations it is usually taken as 10 per cent of the rope tension for each sheave passed over. There being five such sheaves, the pull on the hauling line when the load is being lifted uniformly is about 0.32 times 2,750 lb, or 880 lb. But few loads can be lifted smoothly. They may swing, or they may vibrate owing to worn winch gears, or they may be acceler- ETC 02709 FIBER ROPE 19 afced rapidly, or in the case of hand-power hoisting the pull may be jerky. This greatly increases the stress in the rope, sometimes several hundred per cent. In our imaginary problem let us assume that the stress is thus increased 100 per cent, which is not unrea sonable. This gives a true tension on the hauling rope under actual working conditions of twice 880 lb, or 1,760 lb. Now let us turn our attention to the rope itself. When the rope was new, its nominal breaking strength was 5,400 lb. This was the strength of the rope when brand new. Our rope, however, has seen some hard service. Fibers and even a few yams are broken. The rope has somewhat dried out, and it is otherwise reduced in strength, although it is still serviceable. In other words, it is the type of rope that is frequently used for such purposes. Let us as sume that it has lost 25 per cent of its original strength, or that the present strength is about 4,050 lb when subjected to a straight pull. Now it is a characteristic of a manila rope that it cannot be used without being bent. In bending a rope over a pulley or around the eye of a hook or around itself as in a knot, the individual fibers are subjected to severe bending stress, which must be deducted from the breaking strength of the rope to obtain the net strength. Tests show that sharp bends and knots frequently reduce the strength of a rope as much as 50 per cent, so we shall assume that our hypothetical rope has been thus weakened and the net strength reduced to about 2,025 lb. This is the maximum load which the rope may be expected to carry. We started our calculations by believing that we had a factor of safety of 10, or that the rope had a strength ten times as great as the load imposed upon it. Actually, we find that the strength is about 2,025 lb while the load on it is about 1,760 lb, which gives a tme safety factor of only 1.15. Keep in mind that factor of safety of 1 means no safety at all and that the rope will fail. Again, let it be said that this may be an exceptional but by no means impossible combination of conditions. This analysis, it is hoped, has demonstrated why a factor of safety of 10 is necessary when only the estimated weight and the nominal strength of a rope are known. Many rope users and, in fact, some rope manufacturers consider a safety factor of 5 or even lower sufficient, but in the interest of safety to personnel and to property it is believed that a factor of safety of 10 is absolutely necessary. airifoSjr- ETC 02710 20 HANDBOOK OF RIGGING Lay of the Rope. Practically all fiber ropes are laid up righthanded, so only right-lay rope has been considered in this discus sion. Soft-laid rope is slightly stronger than hard-laid rope but is less resistant to abrasion. For general use a medium lay is recommended. Waterproofing. Most rope manufacturers produce a special waterproofed rope bearing a trade name. Waterproofing helps a rope to retain its flexibility even though wet, reduces the liability of kinking, and makes the rope easier to handle. All this is, of course, in addition to preserving the rope from decay. Inspection. In order intelligently to estimate the loss of strength in a worn rope, such as was just described, it should be inspected periodically. When a used rope is inspected, the first touch will frequently give an idea of its general condition, but such a casual examina tion is not sufficient. A rope upon which a man expects to trust his life should not be inspected in any but the most thorough man ner. This means going over every foot of its length. Like the proverbial chain, a rope is only as strong as its weakest part, and it is the inspector's duty to find that part. Examine the outside of the rope, and observe the number of broken fibers or broken yams, keeping in mind that these failures represent just so much loss of strength. Do not be misled by dirt on the surface; any rope that has been used will be dirty on the outside. Open up the rope by untwisting the strands so that you can observe the condition of the inside, but try not to kink the strands. The interior of the rope should be as bright and clean as when the rope was new. Observe if there are any broken yams inside or if there is an accumulation of a powderlike sawdust, which indicates excessive internal wear between the strands as the rope is flexed back and forth in use. Then, if the rope is large enough to permit, open up a strand and with a lead pencil or other blunt instrument try to pull out one of the inside yams, keeping in mind that, if a rope has been over loaded, it is the interior yams that will have failed first. Excessive oil on the outside of a new rope is also an indication that it has been overloaded. If it is a four-strand rope with a heart, try gently to pull out the heart. If the heart readily comes out in short pieces, this rope likewise has been overloaded and should not be used for hoisting. FIBER ROPE 21 If possible, pull out a couple of long fibers from the end of the rope and try to break them between the hands. The finer fibers are relatively stronger than the coarser ones, and all should be broken only with difficulty. In fact, believe it or not, some fibers have a tensile strength as high as 30,000 lb per sq in. If the inside of the rope is dirty, if the strands have begun to unlay, or if the rope has lost its "life" and elasticity, it should not be used for hoisting purposes. If the rope is high-stranded and presents a spiral appearance, or if the heart protrudes, the load will not be equally distributed on the strands and a very short life may be expected. Often the surface of a rope feels dry and brittle, or it may show evidence of having been in contact with a hot pipe or other source of heat, or it may be discolored as the result of exposure to acid fumes, in which cases it should be discarded. Condemning an Unsafe Rope. When a rope has been con demned, it should be destroyed at once or cut up into short hand lines so that it cannot again be used for hoisting purposes. Some organizations even prohibit the use of rope over 2 years old for scaffold falls. To ensure that older rope will not be used, their pulley blocks are painted a different color each time a new rope is installed, in order to indicate which are new and which are last year's ropes. Also the date of reroping is stamped on the lower or single block. Judging the condition and strength of a manila rope is not so simple as you may have been led to believe. It takes a lot of experience and good judgment, and even then the chances of error are veiy great. Knots, Bends, and Hitches. There are hundreds, if not thou sands, of different rope knots, bends, and hitches, but the average rigger can get along with the knowledge of a comparatively few. Technically speaking a "knot" is the intertwining of the end of a rope with a portion of the rope. A "bend" is the intertwining of the ends of two ropes to make one continuous rope. A "hitch" is the attachment of a rope to a post, pole, ring, hook, or other ob ject. A "splice" is the joining of the ends of two ropes or of the end of a rope with the body of the rope by weaving the strands over and under the strands of the other part. Actually, the names are not always correct designations; for instance, the bucket hitch is also known as the fisherman's bend or the anchor knot. A few of the most important fastenings are shown in Figs. 4 to 108, in clusive, those marked by a star (*) being the most commonly used. ETC 02712 22 HANDBOOK OF RIGGING There is one little trick to remember in tying any knot if you do not want it to slip; if two parts of the rope are squeezed to gether, they should be arranged so as to have a tendency to pull in opposite directions. For instance, compare the reef knot with the granny. Manila rope, when dry, is an excellent electrical insulator. The dielectric strength or insulating ability of a wet rope depends upon the percentage of moisture in the rope. Inasmuch as water proofed rope absorbs less moisture than ordinary rope, it is a better insulator and therefore is safer for use when material must be hoisted in the vicinity of high-tension electrical apparatus. The following data (Table III) are furnished by Columbian Rope Com pany and are the result of tests made on 5-ft long samples of manila rope suspended vertically with a 6-lb weight attached to the lower end. Table III. Electrical Conductivity op Manila Rope (5 ft between electrodes) Rope Exposure to rain, hr Current leakage observed at, volts Severe leakage at, volts Ordinary...................................... Waterproofed............................. Ordinary...................................... Waterproofed............................. Ordinary..................................... Waterproofed............................. Dry (no exposure) Dry (no exposure) 24' 24 4 4 160,000 160,000 8,000 21,000 5,000 17,000 11,000 25,500 7,000 19,000 Fig. 4. Bight, or simple loop. A loop in a rope, as distinguished from its ends. A part of all knots. Fig. 6. Figure-eight knot. To pre vent unreeving. Fig. 5. Overhand knot, or single knot. To prevent unreeving. Forms eccen trically on rope. Part of many knots. Efficiency 45 per cent of strength of straight rope. Fig. 7. Marline spike hitch, or boat knot. For drawing seizing tight. ETC 02714 ETC 02715 FIBER ROPE 25 Fig. 30. Two half hitches, or studdingaail tack bend.* For attaching rope to a ring. Fig. 35. Studding-sail hitch. For fas tening a rope at right angle to a. post. For hoisting timber, etc. Fig. 31. Round turn and double hitch. For securing a rope to a ring. Should not be used for hoisting. Fio. 32. Slippery ring. For tempora rily securing a rope to a ring. Easily untied by pulling end of rope. Fig. 36. Timber hitch. For fastening a rope at right angle to a post. Will not slip under load, but will readily loosen when strain is relieved. Effi ciency 65 per cent. Fio. 33. Half hitch and seizing. Not recommended unless end of rope is strongly seized to standing part. Fig. 37. Clove hitch, two half hitches, heaving line bend, or builders' knot.* For securing a rope at right angle to a post. m j Fio. 34. Fisherman's bend, anchor knot, or bucket hitch. For fastening a rope to a ring or post. Fig. 38. Mooring knot, or magnus hitch (also see rolling hitch). For fastening a rope at right angle to a post. etc 02H1 Fig. 48. Strap on a rope. A means of securing a grip on a rope temporarily so as to relieve the strain on the latter. crown knot Fig. 49. Rolling hitch.* For fastening a rope to another rope or a pole parallel to it. For attaching a life-belt rope to a hanging life line. Grips tightly if pulled in direction shown, but is easily moved along rope or pole when strain is relieved. Fig. 54. Crown knot.* A stopper, to prevent unlaying of strands at end of rope. Generally used in combination with wall knot. Fig. 55. Stevedore's knot. To pre vent unreeving of rope. Fig. 50. Timber hitch and half hitch.* For hoisting or hauling poles, pipes, etc. Easily released when strain is relieved. Fig. 51. Well pipe hitch. For hoisting or hauling pipes and poles. Fig. 56. Harness hitch. For attach ing men to a toe line, loops being placed over the men's bodies. If only one end of rope is subject to pull, knot will slip. i ETC 02718 ETC 02719 Fig. 66. Long splice. For joining two ropes together (three-strand rope shown). Will pass through pulley blocks. Unlay each rope for a distance equal to twentyfive times its diameter, and place to gether as shown. Unlay one strand in the left-hand rope, and wind in its place one strand from the right-hand rope. Repeat on other rope. To terminate, divide adjacent strands in half, tie half strands of left-hand rope to half strands of right-hand rope, and then tuck ends under strands. Fig. 69. Pole and ledger lashing. For lashing poles at right angles to each other. Fig. 70. Pole lashing. For lashing two poles together. Two such lashings should be used. Start Fig. 67. Cut splice. An eye in the middle of a continuous rope. Place ropes as shown, and tuck as in eye splice. Fig. 71. Portuguese knot, or necklace tie. For lashing shear legs together. Spreading of legs puts strain on knot. Fig. 68. Flagpole hitch. Similar to a clove hitch. For attaching a boatswain's chair to a pole. Fig. 72. Snubber.* For holding or slowly lowering a heavy load. Strain on hand line is only a fraction of strain on load line. Three or four turns should be taken. ETC 02 720 30 HANDBOOK OF RIGGING Fig. 73. Spanish windlass.*' An end less rope used to pull two objects toward each other, similar to a turnbuckle. Stick is placed between parts of rope and rotated. To hold strain, the end of the stick is lashed to a fixed object. Fig. 77. Scaffold hitch. For suspend ing a scaffold plank. Will prevent plank from tilting. Can also be used on plank on edge. Fig. 74. Slippery hitch. A rope anchor age that is readily released by pulling on. short end of rope. Fig. 78. Scaffold hitch. For suspend ing a scaffold plank. Will prevent plank from tilting. Can also be used on plank on edge. Fig. 75. Belaying-pin hitch. An anchorage for securing a rope. Several figure-eight turns may be required to hold the load. Easily cast off. Fig. 79. Scaffold hitch. For suspend ing a scaffold plank. Will prevent plank from tilting. Can also be used on plank on edge. Fig. 76. Regulating lashing. For reg ulating the length of tent ropes. Fig. 80. Rivet scaffold hitch. For sup porting needle beam of riveter's scaffold. Loose end of rope should be several feet long. ETC 02722 ETC 02723 FIBER ROPE 33 Fig. 100. Flemish eye knot. Safer than double overhand knot. Fig. 105. Stopper knot, To prevent unlaying of strands. Fig. 101. Killick hitch. For securing a rope to a post. Formerly used to at tach rope to a stone anchor. Fig. 106. Rope yarn knot. For splic ing yarns used for seizing and other pur poses. Fig. 102. Diamond knot. A stopper to prevent unlaying of the strands at the end of a rope. Fig. 103. Sheepshank, knotted. For shortening a rope without cutting it. More secure than ordinary sheepshank. Fig. 107. Topsail halyard bend. For fastening a rope to a spar. Fig. 104. Lanyard knot. To prevent unlaying of strands of a four-strand rope. Fig. 108. Bell-ringer's knot. For tem porarily tying up the lower end of a hanging rope. ETC 02724 ETC 02725 WIRE ROPE 35 as "right-lay, Lang-lay" rope, or if both are laid left-handed, it would be known as "left-lay, Lang-lay" (see Fig. 1). Construction. There are a great number of different possible constructions of wire rope. These are described by indicating first the number of strands, then the number of wires in each strand, namely, 6 X 7, 6 X 19, or 6 X 37. The smaller (and more numerous) the wires the more flexible the rope but the less resist ant to external abrasion. To overcome this, the Seale-lay rope was designed. It consists of comparatively small interior wires for flexibility with larger outside wires to resist abrasion. War rington-lay rope has alternate larger and smaller outside wires. These facilitate its identification. Figure 2 shows the exterior view as well as the cross section of some of the more common constructions. These views may help to identify a rope when its end cannot be examined, such as when it is spliced or socketed. Table I. Common Uses of Various Constructions of Wire Rope 6X7 regular lay...................... 6X7 Lang lay......................... 6 X 19 Seale, regular lay. . . 6 X 19 Seale, Lang lay.......... 6 X 19 filler wire, regular lay 6X19 filler wire, Lang lay................. 6 X 19 Warrington, regular lay.......... 6 X 37 regular lay.................................. 6 X 37 Lang lay...................................... 8 X 19 Seale, regular lay...................... 8 X 19 filler wire, regular lay.............. 8 X 19 Warrington, regular lay.......... Flattened strand..................................... 6X6X7 tiller rope............................. 6 X 6 X 19 cable lay............................. 18X7 nonrotating................................ Ropes with iron-wire-rope centers -- Guys, highway guards, oil wells Haulage systems having large sheaves and drums, cableways Mine incline hoists Haulage systems, mine inclines, cable- ways Miscellaneous hoists, derricks, cranes, tackle blocks, clamshell buckets, mine hoists, elevators Mine hoists, power shovels Mine hoists, drum-type elevators, oil wells Heavy-duty cranes, mill hoists Power shovels Hoists, traction elevators Light-duty hoists, elevators Light-duty hoists, elevators Coal unloaders, haulage lines, trans mission Small-boat steering, elevator hand ropes, signal ropes Heavy-duty cranes Hoists having single-line suspension On installations where cable overwinds on drums, where exposed to heat, or where additional strength is required TC 02727 ETC 02728 38 HANDBOOK OF RIGGING the rope is cut, the wires unlay and broom out if not held in place by seizings. In preformed rope any combination of wires and strands and any quality of steel can be used, but when laying up the wires into the strands and also the strands into the rope, they are bent slightly beyond the elastic limit in the curve they will finally assume, but they spring back sufficiently so that when in position they will he "dead." An example of this preforming is the curve assumed by a piece of soft wire that has been pulled around a screw driver or hammer handle to remove the kinks. Although the desirability for seizing the end of wire rope is not eliminated, a preformed rope can be cut without the wires and strands unlaying. Grades of Steel. Wire ropes are made of various grades of iron and steel, depending upon the needs. Iron wire is low in strength (about 100,000 lb per sq in.) but is quite ductile and can be bent over small sheaves. It is sometimes used for elevators. Traction steel is used principally for traction-drive elevators. It resists fatigue due to bending and causes a minimum of abra sion. Its strength is about 180,000 to 190,000 lb per sq in. Mild plow steel is somewhat stronger (200,000 to 220,000 lb per sq in.) and is tougher; that is, it combines fatigue resistance with strength. Plow steel is stronger and tougher than the mild grade. Its strength is about 220,000 to 240,000 lb per sq in. Improved plow steel is the best grade,, and each manufacturer usually applies a trade name to his rope. It possesses the highest strength (240,000 to 260,000 lb per sq in.) and abrasion-resistant properties. Purchasing. In purchasing wire rope, it is essential that suffi cient study be made to select the rope best suited to the job. The specification or purchase order should include the following in formation: 1. Length, such as.... 2. Size.......................... 3. Construction........... 4. Right or left lay___ 5. Regular or Lang lay 6. Preformed or not... 7. Grade of steel......... 240 ft X in. 6 X 19 filler wire Right lay Regular lay Preformed Improved plow steel WIRE ROPE 3Q Identification. Many wire-rope manufacturers identify their improved plow steel rope by a trade name and by a colored strand or other means, such as Roebling.................................... Leschen...................................... American Steel and Wire.......... M acwhyte.................................. Broderick & Bascom................. Bethlehem Steel........................ American Chain and Cable.... "Blue Center" "Hercules" "Monitor" and "Tico Special" " Monarch Whyte Strand ' ' "Yellow Strand" " Purple Strand " "Green Strand" Storage. Wire rope should be stored in a cool dry place away from fumes, chemicals, local heat, dampness, etc. It should be kept on the reel or spool until used. If it is to be stored for a long period of time, the outer layer of rope should be coated with a good moisture-resistant lubricant. Tar or asphalt in any form should not be used. ! ' 1 Taking from Stock. When a length of wire rope is removed from its spool, it is important that the spool be rotated, either on a spindle resting on trunnions (Fig. 3)', on a small turntable (Fig. 4) ETC 02730 ETC 02731 WIRE ROPE 41 or by rolling the spool or coil along the floor as the rope pays out (Fig. 5). The rope should never be taken off one side of a spool or coil, as a kink will be produced for each wrap on the spool. If it is absolutely impossible, because of space limitations or otherwise, to remove the rope from the spool by one of the meth ods mentioned above, then it may be necessary to resort to the following procedure. With the spool resting on its flanges, un wind several wraps of rope to accumulate sufficient slack. Then back up the rope to make a loose loop of rope on the spool, slip one loop off the right flange, and allow this loop to lie on the floor. ; Fio. 6. A means of removing wire rope from a reel that cannot be rotated on trunnions or on a turntable. Then slip a similar loop off the left flange, and let it also lie on the floor. (The rope on the floor will be in a figure eight. See Fig. 6.) ; Repeat this procedure, first on the right and then on the left, until the required length of rope has been unreeled. Then roll the spool back off the accumulation of rope on the floor, and pull away the end of the rope. The rope should come out of the pile without kinks. Kinking. Keep in mind that, once a kink has been produced in a rope, no amount of twisting or strain can completely remove it and the rope is weakened and may be unsafe for use. A slight, sharp, angular bend, known as a "dog leg," resulting from a par ?* tial kink, will chafe on the flanges of each sheave it passes over, and the rope will be prematurely worn at that spot. Seizing. Before cutting any wire rope (including preformed rs- rope), apply three seizings each side of the location of the proposed ETHYL CORPORATION development SECTION library BATON ROUGE, LOUISIANA ETC 02732 42 HANDBOOK OF RIGGING cut, then cut the rope. Do not cut first and then seize. If cut ting is done by means of an acetylene torch, sometimes the seizings are omitted, as the wires and strands are simultaneously welded together. Measuring. All ropes, both wire and manila, are measured by the diameter of the circle that will enclose the cross section of the rope (see Fig. 7). In other words, the calipers or caliper rule should be rotated or moved longitudinally until the largest diam eter is found. DM DM INCORRECT CORRECT Fig. 7. The nominal diameter of a rope is the greatest diameter it is possible to . (John A. Roeblxng'a Sons Co.) All new wire ropes are made slightly oversize, and this may cause confusion at times. Size of Rope, in. i to i 4 to 1$ H to 14 Oversize, in. 0 to Oto A 0 to -fa Lubrication. When the wire rope is manufactured, lubricant is applied to the hemp center, which acts as a storage medium for the oil and pays it out as the rope is used. Frequent application of proper lubricant to the exterior of a rope helps retain the orig inal lubricant within the rope. When lubricating a rope it is desirable to use a fairly viscous oil recommended by the rope manufacturer. This oil should be heated and applied while quite "thin" so that it will get into the center of the rope, then cool and thicken, which will keep it from being thrown off by centrifugal force as the rope passes over the sheaves. ETC 02733 WIRE ROPE 43 The best way to apply the heated lubricant is by causing a hori zontal cable to move through a long pan of oil or by running a vertical cable through a can of oil with a tight-fitting bushing at the bottom. Wipe off the surplus oil as the rope leaves the bath. Frequent application of proper lubricant during service is neces sary to prevent the hemp core from becoming dry. A dry-core rope will wear and crush more quickly than a lubricated one. Also it will absorb moisture more readily, which will result in interior corrosion of the rope. On traction-drive elevators only a small quantity of very thin oil is used on the ropes in order not to reduce the adhesion between the ropes and the drum. When any rope is observed with the lubricant dry and flaked, the rope should be cleaned with a wire brush and new lubricant applied. Corrosion. Corrosion or rust weakens a rope materially, yet it is very difficult, if not impossible, to estimate its weakening effect. A very rough idea can be obtained by carefully examining the exterior of the rope, and for lack of more definite data it must be assumed that the interior wires are in a like condition. Chemicals. Wire rope must be kept away from all chemicals. Acid will attack the metal. Alkali may destroy the internal lu brication. Damage by chemicals is not always apparent and may greatly weaken a rope when least expected. Design of Installation. It has been said of some machinery manufacturers that they spend much time and energy designing a crane or hoist; then when it is completed, they place a wire rope on it. In other words, they give little or no thought to the rope. Anyway, if the rope does not last long, the rope manufacturer, rather than the hoist manufacturer, will probably be blamed by the operator. A little thought given to the proper design of hoisting equip ment should result in more satisfactory operation, longer life, and lower operating cost. Following are a number of suggestions to be considered in the design of wire-rope installations. Attachments. Crosby clips are probably the most common method of attaching a wire rope to the equipment. The number of Crosby clips required is given in Table II. These clips should be spaced not less than six rope diameters apart, and all clips must be placed on the rope with the U bolts bearing upon the short or "dead" end of the rope (Fig. 8). Of course, a heavy-duty thimble should be provided for every eye, whether clipped or spliced. If 44 HANDBOOK OF RIGGING Table II. Installation of Clips* Rope diameter, in. Number of Crosby clips for eye attachment Spacing between clips, in. i2 A2 12 2 *3 t3 t4 l4 l4 H5 H5 H 2 21 24 3 4 4* 5* 6 7 8 *The proper number and spacing of Crosby clips ia important. properly made, a clipped eye should develop about 80 per cent of the strength of the rope. Beware of treacherous malleable-iron clips. Bind the rope on itself at the toe of the thimble. Then apply the clip farthest from the thimble first, at about 4 in. from the end of the rope, and screw up tightly. Next, put on the clip nearest the thimble and apply the nuts handtight. Then put on the one or more intermediate clips handtight. Take a strain on the rope. Fig. 8. Proper installation of Crosby clips. (1) Tighten clip farthest from eye. (2) Take a strain on the rope. (3) While the rope is under the strain, tighten the other clips. (American Chain <fe Cable Co.) and while the rope is under this strain, tighten all the clips previ ously left loose. In tightening the clips, take a turn alternately on the two nuts so as to keep the roddle of the clip square. After the rope has been in operation a short time, again tighten all the clips. No slack should exist in either part of the rope between the clips. WIRE ROPE 45 Double-base safety clips (Fig. 9) having corrugated jaws to fit both parts of the rope can be installed without regard as to which part bears on the live or dead parts of the rope. They are said to develop about 95 per cent of the strength of the rope; hence it is customary to use one clip less than indicated in the table for Crosby clips. Several patented attach ments are on the market, some of which can be recommended while others that develop high strength depend too much on the human element. If not attached to the rope accord ing to specific directions, they may not be dependable. Each such clamp should be carefully investigated before adopting it for general use. The SafeLine clamp (Fig. 10) is used for securing the end of a rope Fig. 9. Fist-Grip wire-rope clip develops greater strength and can be placed on the rope without crushing the strands. (The Thomas Laugfdin Company.) when making an eye. No strand ends project to cause possible hand injuries. While believed to develop about 100 per cent effi ciency, the device is somewhat heavy when used on slings. It is important, when using left-lay rope, that only clips or clamps designed for left-lay rope be used; otherwise the sharp ridges between the corrugations in the forging will run crossways Fig. 10. Safe-Line cable clamp is strong and is easily installed. (National Pto~ duction Co.) rather than parallel to and between the strands of the rope. Cut ting of the strands thus may result when using ordinary right-lay devices on left-lay rope. Wedge sockets are used on power shovels and similar equipment 46 HANDBOOK OF RIGGING on which it may be necessary frequently to change the attachment of the rope to the dipper or bucket. The efficiency is low, being only about 70 per cent of the strength of the rope. In using the wedge socket care must be exercised to install the rope so that the pulling part is directly in line with the clevis pin (Fig. 11); otherwise a sharp bend will be produced in the rope as it enters the socket. Socket attachments are used on more permanent installations, such as elevators. If properly made, the socket should develop 100 per cent efficiency. In making an attachment the following WRONG Fio. 11. The right and wrong ways of placing the wire rope in a wedge socket. procedure should be adopted. Put a seizing on the rope at a dis tance from the end equal to the length of the socket basket, and two additional seizings spaced one and one-half rope diameters apart immediately back of the first seizing. Unlay the strands of the rope, and cut off the hemp center near the first seizing, then carefully unlay and broom out all the wires in the several strands. It is unnecessary to straighten the wires. Clean with carbon tet rachloride or other solvent the wires that have been separated, then dip them for about three-fourths of their length into a 50 per cent solution of commercial muriatic acid for about a half a minute or until each wire is thoroughly cleaned. Do not allow the acid to reach the hemp center of the rope. Then rinse by immersing in boiling water containing a small quantity of bicarbonate of soda WIRE ROPE 47 to neutralize any remaining trace of the acid. Use care not to allow acid to come into contact with any other part of the rope. Bind the wires together, and insert the end of the rope into the socket so that the ends of the wires are even with the top of the basket, and remove this temporary binding wire. Spread out the wires so as to occupy equally the entire space within the basket. Clay should be applied to the annular space between the neck of the socket and the periphery of the rope to prevent the molten metal from running out. Hold the socket and several feet of rope in a vertical position, and pour in molten zinc until the basket of the socket is full. The zinc must be at the correct temperature. Before pouring, dip the end of a soft pine stick into the ladle for a few seconds, and remove. If the metal adheres to the stick, it is too cold. If it chars the stick, it is too hot. Allow the socket to cool, then remove the seizings, except the one close to the socket. Some wire-rope users, elevator manufacturers in particular, pre fer to use babbitt in place of zinc. In preparing the rope for socket ing the first seizing is If times the length of the basket from the end of the rope. Before pouring the metal, bend all the individual wires backward toward the center of the socket so that the bends are about flush with the top of the socket. Do not use lead for socketing. Even babbitt sockets have considerably less strength than the zinc sockets, sometimes as low as 25 per cent of the zinc. To check an existing installation scratch the metal with a knife. Zinc is quite hard, babbitt is softer, and lead is very soft. Babbitt should never be used for hoisting ropes. It is, however, acceptable for use on elevators for the following reasons: (1) Whereas safety factors of 5 to 7 are commonly used on cranes, etc., the factor of safety on passenger elevators varies from 8f to Ilf, depending upon the speed of the car. (2) A socket of given metal has the same holding power regard less of the strength of the rope. Hence, if a babbitt socket has an efficiency of, say, 60 per cent of the strength of an improved plow steel rope, it has an efficiency of 87 per cent when used on a traction steel rope of much lower strength. All hoisting ropes on elevators and mine hoists should be re socketed at frequent intervals, varying from monthly to bi-yearly according to the severity of service. Before resocketing, the socket should be annealed by heating in wood fire to a cherry-red color and then allowed to cool with the ashes. After the sixth annealing, the socket should be discarded. It should also be noted 48 HANDBOOK OF RIGGING if the neck or throat of the socket is rounded to reduce the wear and cutting of the rope. A spliced eye can also be used for attaching the end of a rope. Of course, a heavy-duty thimble is very necessary to avoid bending the rope too sharply around the pin and to reduce the wear on the rope. No attempt will be made here to describe the method of making an eye splice, as this is a job that no one but an experienced splicer should attempt and an art that cannot be acquired by book knowledge alone. The efficiency of a well-made eye splice with a heavy-duty thimble varies from 95 to 100 per cent for -jSg-in. rope, 90 to 95 per cent for j-in. rope, 85 to 90 per cent for If-in. rope, Fid. 12. Acco-Loc safety splice develops 100 per cent of the rope strength and is neat and compact, but it must be made at the factory. (American Chain & Cable Co.) and 85 per cent for lf-in. rope. All splices should have at least four tucks, and the completed splice should be carefully wrapped with a wire serving to cover the protruding wire ends to eliminate the danger of lacerations to the hands of those handling the ropes or slings. Tying cable into knots is definitely dangerous. The Acco-Loc safety splice (Fig. 12) also develops the full strength of the rope, is very compact, and adds very little to the weight or bulk of the rope or sling. Sheaves. Undersize sheaves are probably directly responsible for more rope failures than any other single cause. Under no WIRE ROPE 49 condition should a rope be operated over a sheave smaller than the "critical" diameter, as sharper bends result in displacement of the strands and overstressing of the wires. The minimum safe operating and the critical diameters given by rope manufacturers are indicated in Table III, where d is the nominal rope diameter. Table III. Sheave Diameter* Rope construction Minimum diameter t Critical diametert 6 X 19 Seale............................................ 6 X 16 filler wire.................................... 6 X 19 Warrington................................ Flattened strand..................................... 8 X 19 Seale............................................ 8 X 19 filler wire.................................... 6 X 22 filler wire.................................... 8 X 19 Warrington................................ 8 X 19 filler wire.................................... 6 X 37 Seale............................................ 6 X 41....................................................... 6X6X7 tiller rope............................. 34d 30d 30d 30d 26d 26d 23d 21d 21d 18d 18d 20d 16d 16d 16d 14d 14d lOd * Courtesy of American Chain and Cable Co. t The minimum diameter of sheave for satisfactory operation, and the critical diameter where rope is damaged, d is the rope diameter. The sheave groove must be large enough to accommodate a new rope (which usually is slightly oversize) and should be within the tolerance indicated in Table IV. Table IV. Sheave Grooves* Rope diameter, in. Tolerances, in. i to 4 A to 1 lj to 2 +-3*J to +A +iV to +-J+A to * Proper groove diameter for sheave is very important. Corrugated grooves will cause a rapid depreciation of a rope. Also, a badly worn sheave groove, which is caused by an old rope, will pinch and wear a new rope when it is installed. To accom modate a new rope the groove should be larger than the nominal diameter of the rope. Test gauges made to the diameters indi cated in Table IV can be used to check the size of the grooves. 50 HANDBOOK OF RIGGING In purchasing sheaves, the nominal diameter frequently indi cates the over-all flange diameter, but in this book the sheave diameter referred to is the diameter at the bottom of the groove, unless otherwise indicated. Reverse bends in a rope should be avoided so far as possible, but where they are unavoidable, the sheaves causing the reverse bend should be spaced as far apart as practicable (A and B, Fig. 13) and the most offending sheave should be made about one-third to one-half larger than the others. Even the equalizing sheave on a hoist block should be kept larger than the critical diameter, for although this is not an oper ating sheave in the ordinary sense of the word, there is a certain amount of motion here that may cause fatigue failure at this point even before the rope fails elsewhere. In the design of sheaves consideration must also be given to the bearing pressure of the rope on the sheave groove. If the rope bears too heavily on the groove of the sheave, and if the metal is softer than the wire rope, the former will become corrugated to fit the contour of the rope strands. These corrugations, in turn, will help to wear the rope, particularly if a new rope is run over a sheave having the groove corrugated to fit a worn and undersize rope. WIRE ROPE 51 The following formula is used to determine the rope bearing pressure: P = 21 DXd where P = bearing pressure, lb per sq in. t = rope tension, lb D = tread diameter of sheave, in. d = rope diameter, in. For regular-lay ropes the bearing pressure should not materially exceed the values given in Table V. ' --* iir'TunmnH ' irifiiliinliilfn 'i H f i l l Table V. Allowable Bearing Pressures* Lb per sq in. Cast-iron sheaves.......................................................................................... 600 Steel casting sheaves.................................................................................... 1,075 Chilled cast-iron sheaves............................................................................. 1,325 Manganese steel sheaves............................................................................. 3,000 * The pressure of the rope on the sheave groove should not exceed the allowable values. Drums. Drums should be designed to conform to the rules for sheaves, although a drum can be made slightly smaller than the minimum recommended size for sheaves owing to the fact that a rope is flexed only once by the drum whereas it is flexed twice each time it passes over the sheave. As far as is practicable, a drum should be designed to accommo date all the rope on one smooth, even layer. Two and sometimes three layers are permitted, but more than three layers may cause crushing of the rope on the bottom layer as well as at the end of any layer where pinching occurs. There is a proper way to wind rope on a drum, and this method should be followed as far as is practicable. If right-lay rope is used, it should wind on the drum in a left-hand helix; if left-lay rope is used, it should wind as a right-hand helix. Fleet Angle. In a properly designed installation the point where the cable leaves one sheave must lie in the plane of the sheave toward which the rope is leading. As in all cases except rope drives the rope runs in both directions, this rule applies to all sheaves. The lead sheave likewise should line up with the center of the width of the drum. The variance from this line is called the "fleet angle" and in the case of a smooth drum should not exceed I5 deg, or 1 in. in 40 in. Two degrees, or 1:28, is permissible with a grooved or scored drum (see Fig. 14). 52 HANDBOOK OF RIGGING If the sheave nearest to the drum can fleet or slide along a fixed shaft, the lead distance is the length of the rope between the drum and the nearest fixed sheave. Bending Stress. Although there is some difference of opinion relative to the exact stresses produced by bending a rope over a sheave, the fact remains that stresses of considerable magnitude are developed, and in some cases the bending stress may exceed FLEET DISTANCE FLEET DISTANCE Fio. 14. The fleet or lead distance is that between the drum and the nearest fixed sheave measured along the path of the rope. that caused by the live load. The handbooks of the various rope manufacturers give rules for calculating the bending stress. The factor of safety must take care of these unknown stresses, assuming that the sheaves are equal to or larger than the recommended minimum size. Displacement of Strands. Any displacement of strands from their original positions will cause a noticeable loss of strength of the rope, because under this condition some strands will take more than their share of the load. If the rope has been crushed or kinked or bent too sharply, it will be flattened and the load will not be equally distributed on the strands. WIRE ROPE 53 If a rope has been improperly seized one of the strands may slip and loosen, thus permitting this strand to be forced out of its posi tions by the adjacent strands and giving the rope a corkscrew appearance. A Lang-lay rope that has not been properly seized may open up and produce a condition known as "bird-caging." The pitch of a used rope should not differ materially from that of a new rope, which is generally about 6f times the rope diameter. In some cases, owing to improper sheaves, that portion of the rope which continually passes over them may have its lay increased, the twists being accumulated at the ends of the rope, as evidenced by the shortening of the lay at these points. Lengthening of the lay at a socket is an indication of an improper socketing job; the end of such a rope should be cut off, and a new socketing job made. Sudden Stresses. Consideration must be given to the stress produced by rapid acceleration and deceleration, jerks, vibration, etc. An automotive crane traveling over a rough road with a load suspended on the boom may have impact stresses of 100 per cent or more added to the sum of the live and dead loads. If a load is accelerated rapidly, such as in the case of a high-lift coal-unloading tower, the acceleration stress can reach great mag nitude. Let us assume the following conditions: Weight of coal and bucket, 10,500 lb. Hoisting speed, 1,800 ft per min = 30 ft per sec. Time to accelerate from rest to full speed, 11 sec. While at rest, the load on the hoist cable is 10,500 lb. To this must be added the force necessary to accelerate the load. This is obtained from the formula ,= m ] ~ 32.161 where / = accelerating force, lb w = weight to be lifted, or static tension on rope, lb v = velocity, ft per sec t = time to reach full speed, sec , 10,500 X 30 ,, ro,, ,, . ,, . / = qo i I" = 6,530 lb m this example UA. 10 X 1 2 Thus, to the static tension of 10,500 lb on the rope must be added the acceleration stress of 6,540 lb, making a total of 17,030 lb. Friction Load. The static tension on a rope is the total weight of the load, load block, hook, slings, etc., divided by the number of parts of rope actually supporting the load block. V* 1 54 HANDBOOK OF RIGGING As a sheave is rotated on its shaft, friction must be overcome. Also, friction is developed when the wires and strands of a rope slide on each other as the rope is flexed in passing on to and off a sheave. Figure 15 gives the approximate tension on the rope for various rigging methods. The figures given represent the pull in pounds to lift a gross load of 1 ton, exclusive of acceleration stress. n 5 PARTS I PART 2 PARTS 3 PARTS 4 HARTS Q8 dd 5 PARTS ddb 6 PARTS 6 PARTS epeo I PART 5n 4 3 QQ : ddob 14 PARTS Fig. 15. The pull on the lead line when hoiBting a load of 1 ton when using various reevingg. Total Stress. The total stress imposed on the operating portion of a wire rope may consist of many or all of the following items: 1. Live load to be hoisted 2. Dead load (lower load block, hook, slings, cable) 3. Additional stress required to overcome friction of sheaves 4. Sudden load due to quick acceleration, deceleration, or shocks 5. Bending stress due to bending over sheaves and drum WIRE ROPE 55 Friction on Drum. In order to reduce to a safe figure the load on the cable anchorage on the drum, it is necessary to leave at least two and preferably three complete wraps of rope on the drum when the load block is at the floor level or lowest position. Fig ure 16 and Table VI indicate the strain at the anchorage in pounds for each 1,000-lb tension in the rope, depending upon the number of wraps on the drum and upon the lubricant on the rope. Fio. 16. The strain on the anchorage of the cable on the drum depends upon the number of wraps of rope on the drum and upon the lubrication. Table VI. Strain on Rope at Given Number of Wraps from Point of Tangency (1,000-lb load) Number of wraps Well-greased rope, lb / = 0.07 r ii i i l H 2 2i 3 3J 4 5 890 788 697 616 485 369 287 220 166 126 95.3 71.6 Dry rope, lb / = 0.17 760 575 361 329 188 101 59.7 33.9 18.4 10.1 5.8 3.1 Breaking Strength. Table VII gives the breaking strength of 6 X 19 wire ropes of various grades of steel. For 6 X 7 ropes use 96? per cent, for 6 X 19 Seale ropes 98 per cent, for 6 X 37 ropes 95 per cent, and for 8X19 ropes 92| per cent of the tabular values. 56 HANDBOOK OF RIGGING Table VII. Breaking Strength of Wire Rope* (Divide by factor of safety to obtain safe load.) Diameter, in. Mild plow steel, lb Plow steel, lb Improved plow steel, lb i 4,860 5,300 6,300 A 7,000 7,600 9,000 i 10,600 11,500 13,500 A 14,500 16,000 18,400 \ 18,400 20,000 24,200 A 22,400 24,600 29,000 i 28,000 31,000 38,000 40,400 46,000 52,600 i 52,000 58,000 70,000 l 68,000 76,000 90,000 i* 86,000 94,000 112,000 H 106,000 116,000 138,000 * For ropes having an independent wire-rope center add about 7 \ per cent to the strengths indicated above. Ropes having an independent wire-rope center are about 7\ to 10 per cent stronger than indicated above. Factors of Safety. In order to ensure against failure of a wire rope in service with possible disastrous consequences, the actual strain on the rope should be only a fraction of the breaking load. Table VIII. Minimum Safety Factors for Wire Rope Slings........................................................................................... Overhead electric hoists (small)........................................... Overhead traveling cranes (small)....................................... Industrial truck cranes........................................................... Locomotive cranes................................................................... Derricks...................................................................................... Grab buckets............................................................................. Overhead traveling cranes (large)........................................ Hoisting tackle......................................................................... Shovels........................................................................................ Derrick guys.............................................................................. Stack guys.................................................................................. Tow ropes................................................................................... Ferry ropes................................................................................ Cableway track ropes.............................................................. Contractor's suspension bridges........................................... Elevators.................................................................................... 8 7 6 6 6 6 5^ 5 5 5 4 4 4 4 3 See local ordinances WIRE ROPE 57 The breaking strength divided by the actual total stress on the rope is known as the "factor of safety" and should not be less than the values given in Table VIII. Breaking In a New Rope. After installing a new rope, operate it for perhaps an hour without the "live" load to ensure that it will accommodate itself to the sheaves and drums before the heavy strain is applied. The time thus spent will ensure longer operation without servicing. As mentioned above, the clips should be tightened after the breaking-in period. After about half of the normal life of the rope, remove it from the equipment, turn it end for end, and reinstall it. The useful life will be much longer than if the rope is left in its original position. Special Rigging. In hoisting operations an improvised support is frequently made by stretching a wire rope more or less tightly between two beams, roof trusses, or other elevated structural, members and attaching a chain hoist at some point in its length. This method of suspending a chain hoist or other load cannot be too strongly condemned, as in practically every instance the loads produced cause excessive stresses both in the cable and in the struc tural supports. This is particularly objectionable in the case of the structural members, as they are subjected to forces in a direc tion for which they probably were not designed. In order that the rigger may approximate the loads imposed on the cable (and on the structural members) by such a rigging, the following instructions should be followed. Draw to any suitable scale an elevation of the structural supports and the cable stretched between them, with particular attention to the amount of sag of the cable, as shown in Fig. 17. Next construct a triangle of forces by first drawing a vertical line DE to represent the vertical load, which includes the weight of the load to be lifted and the weight of the chain block. Draw this vertical line to any convenient scale, such as 5 in. = 1,000 lb, 1 in. = 1,000 lb, 1 in. = 10,000 lb, etc. Then draw a line DF parallel to the portion of the cable AB, starting at D and continuing indefinitely. Next draw a line EG parallel to the portion of the cable BC, starting at E and continuing until it crosses line DF at H. Now by measuring the lines DH and EH with the same scale used for line DE, the stresses can be determined. In this example, the stresses are 14,200 lb in the portion of the cable AB and 14,100 in BC. These forces are imposed nearly horizontally on the structural members. : i: ETc 02748 58 HANDBOOK OF RIGGING Thus, it will be seen that a comparatively light load of 2,000 lb suspended by the cable will impose a horizontal force of over 14,000 lb on the beams, columns, or other structural supports. If there are any shocks or impact stresses, these will be likewise amplified and transmitted to the steelwork. 2 FT. Fio. 17. Triangle of forces is used to calculate the stress in a tightly stretched trolley cable. Likewise, when slings are used as spreaders for picking up loads, their angles are of great importance, as shown in the following sketch. To pick up a load of 2,000 lb on two ropes that are parallel, each rope will be stressed to 1,000 lb (Fig. 18). If these slings are attached to a common hook on the hoist so that their angle to the horizontal is reduced to 60 deg, the stress is increased to I 2POO* Fio. 18. The tension on a sling rope (or chain) depends upon its angle as well as upon the load to be lifted. 1,155 lb. At 45 deg the stress is 1,414 lb, at 30 deg it is 2,000 lb, and at 5 deg the stress has reached 11,470 lb. Not only is there danger of overloading the sling cable and causing its failure, but the crate, box, or even the load itself may be crushed by the ETC 02749 WIRE ROPE 59 force applied at its upper comers. In any event, padding should be provided to protect the slings from sharp bending and possible cutting at all comers of the load. Inspection. One of the difficult problems confronting the equipment inspector is deciding just when a wire rope has reached the limit, of its safe usage and must be discarded. Naturally, it is poor economy to discard an expensive hoisting rope before it is necessary. Likewise, it is dangerous (and it may also prove even more expensive) to continue its use beyond a certain stage. To determine the proper time to condemn the rope a careful inspection should be made not only of the rope itself but also of the sheaves and other parts that affect its use. Some of these factors are as follows: 1. Construction of the Rope 2. Broken Wires. The total number of broken wires in all the strands within a distance of one rope lay (the distance in which a strand makes one complete turn around the rope) at the worst portion of the rope is taken as an index of the reduction in strength due to this cause. In inspecting preformed rope extra care should be exercised, as the broken wires lie flat in position and are often difficult to detect. See Tables IX and X for the number of broken wires allowed for various types of rope with varying amounts of wear. 3. Location of Wire Breaks. It should be observed whether or not several adjacent wires are broken, whether the breaks occur at the point of tangency with the sheave groove (which may indi cate fatigue of the metal) or with the adjacent strands (which usually indicates lack of internal lubrication), whether the breaks are about equally distributed among the strands or are mostly located in a few strands. Unequal distribution of the breaks results in a greater loss of strength than when the same number of breaks are equally distributed (see Tables IX and X). Even a Table IX. Allowable Wibe Breaks and Wear on Mine Hoist Ropes* Broken Wires in One Rope Lay Wear on Outside Wires, % None but 35 3 or 30 4 or 20 5 or 10 6 and 0 * U.S. Bureau of Mines. 60 HANDBOOK OF RIGGING Table X. Allowable Wire Breaks and Wear on Hoisting Ropes* Use Conditions 6 X 19 Warr. 6 X 37 8 X 19 Warr. 6 X 19 Seale Other conditions / Total Cranes.... 1 Adjacent /Total Hoista. . . . \ Adjacent Passenger / Total elevators \ Adjacent 18 4 24 5 12 4 Freight / Total elevators \ Adjacent 13 4 30 24 64 32 5 16 4 18 4 Wear on outside wires in excess of 33% I Wear on outside J8 3 i wires in excess of 33% 9 1 Wear on outside ) wires in excess 3 J of 33% * American Cable Co. recommendations for condemning worn wire rope. single broken wire at the throat of a socket is sufficient cause for cutting off the end of the rope and making a new socket attach ment. 4. Wear on Outside Wires. The length of the shiny, worn spots (Fig. 19) on the outside wires should be measured with a steel scale LENGTH Fio. 10. The length of the long shiny spots on the wires is an indication of the amount of wear. graduated in one-hundredths of an inch, as this is an index of the reduction in area, and likewise in strength of the wires and of the rope due to wear. ETC 02751 WIRE ROPE 61 Where the personal and property hazard (see Item 24) is great, such as in elevators, mine hoists, and hot-metal cranes, a very strict rule should be followed for condemning a rope, such as the rule of the U.S. Bureau of Mines, which is given in Table IX. On the other hand, where personal and property hazard is not great, such as in the case of bucket hoists, skip hoists, unloaders, hand-power cranes, and derricks, a more liberal rule can be followed in condemning wire rope, such as is given in Table X. The term "total" indicates the total number of wire breaks in all strands in one rope lay. "Adjacent" indicates the number of adjacent wires broken. On machinery such as horizontal cable roads, drag lines, and steam shovels, where no danger will ordinarily result from a cable failure, it is sometimes customary to keep the rope in service until an entire strand is about ready to fail. 5. Reserve Strength. This factor is the ratio of the crosssectional area of all the inside wires to the area of the rope. In other words, in case of failure of all the outside wires, the strength of the inner wires should remain as a reserve. Seale-lay ropes have the lowest reserve strength, and 37-wire-strand ropes the highest. 6. Corrosion 7. Kinks 8. Crushed Strands 9. High Stranding 10. Bird-casing 11. Pitch of Rope Lay 12. Attachments 13. Splices 14. Turns in the Rope. In the case of hoists, derricks, etc., having multiple reeving of the rope in the pulley blocks, the rope during its early life will stretch and unlay slightly, causing the load block to rotate and the several parts of the ropes to twist around themselves. In such a case the end of the hoist rope, whether it be at the load block or at the boom head, should be detached and rotated so as to remove the turns. In the case of a new rope a few more turns than are necessary can be made in the rope in anticipation of the subsequent stretch. 15. Frequency of Use. The number of hours per day or week dur ing which the rope is in use is an important factor. The inspector should consider how much use and depreciation a rope may be ETC 02752 62 HANDBOOK OF RIGGING expected to have before the next inspection. In other words, con sider two ropes in identical conditions and under similar loads. One rope is used only an hour or so a week and probably will be safe for use at least until the next inspection, while the other rope, which is in use 8 hr a day, will probably be in a dangerous condition in a much shorter time. Therefore, the much-used rope might be condemned while the other might be accepted for further use. 16. Rope Speed. A high-speed rope will have a much shorter life and also expectancy of life than a slow-speed rope and therefore should be given a more severe inspection. 17. Rope Bends 18. Sheave and Drum Grooves 19. Sudden, Loads and Shocks 20. Equalizing Sheave 21. Multiple Winding on Drum 22. Lubrication 23. Weak Points. The weakest part of a rope, like the prover bial chain, determines the strength of the rope. This weak point may be where the rope is badly worn, where it has a number of broken wires, where the stresses are unequal in the strands,' where the local stresses due to bending the rope over a sheave are exces sive, or where the rope is attached to the equipment upon which it is used. For instance, if a f-in. plow steel rope has a safe load of 9,200 lb under direct tension, and if the bending stress at the sheaves reduces the strength to, say, 75 per cent of this load, then there is no need to be concerned over the use of a clipped eye that has an efficiency of about 80 per cent, for it is still stronger than that portion of the rope passing over the sheave. Also, the strength of the rope itself will eventually be reduced by wear, while the strength of the attachment should remain unchanged. 24. Personal and Property Hazard. Consideration should be given to the possible consequences resulting from failure of the rope, especially where men are hoisted, as in elevators or mine cages, or where heavy loads are carried above men or valuable machinery. 25. Original Safety Factor. Where a liberal factor of safety had been allowed when the rope was new, naturally a greater depreciation can be allowed than if a low initial safety factor had been used. Each of the above factors should be thoroughly in vestigated. This means inspecting every foot of the length of the cable, as the spot that is overlooked may contain the weakest part >*r; ^ WIRE ROPE 63 of the rope. These factors are then summed up in relation to the personal and property hazard and the original safety factor in order to determine whether the rope should be continued in service or condemned. Where ropes habitually depreciate rapidly at one end owing to the character of the equipment upon which they operate, it is economical to reverse the ropes end for end before they become bad enough to condemn. It is recommended that all wire rope issued from the company storehouse be identified by a metal tag bearing a serial number that will, in turn, afford such pertinent information as the date issued, quality of the rope, manufacturer, etc. Some organizations use a 1-in. length of aluminum tubing, just large enough to slip over one strand of the rope at the seizing, socket, or eye splice, with the serial number stamped on it. Where it is not desirable to do this, only one grade of rope should be kept in stock, for if several grades are stocked, there will be no means of differentiating between them once they are removed from the manufacturer's spools, and accidents may result from assuming a rope to be of a higher grade than it actually is. As can be learned from the above text, properly inspecting a wire rope is a man-size job. It is only after years of experience, together with a good knowledge of the technical properties of rope, that an inspector can learn just when it is economical to condemn a wire rope and still be thoroughly safety-minded. ETC 02754 CHAPTER IV HOISTING CHAINS AND HOOKS The manufacture and use of chain dates back to centuries before the Christian era. Modem chains are the result of many improve ments in the material and in the method of manufacture, alloy steel chains having the greatest strength. Originally chains were used almost exclusively for heavy hoisting, such as on cranes, but today they have been largely superseded by wire rope. There are jobs, however, on which chain is better suited than wire rope, and consequently many chains are in service today. They are particularly well suited for slings for lifting rough loads such as heavy castings, the handling of which would quickly destroy wire-rope slings, owing to bending them sharply over the edges of the castings. Chains are also used extensively for dredg ing and other marine work, as they will withstand abrasion and corrosion better than cable. A link of a chain consists of two sides, either of which in failing would cause the link to open and drop the load. A wire rope, on the other hand, is frequently composed of 114 individual wires, all of which must fail before it parts. Chain may thus be said to have less reserve strength, and it should therefore be more care fully inspected. In the case of manually welded chain, the welds depend largely upon the human element. When a wire rope is fatigued from severe service, the wires break one after the other over a relatively long period of time and thus afford the inspector an opportunity to discover the condition. If severely overloaded, the wires and strands will break progressively over a period of perhaps several seconds, and with resultant noise, before complete failure occurs. This affords the man handling the load a brief time in which to jump to safety before it is dropped. Chains, on the other hand, will usually stretch under excessive loading, the links elongating and narrowing down until they bind on each other, thus giving a visible warning. However, if the overloading is great enough, the chain will ultimately fail with less warning than wire rope. Should the weld be defective, a chain may break with little, if any, warning. 64 HOISTING CHAINS AND HOOKS 63 Owing to the construction of wire rope, with the individual wires running in a spiral direction, it has more stretch and will therefore be more resistant to sudden loads or shocks than will chain. According to the Chain Institute: The safe working load is the maximum load in pounds which at any time or under any condition should be applied to the chain or the attach ment thereon, even when the chain is in the same condition it was in when it left the factory, and even when the load is applied only in direct tension to a straight length of chain or to an attachment thereon. . .. Any change in the above factors, such as twisting of the chain, deterioration of the chain or attachment thereon by strain, by usage, by weathering, or by lapse of time, or acceleration in the rate of application of the load or varia tion in the angle of the load to some sharper angle resulting from the con figuration or structure of the material constituting the load will lessen the load that the chain or the attachment thereon will safely withstand. Table I gives the working loads for various types of chain, based on a factor of safety of about 3^, that are recommended by many chain manufacturers. Yale & Towne Mfg. Co., how ever, uses a safety factor of 5^ to 6^ on their f- to 2-ton chain hoists. Considering the fact that a minimum factor of safety of 5 is recommended for wire rope, and considering the limitations indicated in the previous paragraph, the author advises working loads, particularly for slings, not much in excess of one-half the values given in the table (except Yale & Towne chain). The tabular working loads are undoubtedly safe for straight pull, as stated by the Chain Institute, but there is no assurance that the weight of the load is not underestimated, that the chain has not been weakened by usage or by weathering, or that there will not be accidental shock or impact loading. To cover all these possi bilities the higher safety factor is recommended. Iron hoisting chains should be annealed every two years to relieve work hardening; those used as slings should be annealed annually. After six annealings, the chains should no longer be used for hoist ing purposes. Steel chains should not be heat-treated after leaving the factory. , Inspection. Let us consider the inspection of chain from a safety viewpoint. All chains should be thoroughly inspected at least once a month by a competent inspector. Every chain, whether attached to a piece of equipment or used as a sling, should be given a serial number, which can be stamped on a metal tag attached to the end link or ring. A book record should be kept 66 HANDBOOK OF RIGGING Table I. Safe Working Loads Recommended by Chain Manufacturers (For rigging operations using about one-half these values.) f'enyl ey(?)) fenU) ifyn)j Nom inal Iron chain, size lb Acco Endweldur Taylor No. 125, lb No. Flash- Heavi85, Alloy, Lift, lb lb lb HereAlloy, lb Yale <fe Towne chain hoist, lb i it li il n H u 1O 2 s 1,060 2,385 4,240 6,630 9,540 12,960 16,950 20,040 24,750 2,750 2,150 2,750 2,100 6,600 4,275 6,600 4,300 11,250 7,000 11,125 7,000 16,500 10,125 16,500 10,100 23,000 14,000 23,000 14,000 28,750 19,125 28,700 19,100 38,750 24,250 38,750 24,250 44,500 30,250 44,500 57,500 37,500 57,500 Proof load Proof Proof Proof Proof load load load load 7,600 14,400 20,600 26,250 42,000 Proof load 1% ds 2 2222 1.35 2,000 4,000 Breaking load 5 of each chain, including the date of purchase, make, grade of steel, safe working strength (when new), length for five links (exact), etc. At his periodic inspection the inspector must carefully examine each link in the chain. Remember the proverb about a chain being only as strong as its weakest link. If you overlook one link, that one may be the defective link. It will be necessary to wipe off most of the grease to make the inspection properly. Look for links that may be elongated owing to overloading. If the links bind, condemn the chain. A free-hanging chain that is not perfectly straight is indicative of binding links. If there is HOISTING CHAINS AND HOOKS any question as to the stretching of the chain, measure five links and compare the present length with the original length as indicated in the record for this particular chain. Condemn the chain if the stretch exceeds 10 per cent. Watch for links that may have become slightly bent when the sling was used to pick up a load with sharp steel or iron edges. The presence of a crack, however fine, particularly at the weld, is suffi cient cause for having the link removed from the chain. If gouges or cuts are observed in the links, they should be very carefully inspected. If the cross section of the link is materially reduced, that link should be cut open and removed from the chain. Watch all sharp nicks and cuts, as it is in these spots that cracks will usually start. Any link that shows evidence of a crack should be removed from the chain without hesitation. Where a crack is suspected, the link may be soaked in thin oil and then wiped dry. A coating of powdered chalk or other white material is applied to the surface and allowed to remain there for several hours. If a crack exists, the oil pocketed in it will be drawn out by capillary action and will noticeably discolor the white coating. Small dents similar to peen marks on the surface of the links or even a bright or polished surface usually indicate that the chain has been work-hardened or fatigued. With the chain lying slack on the floor observe the wear, if any, where the links bear on each other. Figure 1, which has been plotted from data contained in the American Standards Associa tion Safety Code for Cranes, Hoists, and Derricks, shows the reduc tion in working load on chain, corresponding to different amounts of wear. Enter the chart at the bottom from the nominal size of the chain (the actual size is very slightly larger). Also enter from the left side of the chart at the worn dimension, and observe where the lines intersect. If the intersection is below the lowest line, the chain should be removed from service at once. Strange as it may seem, there is relatively little difference be tween the strength of a new or worn chain having the same B dimension. For instance, a f-in. chain that is worn down to f in. has approximately the same strength as a new f-in. chain, but the limit of wear in this case is 25 per cent reduction from A to B dimension. If the chain is taut, it may be desirable to caliper the two links as they bear on each other, then divide by 2 to obtain the B dimension. ETC 02758 68 HANDBOOK OF RIGGING Lifting of a fin at the weld is evidence of severe overloading. When a defective link is observed, it should be marked with crayon or chalk and then cut out of the chain. A repair link can be used to attach the pieces of the cut-up chain. Never use bolts to join chains together. And do not shorten a sling by twisting the chain, for this will cause a great loss of strength. In Table I the sketches of the links will assist in identifying the make and the grade of steel in the chain. For instance, iron chain ETC 02759 HOISTING CHAINS AND HOOKS 69 has a relatively smooth link with an inconspicuous weld. ACCO Endweldur chain has the weld at the end of the link, being quite prominent on the inside of the link. The figures 85 or 125 are stamped on the side of each link. Taylor Flash-Alloy and Heavi-Lift chains of larger size have welds on both sides of each link, being prominent on the inside of the link. Herc-Alloy chain has a weld on one side of the link, noticeable on the inside of the link. Yale & Towne chain for chain hoists has the weld on one side of the link but is a uniform cylindrical bulge. The ring of a sling chain may be considered as a large link and should be inspected as is the chain itself. Fia. 2. If the inside contour of the hook is not a true arc of a circle the hook has been badly overloaded. Photographs show a 1-ton hook subjected to various loads. (A) 4,000 lb. (B) 5,800 lb. (O 6,800 lb. (>) 7,400 lb. (E) 7 (Yale & Towne Mfg. Co.} The hook should be the weakest part of any crane, hoist, or sling. It seldom, if ever, breaks, but it may fail by straightening out and finally releasing the load. A distorted hook is prima-facie evidence of overloading, for as shown in Fig. 2, 100 per cent overload does not change the contour of the hook. One hundred and ninety per cent overload is hardly noticeable. Yet it is not uncommon to find hooks spread as shown in the third illustration in Fig. 2. Reforg ing and/or annealing of spread hooks should not be permitted. When inspecting a hook- pay particular attention to the small radius fillets at the neck. The strength of eyebolts to which a sling can be attached is also of utmost importance, as it is influenced greatly by the direction of pull, as indicated in Table II. When bridle slings are used, an angular pull is always developed in the eyebolts unless a spreader 70 HANDBOOK OF RIGGING bar is provided as part of the sling. See Chap. V for tension, in slings used at various angles. Table II. Safe Loads on Eyebolts 4" 1,100 lb *" 1,5001b 4" 1,8001b r 2,8001b Sin 3,9001b i" 5,100 lb ii" 8,400 lb W 12,200 lb ir 16,500 lb 2" 21,800 lb Drop Forged Steel 501b 701b 901b 1351b 2101b 2801b 5001b 7701b 1,0801b 1,4401b 401b 501b 651b 1001b 1501b 210 lb 3701b 575 lb 8001b 1,140 lb tY' 44" 4" i" if" 44" i*" if" ir ir ir iA" itt" 144" HF 2tY' 2&" 2tV' 3tV' 3tV" 4" If" If' 2|" 2f' 24" 24" 34" 34" 34" If" 10,300 lb If" 11,0001b 2" 14,000 lb 2f" 16,000 lb Welded Wrought Iron 8001b 6601b 8851b 1,050 lb 6001b 485 lb 655 lb 7701b 14" 3" 34" 14" 4" 4" if" 5" 54" 2" 6" 5f" To attach slings, either of chain or wire rope, to eyebolts on the load to be lifted a shackle is usually used. Table III gives the safe working load on shackles, using a factor of safety of 5. HOISTING CHAINS AND HOOKS Table III. Safe Load on Chain Shackles (From data by Boston A Lockport Block Co.) 71 Size shackle Safe Pin Shank Inside Inside load, lb* diameter, in. diameter, in. width, in. length, in. * 3,650 A 4,800 4 5,720 4 8,400 4 9,600 l 13,200 ii 15,200 n 17,200 14 22,600 14 25,600 if 31,200 14 38,200 2 48,200 * Safety factor = 5. f 4 4 4 l 14 14 14 14 if 14 2 24 4 4 14 A A2 4 4 2A 4 4 24 4 4 3A l l 34 14 14 344 14 14 44 14 14 444 14 14 54 14 14 14 14 &4 2 2 74 11 ETC 2762 CHAPTER V SLINGS Adequate consideration may be given by the designing engineer to the choice and installation of the component parts of the hoisting tackle on a crane or derrick, including the hoisting cables, their attachments, sheaves, pins, blocks, and hooks, but his effort may be largely nullified should the riggers who eventually operate the equipment use improper slings or use the correct slings in an improper manner. Manila rope and iron and steel chains have been largely super seded by steel wire rope for the hoisting tackle on such equipment, with resultant increase in safety and with the ability to lift much greater loads. It must be kept in mind that manila rope and chain both have their proper places on rigging jobs; manila rope is used for lifting comparatively light loads and on temporary work, while chains are frequently used in foundries where exposed to high tem peratures. But on permanent installations and in heavy-duty operations they have their limitations. Manila rope deteriorates rapidly when exposed to the weather, and after such exposure its actual strength is very difficult to estimate. Chain has much greater resistance to the effects of exposure to the elements but has other shortcomings. In hand-forged chains there is ever present the human factor in the form of the welder who may or may not have made a perfect weld. Electrically welded steel chain is considerably more uniform in quality, but even its safety depends upon the proverbial "weakest link," as the failure of any one link will allow the load to drop. Wire hoisting rope, on the other hand, is frequently of the 6 X 19 construction; that is, it consists of six strands, each containing 19 wires, laid around a hemp-rope center. Unlike the chain, failure of one of the component parts (a wire) will result in a reduction in strength of less than 1 per cent, which is insignificant. This is the primary reason why wire rope has been almost universally adopted for hoisting operations. But properly designing a piece of hoisting equipment to lift a given load on the hook safely is not the only problem. That load 72 ETC 02763 SLINGS 73 must be secured to the hook, and the attachment must be of ade quate strength to lift the load safely. Thus is presented the problem of properly designing and using slings, about which this chapter is written. Just as in the case of hoisting tackle, various materials can be used for slings. For the very lightest loads an endless manila rope, looped into a noose around the object to be lifted, is satisfactory. Such a sling is inexpensive, of light weight, flexible, and easy to handle. It can be bent around the comparatively sharp edges of boxes or crates but should be padded when passing over the sharp machined edges of metal parts. Even on some heavier jobs, such as handling of steel shafts which must not be scratched or burred, manila-rope slings have found favor. Coil chains have a limited application as slings, being used principally in foundries where they are exposed to high tempera tures and where they are to be used to pick up rough castings that would quickly destroy other types of slings. Like manila rope, a chain should preferably be padded where bearing on sharp edges of metal parts; otherwise some of the links may be subjected to severe bending stresses for which they were not designed. Also, the chain may bruise or otherwise damage the edges of the piece being lifted. For special work, slings are sometimes made of other materials such as roller chains, leather, and cotton webbing, but by far the greatest number of slings in use today are of wire rope. From the safety viewpoint, wire-rope slings possess the same points of superiority as do wire ropes for hoisting tackle mentioned above. But even wire-rope slings must be carefully chosen for the service in which they are to be placed, as they also have certain limitac tions. Like manila-rope and chain slings, wire-rope slings should be padded where being bent over sharp edges of the object to be lifted. Although the edge may be of soft material such as a wood crate or skid, which will not cut the sling, nevertheless the individ ual wires being bent sharply will be highly stressed, possibly beyond the elastic limit, even before the live load is applied. Wire-rope slings must not be allowed to become kinked, as this also causes severe bending stress and, in addition, the strands that have been displaced are subject to unequal distribution of the live load, some .strands taking more than their normal load, in addition to the stress produced by the sharp bending. Even though an attempt is made to remove a kink, the damage done to 74 HANDBOOK OF RIGGING the rope is usually permanent. This accounts for many sling fail ures. Most wire-rope slings, like hoisting cables, are of 6 X 19 filler wire construction and of improved plow steel grade. Slings of 5-in. rope and larger should be made from wire rope with an independent wire-rope center. This will reduce the probability of the rope being crushed in service. The very large sizes are often made of 6 X 37 or 6 X 6 X 19 construction to increase the flexibility. All slings that have at one time or another been bent sharply become "cranky"; that is, they have developed permanent deflections, so that, when the strain is relieved, they will snarl in some unpredictable manner. This is very annoying, to say the least, and it means continual vigilance to keep them from develop ing kinks when taking a strain pre paratory to lifting a load. Slings made of preformed rope behave some what better than those made in the conventional manner and also have the advantage that broken wires Mil not so readily wicker out and present a hand hazard to the rigger but rather tend to lay "dead" in the original position. The term "sling" includes a wide variety of designs. Perhaps the sim plest is the grommet or endless type (Fig. 1). If of wire rope, it is made Fig. 1. Endless sling or grom- by using six complete loops of a single strand laid or twisted around itself on each successive loop. The ends are then tucked into the space where a short length of the hemp center has been removed, such as is done in making a long splice. This type of sling is usually formed into a noose known as a "choker hitch," or "anchor hitch," which is. slipped around the object to be lifted, and the free bight is placed on the crane or derrick hook. When a strain is taken on the sling, it crowds in nnd squeezes the load, but to assure that it grips the load firmly, it is good practice to strike the bight that bears on the hauling part with a 2 X 4 so as to make three 120-deg angles between the component parts of the sling at the bight. For handling miscellaneous loads the rigger should have avail able four single slings, six shackles, four hooks, and a ring. With Fig. 2. Component parts Cor a single sling, choker sling, or basket sling. (Amer ican Chain & Cable Co.) Fig. 3. Basket hitch. If the load is prevented from tilting, such as by the use of two hoists or cranes, this hitch is suitable for lifting shafts, boiler drums, tanks, etc. (American Chain <& Cable Co.) Fig. 4. A choker sling gets a viselike grip on the load. (American Chain & Cable Co.) this equipment he will be able to lift almost any type of load, pro vided it is not too heavy or too large for the particular slings. Having one single sling and the acces sories shown in Fig. 2, he can lift many loads safely with or without these ac cessories. It can be used as a basket sling (Fig. 3) for lifting certain types of loads. The middle of the sling is placed through the load to be lifted, and both spliced eyes are placed on the crane or hoist hook. Or the sling can be wrapped around the load, one eye threaded through the other eye and then placed on the crane hook. This is known as a "single choker sling" (Fig. 4). If it is not convenient to slip the ^ noose on and off the end o! the load, Fio. 5. Choker sling can also used mth ,a hook where it is more convenient. (American Chain & Cable Co.) ETC 02766 76 HANDBOOK OF RIGGING the shackle can be used to attach the hook to the lower eye. The sling is then passed around the load and hooked into itself to form a choker (Fig. 5). In order to reduce wear and sharp bending where the hook bears on the body of the sling, a special forging is sometimes threaded onto the sling. The eye is made so as to cause a minimum bending of the rope, and it has a hook onto which the eye of the sling is placed. The choker sling can be used to lift one 0 Flo. 6. A single-leg sling can be used for a direct lift where the hoist hook is too big to engage the Lifting bolt or pin on the load. (American Chain & Cable Co.) Fio. 7. Component parts for a two-leg bridle sling, two basket slings, two choker slings, etc. (American Chain & Cable Co.) or a bundle of pipes, rods, etc., but such loads should be carefully balanced to avoid the possibility of one of the interior pieces slipping out of the bundle. For lifting such loads as motors which have lifting eyebolts, the single-leg sling can be used straight (Fig. 6). Two of these slings can be used as a pair being known as a two-leg sling (Fig. 7). Without the accessories, they can be used as a double basket sling (Fig. 8) for lifting almost any type of load, such as stacks of sheets or plates. Or they can be used as a double choker for handling an irregular-shape load (Fig. 9). With the SLINGS 77 shackles and hooks attached, the slings can also be used as a double choker (Fig. 10) for picking up any long round, square, or irregular- shape load. Figure 11 shows these slings used as a bridle sling for hoisting large pipe or for handling other objects having lifting bolts or other means of attachment. Four of the single slings can also be used as a unit (Fig. 12). Without the accessories they can be used as a four-leg bridle sling for lifting an object that has the necessary lifting lugs or handles (Fig. 13), or with the hooks attached they can be used to attach to eyebolts or holes in the object (Fig. 14). With the hooks removed but with the eyes of the slings joined by the shackles, the Fio. 8. In using the double basket sling, watch that one part does not tend to slip along the load and allow it to tilt and drop. (American Chain & Cable Co.) slings can be lengthened as required for lifting larger loads (Fig. 15). If still greater length of sling is required, two additional slings (Fig. 16) can be used in conjunction with the four-leg sling to form a double basket. When shackles are used as indicated, short pieces of tub ing or pipe should be placed on the shackle pins to in crease their diameter and thus avoid bending the sling eye too sharply. For lifting sturdy shipping cases, a special sling (Fig. 17) will be very useful. By means of the small sheaves, the sling Fia. 9. Double choker sling with spliced causes the grab hooks to be eyes. (American Chain & Cable Co.) forced into the wood. With the use of a similar sling but with blunt hooks, drums or barrels can be handled with ease and safety. The special tumbuckle sling shown in Fig. 18 is used for lifting 78 HANDBOOK OF RIGGING turbine casings, which have to be raised on an even keel in order not to foul the turbine blading. In recent years a type of wire-rope sling has been developed that is replacing many of the conventional type using the ordinary straight cable. This new type is the interwoven or braided sling made up of a number of smaller size wire ropes, usually 6 but occasionally as many as 48 parts. Figure 19a shows a Macwhyte Fio. 10. Double choker sling with hooks attached for more readily attaching and de taching. (American Chain & Cable Co.) Fio. 11. The bridle sling. 0American Chain & Cable Co.) Fio. 12. Component parts for making any of the above illustrated slings or for four-leg bridle sling or double basket sling. (.American Chain <k Cable Co.) Fio. 13. Four-leg bridle sling with spliced eyes. (American Chain cfc Cable Co.) SLINGS 79 Drew sling composed of one piece of wire rope spliced endless before braiding into a flat multiple-part body. In Fig. 196 is shown an Atlas sling, which has a round braided body made from two pieces of wire rope, one right lay and one left lay. The two ropes are spliced endless, folded to secure the required numbers of parts, and then braided. All ropes form a continuous, uniform spiral throughout the entire length of the sling. Some of the larger sizes are braided around a hemp-rope core, which acts as a cushion and assists in keeping the sling nearly round in cross section. Even on the eight-part slings the spiral braiding gives a Fio. 14. Four-leg bridle sling with hooks for use where lifting holes or eyebolts are provided. (American Chain cfc Cable Co.) much lower modulus of elasticity than a single cable of the same capacity. This greatly reduces the stress on the individual wires when a load is applied rather suddenly, thereby increasing the safety factor. Braided slings are also constructed so as to be almost flat in the general cross section, these being used partic ularly for basket-type hitches, especially when lifting heavy shafts. For the basket hitch, when the diameter of the object hoisted is very large such as a locomotive boiler, a sling made up of a number of parts of wire rope wound back and forth be Fiq. 15. Where a large load requires longer slings, the four legs can be used as shown to form a double basket sling. (American Chain <fc Cable Co.) tween two heavy-duty thimbles is used. These parts of the rope are laid parallel to each other and are served at fre quent intervals to bind them into one unit. Such a sling should never be bent around small diameters or passed over sharp edges of the load. 80 HANDBOOK OF RIGGING Of course, all slings should be made of improved plow steel rope which is usually identified by various trade names and trade markers. All eye splices should be made by experienced splicers and should be properly served to conceal the sharp protrud ing ends of the wires, which frequently cause injury to the riggers handling them. While not absolutely necessary, it is good practice to place thimbles in all spliced eyes. Socketing, likewise, should be done only by experienced men. Care should be exercised when sock eting not to allow the twist or lay to come out of the rope as it enters the throat of the Fm. 16. Where a still larger load is to be lifted, a four-leg bridle sling can be made into a large double basket sling by the use of two additional single-leg slings. (Amer ican Chain & Cable Co.) socket. When not in use, slings should be hung up in an orderly manner on special hooks or brackets so as to keep them as straight as practicable. Special consideration should be given to the angle that the legs of a sling make to the horizontal, as the lifting capacity is reduced much more rapidly than might be expected as the angle is reduced. Fig. 17. A special sling for handling small packing cases, etc. Fig. 18. Where the load to be lifted must be maintained in an absolutely level position, turnbuckles can be made an inte gral part of the sling. For a single leg or part of the sling at an angle of 60 deg, the lifting capacity is only 87 per cent of that at 90 deg or vertical, at 45 deg it is 71 per cent, and at 30 deg it is only 50 per cent. ETC 02771 SLINGS 81 Table I gives the safe working loads for the conventional wirerope slings, iron-chain slings, alloy steel slings, and braided slings. For manila-rope slings a safety factor of 10 is used. The loads are given for two-leg slings at various angles. For three-way and four-way slings these loads can be increased 50 per cent and one hundred per cent, respectively. According to the ASA Safety Code for Cranes, Hoists, and Derricks, chain slings should not be loaded to more than one-half of the proof test load. a i> Fio. 19. (a) Six-part flat-braided sling, (b) Eight-part round-braided aling, CMacwhyU Company.) Of course, slings should be inspected periodically and condemned when found in an unsafe condition. A few broken wires do not perceptibly weaken the sling unless located near the throat of a socket, in which case they may indicate fatigue of the metal of the rope. If crushed not too severely the strands can be hammered back into shape by means of a wood mallet and a wood block. Slings, regardless of type, should be protected from corrosion and from contact with injurious chemicals. With reasonable care a sling should last indefinitely and should be one of the safest parts of the hoisting equipment. T able I. 1 y N om i nal size, in. Single sling, lb 6 6L TS a f e W o r k in g o a d s o n V a r io u s y p e s o f S l in g s 1 y1 y Tw o-leg slings (F o r three-leg sling m u ltip ly by l . For four-leg sling m u ltip ly by 2) WA Choker sling, lb U sling, lb Basket 60-deg sling, lb i bridle, lb 45-deg bridle, lb 30-deg bridle, lb W eight per ft (exclusive o f hook, ring, thim ble, or splice), lb <CON--CO^--C<O0COC*CO ddddod^- t-^00 CO ^00 t> CO oo -- ufcT Oa-- O<OM O-- OOOQOOiO --`c<fco <*8.4c *40 -+-* to i vO_) 82 6 X 19 im proved plow steel rope (Federal spec. R R -R -5 7 1 ) Factor of safety = 8 Splice efficiency = 80% Rope diam eter -- 1,350 1,840 2,420 2,900 3,800 5,260 7.000 9.000 11,200 13,800 Oioo --C0O0 --00t----00 0^5Clb*TfCO -- -- -- cnTcTT to ao --" ~vfw -- -- -- wn lo ?<rr CO W C^O C^TCO^ id*D Ci C--* u--o G--i iiMf <o ofe--iu--i c--?eOo* c4Vo CO -- --^ xft -- -- 1C Tj* 1,350 1,840 2,420 2,900 3,800 5,260 7.000 9.000 11,200 13,800 c**0coi--OiO -- c^Tfcdoriocd 3S338S3S ^r^oot^wst-uo eo** oo e--fb--TcMoCO~CoOd Iro n crane chain (A S T M spec. A 56-39) Factor of safety = 5 S tock d ia m e te r -- - 1,710 2,845 4,380 6,415 8,850 11,750 15,350 19,250 1,280 2,130 3,280 4,820 6,630 8,800 11,500 14,400 888 888to88t- CO^t^C--si`i--O<N'MCCOO 2,970 4,940 7,600 11,150 15,350 20,400 26,650 33,500 2,420 4,030 6,200 9,100 12,680 16,650 21,700 27,250 ETC 02774 CHAPTER VI WOOD FOR STRUCTURAL PURPOSES Wood is one of the most common materials in use today, par ticularly in the construction industry, and it is one of the oldest materials. Notwithstanding these facts, relatively very little is understood of the behavior of wood under stress by the average carpenter, engineer, or rigger. It therefore becomes the duty of the engineer or other person charged with inspecting structures or objects made of wood not only to check the depreciation and loss of strength of the material but also to investigate if the correct species and quality of wood were used originally. It is admitted by authorities on the subject that only extreme care in examining a specimen by a competent inspector can even roughly determine the actual condition of a piece of wood that has been in use for some time and exposed to the elements. Surface defects are more readily observed, but defects such as decay often destroy the entire heart of a timber without any trace on the surface. Admitting the limitations of even the most experienced inspector, the following data are presented so that the engineer, rigger, or job foreman can make his inspections with somewhat greater accuracy. While the information contained herein is of a general nature, it has been compiled with particular reference to structural timbers, rigging and shoring timbers, scaffold planks, ladders, etc. It includes some of the basic information relative to the structure of wood and its inherent defects, utilization, and identification. In order that the reader can more fully understand the references made herein to the parts of the material, its characteristics, defects, infection, infestation, etc., it is important that he fully understand the various definitions. Hence, the following list of definitions should be carefully studied. Annual Rings. The concentric but often irregular, recurring rings that appear in whole or in part upon the cross section of any native wood, whether it be in the form of a tree, log, 84 timber, plank, or finished wood part. Each complete annual ring consists of an inner band of low-density wood (springwood) and an outer band of higher density wood (summerwood). Bastard, Sawn. Lumber so cut that the annual rings make an angle of between 30 and 60 deg with the faces of the piece. Blue Stain. A bluish or grayish discoloration of sap wood of certain species caused by the growth of certain moldlike fungi on the surface and in the interior of the wood. Boxed Heart. A timber is said to have boxed heart when the pith is located within the piece. Brashness. A brittle condition of wood characterized by a more or less abrupt failure across the grain, instead of a tendency to splinter, when broken. Brown Stain. A chemical discoloration of white pine and yellow pine apparently due to oxidation and accumulation of extrac tives under certain conditions during the drying of various species. Bruise. An injury to the wood at or near the surface caused by its having been struck by a hammer or other object. Such spots are vulnerable to decay. Check. A lengthwise separation or split in the wood that occurs radially, or normal to the annual rings, as seen on the cross section. This is the result of uneven shrinkage of the wood. Compression Failure. The buckling of fibers due to excessive compression along the grain as a result of flexure or end com pression of the piece. It may occur as a result of severe bend ing of a tree by wind, ice, and snow or by stressing wood structural members beyond the proportional limit. Compression Wood. An abnormal growth occurring in conifers and characterized by relatively wide annual rings, usually eccentric, and a comparatively large proportion of summerwood (usually 50 per cent or more), which merges into the springwood without a marked contrast in color. Conifer. A tree bearing seed cones, usually an evergreen, the wood from which is known as "softwood." Cross Break. The separation of wood cells across the grain, such as may be due to tension resulting from unusual shrinkage or mechanical stresses. Cross Grain. The grain, or direction of the cells in a piece of wood, that does not run parallel with the axis of the piece. ETC 02776 86 HANDBOOK OF RIGGING Burl. A local disturbance in the grain, usually associated with knots, or undeveloped bands produced by the healing of wounds during the life of the tree. Curly Grain. When the fibers are irregularly distorted as in maple, birch, and other species. This may be several inches long as observed on the tangential surface. Diagonal Grain. When the fibers run diagonally across the piece as a result of the latter having been sawed at an angle across the annual rings. It may be observed on the radial and occasionally on, the tangential face. Dip Grain. A wave or undulation such as occurs around a knot, pitch pocket, or other defect. Interlocked Grain. An instance in which spiral grain occurs in one direction for a number of years, then in the other direction for a number of years. Observed when split on a radial line. Spiral Grain. When the fibers take a spiral or winding course in the tree or log. May be detected on the flat grain surface. Cross Section. The section of a tree, at right angle to the pith or axis, as observed on the end view of a log or piece of wood cut from it. Decay or Rot. Disintegration of the wood substance due to the action of wood-destroying fungi. Edge Grain, Vertical Grain, Rift Grain, Comb Grain, or Quarter Sawed. Lumber that has been sawed so that the annual rings run at an angle of 45 deg or more with the wide face of the piece (see Fig. 1). Flat Grain. Lumber in which the annual rings form an angle of less than 45 deg with the wide face of the piece. Also called slash grain, plain sawed or tangential cut (see Fig. 1). Heartwood. The inner and usually darker portion of the cross section of a tree, all cells of which are lifeless cases and serve only the mechanical function of keeping the tree from breaking under its own weight and from the force of the wind. Hollow Heart. A cavity in the heart of a log resulting from decay. Honeycombing. Open checks in the interior of the piece of lumber, often not visible on the surface. Knots. Cross sections of branches or limbs of a tree within the lumber such as cut from the trunk of a tree. Knots may be round or spiked, sound or unsound, tight or loose, decayed, intergrown, encased, not firm, pith knot, or hollow knot. WOOD FOR STRUCTURAL PURPOSES 87 Live Timber. Timber cut from a tree that was living at the time of cutting. Low-density Wood. Wood that is exceptionally light in weight for its species, due usually to abnormal growth conditions. It is frequently referred to as "brash wood" and breaks with a splinterless fracture. Pitch. A poorly defined accumulation of resin in the wood cells in a more or less irregular patch. Flo. 1. How edge-grain and flab-grain boards are cut from a log. (Forest Products Laboratory.) Pitch Pocket. A well-defined opening between annual rings, con taining more or less pitch. Pith. The soft core at the center of the trunk or limb of a tree or log. Pores. The hollow cells or vessels of which the wood is com posed, usually being larger and thin-walled in the springwood, and smaller and heavy-walled in the summerwood, as observed on the cross section under a microscope. These cells, tubes, pores, or .tracheids run vertically in the tree and conduct the sap up and down the tree. 7 ETC 02778 88 HANDBOOK OF RIGGING Radial Face. That face of a piece of wood which extends in a generally radial direction in the tree. This surface cuts the annual rings at nearly a right angle and usually presents edge grain. Rays. The tiers of cells extending radially in the tree. They are seen as bands on the radial face of a piece of wood and as dashes on the tangential face. The entire radial face will be seen almost covered with these tiny structures, which appear as fine to conspicuous short lines. Red Heart. The incipient stage of a destructive heart rot in certain coniferous trees caused by Fomes pini. It is charac terized by an abnormal pink to purplish red or brownish color in the heartwood. Resin Ducts. Very small irregular openings. These are visible on all three sections of a tree, but sometimes appear as fine pin scratches on the tangential section. They occur normally only in pines, spruces, Douglas fir, larch, and tamarack. Sap. All the fluids in a tree. Sapwood. The zone of light-colored wood near the bark on the cross section of a tree, about 1 to 3 in. wide and containing 5 to 50 annual rings. The cells in the sapwood are active and store up starch and otherwise assist in the life processes of the tree, although only the last or outer layer of cells forms the growing part and true life of the tree. Second Growth. Timber that has grown after the removal of all or a large portion of the previous stand, whether by cutting, fire, wind, or other agency. Second-growth material is fre quently of rapid growth during its early life. Shake. A lengthwise separation ofthe wood that occurs usually between and parallel to the annual rings. A through shake is one extending between two opposite or adjacent faces of a piece of wood. Sound Wood. Wood that is not affected by decay. Split. A lengthwise separation of the wood, extending from one surface through the piece to the opposite or adjacent surface. Springwood. The inner portion of the annual ring, which is grown in the spring season. This portion of the ring is less dense than the summerwood. Stain. A discoloration occurring on or in lumber of any color other than the natural color of the piece. Tangential Surface. That face of a piece of wood which is tan gent to the annual rings in the piece, usually showing flat grain. Wane. Bark or lack of wood on the edge or corner of the piece. Warp. Variation of the piece from a straight plane surface: Bow. Deviation flatways from a straight line. Crook. Deviation edgeways from a straight line. Cup. Deviation crossways from a straight line. Twist. Deviation spirally from a straight line. FTTH RAY Fiq. 2. A jV'11- cut>e of hardwood greatly magnified. (Forest Products Laboratory.) ETC 02180 ETC 02781 WOOD FOB STRUCTURAL PURPOSES 91 tree consists of lifeless cells and is "as dead as a log," this area being known as "heartwood." Moisture taken in by the roots of the tree ascends through those cells constituting the band of sapwood and travels out through the branches to the leaves. Here it combines with carbon from the air to form food material that descends through the inner bark adjacent to the wood and part of which develops into wood cells and part into bark. Fia. 4. Cross section of a nonporous wood, magnified about 15 times. During the winter season the flow of sap is interrupted and tree growth ceases in temperate climates. When the rainy, spring season arrives, tree growth is resumed and large but thin-walled wood cells are produced quite rapidly in order to supply the grow ing tree with sufficient moisture. During the hot summer months the cells produced are smaller but have thicker walls, thus making this portion heavier and stronger than that developed in the spring season. So each year an additional pair of concentric rings is added to the tree, the lighter part being known as "springwood" and the denser part as "summerwood." Collectively, they are known as one "annual ring." Domestic woods are divided into two classes: hardwoods and ETC 02783 WOOD FOR STRUCTURAL PURPOSES 93 softwoods. However, all hardwoods are not hard, and all soft woods are not soft. For instance, longleaf yellow pine is nom inally a softwood, while poplar and cottonwood are called hard woods. The answer to this puzzle is that domestic woods are classed botanically rather than according to physical and mechani cal properties. In other words, the wood from all coniferous trees is known as softwood and is nonporous in structure (see Fig. 4). Hardwoods, on the other hand, come from trees having broad leaves and are subdivided into two types: ring porous, such as oak, ash, and hickory, in which the pores are arranged in definite rows or rings along the layer of springwood (Fig. 5), and diffuse porous, l such as gum, walnut, and maple, in which pores of more uniform size are scattered throughout the annual ring (Fig. 6). DEFECTS AND OTHER CHARACTERISTICS AFFECTING STRENGTH Knots. The most common defect in wood is the knot. This may appear either round or elongated, being round where the branch or limb extended at about a right angle to the face of t r Fig 7. Sound or intergrown knot. the piece containing the knot, and elongated or "spike" where the limb extended more nearly parallel to the surface. In-judging the strength of a piece containing a knot, it should be borne in mind that the axis of the knot extends to the pith of the tree, the form of the knot being conical with the apex at the pith. A "sound knot" is one that shows no evidence of decay. An "intergrown knot" (Fig. 7) is one in which the fibers of the knot ETC 02784 ETC 02785 SHAKE MOST OBJECTIONABLE HERE KNOTS MOSTOBJECTIONABLE HERE Fig. 10. Diagram showing the areas in a wood beam in which certain defects are most objectionable. In long columns, where stiffness rather than direct crushing strength is the controlling factor, the loss of strength due to knots or other defects is relatively small. In joists or planks knots are measured by their average diame ters. In short or intermediate-length columns the reduction in strength is approximately proportional to the size of the knot. On heavy beams knots on the top and bottom faces are measured between lines drawn tangent to the knot and parallel to the edges of the beam. On the vertical faces of such beams, knots are meas ured by their minimum diameters. Checks. Perhaps the next, most common defect is the check (Fig. 11). Checks develop owing to uneven shrinkage when the wood is dried. The result is the pulling apart or separating of the rows of cells in a radial split, starting usually at the bark or outside of the timber. The width of a check has comparatively little effect upon the strength of a timber, as a check of almost imper ceptible width is as detrimental as a wider one. " ETC 02786 ETC 02787 WOOD FOR STRUCTURAL PURPOSES 97 provided the beam is not subject to lateral bending. Internal checks (on the cross section) often are not apparent on the surface of the piece but may nevertheless greatly reduce its strength. The effect of checks on the resistance to horizontal shear can be roughly calculated by estimating the actual reduction in area in a horizontal plane at the neutral axis within a distance from the end of the beam equal to three times the depth of the beam. Checks have little, if any, harmful effect on poles except that they permit the entrance of moisture. Shakes. Shakes (see definition), like checks, are most objection able when occurring at the points of maximum horizontal shear. They are measured between vertical lines enclosing the shake, and never should a shake extend to the surface of the piece (see Fig. 13). Fio. 13. A shake is a separation between successive annual rings. In poles, shakes should not be permitted if they enclose more than 10 per cent of the area of the cross section. In other words, the diameter of the wood enclosed by the shake should be not more than one-third the pole diameter. Occasionally an old timber in a structure may be observed with splits running longitudinally on one face and diagonally on the adja cent face, thus posing the question as to whether the grain is straight or spiral. Upon careful examination it will often be found that the diagonal splits are checks, indicating the presence of spiral grain, while the longitudinal splits will be found to be shakes, not checks. Inserting a knife blade into the split and then running it lengthwise should show if it has a tendency to rotate around the ETC 02788 98 HANDBOOK OF RIGGING pith. If it does, the split is a check; if not, it probably is a shake, assuming that the rings cannot be observed at the end of the timber. Pitch Pockets. This type of defect in large-size pieces is not too serious, provided the dip grain that accompanies it is not exces sive. A number of pitch pockets (see Fig. 14) in the same year's growth in a piece indicates lack of bond of the wood and the prob able presence of a shake. Pitch pockets are characteristic of the pines, the spruces, larch, tamarack, and Douglas fir. Fiq. 14. Pitch pockets occur only in certain softwoods. Cross Grain. This is one of the most treacherous defects in a piece of wood, inasmuch as it is often difficult to detect. Cross grain is a general term that includes diagonal grain, spiral grain, interlocked grain, dip grain, wavy grain, curly grain, etc. Diagonal grain is the result of sawing a straight piece from a crooked log, or not sawing parallel to the bark in a straight but tapered log, in which case the wood fibers do not run parallel to the edges of the piece. Diagonal grain may occur on either the edge-grain or flat-grain face of the piece, generally on the former, in which it is usually readily discernible by the angular direction of the annual ring markings. If it occurs on the flat-grain face, it will be considered in the same class with spiral grain. Spiral grain is not so easy to detect. In the growing tree, and consequently in the log cut from it, the wood fibers run in a gener ally longitudinal direction. In some trees, however, the fibers run at a slight angle, thus taking a spiral path around the tree. Such spiral grain may frequently be observed on telephone poles, flagpoles, etc., where it is definitely indicated by the checks. On the flat-grain face of a piece of wood the markings of the annual rings do not indicate the direction of the grain (Fig. 15). If there are a number of herringbone V's on this face, they indicate WOOD FOR STRUCTURAL PURPOSES 99 diagonal grain, but the angle must be measured on the edge-grain or radial face. If the points of these V's are not in a line parallel to the edge of the piece, spiral grain undoubtedly exists. In order to demonstrate spiral grain the model shown in Fig. 16 was constructed. It is intended to represent a log with a "beam" cut from it. The annual rings, being for all practical purposes a number of concentric cylinders, intersect the radial face of the beam and produce numerous parallel markings commonly called Fig. 15. Indications of spiral and diagonal grain and combinations thereof. Annual rings parallel to edge of piece: (A) spiral grain; () diagonal grain. Annual rings oblique to edge of piece: (C) spiral grain; (D) diagonal grain. Spiral and diagonal grain in combination: (E) rings parallel to edge; (F) rings oblique to edge. "comb grain." These markings, running parallel to the edges of the beam, indicate freedom from diagonal grain, and many a rigger or carpenter might consider this beam safe to support a heavy load. But if we look on the flat-grain face of the piece, we can detect numerous brownish markings not unlike pin scratches. These are resin ducts (they occur normally on the pines, spruces, larch, tamarack, and Douglas fir) which definitely indicate the direction of the grain. On this beam these resin ducts are at an angle of 1:7, which is far beyond the safe angle of 1:15 to 1:20. ' K-V. 100 HANDBOOK OF RIGGING Rotating the "log" so as to observe the other side, we note that there are several checks running spirally at the 1:7 angle. If spiral grain exists in the log, of course it must also exist in the beam cut from it, which verifies our interpretation of the resin ducts. To make assurance doubly sure, a large nail was driven into the end of the beam, with the result that a piece split off on the 1:7 angle. This piece is therefore declared unfit for struc tural purposes, although to the uninformed it would probably be accepted as a perfect specimen. Fig. 16. Beam cut from a large log. Spiral grain is indicated by checks and split. The foregoing will demonstrate the futility of attempting to judge the grain of a piece of wood by the so-called "visible grain" (see Fig. 15). To determine the direction of the true grain in a piece of wood, the markings, or so-called "visible grain," on the radial face are first observed. If these do not run parallel to the edge of the piece, it is indicative of diagonal grain, the angle being measured by the length required to produce a deviation of 1 in. Next, we observe the tangential or fiat-grain surface. Checks, if present, indicate the direction of the grain. Also, in hardwoods the direc tion of the rays or the direction of the large pores definitely indicate the grain. In certain softwoods (those which may contain pitch pockets as mentioned above) the resin ducts are positive indicators of the grain. (These resin ducts appear as fine brownish lines similar to tiny pin scratches.) If none of these indicators is observed, apply the point of a fountain pen to the wood, and note the direction in which the ink runs in the wood cells. The mark thus produced may be only about | in. long, so place a straightedge along this ink mark and WOOD FOR STRUCTURAL PURPOSES 101 with a pencil draw the line several inches long. Another test is to jab the point of a small sharp knife blade into the tangential face at an angle of about 15 deg to the surface, with the knife in a direc tion crossways to the length of the piece. Then slowly rotate the knife blade with the cutting edge toward the piece of wood. This will lift up a splinter above the surface, and the direction in which the fibers tend to pull out indicates the direction of the grain. A Fig. 17. Method of measuring the angle of diagonal and spiral grain when the rings are oblique to the edge of the piece. sharp pointed instrument, such as a scriber, pulled loosely in the general direction of the grain along the surface will closely follow the grain. Tom (or chipped) grain on the radial face also indicates spiral grain. Spiral grain should always be measured on the flat-grain surface farthest from the pith. If the annual rings on the cross section run diagonally across the piece, or in other words, if there are no true flat-grain or edgegrain faces, determining the angle of cross grain is more involved. To measure the angle of diagonal grain on such a piece, locate on the end (the cross section of the piece) that comer which is farthest from the pith (see Fig. 17), then from this comer draw a 102 HANDBOOK OF RIGGING line radially, or at right angle to the rings. On this line, if the size of the piece will permit, measure 1 in. from the comer; then follow the annual ring markings until they intersect that edge far thest from the pith. The ratio B: A indicates the angle of diagonal grain. To measure the angle of spiral grain on a piece of wood whose faces are neither radial nor tangential, mark a point some distance from the end on one of the edges that are neither nearest to nor farthest from the pith and follow along the fibers or a check or parallel to a check to the end of the piece. Then draw a line from the end of this line radially toward the pith. The minimum dis tance of this radial line from the starting edge D, as shown on Fig. 17, used in conjunction with the distance of the starting point from the end of the stick C will give the angle of spiral grain. Some wood may contain both diagonal grain and spiral grain. To obtain the true angle of the grain in such a piece, first obtain the angles of the spiral grain and the diagonal grain, both being expressed decimally. Thus, an angle of 1:15 is ^ or 0.066. Square the angle of diagonal grain, and add to it the square of the angle of spiral grain. Then extract the square root of the sum to obtain the true angle of the grain. Table I gives the effect of cross grain on the strength of beams and posts. It will be noted that even an angle of 1:15 consider ably reduces the strength of a timber. Table I Slope of grain Strength in % of strength of straight-grain wood* Beams t Posts and columns t 1 :40 1 : 20 1 :18 1 : 16 1 :15 1:14 1 : 12 1 : 10 1: 8 1: 6 100 85 to 100 80 to 85 76 to 80 74 to 76 69 to 74 61 to 69 53 to 61 50 to 53 50 to 53 100 100 up to 100 up to 100 87 to 100 82 to 87 74 to 82 66 to 74 56 to 66 50 to 56 Cross grain causes a noticeable ioes of strength in beams and columns, t Applies only to middle half of length. X Applies to entire length. WOOD FOR STRUCTURAL PURPOSES In measuring the angle of cross grain on a timber the average over a distance of a foot or so should be taken, local irregularities in the grain not being measured except in small pieces. Small pieces of wood are greatly weakened by the presence of dip grain or burls, which are usually the result of defects that may or may not exist in the piece. Figure 18 shows dip grain in one piece resulting from a knot in the adjacent piece cut from the log. The cross grain in the "dip" usually runs at a severe angle and greatly reduces the strength, particularly when this defect is on the tension side of a beam. DIP GRAIN To determine the strength of a beam of small cross section such as a ladder side rail con taining dip grain at the tension Fig. 18. A knot in one piece of wood may cause dip grain in the adjacent piece. face, it should be assumed that the dip cannot take tensile stress, and therefore the depth of the sector should be deducted from the depth of the beam. In the material for poles, such as flagpoles and telephone poles, spiral grain is acceptable provided the checks or other indicators of the grain do not make one complete turn around the pole in a distance of less than 20 ft. To ensure straight grain in ladder rungs, they should be hand- shaved, or the piece from which the rung is to be turned should be split (not sawed) in both planes from the board or plank. As ladder rungs are frequently made of red oak, a test for straight grain can be made by wetting one end of the rung with saliva or soapy water and then blowing into the other end. If perfectly straight grain exists, all the wood pores that comprise the circular area at one end of the rung would, if extended, come out within the circular area at the other end of the rung. Thus, when blown into, the air should produce bubbles over the entire area at the other end of the piece. If only part of the area shows bubbles, or if no bubbles show, cross grain is evidenced. (Remember: This can be done only with red oak.) Brashness. This is an abnormal condition which causes wood in bending to break suddenly and completely across the grain when deflected only a relatively small amount. Brashness is ETC 02794 104 HANDBOOK OF RIGGING usually associated with slow-grown hardwoods, very fast- or very slow-grown softwoods, and wood with pre-existing compression failures. Wood that is exceptionally lightweight for its species is usually brash, as is wood that has been exposed to high tempera tures for a long time, such as wood ladders used in boiler rooms. A piece of tough wood and a piece of brash wood may have identical strengths in static bending, but under impact the brash piece will fail at a much lower stress. Under ordinary conditions the strength of wood in tension is from two to four Fig. 19. A typical fracture in tough wood. Note the relatively long splinters. times the compressive strength, but this ratio is greatly reduced in brash wood. The length of the splinters produced on the tension side of a beam that has failed in bending is proportional (approximately) to the span of the beam. Thus, in beams of very short span the splinters produced are very short. Dry wood usually breaks more suddenly than moist wood, but still the fracture contains splinters (see Fig. 19). Fiq. 20. A typical fracture in brash wood. Note the absence of any splinters. In making the splinter test with the knife small chips of wood fly out. On the other hand, brash wood usually fails with a splinterless fracture, which gives a suggestion of crystallization, with the open ends of the cells or pores conspicuous, especially under a magni fying glass (see Fig. 20). As mentioned previously, summerwood is mor6 dense and has greater strength than springwood. In softwoods, wide rings may WOOD FOR STRUCTURAL PURPOSES 105 be predominately spring-wood, which is one of the reasons why wide-ring softwoods are brash. On the other hand, the difference between wide- and narrow-ring ring-porous hardwoods is usually mostly in the summerwood, which means that in very narrow rings the wood is mostly porous springwood and consequently low in strength and brashy. See Fig. 21, which shows sections of fastgrown and slow-grown red oak, the former having a much higher percentage of strong summerwood. Splintering occurs only in the tension half of a fracture, even in tough wood, so the abrupt failure on the compression half should not in itself be taken as an indication of brashness, compression failure, or other defect. Fio. 21. Cross sections of (a) fast-grown and (6) slow-grown ring-porous hard wood indicate the greater percentage of strong, dense summerwood in the former. {Forest Products Laboratory.) Abrupt failures are not usually caused by exposure to excessive heat unless the temperature has been high enough to darken the wood throughout. Prolonged moderately high temperatures, however, may make the wood brash. Heating wet wood may set up damaging stresses within the piece, especially if it contains the pith and if it is heated to about 160F. Another test for the presence of brash wood is to make a knife test as described under "Cross Grain." If the wood is tough, a splinter will be raised up but will not tear out unless the knife blade is rotated too far. On the other hand, if the wood is brash, the piece will fly out with a faint snap, leaving a recess of punky wood (Fig. 20). Of course there are various degrees of brashness; therefore there is no definite line of demarcation between tough and brash wood. 106 HANDBOOK OF RIGGING Compression Failures. Next to cross grain and brashness, compression failures are perhaps the most hazardous defects in structural wood. This defect fortunately is not too common, but its danger lies in the fact that it is sometimes extremely difficult, if not actually impossible, to detect such a defect with the un aided eye. As mentioned previously, most species of wood are from two to four times as strong in tension as in compression. (This is just the opposite to concrete and cast iron.) If a piece of wood, be it a storm-tossed tree, a falling tree, a log being roughly handled, or a plank or ladder being dropped, is subjected to excessive bending stress, the fibers on the compression side of the neutral plane will be compressed to such a degree that they are buckled. But as these wood fibers have no place to be displaced to, it does not actually collapse, and the timber may be subjected to additional load until final failure occurs on the tension side. If, however, the load is relieved after the compression failure occurred, the piece will be in apparently perfect condition. In fact, even though the average carpenter or rigger is told that a compression failure exists in a piece of finished lumber being examined, the chances are 100 to 1 that he will be unable to locate it. If the piece being inspected is rough-sawed, it is impossible to find the point of failure. Yet the piece has failed halfway through, and if the beam is re versed so that the compression failure is on the tension side, it will collapse without warning under a very small load. Such a break will appear without splinters and may be confused with a fracture in brash wood. To inspect a piece of finished lumber for a suspected compres sion failure, move the wood in relation to a light source, or vice versa, so that there will be reflected glare on the surface of the area being examined. A compression failure can then be detected as a very faint irregular line running crossways to the piece at an angle of 70 to 90 deg to the edge (see Fig. 22). A liberal application of carbon tetrachloride to the surface of wood often makes compres sion failures more easily visible. Compression failures may occur in several places, their spacing depending upon the length of the beam. Usually they occur only on one face and halfway across the two adjacent faces, assuming, of course, that the injury occurred to the piece in its existing dimensions. If, however, the compression failure occurred dur ing the felling of the tree or the handling of the log and consequently WOOD FOR STRUCTURAL PURPOSES 107 caused damage halfway through the log, then perhaps the beam being inspected has been cut from the defective side of the log. In this case, the compression failure should be visible on all four finished faces of the piece. Wood containing a compression failure is extremely weak under impact. Therefore, if the piece suspected of containing a com pression failure is not too heavy, hold one end of it and allow the Fig. 22. A compression failure is one of the most difficult defects to detect. other end to drop onto the concrete floor or pavement. The ease with which a piece containing a compression failure is broken may prove a real surprise. In examining a timber that has failed under load and has an abrupt splinterless fracture, there may be some question as to whether it was caused by a compression failure or by brash wood. To check the condition, examine the width of the annual rings, feel the heft of the piece, and make the knife test for brash wood. If no indication of brashness is observed, it can be assumed that a compression failure existed. Then carefully examine the wood for several feet each side of the break to locate any secondary com pression failures, as described above. Their presence is definite indication that the break was due to a compression failure. 108 HANDBOOK OF RIGGING Compression Wood. Compression wood is a defect found only in softwoods. It is recognized by its eccentric annual rings (Fig. 23), which are of a dense nature and are predominately summerwood. Compression wood on the flat-grain and edge-grain faces is dull and lifeless in appearance. It is the one exception to Fig. 23. Compression wood (A) Longitudinal and cross sections through part of a tree trunk with compression wood on lower side. (B) Cross break in compres sion wood, and split between compression wood and normal wood due to greater longitudinal shrinkage of compression wood. (C) Crook caused by longitudinal shrinkage of the compression wood on the lower side of the piece. (Fores! Products Laboratory.) the rule that the strength of any piece of wood, regardless of species, can be judged by its weight. Compression wood is heavy, but is brash and low in strength, particularly under shock. When a beam containing compression wood fails in bending, the 'break usually does not extend directly across the piece but either zigzags back and forth producing thick blunt splinters or more often extends directly across the grain from the tension side inward and then branches out in two directions diagonally across the beam like a wide Y. Compression wood, by its very nature, should be excluded from all uses where strength under shock or impact is essential. WOOD FOR STRUCTURAL PURPOSES 109 The great longitudinal shrinkage of compression wood (2| to 20 times normal wood) if located near the center of the piece may cause this part of the wood to fail in tension, thereby producing cross cracks in the compression wood (Fig. 235). If located near the edge of a small piece, the compression wood in shrinking will cause crooking or bowing (Fig. 23C). Also, owing to the abnormal shrinkage, spike knots are frequently twisted from their positions and caused to protrude above the face of the material. Poles containing compression wood are hazardous for linemen to climb, for if cross checks develop at the surface, the shell of the outer wood may peel off and cause the points of their climbers to lose their hold on the pole. Decay. Sooner or later nearly all domestic woods when placed in damp locations develop the defect we call decay or rot. This is not an inorganic oxidizing process such as the rusting of steel or the crumbling of stone. Instead, decay is a disease of the wood just as " TB " or pneumonia, for instance, are diseases of the human body. To be susceptible to decay, four conditions must be present: (1) The wood must provide food for the fungus. Unless treated chemically, most woods are able to do this to some extent. (2) There must be a sufficient amount of moisture present. Wood that contains less than 20 per cent moisture will not decay. But neither will wood that is submerged in water. (3) There must be air present, a moist stagnant air being most effective. (4) There must be warmth, as wood will not decay in extremely cold climates. We have all seen the fruiting bodies produced by decay fungi on fallen trees, tree stumps, etc., some being in the form of toad stools, shelves, or crusts. On the underside of these fruiting bodies millions of tiny spores or germs are produced, which, when matured, become free and are blown about by the wind. Should they be deposited on susceptible wood, they will germinate and form minute fibrous strands (Fig. 24), which, as they grow, puncture the cell walls and not only feed on the contents of the cells but also actually devour the cell walls. Also, good wood in contact with rotting wood will soon be likewise infected. The term "dry rot" is frequently used, but this is a misnomer as no wood that is dry can rot. It is usually referred to decay where there is no visible evidence of contact with moisture, such as in the case of portable ladders. The moisture had to be present at some time, but not necessarily continuously. Wood that has been ETHYL CORPORATION DVE! OPiVIc'-r SECTION LIBRARY BATON ROUGE, LOUISIANA ETC 02K00 no HANDBOOK OF RIGGING painted while in the "green" or unseasoned state may decay under the coating of paint. In its advanced stage, decay is more readily recognized, but the only remedy then is the removal and replacement of the rotted members. In the incipient stage, it may not be too late to take remedial action, but the symptoms must be first recognized. Among the surface indications of incipient decay are the following: 1. Small bleached or otherwise discolored areas on the surfaced wood. 2. Zigzag zone lines not far from the ends of structural timbers. Fig. 24. Mycelium of typical brown rot on a piece of oak. Also typical cracking. (Forest Products Laboratory.) 3. Oozing out of extractive liquids from the joints between wood structural members. 4. Dark zones in the wood separated by zones of lighter color tissue caused by certain fungi. 5. Persistently moist appearance of freshly cut sections. Further decay can be arrested by keeping the wood dry. Ad vanced decay in the interior of wood structural members can be detected by the following evidence: 1. Sagging of structural members. 2. Jabbing a knife blade into the wood and noting the resistance to penetration. Rotted wood is very soft. 3. Drilling small holes into the timber and observing the resist ance to drilling, and the color of the chips removed. An "increment borer," designed for this purpose, is a hand auger with a hollow bit which removes a sample like a small dowel WOOD FOR STRUCTURAL PURPOSES 111 stick which can then be carefully examined. Dark wood, powder or paste is an indication of internal decay. 4. Striking the timber with the round end of a ball-peen hammer and noting if it sounds "dead" and hollow. 5. Loss of resonance of a stick, when struck, against a concrete floor. Decayed wood is much more combustible than sound wood and therefore presents a greater fire hazard as well as a structural weakness. It is a poor practice to leave the end grain of any wood exposed, inasmuch as it readily absorbs moisture from the air. Heavily painting or tarring the ends of lumber is advisable. The end grain of oak in contact with steel beams or plates will cause rapid local corrosion of the metal. Contact with galvanized metal will cause local rotting of oak. A relative humidity in buildings sufficient to bring about con densation is conducive to decay, in some instances the beams being destroyed in two or three years. It should be remembered that the humidity is much higher near cold-water pipes, skylights, unin sulated roofs, etc., so that condensation and decay usually occur first at such locations. Wood of low decay resistance or that containing a considerable amount, of sapwood should not be used in basement or first-floor construction close to the ground unless chemically treated. No wood that shows evidence of incipient decay should be used where shock or impact loads are possible. Ordinary paints, varnishes, and similar protective coatings can not be relied upon to preserve wood against decay, because they contain no substances poisonous to fungi and they may themselves support the growth of fungi in the presence of dampness. Al though protective coatings retard the absorption of moisture by wood, they also retard the drying out of wood that has taken up moisture through an uncoated surface or joint. For example, joints between end-grain and side-grain wood can rarely be kept tight by coatings; rain water can readily enter the joint and be absorbed by the wood, after which its drying out again may be retarded by a coating of paint on the surfaces exposed to view. In such case painting may hasten rather than retard decay. Sap Stains and Molds. Generally, stains of the sapwood are caused by fungi similar to those which cause decay, except that 112 HANDBOOK OF RIGGING they attack mainly the contents of the wood cells, not the cell walls. Consequently sap stains are not considered a defect in most struc tural wood. Heavily stained wood is likely to be low in shock resistance, however, and should be utilized accordingly. More over, it may be accompanied by incipient decay inasmuch as the same factors favor the development of stain and decay fungi. But where wood is to be varnished, shellacked, or stained to improve its appearance, such as the trim in house construction, sap stain is, of course, considered a serious defect. Sap stains are found in various colors: blue, brown, yellow, pink, red, etc., but blue (which includes shades almost black) is by far the most common. Stains penetrate deep into the wood and can not be surfaced off. Molds may be yellow, pink, purple, green, or black and can usually be recognized on the sapwood by the presence of cottony or powdery surface growths. These are also caused by fungi. Molds usually appear only on the surface of the wood. Staining of wood may occur very rapidly, a carload of unseasoned lumber being infected while in transit. In using stained wood for structural purposes, keep in mind that in order for the stain to propagate the wood must have been exposed to conditions which are favorable to decay. Therefore, thoroughly examine the wood for evidence of incipient decay. Termite and Other Parasite Attack. The termite is perhaps the most troublesome insect we have to contend with in struc tural timbers. There are two general types of termites, the sub terranean and the nonsubterranean. Only the former is found in the northern part of the country. These insects begin their attack of the wood from the earth, either directly or by building shelter tubes of particles of earth, pieces of leaves, etc., over the intervening masonry in order to reach the wood. Figure 25 shows the two most common forms of termites. The winged adult is probably the most frequently observed, while the grayish-white worker is the most destructive. Termites are softbodied antlike creatures, which conceal themselves within the wood, in the earth, or in the shelter tubes. The workers are blind, shun the light, and are seldom seen except when a structure or building is demolished or altered and the timber in which they are living is suddenly cut into or the soil excavated. The winged adult form is brownish or blackish in color with WOOD FOR STRUCTURAL PURPOSES elongated body and with long white wings extending beyond it at the rear. At certain seasons, usually spring and fall, the winged sexual adults migrate in large numbers and at such times may be observed for a short period of several hours. They then lose their wings, enter crevices between timbers, and breed new colonies. Termites frequently eat away the entire inside of a timber, leaving nothing but a thin shell of wood (and possibly paint) and with no exterior evidence of attack until it ultimately fails structurally. Observing the migrating termites, the wings that the termites have shed just before reentering the wood; the pellets of fine, digested, excreted wood similar to sawdust at or on the floor below (M Fig. 25. Two principal forma of the subterranean termite, (o) Winged sexual adult commonly observed when migrating, (b) The tiny but destructive worker, which never comes out into the light and hence is seldom seen. joints in the wood; holes in the surface of the wood about the size of BB shot; or the sagging or collapse of structural members are evidence of termite attack. Also, the earthlike shelter tubes by passing masonry to provide communication between the ground and the wood are unmistakable signs of infestation. Combating termites is nearly a hopeless task unless all the in 1 - fested wood is removed and burned. When contact with a mois ture supply from the earth, leaking water pipe, or roof leak is cut off, the termites depending upon such moisture supply will die. Among the poisons used in combating termites are orthodichloro benzene, Paris green, sodium fluosilicate, and carbontetrachloride. Often termite damage is confused with decay, which is quite differ ent and is caused by fungi. Termite exterminators usually excavate to a considerable depth completely around the building in order to apply their chemicals properly. This is not only expensive but also may cause destruc tion of costly shrubs, trees, lawns, etc. Assuming that the ter mites obtain their moisture from the ground, and not from a leaking ETc 02804 114 HANDBOOK OF RIGGING roof, leaking water pipe, or similar source, then it might be desirable to consider jacking up the house f in. or so off the foundation and inserting a sheet-metal termite shield between the sill and the foundation, after which the house is again lowered onto its founds tion. Such a termite shield should extend about 1 in. beyond the inside and outside faces of the foundation, and these projecting edges bent downward at a 45-deg angle to shed rain water. Keep in mind that insects cannot pass from one side of a thin sheet to the other side via the knifelike edge. The termite-shield method of combating termites should appeal to the rigger. Warping. As mentioned previously, when wood dries it shrinks more tangentially than radially and an almost insignificant amount longitudinally. Unless influenced by outside factors, dimensional changes caused by shrinkage follow a definite pattern (see Fig. 26). Edge-grain planks shrink more on the thickness. Flat-grain planks shrink more on the width. Boxed heart timbers cause all faces to become slightly convex, except if large checks develop the faces will become somewhat concave. Boxed heart planks cause the wide faces to become convex. Timbers with their rings running diagonally become diamond shape. Flat-grain boards "cup" so that the rings tend to straighten out (with the convex side toward the heart or pith of the tree). Long sticks having compression wood near one face bow or crook toward that face (concave on that face). Boards or timbers having spiral grain twist in a direction so as to increase the angle of checks and other evidence of the direction of the grain. IDENTIFICATION OF WOOD Most riggers can readily identify spruce, yellow pine, Douglas fir, and a few other species of wood, while the average carpenter has a much broader knowledge of the various species. The iden tification is more or less by general appearance rather than by any technical knowledge. In fact, we have all heard carpenters say that they can distinguish between longleaf and shortleaf yellow pine. Perhaps, but the experts at the Forest Products Laboratory say that it is impossible to differentiate between these species unless the pith can be observed and even then it requires a chart to make the determination. 1I ( CUPS SO AS TO STRAIGHTEN ANNUAL RINGS CROOKS OR BOWS TOWARO EDGE HAVING WIDE RINGS GRAIN BOARD TIMBER HAVING WIDE AND NARROW RINGS Fio. 26. In drying, wood warps in a certain predetermined manner unless influ enced by outside factors. ETC 02806 116 HANDBOOK OF RIGGING It is possible to identify most species of wood by observing the color (particularly of the heartwood), weight, odor, presence or absence of pores, and arrangement of pores, rays, resin ducts, and other factors. To make an identification of an unknown species, either of the two keys on the following pages may be used. The first key (Table II) is for use with the naked eye and is more difficult to use. The second key (Table III) is for use when a magnifying glass is available. To use either key, first look under I and II and determine whether the wood in question is "Wood with Pores" or Wood without Pores." If the latter, then look under A and B to decide if "Resin Ducts Present" or "Resin Ducts Normally Absent" (Table III). If the former, then under 1 and 2 decide if the resin ducts are numerous or not numerous. If they are numerous then refer to AA and BB to determine if they are hard pine or soft pine. Continue this procedure until the species of wood is determined. As an example, let us consider a piece of wood removed from an old building being demolished. By means of a plane or sharp knife, cut and clean the surface on the two faces and end of the timber so that its structure can be carefully examined. No magni fier is at hand, so the first key (Table II) will be used. Under I or II, are pores visible on the end of the piece? No, so we enter the key under II. Under A, B, or C, are the rays visible or conspicuous? The answer is no, so we proceed to C. Under 1 or 2, are the annual rings clearly defined? Yes, so we proceed to 2. Now, under AA and BB, is the heartwood. distinctly darker than the sapwood? (If the piece being examined is small, it may be difficult to answer this question, so proceed under both AA and BB by trial-and-error method.) Yes, the heartwood is darker, so advance to AA. Under (a) and (b), is the wood pitchy? Yes, so proceed to (a). Under (aa), (bb), and (cc) check the color of the wood. The heartwood is reddish brown so we proceed to (aa). Under (a3) and (b3) the summerwood is found to be very con spicuous, so we advance to (b3), knowing that our wood is a hard pine. Under (b3), consider the weight of the wood (a5) or (b5). It is heavy, so continue under (b5). This indicates one of the eastern species erf pine (including southern pine). WOOD FOR STRUCTURAL PURPOSES 117 To distinguish longleaf pine from shortleaf and loblolly pine (North Carolina pine is loblolly pine), it is necessary first to measure the over-all diameter of the pith and the diameter of the second annual ring. This measurement is taken at the outside of the second year's band of summerwood (see Fig. 27). Then using the chart, draw a horizontal line indicating the pith diameter; also draw a vertical line indicating the diameter of the second annual ring. If these lines intersect above the diagonal line, the wood is longleaf pine; if below the diagonal line, it is either shortleaf or loblolly pine. B 0 .29 50 .75 1.00 1.25 1.50 1.75 2.00 2.25 DIAMETER OF26 AfMUAL RM3.ININC7ES Fio. 27. Identification of longleaf and shortleaf pine when pith and second annual ring can be measured. To identify the individual species of spruce, the following facts may be of help: Eastern and Engelman Spruce. Heartwood is nearly the same color as the sapwood, but usually not clearly defined. Resin ducts not numerous, scattered singly or in tangential groups of 2 to 20 (as observed on the cross section), but not visible without a magni fier. Also, they may appear as whitish specks in the summerwood. Split tangential surface is not dimpled. Sitka Spruce. Heartwood is pale reddish color, slightly darker than sapwood. The split, tangential surface, especially through the summerwood of narrow rings, is characteristically indented or dimpled. Resin ducts are rather inconspicuous. Resinous odor and taste. Silky sheen on split surfaces. 118 HANDBOOK OF RIGGING Table II. Key for the Identification of Woods without the Aid of a Hand Lens * hardwoods I. Pores visible. A. Ring-porous; that is. the pores at the beginning of each annual ring are comparatively large, forming a distinct porous ring, and decrease in size more or less abruptly toward the summerwood. (This feature is often more distinct in the outer sapwood where the pores are more open.) 1. Summerwood figured with wavy or branched radial bands. AA. Many rays broad and conspicuous. Wood heavy to very heavy. . .The OAKS (a) Wood without reddish tinge. The large pores mostly closed up (exception, chestnut oak)........................................................ The WHITE-OAK GROUP (b) Wood with reddish tinge, especially near knots. The large pores mostly open (exception, black jack oak)............................. The RED-OAK GROUP BB. Rays not noticeable. Color grayish brown. Wood moderately light. CHESTNUT 2. Summerwood figured with short or long wavy tangential lines or bands, in some woods more pronounced toward the outer part of the annual ring. AA. The heartwood not distinctly darker than the sapwood (the sapwood may be darker than the heartwood on account of sap stain). The wavy tangential bands conspicuous throughout the summerwood. Color yellowish or greenish- gray. Wood moderately heavy......................................................... HACKBERRY BB. The heartwood distinctly darker than the sapwood. SUGARBERRY (a) Wood with spicy odor and taste: moderately heavy. Heartwood silvery brown........................................................................................................... SASSAFRAS (b) Wood without spicy odor or taste. (aa) Heartwood bright cherry red to reddish brown. Pores in springwood all open and very distinct. Sapwood narrow. Wood very heavy. (a3) Pith large, usually over 0.2 and often about 0.3 in. in diameter. COFFEETREE (b3) Pith small, usually under 0.15 and often less than 0.1 in. in diameter.................................................................... HONEY LOCUST (bb) Heartwood russet to golden brown. Pores entirely closed up except in outer sapwood. Sapwood very narrow. (a3) Wood from very heavy to very, very heavy and exceedingly hard. Tangential bands confined to, or more pronounced in, the outer portion of the annual ring. Rays barely distinct. (a4) Heartwood golden brown with reddish brown streaks; yellowish color imparted in a few minutes to a wet rag or blotter..............................................................OSAGE ORANGE (b4) Heartwood russet brown without reddish brown streaks; color not readily imparted to a wet rag or blotter. BLACK LOCUST (b3) Wood lighter but still classed as heavy and hard. Tangential bands uniformly distributed throughout the summerwood. Rays very distinct...............................................RED MULBERRY (cc) Heartwood grayish brown. Tangential bands short and confined mostly to the outer portion of the summerwood (inconspicuous in black ash). (a3) Sapwood narrow, rarely over $ in. wide. (a4) Annual rings mostly wide, especially within the first few inches from the center. Pores containing glistening tyloses. Pith usually three-sided. Wood moderately light. HARDY CATALPA Unless it is otherwise directed, all observations as to structure should be made on the end surface of rings of average width, cut smoothly with a very sharp knife; and all observations as to color should be made on a freshly cut longitudinal surface of the heartwood. WOOD FOR STRUCTURL PURPOSES 119 (hi) Annual rings mostly narrow, even near the center. Pore* partly filled with tyloses, not glistening. Pith usually round. Wood moderately heavy.................... BLACK ASH (b3) Sapwood over an inch, usually several inches wide. Wood heavy and hard.............................................................................WHITE ASH GREEN ASH (dd) Heartwood brown with reddish tinge. Tangential bands long and very conspicuous throughout the summerwood. (a3) Sapwood very narrow, The porous ring of springwood from 2 to 4 pores wide. Inner bark slimy when chewed. Wood..mod erately heavy............................................................... SLIPPERY ELM (b3) Sapwood moderately wide, the porous ring of springwood only one pore wide except in very wide rings. (a4) Wood heavy. Pores in springwood inconspicuous because comparatively small, not close together, and plugged with tyloses........................................................................... CORK ELM (b4) Wood moderately heavy. Pores in springwood fairly con spicuous because larger than in rock elm, close together and open.................................................................... WHITE ELM 3. Summerwood not figured with radial or tangential bands distinctly visible without a lens (fine tangential lines may be seen in hickory and persimmon with a hand lens). See figure 5. AA. Sapwood wide, over 2 in. (a) Heartwood black, or brownish black (usually very small). Tangential rurface marked with fine bands which run across the grain and are due to the storied arrangement of the rays. Wood very, very heavy. .PERSIMMON (b) Heartwood reddish brown. Tangential surface not marked with fine cross bands. Wood very heavy.........................................................The HICKORIES BB. Sapwood narrow, rarely over \ in. wide. Heartwood grayish brown. Wood moderately heavy........................................................................................ BLACK ASH B. Diffuse-porous; that is, no ring of large pores is formed at the beginning of each annual ring. 1. Individual pores plainly visible. AA. Tangential surface marked with fine bands which run across the grain and are due to the storied arrangement of the rays. Heartwood black, or bro.wnish black (usually very small). Sapwood wide. Wood very, very heavy and hard, PERSIMMON BB. Tangential surface not marked with fine cross bands. (a) Heartwood reddish brown. Sapwood wide. Wood heavy. WATER HICKORY (b) Heartwood chocolate brown. Sapwood from moderate in width to narrow. Wood heavy and hard............................................................ BLACK WALNUT (c) Heartwood light chestnut brown. Sapwood narrow. Wood moderately light and soft........................................................................................ BUTTERNUT 2. Individual pores barely visible under conditions of good light and a very smoothly cut end surface. AA. Pores not crowded. Heartwood reddish brown. Wood heavy. (a) Inner bark with wintergreen flavor. Pith flecks very rare. YELLOW. BIRCH SWEET BIRCH (b) Inner bark without wintergreen flavor. Pith flecks usually abundant. RIVER BIRCH BB. Pores crowded. Heartwood grayish. Wood light....................COTTONWOOD II. Pores not visible. A, Rays comparatively broad and conspicuous. Color in various shades of light reddish brown. 1. The rays crowded. No denser and darker band of summerwood noticeable. Wood usually lock-grained: moderately heavy...........................................................SYCAMORE 2. The rays not crowded. A distinct, denser, and darker band of summerwood present. Wood usually fairly straight-grained: heavy............................................................ BEECH 120 HANDBOOK OF RIGGING B. Rays not conspicuous but distinctly risible. 1. Heartwood deep, rich, reddish brown. Sapwood narrow, usually leas 1 ia. wide. Annual rings clearly defined. Rays very distinct. Wood moderately heavy. BLACK CHEERY 2. Heartwood dingy, reddish brown, often with darker streaks. Sapwood moderately wide, usually over 1 in. Annual rings not clearly defined. Rays relatively not very distinct. Wood moderately heavy.................................................................. RED GUM 3. Heartwood light reddish brown. Sapwood wide. Annual rings clearly defined by a thin, darker reddish-brown layer. Rays very distinct. AA. Wood heavy and hard; difficult to cut across the grain. Pith flecks very rare. SUGAR MAPLE BB. Wood lighter and softer, rather easy to cut across the grain. Pith flecks often abundant................................................................................................SILVER MAPLE RED MAPLE 4. Heartwood light yellowish brown with greenish tinge. Sapwood usually over l in. wide. Annual rings clearly defined. Rays fairly distinct. Wood moderately light. 5. Heartwood creamy brown with occasional darker streaks, sharply defined from the heartwood. Rays fairly distinct. YELLOW POPLAR Sapwood wide and not Wood light. Raya not distinctly visible. BASSWOOD 1. Annual rings not clearly divided into a band of soft springwood and denser and darker band of summerwood and. therefore, not conspicuous. AA. The heartwood distinctly darker than the sapwood. (a) Heartwood reddish brown. Wood straight-grained; heavy. (aa) Inner bark with wintergreen flavor. Pith flecks rare. YELLOW BIRCH SWEET BIRCH (bb) Inner bark without wintergreen flavor. Pith flecks usually abundant. (b) Heartwood grayish brown. RIVER BIRCH (aa) Wood cross-grained; moderately heavy. BLACK GUM COTTON GUM (TUPELO) (bb) Wood fairly straight-grained; light................................COTTONWOOD AA. The heartwood not distinctly darker than the sapwood. (a) Wood odorless and tasteless; light and soft. Color yellowish. YELLOW BUCKEYE OHIO BUCKEYE CONIFERS (b) Wood with spicy odor and taste; moderately light in weight. Color pale brown............................................................................PORT ORFORD CEDAR (c) Wood with resinous odor; heavy to very heavy. Color creamy brown. PlftON (PINE) 2. Annual rings clearly divided into a band of soft springwood and a denser and darker band of summerwood. Although the summerwood may not be pronounced, yet the annual-rings are always clearly defined by it. AA. The heartwood distinctly darker than the sapwood. (a) Wood " pitchy,'' as indicated by the resinous odor and by exudations of resin at the ends, especially from the sapwood, although on cuts made after the wood iB seasoned the resin does not come out unless the wood is heated. (aa) Heartwood creamy or orange-brown to reddish brown. Resin ducts abundant, visible as minute openings or, more often, as darker or lighter colored specks, or as brownish lines oq longitudinal surfaces. Sapwood widely variable in width............................................ The PINES (a3) The summerwood inconspicuous and not much harder than the . springwood..............................................................The SOFT PINES: (a4) Wood soft and moderately light; straight-grained. An nual rings of moderate width. Heartwood light reddish brown............................................WESTERN WHITE PINE LIMBER PINE ETC 02811 WOOD FOR STRUCTURAL PURPOSES 121 (b4) Wood hard and moderately heavy to very heavy, often cross-grained. Annual rings narrow. (ao) Heartwood reddish brown. Tangential surface has numerous slight depressions which give it a dimpled appearance especially noticeable on split surfaces. BRISTLE-CONE PINE (b5) Heartwood creamy brown. Tangential surface not dimpled. Wood sometimes very heavy. PINON (PINE) (b3) The summerwood conspicuously darker and harder than the springwood. (This feature is oot so noticeable in the sapwood of old trees as in the heartwood.) (a5) Wood moderately light. The HARD PINES: WESTERN SPECIES: (a6) The sapwood usually less than 2 in. wide (mostly about 1 in.). Tangential surface has numerous slight depressions, which give it a dimpled appear ance, especially noticeable on split surfaces. Openings of resin ducts not visible without a lens..........................................LODGEPOLE PINE (b6) The sapwood usually over in. wide (mostly over 3 in.). Tangential surfaces rarely dimpled. Openings of resin ducts often visible without a lens........................ WESTERN YELLOW PINE (b5) Wood moderately heavy to very heavy. Heartwood orange brown to reddish brown. EASTERN SPECIES: NORWAY PINE PITCH PINE SHORTLEAF PINE LOBLOLLY PINE POND PINE LONGLEAF PINE SLASH PINE (For distinguishing longleaf from loblolly and short- leaf pine, see Fig. 27.) (bb) Heartwood orange-reddish to red. Resin ducts not abundant, occa sionally visible as whitish specks in the summerwood. Sapwood usually over 1 in. wide. Wood moderately heavy.. .DOUGLAS FIR (cc) Heartwood russet brown. Resin ducts not abundant; usually not visible without a lens. Sapwood usually less than 1 in. wide. Wood moderately heavy. (a3) Annual ringB narrow.........................................WESTERN LARCH (b3) Annual rings moderately wide......................................TAMARACK (b) Wood not "pitchy'' or resinous, although resin may exude from the bark, (aa) Heartwood deep reddish brown; without characteristic odor or taste. Annual rings regular in width and outline. Sapwood over 1 in. wide. Wood moderately light............................................................. REDWOOD (bb) Heartwood light brown to dark, dingy brown, with or without reddish tinge. Odor characteristic but not resinous or "pitchy." (a3) Odor somewhat rancid; heartwood tasteless. Annual rings mostly irregular in width and outline. Sapwood usually over 1 in. wide. Color highly variable from pale brown with or without reddish tinge to blackish brown. Weight variable from moderately light to heavy. Longitudinal surfaces feel and appear waxy.....................................................BALD CYPRESS (b3) Odor aromatic (like cedar shingles); heartwood slightly bitter in taste. Annual ringB narrow but regular in width. Sapwood rarely over 1 in. wide. Wood very light in weight. Longi tudinal surfaces not appearing waxy. (a4) Heartwood brown with reddish tinge. WESTERN RED CEDAR *5 ETC 02812 122 HANDBOOK OF RIGGING (b4) Heartwood brown, rarely with reddish tinge. ARBORVITAE {NORTHERN WHITE CEDAR) BB. The heartwood not distinctly darker than the sapwood. (a) Wood resinous, as indicated by the odor or exudations of reran at the especially from the sapwood. (aa) Tangential surface has numerous slight depressions, which give it a dimpled appearance, especially noticeable on split surfaces. The heartwood sometimes slightly darker than the sapwood. Wood moderately heavy....................................................... LODGEPOLE PINE (bb) Tangential surface not dimpled. (a3) Color pale brown, almost white. Annual rings mostly moder ately wide. Wood light in weight. ENGELMANN SPRUCE (b3) Color creamy brown. Annual rings mostly narrow. Wood heavy to very heavy................................................. PINON (PINE) (b) Wood not resinous. (aa) Odor and taste spicy. Color pale brown. Wood moderately light. PORT ORFORD CEDAR (bb) Odor and taste not spicy, although a characteristic odor may be notice able. (a3) Wood whitish, at least in the springwood; the summerwood may be dark reddish brown, especially in pieces of rapid growth, in which case there is a decided contrast between springwood and summerwood. (a4) Freshly cut surface of dry wood has a mild, rank odor. Little contrast between springwood and summerwood. Growth rings of moderate width. Wood light. ALPINE FIR (b4) Freshly cut surface of dry wood does not have a rank odor; decided contrast between springwood and summerwood. Growth rings fairly wide. Wood moderately light. (a5) Outer bark contains whitish layers.........WHITE FIR (b5) Outer bark contains thin, very dark reddish-brown layers...............................................................GRAND FIR (b3) Wood has reddish hue, the springwood as well as the summerwood being colored. Moderately light to moderately heavy. Fresh pieces have a sour odor. (a4) Wood coarse and splintery, often cup-shaken. EASTERN HEMLOCK (b4) Wood not very coarse or splintery, usually not cup-shaken. WESTERN HEMLOCK Table III. Key for the Identification of Woods with the Aid of a Hand Lens * HARDWOODS I. Wood with pores. The pores are conspicuously larger than the surrounding cells, although in some species they are not visible without magnification. Neither the pores nor other cells are in continuous radial rows. A. Ring-porous; that is, the pores at the beginning of each annual ring are comparatively Urge, forming a distinct porous ring, and decrease in size more or less abruptly toward the summerwood. 1. Summerwood figured with wavy or branched radial bands. The bands visible with out a lens on a smoothly cut surface. Unless it is otherwise directed, all observations as to structure should be made on the end surface of rings erf average width cut smoothly with a very sharp knife and all observations as to color should be made on a freshly cut longitudinal surface of the heartwood. ETC 02813 WOOD FOR STRUCTURAL PURPOSES 123 AA. Many rays very broad and conspicuous. Wood heavy to very heavy. The OAKS (a) Pores in the summer-wood very small and so numerous as to be exceedingly difficult to count under a lens; pores in the springwood usually densely plugged with tyloses. Heartwood brown without reddish tinge. The WHITE-OAK GROUP (b) Pores in the summerwood larger, distinctly visible with (sometimes without) a hand lens and not so numerous but that they can readily be counted under a lens; pores in springwood mostly open, tyloses not abundant. Heartwood brown, with reddish tinge especially in vicinity of knots. The RED-OAK GROUP BB. All rays very fine and inconspicuous. Color grayish brown. Wood moderately light....................................................................................................................CHESTNUT 2. Summerwood figured with long or short wavy tangential bands which include the pores. The bands visible without a lens on a smoothly cut end surface. AA. Careful examination with a hand lens shows the pores of the summerwood to be joined in more or less continuous bands, and the bands to be evenly distributed throughout the summerwood. (a) Sapwood moderate in width or narrow, mostly less than 3 in.; heartwood distinct, light to deep reddish brown. Rays not distinct without a lens. The ELMS: (aa) Large pores in the springwood usually in one row except in very wide rings. (a3) Rows of pores in the springwood conspicuous because the pores are large enough to be plainly visible without a lens; they are mostly open, containing only a few tyloses; and they are fairly close together. Sapwood from 1 to 3 in. wide. Wood mod erately heavy; fairly easy to cut............................... WHITE ELM (b3) Rows of pores in the springwood inconspicuous because the pores are small, being barely visible without a lens; they are mostly closed with tyloses, especially in the heartwood; and they are often somewhat separated. Sapwood from } to l| in. wide. Wood heavy and difficult to cut..................................CORK ELM (bb) Large pores in springwood in several rows; mostly open, containing few tyloses. Sapwood usually less than l in. wide, often only in. wide. Wood moderately heavy. Inner bark mucilaginous when chewed.................................................................................. SLIPPERY ELM (b) Sapwood wide, over 3 in., heartwood indistinct, yellowish or greenish gray. Pores in springwood mostly open, in several rows except in occasional narrow rings where they may form only one row. Rays distinct without a lens. Wood moderately heavy.................................................. HACKBERRY SUGARBERRY BB. Careful examination with a hand lens shows the pores of the summerwood to be joined in more or less interrupted bands or in rounded groups of from 3 to 20 (especially in mulberry and coffeetree), the groups so arranged as to form tan gential bands. In either case the bands are more pronounced in the outer por tion of the summerwood than in the middle of the annual ring, where the pores are often isolated or in rounded groups. (a) Large pores in the springwood containing numerous tyloses. Sapwood nar row, usually less than 1 in. wide. (aa) Wood very, very heavy and exceedingly hard to cut across the grain. Rays not very distinct without a lens. (a3) Heartwood golden brown with reddish brown streaks; coloring matter readily soluble in cold water................OSAGE ORANGE (b3) Heartwood russet brown; coloring matter not readily soluble in cold water......................................... .................... BLACK LOCUST (bb) Wood heavy, but lighter than the above and fairly easy to cut across the grain. Color russet brown. Rays very distinct without a lens. RED MULBERRY (cc) Wood moderately light and easy to cut across the grain. Color grayish brown. Rays not distinct without a lens.... HARDY CATALPA ETC 02814 124 HANDBOOK OF RIGGING (b) Large pores in the springwood open, containing no tyloses bot occasionally a bright-red gum. Heartwood cherry-red to reddish brown. Wood very heavy. (aa) Pores in the outer portion of the summerwood mostly joined into bands, the individual pores of which are not distinctly visible with a lens magnifying 15 diameters. Rays moetly very distinct. Pith small, usually under 0.15 in. Sapwood from | to 2 in. wide on ties, HONEY LOCUST (bb) Pores in the outer portion of the summerwood only occasionally joined into bands, the individual pores being distinctly visible with an ordi nary hand lens. Rays of uniform width, inconspicuous. Pith large usually over 0.2 in. Sapwood from J to 1 in. wide on ties. COFFEETREE CC. Careful examination with a hand lens shows the pores of the summerwood to be isolated or in radial rows of 2 or 3, but surrounded by parenchyma in such a man ner as to appear in wavy tangential bands usually more distinct without a lens than with a lens. (a) Parenchyma projecting tangentially from the pores in comparatively long lines often joining pores widely separated. Sapwood several inches wide* heartwood grayish brown, occasionally with reddish tinge. Wood heavy and hard................................................................................................ WHITE ASH GREEN ASH (b) Parenchyma not projecting tangentially from the pores or only slightly so. Sapwood less than 1 in. wide; heartwood Biivery brown. Wood moder ately heavy. (aa) Rays fine but distinct without a lens; wood has a spicy odor and taste. SASSAFRAS (bb) Rays not visible without a lens; wood does not have a spicy odor and taste.............................................................................................. BLACK ASH 3. Summerwood figured with numerous fine, light-colored tangential lines (parenchyma), which do not embrace the pores. Pores in the summerwood not much smaller than those in the springwood, usually visible without & lens. (Water hickory and per simmon are also classed as diffuse-porous woods.) Wood very heavy to very, very heavy. AA. Lines of parenchyma inconspicuous even under a lens. Raj's in tiers, appearing on tangential surface as fine bands running across the grain. Heartwood black or brownish black.......................................................................................PERSIMMON BB. Lines of parenchyma conspicuous under a Lens, barely visible without a lens. Rays on tangential surface not in tiers; heartwood reddish brown. . The HICKORIES 4 Summerwood not figured with radial or tangential bands. Pores in summerwood very small, not visible without a lens, isolated, or in radial rows of two or three. Sapwood very narrow, heartwood silvery or grayish brown. Wood moderately heavy......................................................................................................................... BLACK ASH B. Diffuse-porous: that is, the pores are of about uniform size and evenly distributed throughout the annual ring, or if they are slightly larger and more numerous in the springwood, they gradually decrease in aixe and number toward the outer edge of the ring. 1. Rays comparatively broad and conspicuous, the widest ones fully two times as wide as the largest pores, appearing on the radial surface as distinct ''flakes" or "silver grain" similar to quartered oak, but finer. Color in various shades of light reddish brown. AA. Practically all rays broad. Pores crowded, decreasing little, if any, in sue at extreme outer edge of the annual ring. Wood usually lock-grained, moderately heavy................................................................................................................. SYCAMORE BB. Only part of the rays broad, the others narrower than the largest pores. Poree crowded in tbe springwood, decreasing in sixe and number toward the outer edge of the annual ring, thereby giving rise to a harder and darker band of summerwood. Wood usually fairly straight-grained; heavy..................................BEECH 2. Rays narrower, but very distinct without a lens, the widest ones of about the same width as the largest pores. WOOD FOB STRUCTURAL PURPOSES 126 AA. Color light brown with reddish tinge. Springwood and summerwood of uniform density. Sapwood wide. (a) Wood heavy, difficult to cut across the grain. Only part of the rays broad, the others very fine, scarcely visible with a lens. Pith flecks rarely present. SUGAR MAPLE (b) Wood moderately heavy, fairly easy to cut across the grain. Practically all the rays broad but not so broad as in sugar maple, therefore not so prominent but giving the appearance of being more numerous. Pith flecks common........................................................................................ .SILVER MAPLE RED MAPLE BB. Color deep reddish brown. Springwood slightly more porous than summerwood. Sapwood narrow. Pith flecks common Wood moderately heavy. BLACK CHERRY 3. Rays comparatively fine, narrower than the largest pores. AA. Pores visible without a lens. (a) Pores comparatively large and conspicuous without a lens, decreasing in size toward the outer limit of each annual ring; not crowded. Fine tangential lines of parenchyma often visible between the pores. (aa) Sapwood wide, usually over 3 in. in ties. (Pores often in a more or less well-defined zone in the springwood, therefore also classed aa ring-porous woods.) (a3) Heartwood black or brownish black. Rays in tiers, appearing on the tangential surface as fine bands running across the grain. Wood very, very heavy................................................PERSIMMON (b3) Heartwood reddish brown. Rays not in tiers. Wood heavy. WATER HICKORY (bb) Sapwood narrow, mostly under 2 in. in ties; white or discolored; heartwood brown. (a3) Wood heavy and hard. Heartwood chocolate brown. BLACK WALNUT (b3) Wood moderately light and soft. Heartwood light chestnut brown................................................................................. BUTTERNUT (b) Pores smaller, but on careful examination still clearly visible without a lens, at least in the springwood. (aa) Pores not crowded, decreasing little, if any, in sue toward the outer limit of the annual ring. Rays distinct under a lens. Heartwood pale to moderately deep reddish brown. Wood heavy. (a3) Pith flecks rare. Inner bark has a wintergreen flavor. YELLOW BIRCH SWEET BIRCH (b3) Pith flecks abundant. Inner bark does not have a wintergreen flavor.............................................................................. RIVER BIRCH (bb) Pores crowded, decreasing somewhat in size and number toward the outer limit of each annual ring. Rays very fine, barely visible with a lens. Pith flecks occasionally present but not abundant. Wood light and soft. Color white to light grayish brown. COTTONWOOD BB. Pores not visible without a lens. (a) Pores appearing comparatively large and conspicuous under a lens. (aa) Pores not crowded, decreasing little, if any, In size toward the outer limit of the annual ring. Rays distinct under a lens. Heartwood pale to moderately deep reddish brown. Wood heavy. (a3) Pith flecks rare. Inner bark has a wintergreen flavor. YELLOW BIRCH SWEET BIRCH (b3) Pith flecks abundant. Inner bark does not have a wintergreen flavor...............................................................................RIVER BIRCH (bb) Pores crowded, decreasing somewhat in sue and number toward the outer limit of each annual ring. Rays very fine, barely visible with a lens. PHth flecks occasionally present but not abundant. Wood light and soft. Color white to light grayish brown. COTTONWOOD *f ,\ !i ETC 02816 126 HANDBOOK OF RIGGING (b) Pores appearing comparatively small under a lens. (aa) Heartwood pale reddish brown. Rays very distinct without a Pores not very crowded. Wood moderately heavy. SILVER MAPLE RED MAPLE (bb) Heartwood dingy, reddish brown. Rays relatively not very distinct without a Lens. Pores crowded. Wood moderately heavy. RED GUM (cc) Heartwood brownish gray. Rays not distinct without a lens. Wood moderately heavy-. (a3> Pores very small, only occasionally in radial rows ol from 3 to 8. BLACK GUM (b3) Pores slightly larger, often in radial rows of from 3 to 6. (These distinctions between black gum and cotton gum. can be applied only by comparison with a piece of wood known to be one spe cies or the other.................................COTTON GUM (TUPELO) (dd) Heartwood yellowish brown with greenish tinge. Rays distinct with out a lens. Wood moderately light...................... YELLOW POPLAR (ee) Heartwood creamy brown. Rays distinct without a lens; not in tiers. Wood light......................................................................................BASSWOOD (ff) Heartwood creamy white. Pores very minute. Rays very fine, barely distinct with a lens; arranged in tiers, producing very fine bands running across the tangential surface. Wood Light. YELLOW BUCKEYE OHIO BUCKEYE CONIFERS II. Wood without pores. The cells (tracheids) very small, barely visible with a lens; practically uniform in size, except in the summerwood, where they are narrower radially; and arranged in definite radial rows. Rays very fine. A. Resin ducts present but often not distinct without a lens. (Exudations of resin over the end surface is a positive indication of the presence of resin ducts.) 1. Resin ducts numerous; scattered singly; conspicuous under a lens and usually visible without a lens as minute openings, or more often as darker or lighter colored specks, or as brownish lines on longitudinal surfaces.....................................................The PINES AA. Summerwood inconspicuous and not perceptibly harder than the springwood. The SOFT PISES: (a) Wood soft and moderately light; straight-grained. Annual rings of mod erate width. Heartwood light reddish brown............. WESTERN WHITE PINE LIMBER PINE (b) Wood hard and moderately heavy to very heavy; often cross-grained. Annual rings narrow. (aa) Heartwood reddish brown. Tangential surface has numerous slight depressions, which give it a dimpled appearance, especially noticeable on split surfaces................................................... BRISTLE-CONE PINE (bb) Heartwood creamy brown. Tangential surface not dimpled. Wood sometimes very heavy.........................................................PIlTON (PINE) BB. The summerwood conspicuously darker and harder than the springwood. (This feature is not so noticeable in the sapwood of old trees as in the heartwood, where the annual rings are wider.).......................................................The HARD PISES: (a) Wood moderately light................................................. WESTERS SPECIES: (aa) The sapwood usually less than 2 in. wide (mostly about 1 in.). Tan gential surface has numerous slight depressions, which give it a dimpled appearance, especially noticeable on split surfaces. Resin ducts small, not visible without a lens............................ LODGEPOLE PINE (bb) The sapwood usually over 2\ in. wide (mostly over 3 in.). Tangential surface rarely dimpled. Resin ducts comparatively large, usually visible without a lens...............................WESTERN YELLOW PINE (b) Wood moderately heavy to very heavy. Heartwood orange-brown to reddish brown............................... EASTERS SPECIES: NORWAY PINE PITCH PINE LOBLOLLY PINE LONGLEAF PINE SHORTLEAF PINE POND PINE SLASH PINE (For distinguishing longleaf from loblolly and ahortle&f pine, see Fig. 27.) ETC 02817 WOOD FOR STRUCTURAL PURPOSES 127 2. Resin ducts not numerous; scattered singly or in tangential groups of from 2 to 20; not visible without a lens, or appearing as whitish specks in the summerwood. AA. The heartwood of the same color as the sapwood, or slightly darker, usually not clearly defined. Wood light.......................................... ENGELMANN SPRUCE BB. The heartwood decidedly darker than the sapwood. Wood moderately heavy. (a) Heartwood orange-reddish to red. Sapwood over one inch wide. DOUGLAS FIR (b) Heartwood russet brown. Sapwood usually lesB than 1 In. wide. (aa) Annual rings narrow.................................................. WESTERN LARCH (bb) Annual rings moderately wide...............................................TAMARACK B. Resin ducts normally absent. 1. The heartwood of about the same color as the sapwood, distinction not clear. AA. Wood has a spicy odor and taste; moderately light. Summerwood incon spicuous. Color pale brown.........................................PORT ORFORD CEDAR BB. Wood does not have a spicy odor or taste, although other characteristic odor may be present. (a) Wood whitish, at least in the springwood; the summerwood may be dark reddish brown, especially in pieces of rapid growth, and in that case forms a decided contrast between the springwood and summerwood. (aa) Freshly cut surface of dry wood has a rank odor. Little contrast between springwood and summerwood. Rings of moderate width. Wood light.................................................................................. ALPINE FIR (bb) Freshly cut surface of dry wood does not have a rank odor. Decided contrast between springwood and summerwood. Rings usually fairly wide. Wood moderately light. (a3) Outer bark containing whitish layers........................ WHITE FIR (b3) Outer bark containing thin, very dark reddish-brown layers. GRAND FIR (b) Wood has a reddish hue; even the springwood has a pale reddish color, thus malfing the contrast between the springwood and summerwood less pro nounced; odor somewhat sour in fresh wood. Wood moderately light to moderately heavy. (aa) Wood coarse and splintery, often cup-shaken. Abnormal resin pas sages not present...................................................EASTERN HEMLOCK (bb) Wood not very coarse or splintery, usually not subject to cup-ehake. Abnormal resin passages occasionally present in tangential rows in the outer portion of the summerwood.......... WESTERN HEMLOCK 2. The heartwood distinctly darker than the sapwood. AA. Heartwood deep reddish brown. Annual rings regular in width and outline. Sapwood over i in. wide. Wood odorless and tasteless; moderately light. REDWOOD BB. Heartwood light brown to dingy brown with or without reddish tinge. Odor distinct when fresh surfaces are exposed. (a) Odor somewhat rancid; heartwood tasteless. Annual rings mostly irregular in width and outline. Sapwood usually over 1 in. wide. Color highly variable from pale brown with or without reddish tinge to blackish brown. Weight variable from moderately Light to heavy. Longitudinal surfaces feel and appear waxy................................................................. BALD CYPRESS (b) Odor aromatic (like cedar shingles); heartwood slightly bitter in taste. Annual rings narrow but regular in width. Sapwood rarely over 1 in. wide. Wood very light in weight. Longitudinal surfaces not appearing waxy, (aa) Heartwood brown with reddish tinge. . . WESTERN RED CEDAR (bb) Heartwood brown, rarely with reddish tinge. ARBORVITAE (NORTHERN WHITE CEDAR) ETC 02818 CHAPTER VII PLANKS FOR SCAFFOLDS Construction jobs of all types require the use of scaffolds in order that workmen can reach and work in locations which are otherwise inaccessible. The larger the job the bigger the scaffold and the more men who entrust their lives to it. Exclusive of the swinging type of scaffold, such as is used by painters, all scaffolds have a decking constructed of planks, any one of which in falling may be the direct or indirect cause of serious injury or loss of life. It is therefore not only desirable but essential that only depend able lumber be used for scaffold planks. Eastern spruce is fre quently used for this purpose, as its strength is high relative to its weight, while southern pine and Douglas fir are stronger but much heavier. In certain sections of the country scaffold planks come 2 in. X 9 in. X 13 ft 0 in., while in other locations 2 in. X 10 in. X 16 ft 0 in. or 2 in. X 12 in. X 16 ft 0 in. is standard. For the erection floor on steel buildings under construction 3-in. planks are used because of the heavy loads placed on them. It is possible to purchase so-called "scaffold planks" from the lumber vendor, but such planks may be of variable or questionable quality. Therefore the purchaser who uses large quantities of scaffold planks should buy them according to specification. It is assumed that the loads can be applied to either the wide or narrow faces of the plank when used as a beam. The plank should have a strength ratio of at least 80 per cent; in other words, the strength of the plank with all its inherent defects should be not less than 80 per cent of the strength of a theoretically flawless plank. This means that the figures published for the strength properties of small specimens of various species of clear, dry wood should be reduced by 20 per cent before dividing by the factor of safety to obtain the safe working load. SPECIES AND GRADES The planks should be of the indicated grade of one of the follow ing species as specified in the purchase order: 128 PLANKS FOR SCAFFOLDS 129 Species Grade Required Eastern spruce (Picea marUmna, P. rubra, P. glauca)................................................................. 1,200 lb for structural spruce Sitka spruce (Picea sitchensis)................................ Structural scaffold plank Longleaf yellow pine (Pinus paiustris)................. Prime structural Shortleaf yellow pine (Pinus echanita)..................Dense structural Douglas fir (Pseudotsuga taxifolia).........................Select structural The planks should conform to the standard grading rules of the lumber manufacturers' associations for the grades specified, within the limitations stated hereinafter. Species Grading Association Eastern spruce..................... Northeastern Lumber Manufacturers' Association Sitka spruce...........................West Coast Lumbermen's Association Longleaf yellow pine...........Southern Pine Association Shortleaf yellow pine.......... Southern Pine Association Douglas fir.............................West Coast Lumbermen's Association DIMENSIONS Planks should be unsurfaced, of the following nominal dimen sions as called for in the purchase order, and the actual dry dimen sions should be not less than indicated below: Nominal Dimensions Minimum Actual Dimensions 2 in. X 9 in. X 13 ft 0 in. 2 in. X 10 in. X 16 ft 0 in. 2 in. X 12 in. X 16 ft 0 in. lj X 8| in. lj X 9J in. l| X Ilf in. Actual lengths should be not more than J in. shorter nor 1 in. longer than the nominal length. QUALITY OF WOOD All planks should be properly seasoned and free from bow, crook, cup, or twist warping. Boxed heart material should not be accepted. Pieces of wood exceptionally light in weight for its species and all brash wood should be rejected. Flat-grain lumber is preferred for scaffold planks. DEFECTS Cross Grain. The slope of the grain, either diagonal or spiral, within the middle half of the length of the plank shall not deviate from a line parallel to the edges of the plank more than 1 unit in a .1 ETC 02820 130 HANDBOOK OF RIGGING ETC 02821 M e th o d o f m easuring the various defects in a scaffold plank. PLANKS FOR SCAFFOLDS 131 length of 17 units (1:17), as indicated by resin ducts, by splinters pulled from the faces of the plank, or by an ink test. Elsewhere the slope of the grain should not exceed 1:12. Local cross grain caused by knots, etc., shall not exceed 1:12 if within j in. of any edge and if within the middle half of the length of the plank. Knots. Knots appearing within the middle third of the length on the narrow faces should not exceed f in. in size. Knots appearing within the middle third of the length near the edges on the wide faces should not exceed the following limits: Width of Plank, in. 9 10 12 Max. Size of Knot, in. Knots appearing at the center line of the wide faces shall not exceed the following limits: Width of Plank, in. 9 10 12 Max. Size of Knot, in. ii 2 2i Knots appearing on the wide faces between the center line and the edges should be prorated in size according to their position relative to the knots described above (Fig. 1). The sum of the sizes of all knots appearing within the middle half of the length of 2-in. planks, on any face, should not exceed 4j times the size of the largest knot allowed in that area, in accord ance with the following limits: Width of plank, in. Max. total for narrow faces, in. Max. total for wide faces, in. 9 ii 8 10 i} 9 12 ii 10 Checks. Checks should not exceed f-in. depth. Length and width are immaterial. Splits. Splits extending more than 3 in. from either end of a plank should not be permitted. Shakes. Shakes, as observed on the ends of a plank within the middle half of the width of the wide face, should not exceed in. ETC 02822 132 HANDBOOK OF RIGGING measured between lines drawn parallel to the wide faces and just enclosing the shake. Shakes should not appear on the faces of a plank. If both checks and shakes are present, the sum of their sizes at any point should not exceed | in. Wane. The diagonal width of wane on any edge should not exceed If in. Compression Wood. Compression wood will not be permitted. Compression Failures. Planks containing or suspected of con taining compression failures should not be accepted. Neither should planks with evidence of other injury. Pitch Pockets. Pitch pockets and bark pockets will be per mitted, provided they are not more than 2 in. long, 5 in. wide, or 2 in. deep, and provided they do not occur less than 4 ft apart. Pitch Streaks. Planks containing pitch streaks of exceptionally large area should not be accepted. Holes. Knot holes and holes from other causes will be limited as are knots, except that holes should not exceed 1 in. in the minor dimension. Any planks that meet the requirements of the specifications but about which the inspector may have any doubt can at his discretion be subjected to a load test as described in Chap. VIII. When finally accepted, the plank should be immediately branded on the ends or otherwise permanently marked as suitable for scaffolding. The use of other than "accepted scaffold planks" for scaffold purposes should be forbidden. Inspected planks should be handled carefully and not dropped in bulk from the delivery truck. They should be handled with care during the construction or demolition of the scaffolding and at all other times, as compression failures may be produced when an approved plank is dropped or when a load of unknown magnitude is applied to it. It is not expected that planks to meet these requirements can be picked from the common grades of lumber; they can be procured only by selecting from the higher grades of lumber. This will undoubtedly increase the cost of the planks, but the additional ex pense is considered well warranted by the greater uniformity and the greater safety afforded the workmen. Figure 2 gives the safe concentrated and uniformly distributed loads which may be applied to scaffold planks. Thought is also being given at this time to the use of metal scaffold "planks." These may be of pressed steel, aluminum, or magnesium having a checkered or other nonslip surface. Such PLANKS FOR SCAFFOLDS 133 planks may be expected to have many advantages over the con ventional wood planks, such as (1) more uniform strength, (2) more readily inspected, (3) lighter weight, (4) fireproof, (5) longer life (as they cannot be cut up and used for blocks or other purposes), (6) will not decay, (7) will not twist warp. An objection will be the much higher cost, but it is believed that the longer life will warrant it. Fig. 2. Safe concentrated loads on scaffold planks. For distributed load, double these figures. (National Safety Council.) ETC 02824 CHAPTER VIII TESTING SCAFFOLD PLANKS There is an urgent need for a means of subjecting scaffold planks to a load test, which it may be assured will not weaken a good plank yet which may be expected to indicate a defective plank. After several years of research and experiment a method has been developed that, though perhaps not infallible, has proved itself reliable during many years of actual practice by lumber inspectors passing on large quantities of newly purchased scaffold planks. In some states the authorities require that all scaffolds be tested each time they are erected for use. This may be interpreted to mean that scaffold planks also shall be tested. It is usually speci fied that the scaffold (or plank) shall be placed a foot above the ground and that three times the normal working load be applied. Such wording of the law or code is rather ambiguous, as it does not indicate whether the load is all to be applied at the middle of the span or is to be uniformly distributed along the length of the plank. A plank or, in fact, any beam whether of wood or of steel will carry a distributed load twice as great as a concentrated load. Then again, there is a marked difference in the strength of a plank under a steady load and under a suddenly applied load. Thus, the test called for by law is very indefinite. In fact, many engineers believe that a load test on a scaffold plank is not only useless but actually hazardous, for unless properly done there is a far greater probability of injuring a good plank than of detecting a defective one that could not have been detected by a visual in spection alone. For this reason they discourage the testing of scaffold planks except insofar as it is necessary to comply with the law or if there is a reasonable doubt in the mind of the inspector. The safest method of ensuring that only good scaffold planks are purchased is to have a competent lumber inspector or an engi neer who is thoroughly familiar with the behavior of wood under stress make a careful visual inspection of all faces and the ends of each plank, looking for oversize knots, splits, compression wood, compression failures, brash wood, shakes, decay, etc., as described in Chap. VII. However, occasionally after having inspected a 134 TESTING SCAFFOLD PLANKS 135 plank and having found no defect to which he can point his finger, the inspector may feel in his subconscious mind that there is a question as to its strength. To satisfy himself, he may then desire to apply a load test to the questionable plank. It is only in instances of this kind that a load test should be permitted, and even then it should be conducted only in a scientific manner according to definite rules if it is to be of any value in enhancing the workmen's safety. Scaffold planks come in different sizes and materials in different parts of the country, 2 in. X 9 in. X 13 ft 0 in., 2 in. X 10 in. X 16 ft 0 in. and 2 in. X 12 in. X 16 ft 0 in. being most common. Although various species are used for this purpose, eastern spruce, longleaf yellow pine, and Douglas fir are most common. For lack of more specific information, we shall assume that on the job one man weighing 160 lb stands at the center of the plank. Three times this figure would give a proposed test load of about 480 lb. Let us say that a rough (unsurfaced) 2 in. X 9 in. X 13 ft 0 in. eastern spruce scaffold plank is to be tested. In prac tice, the span is limited to 10 ft, but for test purposes the fulcrums are placed 6 in. from each end, thus giving a span of 12 ft 0 in. Eastern spruce as used in the scaffold plank having a strength ratio of 80 per cent may be expected to have properties approxi mately as follows: lb per sq in. Modulus of rupture (ultimate strength) under static loading. .. 8,100 Proportional (elastic) limit under static loading............................ 5,200 Proportional (elastic) limit under impact loading.......................... 9,150 Modulus of elasticity.............................................................................1,440,000 It should be noted that the proportional limit under impact is 75 per cent higher than the proportional limit under a slowly applied load; in fact, it is 13 per cent higher than the ultimate strength under static loading. The test stress should not exceed 80 per cent of the proportional limit for static loading, or 4,160 lb per sq in. To develop a bending stress of 4,160 lb per sq in., a concentrated load of about 585 lb has to be applied to the center of the plank, and this will cause the plank to deflect or bend about 5f in. at the center. The 2 in. X 9 in. X 13 ft 0 in. spruce plank is placed on two fulcrums 5f in. high, 6 in. from each end of the plank, on a smooth level floor. A concentrated load of 585 lb will deflect the plank until it just touches the floor and develops a unit stress of 4,160 lb 136 HANDBOOK OF RIGGING per sq in., as indicated above, and no amount of additional loading can cause any greater deflection or stress. Now if this plank was suddenly deflected 5f in., such as by two or three men standing on it and springing it up and down, the stress would likewise be limited to 4,160 lb per sq in. But under impact the test stress would be only 4,160/9,150 = 45.5 per cent of the proportional limit (under impact loading). In other words, the factor of safety relative to the proportional limit is much higher under the impact test. Therefore, there should be little or no danger of damaging a good plank by subject ing it to an impact test. On the other hand, wood that is brash or contains compression failures is noticeably weak under impact. Thus, the test recom mended here is least likely to damage a good plank, yet most likely to break a plank containing the two most treacherous defects. It is therefore considered more desirable to apply an impact load to the plank, assuming, of course, that the deflection is limited. Under no circumstance should an impact load be applied to a plank except when the maximum allowable deflection has been mathematically determined in advance. The recommended test should be accomplished by having two or three men stand close together at the middle of the plank and spring it up and down until it touches or nearly touches the floor several times. The floor, of course, should be a plane surface. If there is no cracking or splitting sound or other evidence of failure under the test, the plank should be turned over and the load applied to the other face. If there should be a faint snapping sound (caused by the wood fibers pulling away from a knot), turn the plank over and apply the test on the other side. Then turn it back, and again test the side that gave the sound. If no further snapping sound is heard, the plank can be accepted, provided, of course, that it has passed the visual inspection (see Chap. VII). This method has been used for testing such planks as had to be tested by a large user of scaffold planks for nearly ten years with very satisfactory results. Table I gives the height of the fulcrums and the approximate static load to deflect to the floor the three most common sizes of planks of spruce, longleaf yellow pine, and Douglas fir. The actual weight of the men making the test need be only about twothirds of the static test load indicated in the table. Figure 1 shows TESTING SCAFFOLD PLANKS 137 Table I. Heights of Fulcrums and Maximum Test Loads fob Scaffold Planks Size of plank Species 2 in. X 9 in. X 13 ft 0 in. in. lb 2 in. X 10 in. X 2 in. X 12 in. X 16 ft 0 in. 16 ft 0 in. in. lb in. lb Spruce..................... si 585 9 510 9 632 Longleaf pine*. . . . 6 845 Of 750 H 902 Douglas fir............. 5! 665 9 598 9 720 . * If necessary, longleaf pine planks may be tested on the same fulcrums as spruce and Douglas a typical fulcrum that can be used for 13- and 16-ft planks of spruce and Douglas fir and, if necessary, for longleaf pine also. The nail points projecting from the blocks will keep the plank from "walking" off the fulcrums as it is sprung up and down. 2 REQUIREO: WOOO Fig. I. Details of fulcrum blocks for testing scaffold planks. CHAPTER IX SWINGING AND SUSPENDED SCAFFOLDS Swinging Scaffolds. In its most familiar form the swinging scaffold consists of a frame similar in appearance to a ladder with a decking of wood slats and supported near each end by a steel stirrup to which is attached the lower block of a set of manila-rope falls. The frame is usually constructed of Sitka spruce rails of the depth at the center, as indicated in Table I, which dimension may be reduced by 1 in. at the ends. The rungs should be of oak, ash, or hickory, at least lj in. diameter and spaced not more than 18 in. apart, and the flooring J X 3 in. The over-all width of the scaffold is between 20 and 30 in. A 1 X 4 in. toeboard is provided on the outboard side and, if hinged, is lowered flat against the flooring when the scaffold is in transit. Also on the outboard side is a guardrail not less than 2 X 3 in. located between 34 and 48 in. (preferably 42 in.) above the flooring, inserted into sockets or loops in the stirrups provided for this purpose. Additional stanchions are provided to keep the span of the guardrail to 10 ft or less. A screen of j-in. mesh "rabbit wire" is recommended between the guardrail and the toeboard. Steel stirrups, which support the platform, should be placed between 6 and 18 in. from the ends of the scaffold and secured to it by U bolts of adequate size. A set of |-in. No. 1 grade manila-rope falls consisting of a double and a single-pulley block should be provided at each end of the scaffold. A safe means of supporting the upper blocks is abso lutely necessary. This may be in the form of roof or cornice hooks, J-in. wire-rope slings, or other approved device. A tieback rope should be used to secure the cornice hook to a fixed anchorage on the roof. It is good practice to wire the hook on the lower pulley block to the "eye" on the stirrup to prevent accidental detachment of the hook. A mousing would ordinarily be used in a case like this, but here it would interfere with the hitch of the rope. The hitch is 138 SWINGING AND SUSPENDED SCAFFOLDS C* *in CO P* co X -in "1" eo -- *- pi' CC xx 2 ~ x t-ec H -p* T a b l e I . a d d e k -t y f e S c a f f o ld sL * M in im u m dimensions and m axim um spans for ladder type swinging scaffolds (N ew Y o rk State D epartm ent of Labor). XX i nhi> w CO <N XX .2 .2 -tf eo X Hn 2 .2 mw N CO (N iO xx Hco H .2 .2 -H- eo ^x 22 22 222 Ss wo 5 -C 2 * g3 s c - sj .. s| 3 2 2 te a| gC< ZQH caZQ d cS H 140 HANDBOOK OF RIGGING made by holding a strain on the rope with one hand and pushing a bight of the slack part of the rope through the inverted V of the stirrup, giving the bight a 180-deg twist and placing it over the bill of the hook. The strain on the "live" part of the rope forces the "dead" part into the V, into which it jams (see Chap. II, Fig. 81). Although a very simple hitch, it is dependable. PROTECT EDGE OF CORNICE- TO ALLOW PLATFORM TO SWING CLEAR OF WALL Fig. 1. installation OF y HOOK (ROOF IRON) Roof anchorages for swinging scaffolds. (Patent Scaffolding Co.) To ensure against the scaffold falling in the event the workman should accidentally lose his grip on the rope while raising or lower ing the scaffold, a special safety latch can be attached to the cheek of the lower block (Fig. 2). The hauling part, or hand rope, is passed through the hole in the hinged plate, and the hitch made in the usual manner as described above. But should the workman accidentally let go of the rope, the safety latch will raise and grab the rope, thus preventing the scaffold from falling. Swinging scaffolds are required by law in some states to be not less than 20 in. or more than 30 in. wide. For special jobs, a "box" SWINGING AND SUSPENDED SCAFFOLDS 141 scaffold shown in Fig. 3 is very satisfactory. The box scaffold provides a two-member guardrail and toeboard on all sides. When men are working on a swinging scaffold, it must always be secured to the building or structure to prevent it from moving away and allowing the workman to fall between. On building walls it is usually difficult to find something to lash the scaffold to, but it is often found practicable to provide a standard attachment Fig. 2. Safety catch for lower block of rope falls. (Consolidated. Edison Co. of New York, Inc.) for a window-cleaner's belt on a short length of manila rope. To hold the scaffold to the wall, the device is attached to the special bolt at the side of one of the windows and the rope secured to the scaffold. Of course, two hanging life lines are required for all swinging scaffolds, one for each workman. Only new rope, j or 1 in. diame ter, should be used, and it should be properly secured at the roof or upper part of the structure. At sharp bends over copings or window sills the rope should be padded against abrasion. Each man should wear a 4-in. life belt of three-ply cotton webbing with a f- or f-in. rope tail line about 6 ft long (see Chap. XII). The tail line should be attached as short as practicable to the hanging life line by a "rolling hitch" (Chap. II, Fig. 49). This hitch can readily be slid up or down the hanging rope, yet if the man falls, ETC 02833 SWINGING AND SUSPENDED SCAFFOLDS 143 the hitch will jam and hold him. The rolling hitch is similar to the clove hitch except that in tying the first part of the hitch two wraps (instead of one) are made around the hanging fine. Nylon rope may be found suited for life lines, for in addition to being strong it stretches and will stop a falling man more gently. It should not be necessary to say that the life line must reach to the ground or other place of safety and that the workmen must have their life belts on and attached to the life line at all times, particularly when the scaffold is being raised or lowered. On the special scaffold (Fig. 3) trolley cables are run along the upper handrail members, and to the cable at the rear the workman attaches the snap hook of his life-belt tail line. He is then free to walk back and forth in his half of the scaffold. Should a rope fall fail and one end of the scaffold suing downward, the men probably would remain within the scaffold railings, but in the event they were thrown out, their life belts would keep them from falling to the ground. In the preceding paragraphs the discussion concerned manilarope falls for supporting the scaffolds. It is possible and frequently desirable to substitute wire rope and winches for the manila-rope falls. Using The Patent Scaffolding Company winch, it is possible to adapt it to the various type scaffolds by resorting to a few bent bars, rods, or simply a little welding. Figure 4 shows the winch adapted to the box-type scaffold mentioned in the above paragraph. Among the advantages claimed for the winch suspension are the following: 1. Greater safety due to more positive inspections. 2. Ease of handling. The scaffold can be "inched" up or down as desired. 3. Lower headroom. The scaffold can be raised closer to the overhead supports. 4. Less danger of failure when acid is used, as in washing building walls. After the scaffold is erected on a new job, it should be loadtested before men risk their lives on it. Hoist the scaffold about a foot off the ground, and apply a test weight equal to four men for a period of 5 min. Tests should also be made every 10 days if the job continues for more than that time. Where swinging scaffolds are suspended adjacent to each other, planks should never be placed so as to form a bridge between them. Never permit more than two men to work on a scaffold at one time. KTC 02835 SWINGING AND SUSPENDED SCAFFOLDS 145 If the lift of the scaffold exceeds 100 ft, wire rope and winches should be used in place of manila-rope falls. In calculating the strength of scaffolds, a factor of safety of 4 should be used. Occasionally, it may be desirable to install wood bunters with rollers on them to hold the scaffold away from the building wall and to keep it from swinging or swaying. When using The Patent Scaffolding Company winches do not under any condition wire the main holding pawl in the disengaged position (Fig. 5). These "dogs" are provided for a reason, and Fig. 5. The Patent Scaffolding Co. scaffold winch, showing location of two sets of pawls. (The Patent Scaffolding Co.) to disable them is about as foolish as wiring down a safety valve. In lowering the scaffold it is necessary to hold the dog disengaged, but in case of emergency the workman only has to let go of the dog and allow' it to engage the ratchet. The disengaging clips (Fig. 5) that are used to hold the ratchet pawls on the side of the drum in the disengaged position during erection of the scaffold must be removed before the scaffold leaves the ground. Whenever a winch or scaffold is to be removed to another loca tion, always properly wind the cable on the winch; never coil it up on the ground to save time. A kink in the cable will weaken and ETC 02837 o p e ra tio n o f th e B caffold. (C o n tin u e d .) ETC 02838 KTC 02839 n e ith e r be dam aged nor eauae damage. ETr 02840 150 HANDBOOK OF RIGGING The thrust outs or outriggers should not project more than 6 ft 6 in. beyond the point where they bear on the support unless used in pairs. The inboard end should be. anchored to the roof steel by large U bolts and anchor plates. These beams should be not less than 15 ft in length and should be spaced not more than 10 ft apart. ' The suspension cables should be placed not more than 2 and 6 ft, respectively, out from the bearing point of the beam. The platform consists of planks resting on the putlogs or bearers, which are supported by the winches. The width of the scaffold should not exceed 8 ft. The planking should be lj in. thick for spans up to 6 ft and 2 in. thick for spans up to 10 ft. These planks should be laid tight and securely fastened to the putlogs, which they should overlap by not more than 18 in. at each end. A standard guardrail not less than 34 in. or more than 48 in. high and a 9-in. toeboard should be provided along the outer edge of the scaffold. A wire screen between them is recommended. This type of scaffold equipment provides for a 2-in. plank decking or roofing above the workmen. Special hooks should be provided to hold the scaffold close to the building wall. The al lowable loading on an outrigger is approximately 2,000 lb. 'The platforms on the comer scaffolds (Fig. 7) overhang the bearers by considerably more than the allowable 18 in. and are certainly not considered safe practice. To raise the scaffold the levers on the winches are operated up and down to rotate them. To lower the scaffold depress the ratchet handle with the driving pawl held out of engagement, then replace the driving pawl and disengage the locking pawl, so that the weight of the scaffold is sustained on the ratchet handle which is allowed to rise, thus unwinding the cable from the drum. CHAPTER X SCAFFOLDING Built-up Scaffolds. So-called "built-up" scaffolds may be either of the single-pole type, one side of which is supported by poles or uprights and the other side by the wall or structure against which it is erected, or of the double-pole type, which is erected independently of the building or structure. Scaffolds of these types require expert workmanship in their construction and hence should not be undertaken by inexperienced men. Built-up scaffolds are required to be built in conformance with state labor laws, industrial codes, local city ordinances, and national safety codes, all of which are in agreement in most important aspects but which differ in details. Many of the data contained in this chapter are taken from the Industrial Code Rules (No. 23) Relating to the Protection of Persons Employed in the Erection, Repair and Demolition of Buildings or Structures adopted by the Department of Labor of the state of New York. Scaffolds built to meet these requirements should be acceptable in most states and cities. If any portion of a scaffold has been weakened or damaged by storm, accident, or otherwise, it should not be used until the necessary repairs have been made. Care should be taken to avoid overloading any scaffold. When the allowable uniform load is given as, say, 50 lb per sq ft, it means that a 50-lb load can be applied simultaneously to each square foot of deck area. Naturally a man weighs more than 50 lb, yet he can stand on 1 sq ft of flooring, but it is not expected that men will be crowded on a scaffold. In other words, the load should average 50 lb per sq ft. Where there is danger of men at work on a scaffold being struck by material or tools dropped by workmen above, a tight decking or roof of 2-in. planks should be erected above the men. Every scaffold erected 10 ft or more above the ground must have a guardrail and toeboard along the unprotected edges and ends of the work level. On unprotected scaffolds at high elevations the men frequently wear life belts properly anchored to some substan tial part of the structure or sometimes life nets are provided below 152 HANDBOOK OF RIGGING to catch a man should he fall from the scaffold. Guardrails must be at least 34 in. high, preferably 42 in., and must be supported every 10 ft or less. If there is danger of material falling from the scaffold, a J-in. mesh wire screen of No. 18 gauge steel should be provided between the toeboard and guardrail. Spruce, fir, Douglas fir, and southern yellow pine are most com monly used for scaffold work. Spruce has the highest ratio of - Fio. 1. Safe loads on nailed joints. strength to weight and is therefore often preferred. Lumber for scaffold members and planking should be reasonably free from serious defects such as were described in Chaps. VI and VII. A sufficient number of proper size nails, driven in fully, should be used at each joint or splice in the scaffold. Never use nails in tension, such as when the two members have a tendency to pull away from each other. Rather have the nails subject to shearing SCAFFOLDING 153 stress, such as when the members tend to slip on each other. To develop full strength, at least one-half the length of a nail must be driven into the main member to which the secondary member is being nailed. Figure 1 gives the allowable or safe load per nail for different size nails driven into various kinds of wood. The minimum number of proper size nails for securing a board or plank 4 in. wide is two, for 6 in. wide three nails, 8 in. wide four nails, and 10 or 12 in. wide five nails. Fro. 2. Double-pole or independent-pole type of scaffold. (National Safety Council.) It is veiy important that the scaffold uprights or poles be plumb, and they must rest on a proper footing; otherwise as the load is applied to the scaffold, the poles would embed themselves in the ground. Where it is necessary to splice poles, the squared end of the upper member should rest firmly upon the squared upper end of the lower member. To secure these members together, two wood cleats 36 in. long should be nailed on adjacent faces of the poles at the joint. The total cross-sectional area of the two cleats should be at least one-half the cross-sectional area of the pole. ETC 02845 ETC 02846 156 HANDBOOK OF RIGGING Diagonal bracing should be provided for the entire outside face of the scaffold. In erecting built-up scaffolds, whether of wood or tubular steel, it is of utmost importance that they be adequately braced against collapse, both lengthwise and crosswise of the scaffold. If the independent pole scaffold is free standing (that is, away from a building or structure and not attached to it), its width must be at least one-fourth of its height. The decking planks should be laid with their edges close together so that tools and material cannot fall through. The scaffold planks should overlap each other at the bearers by not less than 12 in., or in other words they must project at least 6 in. beyond the bearers. At the end of the scaffold the planks should extend not less than 6 in. or more than 18 in. beyond the last bearer. All structures, in order to be ensured against possible collapse due to horizontal forces such as those caused by the wind, moving loads, etc., should have bracing installed in such a manner as to create a number of triangles. The frame, or "bent," shown in ETC 02847 SCAFFOLDING 157 Fig. 4a is not self-supporting. If a horizontal force or thrust is applied, the bent will assume the shape shown in Fig. 46, which, for clarity is greatly exaggerated. In order to prevent this folding up, a diagonal brace should be installed to form the triangle X shown in Fig. 5a. There is still Fig. 6. Proper and improperly placed braces. the remote possibility of the other pole being bumped into and the lower end displaced, which, of course, would cause collapse, so it is customary to add the horizontal brace shown in Fig. 56, unless both posts are secured to a sill piece. Fig. 7. Alternate methods of installing bracing. Attention is called to the desirability of forming true triangles as shown in the lower panel in Fig. 6a. In the upper panel, the diagonal brace does not intersect the pole and ledger or bearer in a common point, so when a thrust is applied (Fig. 66), the 158 HANDBOOK OF RIGGING lower panel will resist distortion while the upper panel, which is inadequately braced, will be deflected as shown. It is not always practicable to install the bracing properly, owing to the need for avoiding obstruction of passageways. Fig. 8. Additional bracing may be required to support a concentrated load. As higher scaffolds are built, additional panels of two triangles each are added. The diagonal braces may all be arranged parallel (Fig. 7a), or they may be placed in a zigzag manner (Fig. 7b). Or if so desired, a long diagonal brace may extend two panels high (Fig. 7c) provided it is secured to the intervening horizontal member. Where concentrated loads are to be supported, the member or members supporting the load should be properly reinforced or braced. Figure 8a shows an improper arrangement sometimes used. When the load is applied (Fig. 8b), the horizontal member will bend under the weight and the feet of the poles will spread. To overcome this a tie member should be provided (Fig. 8c) to Fig. 9. Long, continuous bracing members for large scaffolds. hold the feet of the poles from spreading or the necessary bracing (Fig. 8d) should be added to prevent the bending of the horizontal member under the load. On large scaffolds that are many panels wide by many panels high, a continuous diagonal brace may be used. Figure 9a shows SCAFFOLDING 159 a diagram of a large scaffold along the face of a big building. The diagonal in this case, as in every other case, should start at the ground level and not one panel above the ground as is occasionally done. If the scaffold is extra long with respect to its height, two or more diagonals may be used, placed either parallel (Fig. 96) or in an inverted V. If the structure is higher than wide, bracing may be arranged as shown in Fig. 9c. Note that the upper brace starts at the same ele vation as the top of the lower brace. On all such scaffolds, diagonal bracing in a plane at right angle to the plane shown should be provided at every second pole and should continue from the ground to the top of the scaffold. Where the height of the scaffold exceeds three times its width, the structure should be secured against overturning bodily. This can be accomplished by means of -in. steel cables attached to the outer poles at c and d (Fig. 10) and extending at about a 45-deg angle in a horizontal plane to building col umns or other adequate supports a and 6. Such tie-ins should be provided at every second or third panel vertically. Where the scaffold is placed against or adjacent to an irregular-shape wall (Fig. 11a and 6), the vertical load from the upper Fig. 10. Anchoring a tall, narrow scaffold. sections of poles should be transferred to the lower sections by using the necessary diagonals. Even under such conditions the primary system of bracing of the scaffold should be kept continu ous. Figure 11c shows a balcony bracketed out from a scaffold. The brace in this case should be clamped also to the projecting horizontal member. Figure 12 shows a gantry built across the entrance to a public building where additional poles would be objectionable. In this case the entire structure must be subdivided into triangles to form the necessary truss. Where built-up scaffolding is used inside a room, and where it extends from wall to wall, the diagonal braces can be omitted pro vided the scaffold is wedged against the walls (Fig. 13) to prevent its collapse. These drawings show the bracing in one plane only. 160 HANDBOOK OF RIGGING It should be thoroughly understood that bracing must be provided in the other plane also. Tubular steel scaffolding, which may be rented or purchased, is to a large degree superseding wood scaffolding, except for the very smallest jobs, owing to its greater strength and safety and the Fio. 12. For long spans trusses must be constructed. ease with which it can be erected and dismantled. Also the mem bers do not deteriorate as do planks and stringers, which warp, split, and decay. The framework of the steel scaffolding, of course, is noncombustible, and when fireproofed planks are used, SCAFFOLDING 161 the danger of a major fire such as took place in the Sherry-Netherlands tower in New York a number of years ago cannot occur. Lightweight tubular steel "bents," or frames, which are essen tially two short poles, a bearer, and bracing members welded to- Fig. 13. No bracing is required where the scaffold abuts the walls inside a room. gether, are now most commonly used. It is said that this design was conceived by an engineer who while confined to a hospital spent many weeks looking at the "head" and "foot" portions of the beds and wondering why they could not be placed on top of iS Fig. 14. Steel scaffolding of the partially prefabricated type. {Safeway Steel Scaffolds Supply Corp.) ETC 02852 ETC 02853 SCAFFOLDING 163 tubing having No. 15 gauge walls. The bracing is f-in. tubing of like thickness. The component parts of the Trouble Saver scaffolding are shown in Fig. 16. Where towers of two bents with their cross bracing are separated by 22 ft or less, truss bridging can be used to connect them to provide the necessary work platform. If the illustrations of the scaffolding are examined carefully, it will be observed that the longitudinal bracing and cross bracing do not form true triangles. The strength of the scaffolding is less than' if it were practicable to arrange the bracing in the most desirable manner, but for ordinary or light duty this scaffolding has a strength of about 5,000 lb uni formly distributed on the bearer. This type of scaffolding, when in the form of relatively small units, can be mounted on casters for readily moving it about, such as for servicing lighting units in auditoriums, etc. If the scaffold ing is more than 15 ft high, it is desirable to use bracing in a hori zontal plane to increase rigidity. Jack screws or wedges should be used to hold the scaffold securely in place while being worked on. For heavy duty or extreme height the Tubelox-type scaffolding is best suited (Fig. 17). This consists of lj-in.-o.d. galvanized steel tubing, which comes in lengths of 6, 8, 10, and 13 ft and is used for poles, ledgers, bearers, and bracing. The pole tubes are joined end to end by placing the female end of a tube onto the male or top end of the tube below and twisting until it locks. For securing ledgers and bearers rigid 90-deg couplers or clamps are used. In erecting this type scaffolding the poles are placed on metal bases, which distribute the load on the footing planks, then the ledgers are clamped to the poles at the desired height. The bearers are clamped to the ledgers close to the poles. The diagonal braces on the outside face of the scaffold are clamped to the pro jecting ends of the bearers close to the poles (Fig. 18), and likewise the transverse diagonals are clamped to the ledgers close to the poles. The bearers should extend beyond the inboard poles and touch the building wall or other structural support. Usually one plank is placed on this end of the bearer between the pole and the wall. As the scaffolding is extended upward as construction pro gresses, the planking can be removed from the lower levels and placed higher up, but the guardrail members should remain to give additional rigidity to the scaffold. The pole splices should be located a short distance above the ETC 02855 1*1G. 16. C o m p o n e n t p a rts o f T ro u b le S a v e r p a r tia lly p re fa b ric a te d ste e l s c a ffo ld in g . (Steel S c a ffo ld in g C o.) 014C 22' Truss F iq . 16. (Continued.) ETC 02856 ETC 02857 ETC 02858 168 HANDBOOK OF RIGGING the upper portions of the wall or cornice. Timbers 3X 10 in., used on edge, are placed horizontally, resting on a piece of plank placed on the window sill, and extend not more than 6 ft beyond the face of the wall. To resist the upward thrust at their ends inside the building, they are usually nailed to planks placed verti cally and wedged against bearing blocks at the floor and ceiling. Cross bridging between the outriggers at the window sill resists any tendency of the planks to roll over. The maximum spacing between outriggers is 10 ft. On the out riggers are nailed 2X9 planks laid close together, although a 3-in. space at the wall is permitted when necessary. The end planks should not extend more than 18 in. beyond the last out riggers. . Standard guardrails and toeboards, as described above, are required along the outboard edge and ends of the scaffold, but in erecting the guardrails special attention should be paid to making the stanchions of adequate strength. Screening of ^-in. square mesh is desirable between the guardrail and toeboard. SCAFFOLDING 169 Needle Beam Scaffolds. This type of scaffold is used only for very temporary jobs, particularly for working on steel structures. No material should be stored on this scaffold. Two needle beams, 4 X 6 in. on edge, are placed parallel to each other in a horizontal or nearly horizontal plane (depending upon circumstances) and not more than 10 ft apart. They are usually suspended by rope near each end, and a center support is always required. The rope should be 1-in. No. 1 grade manila or larger and is attached to the needle beams by a scaffold hitch (Chap. II, Figs. 77 to 79) so as to prevent the beams from rolling over on their sides under load. The rope should then extend up over a structural member, down under the needle beam, and back over the structural member, after which it is secured. The hitch shown in Chap. II, Fig. 80, is fre quently used, although a clove hitch or rolling hitch is preferable. Precautions must be taken to prevent the ropes from slipping off the ends of the needle beams, particularly if the latter are inclined. The decking should be of 2-in. planks having a length at least 2 ft longer than the span between needle beams, and the length of the decking in a direction parallel to the beams should be not less than 3 or more than 6 ft. If the scaffold is not level, the planks should be nailed to the beams or have cleats nailed on their under sides to engage the beams. In constructing or using wood scaffolds and planking, special attention should be paid to the condition of the wood, as described in Chaps. VI and VII. 170 HANDBOOK OF RIGGING FiO. 19. Material hoistway tower of tubular steel. (Courtesy of Dram Carp.) ETC 02862 CHAPTER XI PAINTING AND REPAIRING STEEL STACKS The painting and repairing of steel smokestacks is a perpetual headache to the maintenance men in large and small plants alike. In traveling about, one will observe numerous sheet-steel stacks on laundries, bakeries, small factories, etc., many of which are in a poor state of repair, due primarily to the fact that the plant mainte nance men are unable to take care of them properly. These men cannot be held entirely to blame for the poor condi tion of their stacks, for such maintenance is not in their usual line of duty. Most of these maintenance men have never been up on a stack in the course of their work and probably hesitate to go up unless the safest kind of rig is available. One look at the rusty steel cable hanging from the top of the stack usually convinces them that they were not bom to be steeplejacks. When the stack was erected, a heavy steel hook was engaged over the top sheet and a steel pulley block attached to it, after which a galvanized steel cable (called a "gantline") was reeved through it. But years of exposure to the rain and to the flue gases have caused corrosion of the wire rope notwithstanding the galvanizing. It is customary to attach a simple boatswain's chair to the end of this gantline and to hoist a man to the top, carrying with him a new gantline hook and a set of manila-rope falls which are to be used in painting or repairing the stack. If the permanent gantline is not too badly corroded, he may get to the top safely; other wise . . . ? Not long ago, a painter on reaching the top of a stack in this conventional manner discovered that the hook on the pulley block on which his life depended was very badly pitted and' corroded away. He managed to get down safely but soon began to work up a device to enable a man to reach the top of a small stack in safety. After considerable study and experimenting he developed the safety-type gantline hook shown in Fig. 1, which has proved very satisfactory. A steel bar is forged to the dimensions shown in the sketch, and the permanent gantline, which may be of a questionable strength, is fastened to the middle eye. A set of 172 ETC 02863 manila-rope falls that has just been inspected and found in safe condition is attached to the eye at the base of the hook, and the hook of the pulley block is moused to prevent accidental detach ment. A tag line is then tied to the end eye, and the rig is hoisted by means of the gantline. When raised to the extreme position, GANTLINE HOOK SAFETY HOOK FLATTEN Fig. 1. A special rig to provide a safe means of ascending a steel stack. (Comsolidated Edison Co. of New York, Inc.) the gantline is held stationary while a slight pull is taken on the tag line. This causes the bar to tilt and the hook end of it to pass over and engage the top of the stack. The rope falls that were hoisted in a "block and block" position are pulled down by means of another tag line, and the boatswain's chair, preferably one of the safety type with a body belt to keep a ETC 02864 174 HANDBOOK OF RIGGING man from falling out, is attached to the rope falls, and the painter hoists himself to the top in safety. Never does he trust his life to equipment except that which he has been able to inspect only a few minutes before. Upon completion of the job, the rig is un hooked by holding the gantline taut while pulling on the tag line This detaches the safety hook from the top of the stack. The rig is then lowered and stored in a proper place until next required. On intermediate-size stacks permanent steel ladders are usually provided. These ladders should be of standard dimensions, namely 18 in. wide, 12-in. rung spacing, and 65-in. toe room behind the ladder. Due to the necessary exposure to the weather and to the flue gases, the ladder should be of heavy construction, the rungs being not less than J in. diameter and the stringers about 3 X 5 in. On all long ladders, such as on stacks, it is desirable to provide basket guards or cages (Fig. 2) inside which a man can climb in comparative safety, but on the intermediate-size stack a basket guard may appear all out of proportion to the size of the stack. In fact, it may look more like a basketed ladder with a stack attached to it. Consequently, basket guards are seldom used except on the very large stacks. On these medium-size stacks and on those of larger size which are not provided with basket guards on the ladders, it may be found desirable to stretch a bronze or galvanized steel cable or wire strand up each side of the ladder from the very bottom to the very top of the stack, as shown in Fig. 3. These cables are alter nately anchored to the ladder stringers about every 12 to 15 ft and are then pulled taut by means of tumbuckles. A life belt (Chap. XII, Fig. 2) is provided for each man and is equipped with two forged-steel (not malleable iron) snap hooks, as shown. When starting up the ladder the man snaps his two hooks onto the respec tive cables. After he has climbed about 15 ft, one of the hooks strikes the obstruction. He then detaches that hook and snaps it onto the cable above the anchorage, after which he continues to climb. Fifteen feet farther up the ladder his other hook strikes a similar obstruction and must be unhooked and hooked on again. This is repeated until he reaches the top of the ladder. When disengaging one of the hooks, the man is still protected by the hook at the other side of the ladder. Consequently, there is never a time when he is not safeguarded by at least one hook. Should he feel weak or dizzy or tired, he can attach one of the hooks to the ladder rung for greater security while standing still. It is TOP AND BOTTOM HOOPS ALSO THIS size BASKET GUARD HOOP BOTTOM HOOP FOR BASKET GUARD F ig . 2. D e ta ils fo r safety basket guard used on ta ll steel stacks. ^ u u 111 BASKET GUARD (Consolidated Bdion Co. o f New Y ork, In c .) 176 HANDBOOK OF RIGGING esforH" bolts ,S"3/g BAR 2`-3" -- ?iDlA. RUNGS** 1 18" 1 'WELD OR RIVET 2'xVsAR d. 3 x>SBAR E 8-0 Fia. 3. Safety cable installed beside lad der on steel stack on chimney. (Consoli dated Edison Co. of New York, Inc.) Fig. 4. Details of another type of protection for a stack ladder. (Consolidated Edison Co. of New York, Inc.) ETC 02867 PAINTING AND REPAIRING STEEL STACKS 177 admitted that the use of such equipment is largely psychological, but never under any circumstances can he fall farther than 15 ft. Should he begin to fall, he will be held close to the ladder and will have a better chance of grasping it again. There is another advan tage, and perhaps most important of all, in the use of this equip ment on stack ladders: A man must stop and rest every 15 ft, even if for only a few seconds while reattaching his hooks, and he will arrive at the top in a much better physical condition. Some riggers take pride in proclaiming that they can climb a 250-ft stack without once stopping to rest, but they do not tell how near they come to exhaustion or to having cramps in their arm or finger muscles, which might have fatal results for them. On some large power-plant stacks the ladder is placed about 27 in. away from the stack wall, and the man climbs within this space. Thus, when tired he has merely to lean back against the stack and rest. A further improvement on ladders of this type is the installation of steel guard bars at each side of the ladder well (Fig. 4) to form an enclosure within which he climbs. With the bars located as shown in the sketch, it offers adequate protection for the man against being blown off the ladder by a high wind, yet it does permit him to climb out onto a scaffold if necessary. Shown in Fig. 5 is a stack 21 ft 0 in. diameter at the top and 31 ft 0 in. at the boilerhouse roof with one continuous ladder over 300 ft high. Not only is this ladder equipped with a standard basket guard, but at 50-ft intervals are special seats formed by off setting the bars of the basket guard. Steel plates are provided for the seat and the back rest, and the bars at the top of the recess in the ladder well are at such an angle as to reduce the hazard to a man's head or shoulder when he is about to start climbing the ladder again. While intended primarily as a seat, these landings are sometimes used to stand on while the men rest their feet. Also, these seats offer a safe and convenient means for a man climbing the ladder to pass another man coming down. This type of ladder and basket guard is considered the most desirable in use at present. But merely getting to the balcony at the top of a large stack does not solve the entire problem. This balcony should be pro tected by a handrail at least 42 in. high and a 4-in. toeplate to pre vent tools, etc., from being kicked off the edge. Some stacks have the top of the stack wall about 4j or 5 ft above the grating, which does not afford an opportunity for a man to stand on the platform 178 HANDBOOK OF RIGGING and look down inside the stack. In such cases small checkered plate steps are provided at several places around the periphery of the stack at about 12 or 15 in. above the grating, so that a man can conveniently inspect the upper portion of the stack lining. Where such steps are provided, the handrail is made higher so as to be at least 42 in. above these steps. This may require the railing to be three or four members high, as these bars are usually spaced somewhat closer than on ordinary handrails. Where it is not Fiq. 5. This protected stack ladder is 304 ft high. Seats are provided every 50 ft for resting, or to enable men to pass each other on the ladder. (Consolidated Edison Co. of New York, Inc.) feasible to increase the height of the railing, an eyebolt is placed at each side of each of the small steps just below the stack crown ring, and to these are attached the snap hooks of the body belt used in climbing stacks as mentioned above. The use of such a belt prevents him from falling down the outside or the inside of the stack. In order to facilitate painting large power-plant stacks, a special articulated circular steel scaffold (Fig. 6) has been found very useful. This scaffold was designed for use either on the outside or inside of stacks of about 22 ft diameter. It consists of 12 trapezoidal- PAINTING AND REPAIRING STEEL STACKS 179 shape platforms (part 10 in Fig. 7), each about 5 ft 6 in. inboard length, 6 ft 7 in. outboard length, and 2 ft 0 in. wide. The frame is constructed of ^-in. steel plate, bent to form an L or angle shape with a 3-in. horizontal leg, which supports the floor boards, and a 4-in. vertical leg, which acts as a toeplate to prevent tools, etc., from rolling off the scaffold. These bent plates are mitered and welded together at the corners of the platform. Fig. 6. With this special scaffold a stack 22 ft in diameter and 165 ft high can be painted in 8 hr. (Consolidated Edison Co. of New York, Inc.) The floor boards (parts 1 and 2), which are the only wooden parts of the scaffold, are 1 X 5j in., spaced \ in. apart and bolted to the platform frame. Between the ends of the adjacent platforms are separators (part 9) made in the form of an inverted U. The horizontal web portion of the bent j-in. plate is 3 in. wide by 22 in. long and has vertical flanges at both sides 3 in. deep. Passing through the end toeplates of the adjacent platforms and through short lengths of tubing welded to the separator plate are two f-in. bolts 8 in. long, the nuts on which are left about 1 in. slack. Cotter pins are pro vided for security on these bolts. On the top of the bent separator plate is a hinged plate 3 X f X 12 in. long, which is thrown back onto the separator while the scaffold is being hoisted and swung 180 HANDBOOK OF RIGGING out to form an outrigger and stabilizer during lowering and working operations. The scaffold is necessarily discontinued at the ladder, and in order to tie the platforms together into a continuous ring around PtAN Of STACK AND SCAFFOLD Fia. 7. Shop details for the special stack scaffold shown in Fig. 6. (Consolidated Edison Co. of New Yorkf Inc.) the stack a steel bar (part 6) or a f-in. rod is extended from the out board comer of one platform to that of the other platform adjacent to the ladder. At the 11 joints between platforms and at the two platform ends at the ladder, are standard Patent Scaffolding Company handoperated scaffold winches (part 35) designed to accommodate about 250 ft of f^-in. 6 X 19 galvanized-steel wire rope (part 27) for suspending the platform. These cables are provided with eye F ig . 7. ( C o n tin u e d .) ETC 02872 ETC 02873 PAINTING AND REPAIRING STEEL STACKS 183 11 REQO, - STEEL Fig. 7. (Continued.) ethyl CORPORATION ncuri nPWFY.T SECTION LIBRARY ETC 02875 ETC 02876 186 HANDBOOK OF RIGGING splices and thimbles at the upper end for attaching to the " sky hooks " (part 3), which engage the top of the stack wall. In raising the scaffold, the men "pump" the levers on the winches. In lowering, the main dog is held disengaged with one hand while the hand crank on the worm shaft is turned with the other. Never should the dog be wired or tied in the disengaged position. The winch parts are all doubly protected against failure, there being duplicate dogs on the lowering motion and the main dog and the worm drive to hold when hoisting. Two of these devices would have to fail simultaneously to permit the winch to unwind accidentally by gravity. To ensure winding the cable in even layers on the winch drum during the hoisting operation fair-leader (parts 7, 8,11,12, 15,16, 25, and 28) is attached to the upper part of the winch frame, thereby making it possible to feed the rope on the drum as desired. Special plate brackets (parts 4 and 5) are bolted to the lower end of the winch frame, and from those brackets are suspended four hanger bars (parts 13 and 14), which, in turn, are bolted to and support the comers of the adjacent scaffold platforms. These hangers do not he exactly in the planes of the brackets or of the platforms, so in order to avoid the necessity of making them with very slight right- and left-hand twists, respectively, it was found more practicable to allow some play in the bolt holes and to leave about J-in. slack when placing the nuts on the bolts. Of course, all these bolts are provided with cotter pins. At the ends of the scaffold near the stack ladder only two hangers are required, and these are attached to diagonally opposite holes in the two winch brackets so as to keep the winch frame in a verti cal position and the drum shaft radially with relation to the stack. With the platforms thus supported and tied together loosely, as previously described, the scaffold is sufficiently flexible to permit one winch to be raised a foot or more above the next. Although it is not essential to keep the scaffold absolutely level, it should be maintained reasonably so. To accomplish this when hoisting, the men should pump rather uniformly at the winches. Some gangs have found it practicable and entertaining as well to have one of their members sing loudly while they all keep time with their levers. In order to pass from one platform to the next, it was necessary at the time the photograph (Fig. 6) was taken for a man to crawl PAINTING AND REPAIRING STEEL STACKS 187 under the winch. Since that time, however, the inboard hangers (part 14) and brackets (part 5) have been redesigned as shown in Fig. 7. This allows sufficient space for a man to pass between the winch and the wall of the stack by merely stepping over the offset lower ends of the hanger bars. The triangular openings between the platforms and the stack wall at the winches are small enough to prevent a man from falling through. When the outrigger is hinged into the "out" position, it forms a convenient step at this location. Provision is made at each winch bracket (part 4) to support two lengths of f-in. No. 1 grade manila rope (part 26), which act as a handrail along the outboard edge of the scaffold. The purpose of the tie bar (part 6) is to bind the entire scaffold into a unit and to have it completely encircle the stack in order to prevent the ends near the ladder from moving away from the stack wall. Also, if by some stretch of the imagination it could be as sumed that 12 out of the 13 suspension cables had failed, the re maining cable would be expected to cause the scaffold as a unit to tilt and bind on the stack, thus preventing it from dropping farther. This same scaffold is designed for use on the inside of the stack, in which case only nine platforms are used. When erected inside the stack the winch brackets are reversed in relation to the plat form so that the rope railing will be on the inboard (unprotected) side of the scaffold. The actual erection of the scaffold (exclusive of any false work that may be required if the boilerhouse roof is not flat) usually can be accomplished in one day. On the second day 13 men (they are not superstitious even on a job of this kind) place their paint pots and tools on the scaffold and pump it to the top of the stack, just below the balcony. They then paint their way down to the boilerhouse roof, using ordinary brushes and making the entire operation in one 8-hr day on a stack 22 ft 0 in. diameter by 165 ft high above the roof. That portion of the stack above the balcony is usually painted on the preceding day. This type of scaffold has been in use about fifteen years and has met with the unanimous approval of the painters and construction men. When repairs are made to the brick lining of a stack, regardless of the precautions taken chips of brick will frequently fall to the base of the stack, presenting a serious hazard to the men who are at work there. In order to reduce this hazard to a minimum, the men ETC 02878 ETC 02879 CHAPTER XII LIFE BELTS, BOATSWAIN'S CHAIRS, AND LIFE NETS There are a number of appliances or devices that serve a very useful purpose on rigging jobs, especially as regards personal safety. Among these are life belts, life lines, boatswain's chairs, parachute harness, and life nets. Life Belts. Different designs for life belts are available for various special uses. Only webbing-type belts should be used, as leather deteriorates very rapidly and may fail when it is called upon to perform in an emergency. Leather is also very difficult to inspect visually. Some belts are made with only a body belt, some with a body belt and a wider cushion of webbing to reduce "cutting" of the body when the fall is suddenly arrested, and some with shoulder straps to take the weight of the belt. An objection to the last type is that the shoulder straps are frequently made so short that the body belt, instead of being around the waist or soft part of the body, is up onto the lower ribs, which may be fractured by the sudden strain on the belt. Also, this type is not too com fortable to wear, particularly in warm weather. Figure 1 shows a simple life belt that has proved satisfactory in service. The buckle is of ample strength and is of a type that does not require puncturing the webbing at the buckle. It is a very comfortable belt to wear. Depending upon its use, several different types of tail lines may be used. If the belt is to be used to rescue a man entering a hazardous location or area, such as a coal bunker or a smoke- or gas-filled room, a long rope is used. If this belt is used on a scaffold in conjunction with a hanging life line, a tail line 5 or 6 ft long is used, and this short rope is attached to the life line by means of a rolling hitch (see Chap. II, Fig. 49). If the belt is worn by a man at work on the box scaffold (see Chap. IX), the tail line shown in Fig. 1 is used, the snap hook being attached to the trolley cable on the scaffold railing. This tail line can be made with or without the rubber shock cord, but preferably with it, as in the event of a man falling, the rubber can stretch about 18 in. and thereby ease the shock of deceleration. If the shock cord is not used, of course the rope will be shorter in order to 189 ETC 02880 190 HANDBOOK OF RIGGING BUNDLE SHOCK CORO ANO ROP6TOGETHER, ANO 81N0 WITH 12 WRAPS OF GROCERS' STRING -3 FULL LOOPS OF H SHOCK CORO 19 -4 O.A.LENGTHLNA/Y OEPT. SPECIFICATION 49CM RUSSEL MFG. CO. MIDOLETOWN CONN. OR AIR ASSOCIATES, ROOSEVELT FIELD, LONG ISLAND. ^*NO. I GRADE-- MANILA ROPE PLACE ON 0" RING BEFORE MAKING EYE SPLICE LENGTH/OF ROPE BETWEEN THIMBLES* n T H4" I FULL SPUCE TUCK-' RE-FORM SHORTENO OF ROPE S FULL + I HALFSPUCE TUCK 'lS SHOCK ABSORBER ----------SERVING CORO, ARMY SPECIFICATION NO. 15-10 AIR ASSOCIATES, ROOSEVELT FIELO -TERMINATE SERVINGS BY SEWING OR LACING THROUGH ROPE OR SHOCK CORD. TAIL LINE FORGED STEEL SNAP HOOK OF ANY APPROVED OESIGN MUST FIT ONTO V CXA. LAOOER RUNG - ENCASE SHOCK CORD AND ROPE IN BOOT 24" LENGTH OF *15791 UNBLEACHED SLEEVING, 3`WIDE. INTERNATIONAL BRAID CO.,PROVIOENCE,R.!. Z WRAPS - ENO OF SLEEVE TURNEO INSlOE- COMPLETED TAIL LINE .2 WRAPS (INSIOET ORIGINAL 3 STRAND ROPE ^ 3 STRANDS RE-FORMED 'WELD INTO ROPE SECTION A-A SHOWING *D" RING SECTION A-A Fia. 1. A simple and comfortable life belt that affords safety to men at work at elevated locations. {Consolidated Edison Co. of New York, Inc.) Notes: (1) Hardware shall be of mild steel, cadmium-plated. (2) Butt welds shall be ground smooth. (3) Cotton webbing shall weigh not less than 16 lb per etc 02881 LIFE BELTS, BOATSWAIN'S CHAIRS, AND LIFE NETS 191 retain the 2 ft 0 in. over-all length. The shock cord can also be incorporated in the tail line used with the hanging life line. A life line should be strong enough to arrest the fall of a man but need not be excessively heavy or cumbersome. Of course only new or relatively new rope should be used and should be secured to some substantial object overhead. A new j-in. manila rope has a breaking strength of at least 2,650 lb. Any impact that will develop a force of 2,650 lb mil undoubtedly break a man's back and kill him; therefore there is no advantage to be gained by using, say, a 1-in. rope. A |-in. tail line and a f-in. hanging life line are generally used. For climbing long ladders such as on chimneys or gas holders the belt shown in Fig. 2 is very useful, either by attaching the snap hooks to the rungs when resting or by attaching them to the cables beside the ladder as described in Chap. XI. Boatswain's Chairs. For performing small jobs at otherwise inaccessible elevated locations, a boatswain's chair is frequently used. The original type consisted of a flat board with two holes near each end, through which f- or 1-in. manila rope was threaded. But in using this rig, there is always the possibility of a man's falling out owing to sickness or inattention. Thus, a safety-type boatswain's chair, such as the one shown in Fig. 3, is recommended for use. This has a comfortable "har vester" seat and a body life belt. In order to prevent restriction of blood circulation in the man's feet (feet going "to sleep"), stirrups are provided to rest the feet in. Also, to reduce the dis comfort to his knees when working against a wall for a length of time, casters are provided to keep his knees away from the wall. The safety latch on the pulley block (Chap. IX) also adds to the man's security. Parachute Harness. Occasionally it is necessary to hoist or lower a man through a maze of piping or other obstruction or 100 linear ft. (4) Lock stitching shall be as shown. At the buckle and at the "D" ring stitching shall not run transverse to belt. (5) Stitching shall be done with five-cord linen thread, hot-waxed, and having a tensile strength not less than 30 lb. Number of stitches shall be not less than five nor more than 9ix per inch. (6) Shock cord shall be not more than 90 days old when belt is fabricated. Tracers in braid of shock cord to indicate its age: Two green threads together-- 1949; two red threads together--1960; two blue threads together--1951; two yellow threads together--1952, and repeat; one red thread alone--January, February, March; one blue thread alone--April, May, June; one green thread alone--July, August, September; one yellow thread alone--October, November, December. 'r- 192 HANDBOOK OF RIGGING ETC 02883 F ig . 2. Safety belt used b y men clim b in g chimneys and stacks. ETC 02884 ETC 02885 LIFE BELTS, BOATSWAIN'S CHAIRS, AND LIFE NETS 195 CHANNEL ENDS TO BE CURVED UP AND OVER SEAT AS SHOWN AND BRAZED TO SAME ! 4 DIA. BRASS,ROD BRAZED TO CHANNEL AS SHOWN 16 TINNED STEELAIRPLANE CABLE HARVESTER SEAT ..--f 2 x % * %2BRASSi__i DETAIL-A Fig. 3. (Continued.) SPREAD OR WING CHANNEL FLANGES AS SHOWN-ALL SHARP EDGES TO BE PROPERLY ROUNDED AND SMOOTH ETC 02886 196 HANDBOOK OF RIGGING DETAIL - B ETC 02887 ETC 02888 198 HANDBOOK OF RIGGING BRAZE ^x'/gBAR I LG. (STEEL) -^6*^6 BAR \ LG.(BRASS) ROUND CORNERS ON CHANNEL I'j X 3/g x 3/ja i_i (BRASS) PRCWIDE GROCWE FOR 346 CABLE DETAIL - F DETAIL - G Fig. 3. (Continued.) ETC 02889 LIFE BELTS, BOATSWAIN'S CHAIRS, AND LIFE NETS 199 Sr ;i t'l' t! F ETC 02890 200 HANDBOOK OF RIGGING through a manhole or small hatch, in which a boatswain's chair would be too large or too cumbersome. In this case a webbing parachute harness (Fig. 4) is sometimes used. This fits snugly around the man's body and takes practically no more room than his body. The parachute harness, however, is not so comfortable as the boatswain's chair for long operations. If a parachute harness is not available, use can be made of the sling or the knots shown in Chap. II, Figs. 23, 24, or 85, respectively. In either of the latter knots the end of the rope should be left about 4 ft long and tied around the man's waist. Life Nets. On some high jobs, such as erect ing or painting steel structures where it is im possible to wear life belts, it may be practicable to provide life nets below the point where the men are at work. A life net, to be of value, should be placed as near as possible to the level where the men are working; in other words, their falling distance should be reduced to a Fio. 4. The para chute harness can be used in place of the boatswain's chair when clearance is restricted. minimum. Also, keep in mind as in the case of life belts that it is not the fall but rather the sudden stop which causes injury to the man. Therefore the life net should be made as springy as possible. In falling, a man (or any body) develops energy in footpounds equal to his weight in pounds multiplied by the distance he falls in feet. This energy must be absorbed when his fall is stopped. Therefore, the force of impact is equal to the energy divided by the distance in feet in which he is stopped. For instance, a 180-lb man falls 25 ft and develops 4,500 ft-lb of energy. If he is stopped in 1 ft, the force is 4,500 lb. If stopped in 2 ft, it is 2,250 lb. In 5 ft the impact is 900 lb, etc. Some nets are made with mesh ropes parallel-to the border ropes, thus forming squares. A man falling into the net will be stopped quite suddenly, as there will be relatively little stretch to the mesh ropes. The net shown in Fig. 5 follows quite closely the design used by Ringling Brothers-Bamum and Bailey Circus in the nets for its acrobats. The mesh ropes, running at a 45-deg angle, form dia- ETC 02891 ETC 02892 ETC 02893 ETC 02894 CHAPTER XIII LADDERS Many industrial organizations that use a large number of wood ladders have an inspector carefully examine each ladder when received in order to make certain that it meets the requirements of the purchase specifications. Most specifications are based upon the data contained in the American Standard Safety Code for the Construction, Care and Use of Ladders, which is published by the ASA, or else they refer to this code. Therefore, the first duty of the inspector is to check all. the dimensions of the ladder, including the size of the side rails and rungs, to assure himself that they are not less than the minimum allowed by the code (Table I). Well-built ladders usually have their side rails larger than the code dimensions. All wood parts, of course, should be free from splinters. Next, he should examine the hardware to determine if it is of ample strength. Malleable iron and cast iron should be avoided, if possible, for parts subject to bending or tensile stress. Rungs should be tightly fitted into the side rails and secured against turning by the use of finishing nails driven through the side rails and into the tenons, yet they should not be so tight as to split the side rails. Special or "trick" ladders should not be used. These ladders, which can quickly be converted into an extension ladder or stepladder, may possibly be acceptable for household use, but they have no place in industry. On stepladders the spreader bars should be so designed as not to present a serious finger-pinching hazard. Stepladders should not be able to fold up accidentally if pushed along the floor. Extension ladders should have the guide brackets long enough to engage the full width of the side rails on the other section of the ladder. Also, the locks should be of proper design, and the rope and pulley of ample strength. Near the lower end of the upper section of exten sion ladders a rung is often omitted at the location of the locks. A special offset rung may be necessary, but a rung of some description is essential, due to the fact that the sections of an extension ladder are frequently separated and used independently. 204 LADDERS 205 Table I. Minimum Dimensions of Wood Laddebs * (Side rails of spruce, Douglas fir, or southern yellow pine. Rungs of hickory, oak, or ash.) Nominal length, ft Single ladder Two-piece extension ladder Width at base (inside), in. Size of side rails, in. Width at Size of side base rails, in. (inside), in. Overlap of sections, ft 6 n$ 1$ X 2$ 8 ni 1$ X 2$ 10 Hi 14 X 2$ 12 iif 14 x 24 14 12 14 X 2$ 15 . 12J 14 X 24 16 12f 14 X 24 144 1* X 24 3 18 12$ If X 2} 144 3 20 12} If X 2} 144 1AX24 3 24 13f If X 3 144 X 2 3 25 13} 1} X 3 26 134 14 X 3 144 1-^ X 3 28 13} 14 X 3 144 1*X24 3 30 14 14 x 3 16 1-^X2} 3 36 16 1-re X 3 4 40 16 1AX34 4 44 18 1*X34 4 48 18 1} X 34 4 60 18 If X3} 5 If the dimensions of the material are increased the allowable angle of cross grain will be slightly greater. All material should be seasoned and dressed, free from splinters and sharp edges, free from shake, wane, compression wood, compression failures, decay and low density. ' Side rails: Cross grain should be not greater than 1 :12. No knots allowed on narrow faces. On the wide faces knots are permitted if not larger than $ in., if not closer than J in. to the edge, and if not less than 3 ft apart. Checks limited to 6 X J in. Pitch pockets limited to J X 2 X in. and not less than 3 ft apart. Rungs: Not more than 12 in. apart. Not less than 1} in. diameter with tenons } X li in. long. Cross grain limited to 1 :15. Knots limited to $ in. * Data taken from American Standard Safety Code for Wood ladders, ASA A14.1, 1948. Finally, the inspector should make a thorough examination of the wood itself. This is one part of the inspection which is usu ally omitted in part or in its entirety. To many purchasers and, strange as it may seem, even to some ladder manufacturers, wood is wood and nothing more. The data on wood contained in this chapter will therefore be devoted largely to the inspection of the material used in straight or extension ladders, these being the 206 HANDBOOK OF RIGGING types which are responsible for most accidents. For further data on the inspection of wood, refer to Chap. VI. Most ladders of these types are constructed with spruce side rails (preferably Sitka spruce) and with oak or hickory rungs. Oak and hickory are readily recognized, but spruce may some times be confused with other species. Therefore, it may not be amiss to include a few words concerning the identification of spruce. Spruce is nearly white, with no definite difference in color between heartwood and sapwood, except that Sitka spruce does have heartwood with a slight reddish tinge. Spruce averages about 15 to 18 annual rings per inch as measured radially on the ends of the side rails and weighs about 28 lb per cu ft. The summerwood of the annual rings is distinct, but not homy. (For additional information on defects in wood, see Chap. VI.) Resin ducts appear as white specks in the summerwood on the cross section and as faint pin scratches on the longitudinal faces. Pitch pockets are frequently observed, and resin may ooze from newly cut surfaces if exposed to warm atmosphere. Spruce is distinguished from white pine by having fewer and smaller resin ducts than pine and also by the lack of distinct heartwood in all species of spruce except Sitka. It is distinguished from fir by the presence of its resin ducts. Sitka spruce usually has a sheen to the longitudinal surfaces, and the flat-grain face is generally " dimpled " or "pocked," thus distinguishing it from Douglas fir. Sitka spruce comes from larger trees than other species of spruce, and its rings are therefore usually of longer radius. . After the inspector has satisfied himself that the proper kind of wood has been used, he should first check up on the direction of the annual rings as observed on the ends of the side rails. These rings should preferably be approximately parallel to the narrow faces, thus producing edge grain on the wide faces and flat grain on the narrow faces of the rails. With the rings extending in this direction the ladder will be somewhat stronger than if they ran in the other direction, but it will not be quite so stiff. (A springy ladder is unpleasant to work upon, but it has greater resistance to sudden or impact loads.) Also, the harmful effect of cross grain, if it exists, is reduced, and spiral grain is more readily detected by noting the tiny splits at the nails used to hold the rungs from turning. Next, the presence of cross grain should be investigated. Cross grain may be subdivided into "diagonal" and "spiral" types, and LADDERS 207 both either individually or collectively should not exceed an angle of 1 : 15 with the edge of the rail. Diagonal grain is observed on the edge grain face (wide face in this instance) and is indicated by the direction of the annual ring markings. Dip grain, a local deviation from straight grain caused by knots, tree wounds, etc., which may or may not be present in the side rail, should also be given careful study. Such defects are most harmful if occurring in the middle of the length of a ladder. This also means in the top half of the lower section and in the bottom half of the upper section of an extension ladder. It is the angle made by the dip grain at the edge of the side rail that determines its importance, and this angle should not exceed 1:15. Farther back from the edge a slightly greater angle is allowable. Dip grain, of course, should not be permitted near rung holes. Shakes are not permitted in ladder stock. In edge-grain ladder stock, as was previously recommended, checks will seldom be found but if present should not exceed 6 in. in length or in. in depth. Pitch pockets are not objectionable if they are not larger than 2 in. long, in. wide, or ^ in. deep or if they are not closer than 3 ft apart. According to the ladder code, knots are not permitted on the narrow faces. In edge-grain material, such as has just been recom mended, this is the only place where knots could occur. Therefore, all knots are prohibited. Only well-seasoned material should be accepted, as green wood will sooner or later cause the joints to loosen and the ladder will become rickety. Warped material is also unacceptable. Some inspectors insist upon testing all ladders as a final require ment before acceptance. Such load testing is no longer recom mended in the ladder code, and it is frowned upon also by authori ties on wood, as there is far greater probability of producing a compression failure during the test than of discovering one that already exists. Consequently, all testing should be eliminated from the inspection routine. Now to investigate the rungs. Hand-split rungs are preferred, as they are naturally straight grained. If the rungs have been turned, they should be checked for cross grain at two points 90 deg apart, the limit of the cross grain being 1 : 15. Knots over | in. diameter, checks, and other defects are all prohibited. Rungs can be tested for cracks by striking with a light hammer. 208 HANDBOOK OF RIGGING In special ladders that are constructed with side rails consider ably heavier than required by the ladder code, certain defects such as knots, checks, cross grain, etc., may be tolerated at the discre tion of the inspector even though slightly exceeding the figures given previously if the strength of the ladder is otherwise consider ably above the minimum strength. To enable the inspector quickly to check the strength of a ladder, the accompanying chart (Fig. 1) has been prepared. It is based upon an average-weight man standing on the middle rung of a ladder inclined at the recommended angle (the base of the ladder at a distance from the wall equal to one-fourth the length of the ladder). The net area after deducting rung holes has been used, and the unit stress developed should not exceed 1,600 lb per sq in. In order to enable the inspector to make a thorough inspection, the ladders as received from the manufacturer should be of un treated wood; that is, no paint, varnish, linseed oil, or other surface protection should be applied before the inspection. (Unscrupulous manufacturers have been known to paint wood to conceal otherwise visible defects.) The Forest Products Laboratory advises that on objects fabri cated from wood, including ladders, which are coated with ordinary paint, varnish, or similar materials moisture may enter the wood at the uncoated joints such as rung tenons and rung holes. This moisture is then prevented from leaving the wood because of the more or less impervious coating. Hence, they advise that "in some kinds of wood construction involving such joints, the appli cation of protection coatings may favor rather than retard decay." There are available today a number of proprietary chemicals known as NSP preservatives (NSP meaning "nonswelling and paintable"). These consist of a toxic chemical carried in nonaqueous volatile solvent with or without the further addition of water-repelling ingredients. Those without water-repellent con sist typically of a solution of toxic in volatile petroleum solvent, such as mineral spirits or Stoddard's solvent, and in addition may contain a proportion of less volatile solvent such as fuel oil to facilitate spreading the preservative through the wooden struc ture. After a ladder has satisfactorily passed the visual-acceptance examination, it should be heated in a kiln, oven, or warm room and then immersed for 3 min in the cool solution in a shallow pan, after which it is allowed to drain and dry. The solvent is LADDERS 210 HANDBOOK OF RIGGING flammable, but the treated ladder when dry is not any more com bustible than before treating. When thoroughly dry the ladder may, if so desired, be coated with paint, varnish, or enamel to improve its appearance, but these coatings will not noticeably increase the resistance of the wood to decay. If a ladder has been thoroughly inspected prior to painting, the user can rest assured that no defects are likely to develop under a good coat of paint. For instance, knots, cross grain, and com pression wood cannot develop after painting. Checks, if they develop, will surely show on the surface, as will subsequent com pression failures. Decay and brashness due to exposure to heated air can be determined by jabbing with a knife, whether the ladder is painted or not. Once a ladder has been approved by the inspector, it should be branded with the date as a mark of acceptance, and only such branded ladders should be used on the job. In fact, some com panies brand serial numbers on all their ladders for identification and for record purposes. It is believed that, if only properly constructed ladders are allowed to be put in circulation, and if they are treated with reasonable care thereafter, the accidents due to ladder failure can be reduced to an insignificant figure. The inspection of used wood ladders is largely a matter of common sense. For instance, anyone should know enough to condemn a ladder that has a broken side rail or a broken rung or tread. Nor should a ladder be used if it has a rung or other struc tural part missing, although we occasionally find such a ladder in use in spite of our rigid safety inspections. A ladder containing repairs made by any person other than the authorized ladder builder should not be used. We have all seen ladders with broken side rails reinforced by nailing a cleat across the break. Split rungs are frequently observed bound with wire. Be on the lookout for loose rungs or treads that rotate more or less when grasped or stepped upon. Also watch for treads in stepladders that are slipping out of the gains or recesses in the side rails. Rungs that are worn down to f in. minor diameter or treads such as on stepladders that are worn to less than in. at the nosing should be tagged and returned to the ladder shop for reconditioning. Notice if there are any badly worn spots such as are caused by the brackets upon which a ladder may have been hung, especially on a truck. In this case it will be a matter of LADDERS 211 using your best judgment to determine how much the wood may be worn away before it is unsafe for further use. Such wear and also exposure to the weather will cause splinters, which may result in hand injuries. In some instances these splinters are soft and woolly and present only a slight hazard, but in most cases it is advisable to have the ladder sandpapered down. It should be unnecessary to mention that, when such a condition exists, the protective coating of paint or enamel is worn off, leaving the wood exposed to moisture. The importance of preservation of the paint cannot be too strongly emphasized. In manhole ladders, especially, we frequently find the ends of the side rails mushroomed. Where steel shrouds are not provided at the ends of the side rails, the wood sometimes brooms out so as to look like an old paintbrush. This is owing largely to the fact that the ladders stand in puddles of water in the manholes and absorb considerable moisture. Then, again, dropping the ladder carelessly into the manhole does not help matters. Mushrooming to a limited degree may act as a safety foot and help to prevent the ladder from slipping. However, when mushrooming develops, it indicates that decay has also set in, and we cannot tell how far up on the side rail it has progressed beneath the paint. Heavily painting or tarring the ends of the side rails and care in lowering the ladders into manholes will largely increase the life of the ladders. We must watch for signs of mechanical injury such as bruises caused by dropping the ladder against some hard object or by the ladder's being run over or into by a vehicle, by being struck by a hammer, etc. Bruised spots are readily susceptible to dry rot, so when a bruise or other injury is observed, it is advisable to probe around this area with a sharp instrument, care being exer cised not to pierce the paint or enamel any more than is necessary. Soft, punky wood indicates rot, and the inspector will have to judge if the decay has advanced far enough to weaken the ladder, and if so, he should not hesitate to condemn it. Of course, if any nails or screws project or are missing, they can be driven in or replaced, as the case may be, without returning the ladder to the shop. Occasionally we find a ladder with one side rail shorter than the other, thereby throwing it out of plumb. Owing to drying out of the moisture, especially in hot locations such as boiler rooms, the wood may shrink so that the rungs become loose in the side rails, causing the ladder to become rickety. ETC 02902 212 HANDBOOK OF RIGGING A good way to determine the extent of such play is to stand the ladder on a level floor with the wide face of one side rail against a vertical wall or building column. Then while holding that side rail firmly against the wall, raise the other rail until the play is taken up. If this distance is greater than f in., the ladder cer tainly should be condemned. In fact a much lower tolerance is desirable. If unseasoned or improperly seasoned wood has been used in the construction of the ladder parts, the shrinkage may cause the ladder to warp sufficiently to make it unsafe for use. If a test indicates very brash wood and the ladder is therefore condemned, it will be interesting to stand it up and then allow it to fall over and strike against some object near the floor level. The brash side rail may be expected to snap off in a clean splinter less fracture. The discussion thus far has been general; that is, it applies to all types of ladders. We shall now discuss the inspection of various types of ladders. In addition to what has already been mentioned, there are a few more words to be said about ordinary straight ladders. For instance, some straight ladders are provided with safety feet or safety hooks. If the so-called "safety feet" are used, the abrasive or other antislip surface should be in good condition and not gummed up or coated with a foreign substance. Most safety engineers have found that, although safety feet are in themselves a safety device, a great many men using ladders so equipped place undue confidence in them with the result that such ladders do slip. For this reason the writer does not recommend the use of safety feet. Safety hooks, if provided, should be of the proper shape and length required to secure the ladder properly. Extension Ladders. Occasionally we find men using the sec tions of an extension ladder separately. There is little objection to this provided the upper section of the ladder is used upside down so that the rung missing at the locks will be at the top of the ladder where it is less liable to cause an accident. As far as its strength is concerned, it makes no difference which side of an extension ladder is placed toward the building. But there is considerable disagreement on the question as to which way the ladder should be placed. Perhaps 99 per cent of the extension ladders used on construction and painting jobs are placed with the upper, or "fly," section in front of the base section. Most fire departments, including New York City, however, follow the prac- LADDERS 213 tice recommended by the National Fire Protection Association, which specifies that the fly section be at the rear of the base section. They point to several advantages of the NFPA method: 1. In descending the ladder, there is no missing rung near the bottom of the fly section to cause an accident. 2. When changing from the fly section to the base section, while descending the ladder, the rungs of the lower section appear to be farther out, and thus there is less danger of the foot's slipping off the rung. 3. When raising the fly section, the ladder is stood nearly verti cal, but leaning slightly toward the building. Thus, the pull on the halyard largely balances the pull of gravity tending to upset the ladder. On the other hand, the conventional use of the ladder has the halyard behind the ladder, where it is less likely to interfere with the feet when climbing. Stepladders. Stepladders should bear evenly on all four legs on a plane surface or floor. They should have the truss rods under the treads or the step brackets in condition and drawn up tight. The diagonal bracing and the dowels on the rear section should be in good shape and not deformed by men using the rear of the ladder to climb up on. The spreader bars should operate properly and should not present unnecessary finger hazard. Rope spreaders should not be permitted. The auxiliary step at the top of some platform ladders should be carefully examined, as the supporting members are usually veiy lightly constructed and are easily bent out of shape. Sectional Ladders. Sectional ladders are not so common as the other types, but nevertheless many are in use, particularly by window cleaners. In addition to examining them as described in the general discussion above, special attention should be paid to the locking devices for holding the sections together. Whether these be of the friction-button, hook, or wing-nut type, they should operate properly and dependably. Look at the condition of the projecting ends of the top rung of the lower and intermediate sections that support the forked ends of the side rails of the sections above. Also note the condition of these forked ends of the side rails and their reinforcing plates. Trestle Ladders. There is little to be said concerning trestle ladders in addition to what has already been discussed. The inspection should include the spreader bars, the locks for securing ETC 02904 214 HANDBOOK OF RIGGING the extension section, and the wear on the rungs caused by these locks. Also, the ladder should bear on all four legs. As mentioned previously, it is very difficult to draw an arbi trary line to differentiate between a safe and unsafe ladder. No two inspectors will agree as to just how far decay, for instance, may progress before the ladder is rendered unsafe for use. The value of a ladder inspection, therefore, depends entirely upon the judgment of the inspector with the help of a few rules such as just discussed. A ladder of sufficient length shall always be selected for the work to be done. In general, the length of the ladder should be such that the work can be performed from at least the fourth rung from the top of the ladder. This will permit the side rails to be grasped conveniently. If the ladder is too short for the work at hand, get a longer ladder. In selecting an extension ladder for a particular job, it should be remembered that this type of ladder is designated by its nominal length, which is the sum of the lengths of the sections. The usable length of the ladder is 3 to 10 ft less than the nominal length due to the overlap of the sections. This overlap is 3 ft on ladders up to and including 36 ft, 4 ft on 40- and 44-ft ladders, and 5 ft on longer ones. Figure 2 will facilitate determining the nominal length of an extension ladder required to reach to a given height when placed at the proper angle. Before using any ladder, thoroughly inspect it and be satisfied that it is in good condition. Short ladders shall not be spliced together to make a long ladder. Ladders shall not be used as guys, braces, and skids and (except as noted below) for scaffolding or for any purpose other than that for which they were intended. An extension ladder can be used in a horizontal position as an improvised scaffold staging, provided 1. The ladder is in its collapsed or unextended condition. 2. The ends rest upon fixed supports, never upon suspended ropes. The supports shall be at least 12 in. from the ends of the ladder. 3. A thin plank or board is lashed to the rungs of the top section to form a flooring. 4. The load shall not exceed 300 lb concentrated at the center of the span or 600 lb uniformly distributed over its length. LADDERS 215 When not in use, ladders should be stored in dry locations where they will not be exposed to the elements but where there is ample ventilation. They shall not be stored near radiators, steam pipes, stoves, or other places subjected to excessive heat. Ladders stored in a horizontal position should be supported at a sufficient number of points to avoid sagging and permanent set. Ladders carried on vehicles should be adequately supported on brackets so designed or padded as to avoid chafing of the side rails due to road shock. Fia. 2. Chart showing the nominal length and approximate weight of a ladder to reach to a given height. Ladders that are damaged beyond repair should be destroyed or otherwise rendered useless. Those in need of minor repairs shall be sent to the carpenter shop for reconditioning. When using a ladder, always place it at the proper angle, which is indicated when the horizontal distance from the base of the ladder to a point directly below the upper support is about one-fourth of the inclined length of the ladder from the base to the point of support. This is illustrated in Fig. 3. Rungs are always 12 in. apart, and this makes it easy to measure the length of the ladder. It is poor practice to have the upper end of a ladder extend more 216 HANDBOOK OF RIGGING than 3 or 4 ft above its upper support or to makfe it possible for a man to step onto a rung above the upper support, as this may cause the base of the ladder to "kick out." When using an extension ladder, make certain that both locks are in good operating condition and engaged onto a rung of the lower section. Use the surplus length of the hoisting rope to lash together the adjacent rungs of the two sections. This will be an added safeguard in event of failure of the locks. Fia. 3. Rules for placing a ladder at the proper angle. If practicable, lash the bottom of the ladder to a fixed object to prevent it from slipping. Otherwise, always have a helper hold the base of the ladder while a man is at work on it. Lashing the upper end of the ladder to the structure will also prevent possible upset sideways. When a long ladder is to be raised, place the base against a wall, curbstone, or other fixed object or have a helper squat with his feet against the "heels" of the ladder side rails or on the bottom rung and grasp the second rung with his hands, meanwhile throwing his weight backward as far as possible. Then lift the upper end of the ladder over your head and walk toward the base of the ladder, grasping rung after rung until the ladder is in the vertical position. Then "walk" the ladder to the working position and carefully lower it against the wall. To raise or lower ladders safely the following man power is recommended. Of course, by butting the base against a fixed object the "heel" men may be dispensed with. LADDERS 217 Up to 18-ft straight ladder, 1 man to raise. Up to 25-ft straight ladder, 1 man to raise and 1 man to heel. Up to 30-ft straight ladder, 2 men to raise and 2 men to heel. Up to 24-ftextension ladder, 1 man to raise. Up to 30-ftextension ladder, 1 man to raise and 1 man to heel. Up to 40-ftextension ladder, 2 men to raise and 2 men to heel. Up to 55-ftextension ladder, 3 men to raise and 3 men to heel. No more than two men shall be permitted on a straight, exten sion or stepladder at one time, and they shall not ascend or descend simultaneously. Wood ladders should not under any condition be given a load test in excess of the normal load expected to be placed on same, as there is far greater probability of weakening a good ladder than of detecting a weak ladder. This chapter would not be complete without reference to the aluminum and magnesium ladders that are now becoming quite extensively used. These ladders are stronger than wood ladders, are more readily inspected, will not decay, do not become brash when exposed to high room temperatures, and the weight of magne sium ladders is much less than that of wooden ones. Their first cost is much greater than for wood ladders, but this is largely offset by their longer life. Weights furnished by well-known manufacturers are as given in Table II. Table II. Comparative Weights of Wood, Aluminum, and Magnesium Ladders Type Length, ft Wood, lb Aluminum, lb Magnesium, lb 1 20 18$ Straight............ 12 24 22 14 28 25$ 16 32 29$ (24 43 50 Extension........ 32 58 64$ 36 72 72 140 100 79 9 14 16 18 32 49 55 61. Note: Wood ladders: Chesebro-Whitman, " Gold Medal." Aluminum ladders: Mason Products Co., "Maproco." Magnesium ladders: White Aircraft Corp., "White-light." Warning. Metal ladders should not be used near exposed elec trical equipment, including overhead distribution wires, craneway trolley conductors, switchboards, etc. CHAPTER XIV STRENGTH CALCULATIONS FOR TIMBERS The charts given in this chapter will prove helpful to the rigger in selecting the proper timbers to be used as beams and posts for supporting heavy loads. It should be understood that the strength of any species of wood varies considerably with the width of the annual rings, nature of defects, etc., so the loads given in these charts may not agree exactly with the results obtained from other sources. There are a few general rules to remember concerning the safe loads and deflection of wood beams. For instance, 1. The safe load on a beam varies directly as the width. Thus, doubling the width of the beam doubles the safe load. 2. The safe load on a beam varies as the square of the depth. Thus, doubling the depth gives a safe load four times as great. 3. Placing two planks on top of each other gives twice the strength of one plank, but securely nailing or doweling their ends together to prevent slipping of one plank on the other gives four times the strength of one plank or twice the strength of the two planks placed on each other. 4. The safe load on a beam varies indirectly as the span. Hence, doubling the span cuts the safe load by one-half. 5. A beam of a given size, material, and span will carry a uni formly distributed load twice as great as a concentrated load applied at the center of the span (provided the unbraced span is relatively short). 6. The deflection of a beam of given size, material, and span varies directly as the load. Doubling the load doubles the deflection. 7. The deflection of a beam of given size, material, and loading varies as the cube of the span. Thus, doubling the span gives eight times the deflection. In order to show the use of the charts, it is desirable to work out some practical problems step by step, keeping in mind that the span is the distance from center to center of supports. 218 STRENGTH CALCULATIONS FOR TIMBERS 219 Problem 1. Given an 8 X 12 in. southern yellow pine beam of select grade, placed so as to have a span of 18 ft. Required to find the safe concentrated load. Enter the chart (Fig. 1) at the bottom of "18-ft span," and follow upward to the curve representing a 8 X 12 beam, then Fig. 1. Safe concentrated loads on dry wood beams of select-grade southern yeUow pine. For other species multiply by the following factors: Douglas fir.................... 1.00 Redwood........................... 0.75 Oak......................... ..... . 0.87 Sprude. eastern hemlock 0.70 Weet-coaat hemlock . . 0.80 (Note: Arrows on chart refer to Problem 3.) 220 HANDBOOK OF RIGGING follow to the left and read 3,250 lb safe concentrated load on the southern yellow pine beam. However, if the beam were of red wood we should multiply the 3,250 lb by 0.75 and obtain a safe load of 2,435 lb. (The strength of other species of wood relative to southern pine is given with the chart, Fig. 1.) Problem 2. Given a 4 X 6 in. spruce needle beam on a 9-ft span supporting half of a scaffold. What uniform load will the scaffold safely carry? Again, enter the bottom of the chart at 9-ft span, follow upward to the 4 X 6 curve, and read 850-lb safe concentrated load on a southern pine beam. Taking .70 times 850 gives 595-lb concen trated load on a spruce beam. The span being less than 12 ft, the safe uniformly distributed load is twice 595, or 1,190 lb, and inasmuch as two needle beams support the scaffold the safe load on the scaffold is twice 1,190, or 2,380 lb. Problem 3. Given a concentrated load of 10,000 lb. (including the weight of the chain hoist, Fig. 2) on a beam on an 8-ft span. What size southern pine beam is required? Enter the chart from the bottom at 8-ft span, and draw a vertical line. Also, enter from the left at 10,000 lb, and draw a horizontal line (see lines drawn on Fig. 1) until it crosses the vertical line, ETC 02911 STRENGTH CALCULATIONS FOR TIMBERS 221 which is almost on the 10 X 12 curve. Thus, we can use the 10 X 12 beam or any beam of larger size (above it on the chart). For any other species, first divide the load by the factor given below Fig. 1 and then enter the chart from the left by using this corrected figure. Fia. 3. Safe loads on dry wood columns or posts of select grade lumber. Values indicated are for select southern yellow pine. For other species multiply by the following factors: Douglas fir (coast region) 1.00 Oak and redwood . . . 0.78 West coast hemlock . . 0.70 Spruce.................................0.62 Eastern hemlock . . . 0.55 Likewise, we can work out some problems in the use of wood posts or columns. In such cases the unbraced height of the column divided by the least dimension of the timber governs to a large degree the load the column may safely carry. ETC 02912 222 HANDBOOK OF RIGGING Problem 4. Given a 6 X 8 in. southern yellow pine post having an unbraced height of 18 ft. What load will it safely support? Enter the chart (Fig. 3) at the bottom at 18 ft, follow up to the 6X8 curve, and then follow to the left and read 14,000-lb safe load. If any other species of wood were used, the 14,000-lb load would then be multiplied by the factors below the chart. Problem 5. Given a 4 X 6 Douglas fir post 10 ft high. What load will it safely support? Also, what is the safe load if the addi tional bracing shown in Fig. 4 is added to reduce the unbraced height to 5 ft? 10,000* SAFE IjOAO IOjOOO* 22,500* SAFE LOAD 22,500* Fig. 4. Loading of poorly braced and well-braced wood posts considered in Problem 5. Enter the chart at the bottom at 10 ft, follow upward to 4 X 6, then left, and read 10,000-lb safe load for select southern pine. Inasmuch as Douglas fir has the same strength, the safe load is still 10,000 lb. Again let us enter the chart at 5 ft, follow upward to 4 X 6, and we read 22,500-lb safe load for southern pine (and for Douglas fir). This should emphasize the importance of adequate bracing on all posts and columns. Problem 6. Given a load of 100,000 lb to be carried on a west coast hemlock post 20 ft high between braces. What size timber should be used? From the table at the top of Fig. 8, we find that west coast hem lock has a strength of 0.70 times that for southern pine. In other STRENGTH CALCULATIONS FOR TIMBERS 223 words if a west coast hemlock timber would support 100,000 lb, then a southern pine of the same size would carry 100,000 -3- 0.70 = 142,800 lb. Hence, we enter the chart at the left at 142,800 lb and at the bottom at 20 ft. These lines intersect slightly below the 12 X 14 curve, so a 12 X 14 or any larger size will suffice. However, if we want to economize on the size of timber used, let us assume that the posts are braced 10 ft above the ground. Thus, entering the chart at 142,800 lb and at 10 ft, we find that a 10 X 14 post will safely carry the load. The difference is more noticeable on the smaller sizes with relatively longer unsupported lengths. Of course all posts should have square ends and should rest on sills to distribute the load over a larger area of the ground. Also, the bracing should be adequately nailed or bolted to the posts in order to provide the required rigidity. The mathematical calculation of timber beams is quite involved, owing not only to the effect of the direct load on the beam but also to the presence or absence of horizontal bracing to prevent the beam from deflecting sideways and then rolling over on its side and failing. And, in addition, on short deep beams there is a tendency for the beam to split along its neutral plane and fail like two separate beams or planks placed one on top of the other. Hence, the mathematical calculations are very complicated and are omitted from this chapter. CHAPTER XV STRENGTH CALCULATIONS FOR METAL BEAMS Before proceeding with the discussion of steel and light metal beams, it might be well to describe briefly the standard structural shapes. In standard WF (meaning "wide flange") beams, I beams, and channels the vertical central portion is called the "web" while the horizontal top and bottom parts are called the "flanges." In the WF beams the flanges are, as the name indicates, wide in relation to the depth of the beam. Also these flanges are of uniform thickness. American standard I beams have relatively narrow flanges which are tapered, being thinner at the "toe" of the flange. Channels appear like half of an I beam, the flanges being on only one side of the web. In locating WF or I beams, the dimension indicates the center of the web. Channels are located by measuring to the back of the web or "heel" of the flanges. The span of a simple beam sup ported at or near the ends is the distance between supports and is always measured in inches. The length of the span depends to a degree upon the nature of the material upon which the beam rests. Figure 1 shows simple beams with their deflections exaggerated for clarity. If the supports are very hard, such as heavy steel or con crete, the effective span is from edge to edge of supports (Fig. la). On the other hand, if the beam rests upon timbers that compress slightly under the bearing load (Fig. 16), or if the steel beams upon which it rests can rotate slightly under the beam (Fig. lc), then the span is measured from the center of one bearing to the center of the other bearing. When selecting a metal beam, keep in mind the following rules: 1. A beam of given size and span will carry a uniformly distrib uted load twice as great as a load concentrated at the center of the span. In other words, if from the table we find that a certain beam on a given span will safely carry a concentrated load of 7,500 lb, then if the load is spread out over the entire length of the beam, 15,000 lb may be safely applied. Likewise, on a cantilever beam 224 STRENGTH CALCULATIONS FOR METAL BEAMS 225 the allowable distributed load is twice the allowable concentrated load. 2. The safe load on a simple beam varies indirectly as the span. Hence, with a beam of a given size if we double the span, we reduce the safe load to one-half. Likewise, on a cantilever beam if the lever arm is reduced to one-half the length, the load may be doubled. 3. The deflection or bending of a simple or a cantilever beam under load varies directly as the load. Thus, doubling the load will ordinarily double the deflection. LOAD 1 1 _z SOLID -/ ta)zi- SUPPORTS - a LOAD Fig. 1. Sketches showing how the length of the span of a beam is measured. 4. The deflection of a simple beam of a given size and load varies as the cube of the span. Thus, if we multiply the span by 2, then we must multiply the deflection by 2', or 2 X 2 X 2 = 8. If we multiply the span by 2\, then the deflection is (2)3, or 2| X 2| X 2 or 15f times as great. 5. The load applied to a beam must include not only the useful load to be lifted but also the weight of the slings, the hoist tackle or chain hoist, the pull on the hauling line or on the hand chain, and (if the beam is very heavy) the weight of the beam itself. 226 HANDBOOK OF RIGGING Table I. Strength op Steel, Aluminum, and Magnesium Beams * A, STEEL WF BEAMS 18.000 lb per sq in. Nominal size, in.t Maximum bend- Weight ing moment per ft, lb 36 X 16} 33 X 15} 30 X 15 36 X 12 33 X 111 27 X 14 24 X 14 30 X 10} 21 X 13 24 X 12 27 X 10 14 X 16* 18 X Ilf 21 X 9 24 X 9 16 X 11} 14 X 14} 21 X 8} 14 X 12 18 X 8} 15.000.000 12,070.000 9,500,000 9,050.000 7.300.000 7.260.000 5,950,000 5.900,000 4,500.000 4,480.000 4.380,000 4.085.000 3,310,000 3,250.000 3,150,000 2.720,000 2.485,000 2,270.000 2,180,000 2.110.000 230 200 172 150 130 145 130 108 112 100 94 142 96 82 76 88 87 62 78 64 A. STEEL WF BEAMS 18,000 Jb per sq in. Nominal size, in.t Maximum bend- Weight ing moment per ft, lb 16 X 8} 14 X 10 18 X 7} 12 X 12 12 X 10 14 X 8 16 X 7 10 X 10 12 X 8 14 X 6} 10 X 8 12 X 6} 8X8 10 X 5} 8X6} 8 X Si 6X6 5X5 4X4 1.692,000 1,660.000 1,602,000 1.583,000 1,273.000 1.139,000 1,014.000 983,000 934,000 752,000 630,000 614.000 493,000 387,000 375,000 254,000 182,000 153,000 75,000 58 61 50 65 53 43 36 49 40 30 33 27 31 21 24 17 I5j 16 10 8. STEEL I BEAMS 18,000 lb per sq in. Nominal size, in. Maximum bend- Weight ing moment per ft, lb 24 X 7 J 24 X 7 20 X 7 20 X 6} 18 X 6 15 X 5} 12 X si 12 X 5 10 X 4} 8X4 7 X 3| 6X3} 5X3 4X2} 3X2} 4,210,000 3,130,000 2,700.000 2.180,000 1.590,000 1,060,000 806.000 648.000 439.500 255.500 187,000 131.500 86.300 54,000 30.600 106 80 85 65 55 43 41 32 25 18 15 12} 10 8 6 C. MAGNESIUM I BEAMS Alloy J-l or 0-1 10,000 lb per sq in. Nominal size, in. Maximum bending moment Weight per ft, lb 6X3} 5X3 4X2} 3X2} 73,600 49,000 30,300 16,800 2.81 2.24 t.73 1.28 Z>. MAGNESIUM H BEAMS Alloy J-l or 0-1 10,000 lb per sq in. Nominal size, in. Maximum bend- Weight ing moment per ft. lb 6X6 5X5 4X4 146,900 95,300 53,600 5.10 4.21 3.07 * Tables are arranged in the order of their bending momenta. t" Nominal size*' is depth by flange width. J Actual depth varies considerably. STRENGTH CALCULATIONS FOR METAL BEAMS 227 E. ALUMINUM H BEAMS Alloy 17ST 15,000 lb per sq in. Nominal size, in. Maximum bending moment Weight per ft, lb 8X8 6X6 5X5 4X4 425,000 220,000 143,000 80,500 11.51 8.04 6.63 4.85 F. STEEL JOISTS 18,000 lb per sq in. Nominal size. in. Maximum bending moment Weight per ft, lb 12 X 4 10 X 4 8X4 6X4 226,500 189,000 140,000 91,100 14 Ui 10 8} G. STEEL CHANNEL BEAMS 18,000 lb per sq in. Nominal size. in. Maximum bend- W eight ing moment per ft, lb 18 X 4 15 X 3} 12 X 3 10 X 2f 9 X 2} 8X2} 7X2} 6X2 5X1} 4 X 1| 3 XU 1,100,000 750,000 385,000 241,500 189,200 145.700 108,000 77,500 54,000 34.200 19.800 43 34 21 15 13 nf 10 8 7 5 4 H. ALUMINUM I BEAMS Alloy 17ST 15,000 lb per sq in. Nominal size, in. Maximum bending moment Weight per ft, lb 12 X 5 10 X 4f 9 Xlft 8X4 7 X 3| 6X3} 5X3 4X2} 3X2} 425.000 296,000 229,500 173,000 136,000 88,500 59,000 36,400 20.200 11.31 9.01 7.72 6.53 5.42 4.43 3.53 2.72 2.02 Calculations for steel or light metal beams are not too difficult if certain facts are known. For instance, Known Required Span of beam, size of beam, material....................................Safe load Span of beam, load, material...................................................Size of beam Size of beam, load, material..................................................... Maximum span Inasmuch as the same unit stress (18,000 lb per sq in.) is used for all steel beams, Table I lists the product of the unit stress and the section modulus under the heading of maximum bending mo ment. This saves one step in the calculations. Figure 2 gives the formulas for determining the bending moment when the size of the beam is to be calculated. Conversely, if the beam size is known, the formulas may be used to find the maximum span or load. In all instances M = bending moment, lb-in. (lb multiplied by in.) P = concentrated load, lb W = total uniformly distributed load, lb L = length of span, in. ETC 02918 228 HANDBOOK OF RIGGING Perhaps the best way to explain the method of making the cal culations is to work out some practical problems. In all instances unless the beam is very narrow relative to the span, the calcula tions are quite simple. But on beams with a high "slenderness ratio" additional investigation must be made. The slenderness ratio is the length of the span between lateral bracing of the com pression flange divided by the width of the beam flanges. CONCENTRATED lOAO <a) simple beams SPAN L UNIFORMLY QISTRlBUTEQ LOAQ "x >-" (bl LENGTH L CONCENTRATED LOAD M*PL P*- UNIFORMLY OlSTRlflUTEQ lQAQ (C) cantilever beams Fig. 2. Formulas for calculating the bending moment of a beam under various types of loading. The reason we are interested in the slenderness ratio is that, if a beam is very slender and an excessive load is applied vertically, there is a tendency for the beam to deflect sideways, then twist and roll over on its side. The beam, being much weaker on its side, will fail and allow the load to drop. Bracing the compression flange against deflection sideways, so that the slenderness ratio of the longest unbraced part of the span is 15 or less, will prevent this from happening, and the full calculated load can be safely carried. Problem 1. Given a steel beam that measures 12 in. deep with an 8 in. wide flange and used on a span of 9 ft (108 in.). What load concentrated at the center of the span will it safely support? The dimensions indicate a 12 X 8 WF beam. (All beams are manufactured in several thicknesses and weights, but as the lightest weight beams of each size are most readily obtainable, only these ETC 02919 STRENGTH CALCULATIONS FOR METAL BEAMS 229 are listed in the table.) From Table 14 we find that the allowable bending moment for a 12 X 8 WF steel beam is 934,000 lb-in. In Fig. 2a we find that P = 4M 4 X 934,000 = 34,590-lb safe load L 108 But before we accept that figure as final let us check the slender ness ratio. 108/8 = 13.5. Referring to Fig. 3, we find that the full load can be carried. 50 ; E 40 : E 30 E E 20 Ey 1 1 1 E1 10 i~ E 1 I ''10Z0UJ-L9Ji5XL9101 .81 I5lt8L 0til7l 511711 0U6-Ll.560xui5511U50 STRENGTH IN % OF STRENGTH OF WELL-GRACED BEAM Fig. 3. Chart for estimating the reduction in strength of a steel beam due to a long span unbraced laterally. Problem 2. Given a load of 22,000 lb uniformly distributed along the length of a simple beam having a span of 16 ft 0 in. (192 in.). What size beam is required? . Using the formula in Fig. 26, we find that M = WL 8 22,000 X 192 8 = 528,000 lb-in. Looking in Table I, any beam having an allowable bending moment of 528,000 lb-in. or more will be acceptable. We shall select the 12 X 65 in. beam (indicated in Table 14), which has an allowable bending moment of 614,000 lb-in. Now let us investigate the slenderness ratio. 192/6 = 29^. Referring to Fig. 3, we enter the chart from the left at 29j, then 1 !? ION ! 1 SECTION LIBRARY' ROUGE. LOUISIANA ETC 02920 230 HANDBOOK OF RIGGING read at the bottom 78 per cent. So taking 78 per cent of 614,000 lb-in. we get 478,000 lb-in. This is less than the 529,100 linn, required, so this beam is not strong enough. The next heavier beam will be investigated. The 10 X 8 in. WF beam is good for a bending moment of 630,000 lb-in. The slenderness ratio is 192/8 = 24. From the chart we find that the safe load is 86 per cent of 630,000 lb-in., or 542,000 lb-in. Thus, the 10 X 8 WF beam is acceptable. Problem 3. Given a concentrated load of 12,000 lb and a 10 X of WF beam. What is the longest span that can be had and yet safely support this load? From Table IA we find that the 10X of beam is good for a bending AM moment of 387,000 lb-in. From Fig. 2a we find that L = ~-pr- -- 4 X 387,000 = 129 in. or 10 ft 9 in., provided, of course, that the 12,000 slenderness ratio permits. The slenderness ratio is 129 in. 5f in. = 22i and the allowable load (from Fig. 3) is 885 per cent of 12,000 lb, or 10,620 lb. The load is definitely 12,000 lb, so the span must be shortened and the calculations repeated. An alternative, providing, of course, that the maximum possible span is desired, is to install rigid lateral braces against the top flange of the beam at the middle of the span to prevent it from deflecting sideways. If this is done, the slenderness ratio will be 64j 5f = 11.2 and the full 12,000-lb load can be safely carried. Problem 4. Given an outrigger scaffold 3 ft 0 in. wide, sup ported by 7-in. aluminum I beam outriggers spaced 8 ft 0 in. apart. The scaffold deck is made up of four 2 X 9 in. spruce planks laid abreast of each other. The general design of the scaffold is as shown in Fig. 4. What safe load can it carry, in pounds per square foot of scaffold deck? The strength of this scaffold may be limited by 1. The strength of the deck planks. 2. The strength of the outriggers. 3. The strength of the anchorages for the outriggers. First, let us consider the strength of the planks. From Fig. 2 in Chap. VII we find that a 2 X 9 spruce plank on an 8-ft span is good for about 116-lb load concentrated at the center of the span or double that amount (232 lb) if the load is uniformly distributed ETC 02921 ETC 02922 ETC 02923 CHAPTER XVI CRANES, HOISTS, AND DERRICKS There is almost no limit to the number of different designs of cranes that can be built. Basically, a crane is described as a piece of hoisting equipment designed to pick up a load, transport it a reasonable distance, and land it again. A so-called "hoist" may be a complete hoisting unit mounted overhead in a fixed location or suspended from a small trolley attached to an I-beam truck. Or the term "hoist" can be applied to the power-driven mechanism and drums that are used in conjunction with a derrick, gin pole, or even a material-hoisting elevator. Fig. 1. Overhead or traveling crane. (American Standards Association.) The traveling crane, gantry, half-gantry, bridge, and wall cranes operate on fixed straight tracks and usually have their hoist mechanism mounted on a movable trolley. These types are shown diagrammatically on Figs. 1 to 5 inclusive.* The hammer head, pillar, and jib cranes have a fixed location with a boom that rotates or slews around it (Figs. 6 to 10). The portal crane is a pillar crane mounted on a gantry (Fig. 11). These cranes and the monorail hoist as well are all equipped with two brakes on the hoist motion, usually a solenoid-operated * Figures 1 to 18 inclusive are reproduced through the courtesy of the American Standards Association. 233 234 HANDBOOK OF RIGGING brake on the motor shaft and a mechanical load brake on one of the intermediate gear shafts. Each brake should hold at rest a load of 1 times the rated load. These cranes always have a limit device on the hoist motion to stop the motor automatically in the event the operator fails to shut off the power when the lower load block reaches the safe limit of travel. The limit device is installed only as a safety feature, and it should not be depended upon in place of alertness on the part of the operator to shut off the power during normal operations. Fig. 2. Gantry or bridge crane. (American Standards Association.) Before starting operations at the beginning of the day's work always pick up a capacity load a foot off the ground to test the brakes. Of course, on very large cranes this is impracticable, for capacity loads are not always available. Lower the load an inch or less at a time, and observe the drift, if any, due to faulty brakes. The operator should always accelerate and decelerate the bridge and trolley motions slowly in order to avoid unnecessarily swinging the load. Where a crane handles a large number of small loads daily, such as in a storehouse, the operator may learn by experience how to stop his crane quite quickly by aiming at a spot perhaps a foot short of the location where the load is to be placed; then as the load swings ahead of the crane, he releases the foot brake and ETC 02926 ETC 02927 ,CRANES HOISTS, AND DERRICKS Fiq. 7. Tower crane. (American Standard* Association.) o ETC 02 92.9 CRANES, HOISTS, AND DERRICKS 239 Fio. 11. Portal crane. (American Standards Association.) Fig. 12. A-frame derrick. (American Standards Association.) 240 HANDBOOK OF RIGGING o ETC 02932 ETC 02933 CRANES, HOISTS, AND DERRICKS 243 allows the crane to move ahead and come to rest over the load, which by this time has stopped swinging. Cranes of these types should be thoroughly inspected at least once each month. Before starting the inspection, have the operator lower the load block and land it on the floor or ground and allow the cables to become slack. If properly installed, there will be sufficient cable on the drum to permit this without bending the rope backward at its anchorage. Then open the power switch, and apply your own personal padlock to prevent anyone from accidentally energizing the crane while the inspection is in progress. If a lock cannot be applied, attach a warning sign to the main switch. 244 HANDBOOK OF RIGGING First examine the structure of the crane for bent or damaged members, corrosion, loose rivets and bolts, etc. Look at the bridge end-truck wheels for flat spots or worn or broken flanges. Check the alignment at the runway rails, and observe if the crane bridge is square with the runway. Inspect every foot of hoist cable, giving special attention to that part which bears on the equalizing sheave, as this is often the first part of the rope to show evidence of failure. Sliding a rag along the cable will frequently help find broken wires, as it will usually catch on them. Note the condition of the cable anchorages on the drum, and look for broken wires where the rope is bent sharply to enter the hole. Also observe if the sheave grooves are of proper size for the rope and if the sheave and drum grooves have been corrugated so as to wear the rope excessively. Make sure that the cables are properly lubricated. Try operating the limit device manually to make sure that it works freely. Pry open the solenoid brake to observe if the lining is coated with oil or grease. Open up the gear case, and ascertain that there is sufficient oil in it, and at the same time observe the condition of the mechanical load brake. The load brake is a special brake that prevents a descending load from turning over the hoist mechanism and motor. It is frequently of the disk type with an automatic retaining band G, which grips the brake wheel A (Fig. 22) and prevents it from turning in the lowering direction. Asbestos friction material is used for lining the disks as well as the retaining band. In operation the load tends to revolve the load brake pinion F. This pinion, in turning against the helix D, is thrust endwise on the shaft and forces the disk B against the brake wheel A, which is automatically held from revolving by the retain ing band G. In this manner the hoisted load is locked and held from lowering. To lower the load, the motor is run in the lowering direction whereby the helix D is released and the pressure of the disks B and C on brake wheel A is decreased sufficiently to allow slipping between these parts. This permits the load to be lowered. In creased motor torque and speed tend to open the brake against the load reaction, increasing the lowering speed, while a decrease in motor torque and speed is overcome by the load reaction, and the movement in lowering slows down or stops. Observe the condition of the electric current collectors, trolley wires or collector rails, controllers, switchboard, and motors. CRANES, HOISTS, AND DERRICKS 245 Then, if everything so far has been found to be satisfactory, make sure that all persons are clear, close the main power switch, and pro ceed with the test of the crane. Try the foot-operated bridge brake, and make sure that the pedal does not strike the floor. Then travel the bridge at about half speed, and apply the brake. Repeat A a P in the opposite direction. Run the crane the entire length of the runway, and note any irregularities in the track, any unusual vibration, or binding of the wheels on the rails. At each end of the runway check if the bridge is square with the runway by gently striking the rail stops. Next test the trolley, remembering that very few cranes have 246 HANDBOOK OF RIGGING brakes on this motion. Move it part way across the bridge, and stop it as gently as possible by "plugging'' or reversing the motor. Finally, test the hoist mechanism by running the load block up and down several times and observing the "feel" and the sound of the mechanism. Then carefully run the block up until it causes the limit device to trip out. Repeat at a somewhat higher speed and finally at full speed to make sure that the drift will not permit the block to strike the trolley structure. Make certain that the limit device is so wired that it will open the circuit rather than close it when functioning. Next, have the regular operator take over the controls while you proceed to a position on the trolley. As the operator raises and lowers the load block at your direction, observe the action of the solenoid brake. (Make certain of your footing on the trolley and that you are clear of all moving parts. Also, keep your head low so as not to strike an overhead beam or roof truss should the bridge be moved unexpectedly.) Block the solenoid brake in the "off" position, and have the operator lift a near-capacity load. The mechanical load brake alone must hold the load. Then, if the construction of the par ticular crane will permit, block off the load brake by disengaging the pawl or the band brake, and lift the load again. The solenoid brake alone must hold the capacity load. Check the warning gong or horn, the fire extinguisher, condition of the rubber floor mat, etc. If it is an outdoor crane, make sure that the rail clamps or other anchorages against the wind are in good condition. If the crane is floor-operated, it can be controlled by a pendent push-button control box or by means of six drop cords with handles on them. In order to prevent accidentally grasping the wrong handle when the operator is also acting as the rigger, it is suggested that each handle be different from the others as a means of identifi cation. Figure 23 shows recommended shapes for the handles. The movable or mobile cranes include the locomotive crane, crawler crane, automobile-truck crane, and the smaller gasoline or storage battery cranes (Fig. 24). To inspect these cranes, have the operator lower the boom nearly horizontally or until the load block rests upon the ground; then stop the engine. Examine the boom carefully, both from the ground and by walking out on it. Strike all rivet heads with a machinist's hammer to detect any loose ones. Note all bent structural members (legs, lattice mem- CRANES, HOISTS, AND DERRICKS 247 ETC 02938 248 HANDBOOK OF RIGGING bers, gusset plates, etc.) and any parts worn by the cables. Check for excessive corrosion. Also inspect the structural members that form the anchorage for the boom hoist cable. Note any loose bolts. Strike each sheave with the hammer to detect any cracks. Of course, check the cables, anchorages, etc. Inspect the crane engine and hoist mechanism, paying attention to loose or worn pins, keys, cotter pins, broken gear teeth, etc. Check the running gear, including wheels, crawler treads, axles, gears, sprockets, turntable, rollers, center pin, and other vital parts. Make sure that the rail clamps and out-riggers are in good condition. Have the operator start up the engine and raise the boom to the normal operating position, then pick up a fair-size load and test the brake and frictions. Check the latch (if provided) on the foot brakes to ensure positive holding. Observe the capacity plate or chart on the crane, making note of the safe lifting capacity at various radii. Keep in mind that the radius is measured from the center pin, not from the hinge pin. If weights of known magnitude are available, pick them up at the maximum safe radius, handle them at normal operating speeds, ETc 0293 CRANES, HOISTS, AND DERRICKS 249 and note any tendency to overturn when suddenly stopping a descending load. On some of the smaller cranes that are subject to operation by the rank and file of employees rather than by an experienced operator, limit devices are installed on the load hoist and boom hoist, and these should be tested to ensure proper operation. Figure 25 shows an indicator that can be constructed and installed by any mechanic on a boom crane to indicate directly the safe load with the boom at any angle. After the device is installed, the boom is placed at such an angle that the radius from the center pin to the load is in agreement with the data on the name plate and the safe load marked on the dial. For instance, if the name plate reads 9,500 lb at 20 ft radius, raise or lower the boom until the radius is 20 ft by actual measurement, then paint 9,500 lb on the dial. When operating a boom crane, always make certain that the chassis is on an even keel; in other words do not have the treads or wheels on one side higher than on the other side, particularly if the load is picked up with a high boom. When the crane is out of level, there is a side bending on the boom under certain conditions, and failure to recognize this has resulted in fatal accidents. Do not slew the crane too rapidly while carrying a load, for not only is there danger of striking persons but there is also the possi bility that the centrifugal force thus developed may upset the crane. For jobs such as steel erection, it is quite common to unbolt a two-piece boom at the middle of its length and insert an extension piece for the purpose of lengthening the boom. Too much empha sis cannot be placed upon the necessity of carefully checking the boom before picking it up again. In one instance the mechanics accidentally left out one of the bracing members at the splice, thus making discontinuous the system of lattice bracing on the boom. When the load was picked up, the boom legs folded zigzag at the splice and the boom collapsed with the loss of several lives. So always check and double-check the boom splices before picking up the boom from the horizontal position. There are three principal types of power-operated derricks: the guyed type, the A frame, and the stiff-leg types. (And there are the portable hand-operated breast derrick, sulky derrick, tripod derrick, and others.) Let us first consider the size of the boom timbers (steel booms are complicated and each must be calculated individually), which F-TC 0 2 941 CRANES, HOISTS, AND DERRICKS Table I. Safe Loads on Yellow Pine Booms (In tons.) Radius to load, ft yi U1AI1U) 11/ 10 15 20 25 30 35 40 Mast 17 ft high 6 X 6 X 20 5 5 5 6 X 6 X 30 2 2 2 1 1 8 X 8 X 20 10 10 10 8 X 8 X 30 6 6 6 6 5 8 X 8 X 40 3 3 2 2 i Mast 30 ft high 8 X 8 X 30 11 11 11 11 10 8 X 8 X 40 7 6 5 4 2 1 10 X 10 X 30 21 21 21 21 21 10 X 10 X 40 14 14 14 13 11 9 8 10 X 10 X 50 9 8 6 5 3 1 Mast 40 ft high 10 X 10 X 40 17 17 17 16 14 12 10 10 X 10 X 50 11 10 8 6 4 2 12 X 12 X 40 28 28 28 28 28 26 24 12 X 12 X 50 20 20 20 17 15 12 10 12 X 12 X 60 14 13 10 7 5 2 14 X 14 X 40 42 42 42 42 42 42 41 14 X 14 X 50 31 31 31 31 29 26 23 14 X 14 X 60 23 23 22 19 16 13 10 Gin pole--no mast 6 X 6 X 20 4 8 X 8 X 20 8 8 X 8 X 30 7 6 10 X 10 X 20 14 10 X 10 X 30 13 11 10 X 10 X 40 11 10 9 12 X 12 X 30 20 18 12 X 12 X 40 18 17 15 12 X 12 X 50 16 15 14 11 14 X 14 X 30 30 26 14 X 14 X 40 28 25 23 14 X 14 X 50 25 23 21 20 14 X 14 X 60 21 20 18 15 12 45 7 20 7 251 50 5 17 3 ETC 02942 252 HANDBOOK OF RIGGINGare of approximately the same strength whether used on a derrick or as a gin pole. Table I indicates the safe live load for longleaf pine booms of the following dimensions, provided their length is not in excess of that indicated. Masts for guy derricks are usually made one size larger in cross section than the booms and are usually 10 ft longer. Figure 26 gives the approximate maximum lift of the load hook of a derrick with the boom at various radii, taking into consideration, of course, the height of the upper and lower blocks and the hook. On permanent installations, guy derricks always have a large number of guys. For temporary jobs four are quite common, but it is important that they be evenly spaced. An odd number is preferred. With an even number, when the boom is close to one guy, all the strain comes on the opposite guy. To facilitate estimating the stress on the guy, Fig. 27 will be of assistance. Draw a diagram to scale of the derrick, making certain that the guy is at the correct CRANES, HOISTS, AND DERRICKS 253 angle. Then draw a triangle of forces (Fig. 27b). Assume that the load is 4 tons, or 8,000 lb; then on the diagram draw a vertical line ge to any suitable scale. If 1 in. = 10,000 lb is used, then 8,000 lb would be represented by a length of 0.8 in. From the top Fio. 27. Typical stress diagrams for calculating the stresses on boomt mast, and guys of a derrick. of this line draw a line gh parallel to the topping lift CB, and from the bottom of the vertical line draw a line ef parallel to the boom AB. These lines cross at point k. Using the same scale of 1 in. = 10,000 lb, the stress on the boom can be determined by SCALE IN POUNDS (b) tc? Fio. 28. Typical stress diagrams for calculating the stresses on a gin pole and its guys. measuring the length of line ek, while the load on the topping lift is indicated by line gk. Now, knowing the pull of the topping lift on the head of the mast, we shall draw another diagram of forces (Fig. 27c) in which a line gk ETC 02944 254 HANDBOOK OF RIGGING 3: OR TO SUIT CUT AWAY FIBRE TO CLEAR CHAIN HOOK IT ORILI II H" r-i" l^" BRASS PIPE / T BRASS^ 3}" A" DRILL r r -u" 4 1.6rCHA FIBRE/ BLOCK (6j iS} BRASS' BOLTS rI ORIU HOLES TO SUIT conouit straps Fig. 29. Shop details for a limit device for the hoist motion of a gasoline-driven crane. I ETC 02945 CRANES, HOISTS, AND DERRICKS 255 is reproduced (the same length and at the same angle). From gdraw a line parallel to the mast (vertical) and a line from k parallel to the guy CD. These lines cross at m. Using the same scale, measure the length of line km to determine the stress on the guy and line gm to find the load on the mast. These determinations Fio. 30. A special shackle for readily changing from a three-part to four-part fall, or vice versa, with the minimum injury to the cable. will be accurate enough for all practical purposes. It is then necessary to install a guy rope of adequate strength to carry this load safely. Likewise the strain on the guys for a gin pole can be determined by a stress diagram. As shown in Fig. 28a, the gin pole is drawn to 256 HANDBOOK OF RIGGING scale, with one guy assumed to be taking the entire load. (If two guys are arranged not more than 90 deg apart, in plan, the stress on each is the same as on one guy taking all the load.) Line uv is drawn vertical to represent the load, uw is parallel to the guy, and vw is parallel to the pole, thus indicating the respective stresses. One very important point to be stressed, particularly on guy derricks and gin poles, is the need for anchoring the base of the mast or boom, respectively, so they will not kick out under load. The amount of this kick can be roughly determined by using the stress diagram (Fig. 28c). Draw a line vw (Fig 28c) equal and parallel to vw in Fig. 28b, or use the line in that diagram; then draw a vertical line wx, which will represent the load on the ground caused by the boom, and a horizontal line vx, which will represent the magnitude of the "kick" caused by the boom. The necessary blocking or lashing should be provided to prevent this kickback. Likewise, do not neglect to consider the horizontal pull on the hoisting cable between the base of the mast and the hoist engine. If the tensions on the load and boom cables are, respectively, say, 4,000 and 3,000 lb, then the foot blocks and the hoist engine must both be anchored to resist a force of 7,000 lb. This can be accom plished by lashing both to building columns or other anchorages or by installing shoring timbers between them. CHAPTER XVII CHAIN HOISTS No general description is needed of a chain hoist, for any rigger worthy of the title is well acquainted with it. There are, however, four types of chain hoists, namely, the spur-geared, the screwgeared, the differential, and the pull-lift types. The first three types are used for hoisting, while the last type is used primarily for pulling in a horizontal direction. For frequent use and where a minimum of labor is available to operate it, the spur-geared hoist is recommended. Although the cost of this hoist is the highest, it will prove most economical to operate. Where the hoist is to be used infrequently, such as in a public garage, and where the first cost is a consideration, the screw-geared hoist is commonly used. For very infrequent use, such as in a private garage and where light weight and low cost are important, the differential hoist finds its place. In the screw-geared hoist about 85 per cent of the energy the operator exerts is converted into useful work lifting the load; the other 15 per cent is wasted in overcoming friction in the gears, bearings, chains, etc. The screw-geared hoist transforms from one-third to one-half of the energy into useful work, while the differential hoist utilizes only about one-third of the energy input. Some hoist manufacturers produce a special ball-bearing differen tial hoist, which has a higher efficiency. The screw-geared and differential hoists have sufficient internal friction to prevent the load from running away on the lowering motion. Such is not the case with the spur-geared hoist, so a load brake similar in principle to that described in Chap. XVI is incorporated in it. All chain hoists are designed with their lower hooks as the weak est parts, the two hooks not being interchangeable. In other words, if the hoist is overloaded it is first indicated by the spreading or opening up of the lower hook. As designed, the inner contour of the hook is an arc of a circle, and any deviation from a circle is evidence of overloading. If sufficiently overloaded, the hook will gradually straighten out (see Fig. 2 in Chap. IV) until it finally 257 ETC 02949 CHAIN HOISTS 259 is no excuse whatsoever for overloading any chain hoist to this extent. When a hook has been severely overloaded, it should be replaced by a new hook. Never attempt to forge a spread hook back into shape. A new hook is too cheap to warrant taking any chances r\ with an overloaded hook. If there is evidence of severe overload ing, have the chain hoist sent to the main tenance shop for a complete internal ex amination and overhaul. Pay particular attention to the wear on the brake caused by the excessive load. Occasionally in a manufacturing plant a chain hoist is used for lowering material i into oil baths or for holding material while it is sprayed with oil. In either case the ! load chain may be coated with an excessive ; amount of oil, and when the hoist is oper ated the oil is transferred to the sprocket and may eventually find its way into the Fio. 3. Typical- differ ential-type chain hoist. (Yale <& Tovme Mfg. Co.) Fio. 4. This hook was condemned by the safety in spector. Upon removal from the chain hoist the worn link was discovered. load brake, thus reducing its holding power. For service such as this the screw-geared or differential hoist should be used. Only forged steel should be used for hoist parts that are subject to stress, such as the hooks, swivels, chain, sprocket, gears, and similar parts. Yet some hoists are made by reputable manufac turers with some such parts made of cast iron or malleable iron. ETC 02950 260 HANDBOOK OF RIGGING la inspecting a chain hoist it is not only necessary to examine the hooks and the general appearance of the chain carefully, but a more thorough examination is very important. Figure 4 shows a hook of a chain hoist that was used in an industrial plant for con tinuous service on three shifts. A safety inspector observed that the hook was badly worn, and he ordered it replaced by a new hook. However, he failed to inspect the chain thoroughly. Much to the surprise of all concerned, when the hook was removed, it was dis covered that the chain was in even worse condition than the hook, as indicated by the one link remaining attached to the hook. For pulling horizontally, such as when removing tree stumps, boiler tubes, or vehicles stuck in the mud, a screw-geared chain hoist or a special lever-operated hoist (sometimes called a pull-lift) is recommended. In this service it is almost impossible to estimate even roughly the load imposed on the hoist, and there is a possi bility of overloading it. However, if only one man pulls on the hand chain of the chain hoist, or if only one man operates the lever of the pull-lift without lengthening it by means of a piece of pipe, then there is little or no danger of overloading. Table I. Data on Spub-geared Chain Hoists Rated capacity, tons Pull on hand chain to lift Hand chain overhauled to rated load, lb raise load 1 ft, ft 1 75. 100 2 no 3 102 4 112 5 98 6 115 8 120 10 125 31 35 43 70 85 128 128 170 213 In order to develop a standard for inspecting the load chains of chain hoists, one user of a large number of hoists has developed a set of feeler gauges shown in Fig. 5. The opening at the wide end of the gauge is used to caliper a chain link in order to make certain that the proper gauge is being used. Then, with the chain hanging freely, attempt to insert the small end of the gauge between the links as illustrated. If it is too wide, it indicates that the links have elongated and narrowed down due to overloading. CHAIN HOISTS 261 Test Gauges fob Chain Hoists, Yale and Towne Spur-geared Fig. 5. Test gauge designed by user of many chain hoists for checking the condi tion of the load chain. (Consolidated Edison Co. of New York., Inc.) If the gauge enters the link on the first step only (stamped "OK"), it indicates little or no wear on the links. If it enters to the second step (stamped "R" to indicate "recondition"), there is evidence of considerable wear and/or stretch, and the chain hoist should be sent to the maintenance shop for reconditioning. Should the gauge enter the link to the third step (stamped "C" for "condemn"), it shows excessive wear and/or stretch and the chain should be condemned and replaced by new. ETC 02952 ETC 02953 ETC 02954 264 HANDBOOK OF RIGGING In raising a load on a jack, it is important that it should not be raised so high as to run the ram or screw or ratchet out of the base and thereby drop the load. Jacks designed in accordance with theAmerican Standard Safety Code for Jacks have "positive stops to prevent overtravel unless this is impracticable, in which case it shall carry a warning to that effect." Always make certain that the jack is in a true vertical position (when lifting) and resting on a good footing. Never place a jack directly on the ground, even though the soil appears to be firm. If the load is to be raised in its entirety by several jacks, it should be secured laterally by struts to prevent all the jacks from upsetting in unison. After the load has been raised to the required height, shoring or cribbing blocks should be placed under the load and wedged to take the load off the jacks or to be ready to take the load should a jack fail. When operating a jack, particularly the ratchet and lever type, do not lean over the lever unless you are holding onto it. Hydraulic jacks are filled with special hydraulic fluid, which will not freeze. Never use water in a jack. Keep the threads of a screw jack free from grit and dirt. Lubricate the screw frequently. Hydraulic jacks have the safe load indicated on the name plate, but screw jacks are occasionally not labeled. Nevertheless, it is possible to overload a screw jack and cause it to fail. A very rough estimate of the safe load on a screw jack can be made by using the following formulas: W = 31,400 dt or W = 14,000 cP, whichever is the lesser where W = safe load on jack, lb d = diameter of screw at root of threads, in. t = thickness of nut, or length of thread engaged, in. The load that it should be possible to lift on a screw jack should be approximately as indicated by the following formulas: . ,,-set where W = load, lb / = force on lever (assumed to be 120 lb) L = length of lever, in. P = pitch of screw thread, in. r = average radius of screw thread, in. ETC 02955 JACKS, ROLLERS, AND SKIDS 265 Each jack should be thoroughly inspected periodically, depend ing upon the service conditions. Inspections should be made not less frequently than 1. For constant or intermittent use at one locality, once every 6 months. 2. For jacks sent out of the shop for special jobs, when sent out and when returned. 3. For a jack subjected to abnormal load or shock, immediately before and after making the lift. These inspections should be made by the foreman. Fig. 2. Unloading a 120-ton generator stator from a lighter prior to skidding it into the power plant. (Consolidated Edison Co. of New York, Inc.) After a jack has been repaired and before it is returned to serv ice, it should be tested as required by the American Standard Safety Code for Jacks, namely, 1. A load equal to the rated capacity of the jack shall be lifted to within 1 in. of its full travel under the prescribed operating con ditions for the particular type of jack being tested. 2. An additional load equal to one-quarter of the rated load shall then be added to the original load applied to the jack. Any evi dence that any part of the jack is stressed beyond the yield point of the material forming any part shall disqualify the jack for service. 3. When testing a jack it is important that, as the load is lifted, blocks be placed under the load to hold it in event the jack should ETC 02957 CHAPTER XIX HOIST SIGNALS To reduce to the absolute minimum the number of accidents due to faulty or misunderstood signals when handling loads with cranes and hoists, it is deemed desirable to include this chapter. The signals should be thoroughly understood by the signalman and the operator, and only the approved signals should be used. It may be desirable to post a copy of the signal code in the crane cab and another copy where the signal man can occasionally refer to it. The crane operator should take signals from no one but the authorized signalman. Where it is necessary to change signalmen frequently, they should be provided with one arm band, conspicu ous hat, glove, or other "badge" of authority, which will be in the possession of the man in authority at the time. Figure 1 indicates the hand signals adopted by the ASA. With forearm vertical and forefinger pointing upward, move hand in a hori zontal circle. With arm extended and palm downward, wave hand down and up. With arm extended and fingers clenched, jerk hand horizontally, pointing the direction with thumb. Fig. 1. Standard one-hand crane signals. 267 ETC 02959 HOIST SIGNALS 269 For derricks and special temporary hoists where the hoist engi neer cannot observe the signalman, bell or whistle signals may be used, different sounding bells being used for load hoist and boom hoist motions. The signals customarily used are as follows: Hoist Signals To hoist............................................Two quick signals To lower.......................................... Three quick signals To stop.............................................One quick signal For emergency stop...................... Series of quick signals For slow or cautiousmotion, use slower signals and hold the last signal until it is desired to stop the motion. Releasing the signal cord indicates "stop." ETC 02960 CHAPTER XX ACCIDENT PREVENTION This book would not be complete without reference to recom mended safe practices of riggers and the safeguarding of their equipment. Practicing safety in his work does not bring discredit upon a worker as some people seem to think. On the contrary, if an operation is made safe, it can be done more quickly, as it will be done correctly and in an orderly fashion. Certainly no one wants to get injured, so using care will be beneficial to both the worker and the employer. The first rule in safety is the Golden Rule: Do unto others as you would have them do unto you. Use a little forethought before you drop or throw things from an elevation to the ground by warn ing those below. Do not allow persons to walk below a suspended load or near a slack cable that may suddenly be pulled taut. Avoid frightening anyone intentionally or by otherwise engaging in horseplay. Loose clothing should not be worn where it might be caught in moving machinery. Hard fiber safety helmets are generally worn by men at work where exposed to falling bolts, nuts, rivets, or other small objects. Safety shoes should be worn by all men on all rigging and construction jobs. This means by the foreman as well as by his men. These shoes with pressed steel caps over the toes cost no more than high-grade work shoes but are usually made of better materials and with better workmanship, and in addition they offer protection to the toes. A worker had his foot run over by a wheel of a truck, and although the wheel load was in excess of 3,000 lb, his toes were uninjured. Safety shoes can be obtained in dress oxfords as well as in high and low model work shoes, and many men wear safety shoes even for dress occasions. Of course, shoes of any type should be kept in good repair and with unbroken soles. Where a man is exposed to the danger of falling a great distance, and where local conditions do not prohibit it, a life belt should be worn. The tail line should be as short as practicable, and it should be made fast to a substantial anchorage above the man's ACCIDENT PREVENTION 271 waist. The mere wearing of a life belt just to comply with ruies does not ensure safety. An instance may be cited of a painter who was observed at work painting the underside of the high roof over a traveling crane. A 24-ft extension ladder was placed on the bridge girder of the traveling crane, and its upper end lashed to the roof truss above at a point nearly 100 ft above the floor. Yes, the painter wore a life belt, and he had the tail line securely an chored. But the tail rope was not made fast to the truss member, but to the railing on the crane walkway 20 ft below him. In other words, had he fallen, he could have dropped about 40 ft before the slack in the rope took up. This would have meant as certain death as if no life belt had been worn. Where there is a hazard of dust and flying particles entering the eyes, safety goggles with hardened glass lenses should be worn. These offer protection to the eyes from small flying objects such as burrs from the mushroomed head of a cold chisel, chips from a chipping hammer, etc., and they will not shatter even though struck by a flying object of considerable weight and velocity. Do not leave bolts, tools, slings, and other equipment lying on beams or other supports where they can become dislodged and fall onto passers-by. The gears, couplings, and other hazardous parts of hoist engines should be protected by proper guards, and they should be kept in place at all times when the machine is in service. Watch out for the fingers when operating dogs on ratchets of hand-operated hoists. If the hoist is motor-operated, the frame of the machine should be electrically grounded to prevent possible electric shock or electrocution. Gasoline engines should not exhaust their poisonous gases into confined locations or pits where men may enter unsuspectingly and be asphyxiated. Care should be used when gassing up hoist engines. Only an approved safety can with a self-closing cap on the spout should be used for transporting gasoline. Gasoline vapors are heavier than air, and if gasoline is spilled, the vapors will flow like water to the lowest point, where they will accumulate. Should a spark from a welder's torch or from any other source drop into the vapor, a flash or violent explosion may result. Of course, gasoline should never be used for cleaning or degreasing purposes. All injuries, however slight, should be reported, and first-aid treatment given at once in order to avoid infections and other complications at a later date. 272 HANDBOOK OF RIGGING Accident prevention is very important in all trades, but in perhaps no other trade is the danger of serious or fatal accidents so great as in rigging. Therefore, the rigger as a matter of self- preservation should be wholeheartedly interested in safety. The description of a few unusual accidents and near accidents may be of'interest. Housings are frequently placed on hooks as a safety precaution to prevent accidental detachment of the sling, but in one instance at least a mousing was the direct cause of a serious accident. The sling was placed on the hook and the hook properly moused, but when the latter was being raised off the floor, the stiff sling rotated unnoticed and its weight rested on the mousing (Fig. 1). The mousing was strong enough to take the weight of the rope falls but failed when an additional load was applied. In another instance a 6-ton chain hoist was suspended from a sling attached to an Fig. 1. The upper hook of the scaffold rope fall was attached to a sling and moused (while lying on the floor). When the sling, and the pulley block, was hoisted into position the sling be came displaced and rested upon the mous ing, unknown to the rig ger. The scaffold was hoisted into position, but when the rigger climbed a ladder and stepped onto the scaffold the mousing faded and the scaffold fell. overhead timber. As is common knowledge, chain hoists of this capacity hang on an even keel when under load, but when not loaded they tilt at a considerable angle owing to the heavy gear housing being off to one side of the upper hook. In this case a load of about 4 tons had been lifted a few inches when a part of the rigging failed and dropped the load without personal injury or property damage. But being suddenly relieved of its load, the chain hoist momentarily swung to beyond the normal tilted position and de tached itself from the supporting sling and fell, narrowly missing the men below. As a safety precaution always stay out from under the hoist as well as from under the load. Figure 2 shows a typical chain hoist of 6 tons' capacity with the upper hook as it was at the time of the accident. To prevent a recurrence, swivel the hoist 180 deg relative to the hook so that it faces in the opposite direction. This recalls to mind an accident that resulted from using two single slings at a very wide, flat angle. As shown in Fig. 3 a portion of a loading platform had to be made removable in order ETC 02963 "' a.,. ACCIDENT PREVENTION 273 to permit trucks to pass by in an alley, at which time this part of the platform was placed upon the permanent platform. This meant that there was only a limited headroom under the monorail- type electric hoist. There was no means of attaching the two single slings to the platform except at its sides, and this meant having the slings at about 15 deg to the hori zontal. Under normal conditions this is poor practice, but as -in. wire-rope slings were avail able and their safe capacity at this angle was about 1,260 lb while the load was only about 1,000 lb, it was believed that the load could be safely lifted. But the rigger failed to take one fact into consideration. The contour of the inner part of a hook is an arc of a true circle from about 45 deg above the horizontal at the back of the hook to about 45 deg below the horizontal at the side toward the bill. The one sling, pulling at 15 deg below the horizontal toward the bill of the hook, slid up the bill to the safety finger. The finger, not being designed for a force of this magnitude, sprang out of shape, the hook tilted, and the sling slipped off the bill of the hook and allowed the load to drop. So when ever it is necessary to use slings at a wide angle, use a two-leg sling with a ring on the hook rather than two single slings placed on the hook. In one large plant handling bulk material, a Fig. 2. A typical 6-ton chain hoist that became de tached from the supporting sling when the load was suddenly released. gang of laborers was assigned the task of moving a large roll of wide conveyor belting from the storehouse to a location below a hatch in one of the conveyor bridges. Then riggers were to hoist the load up through a hatch to its destina tion. These laborers, who were a little above the average in ambition but a little below par in intelligence, decided to hoist the load themselves. They located some old rope that had been discarded, but not destroyed, and some pulley blocks. There was a car puller handy, so they got a hitch on the load and began to hoist. When the load was about 6 in. off the ground, one strand of the old rope snapped, and the broken ends began to unlay, so they immediately landed the load. ETC 02964 274 HANDBOOK OF RIGGING The laborers went into a huddle to decide what to do next, for they realized that the strand ends would not pass through the pulley blocks. So they carefully laid the broken strand ends back into their original positions in the rope, then wrapped the rope with friction tape at this point to hold them in place, after which they proceeded to hoist the load. Strangely, they did succeed in hoisting it about 50 ft when the other two overloaded strands failed and the load dropped. These men should have realized that if three strands would not support the load, then certainly two strands would not. This incident demonstrates the need for always cutting all discarded rope into short lengths suitable only for hand lines, etc. In another plant an automobile-truck crane had the load cable anchored to the boom by an ordinary wedge socket. The crane operator, in picking up a load, carelessly allowed the load block to be raised beyond the safe limit. The bolt of the sheave block struck the wedge and forced it back in the socket (Fig. 4), thus releasing the end of the cable, which pulled out and dropped the load. To prevent recurrence, a cable clip was put on the two parts of the rope just ahead of the wedge. An unusual accident occurred that resulted in minor injuries to a man working on a special lightweight 28-ft extension ladder. ACCIDENT PREVENTION 275 Through the coincidence of the nine unsafe conditions the accident occurred (Fig. 5). 1. Dip grain existed in the side rails, and this always causes weakening of a wooden member (see Chap. VI, Fig. 18). 2. When the hardware was placed on the ladder sections, it was so installed that the dip grain was on the lower or tension side of the side rails, and dip grain is exceptionally weak in tension. Fia. 4. Raising the load block too high caused this cable to pull out at its socket. 3. The side rails were both cut from the same plank, and thus both rails contained this defect. They were placed in the ladder in the same relative position as in the plank; thus the defects were both at the same place in the ladder. 4. The ladder builder apparently paid no attention to the dip grain, for he drilled his rung holes in both rails in the remaining good (and overstressed) wood opposite the defect. 5. In the course of its use the ladder must have been allowed to fall and strike a relatively sharp cornered object, for also in the 276 HANDBOOK OF RIGGING 0 Dip grain, caused by a knot in the adjacent wood before sawing it up, re duced the strength of the side rail materially. 0 Dip grain is particularly bad when on the tension side of a beam (the under side of a ladder side rail) as the lens-shape piece of wood tends to drop out. 0 Both side rails had been cut from the same plank, and placed in the ladder in their original relation to each other. Hence the dip grain caused both side rails to be weakened at the same point. 0 Ladder builder carelessly drilled the rung holes in the remaining good wood at the dip grain. 0 The ladder had been damaged and both side rails at the only remaining good wood were crushed. 0 Ladder was extended until bottom of fly section was at weak spot. This caused additional stress at this point. 0 Ladder was placed at a too-low angle, thus increasing the stress on side rails. 0 Man was standing on rungs at weak point on ladder. 0 Man was exceptionally heavy, weighing over 200 lb. ACCIDENT PREVENTION 277 remaining good wood opposite the dip grain in both side rails were crushed or bruised spots to in. deep. 6. The defects were in the lower section of the ladder, and as the fly section was raised, its lower end was at the rung that was inserted in the weakened wood. And as is readily understood, at the upper end of the overlap of the sections of an extension ladder there is a pull of one section away from the other, while at the lower end of the overlap the sections are forced together, thus placing an additional bending load on the lower section at this point. 7. The ladder was erected at a bad angle (not steep enough) and therefore was subjected to excessive bending stress. 8. The man stood on this particular rung to work and to lift a small object. ' 9. The man using the ladder was extra heavy, weighing over 200 lb. This was the man's unlucky day, for if any one of these condi tions had not prevailed, he probably would not have been injured. It was a very unusual set of conditions, but there is no reason why similar, simultaneous conditions cannot cause accidents in the future. It is fitting that a few words be said here relative to the physical strength of men. If done in a proper manner, a man can lift loads of considerable weight; yet lifting a comparatively light load improperly may result in a hernia. However, with power hoisting equipment readily available as it is today, there is little need for manually lifting heavy loads. Before attempting to lift any load, estimate its weight and be sure that it is not too heavy for you to lift. Get your feet on a good flat surface where they will not slip and as close to the object as practicable. Then squat down, bending the knees but keeping the back straight. Get a good firm grip on the object, and holding it close to the body, lift with the leg muscles (Fig. 6). Remember that the leg muscles are stronger than those in the back. If the object is to be moved only a very short distance, do not twist the body, for that movement might result in a severe strain. Rather stand up, then step to the desired location and set down the object. To place a load on the floor, reverse the above procedure. Keep ing the' back straight, bend the knees and carefully lower the object until one comer or one edge touches the floor, then carefully remove your fingers and allow the other side of the object to rest on the floor. As mentioned previously, the wearing of safety shoes is a "must" on all jobs where loads are to be lifted manually. ff 'i 1 ETC 02968 ETC 02969 ACCIDENT PREVENTION 279 If the load is to be lifted say to the height of the shoulders, lift it in the manner described above and place it on a bench, table, or ledge. Then repeating the procedure, bend the knees and get a new grip on it. Keeping your back straight, straighten your knees as you lift the load. In pushing or pulling an object, such as a suspended load, a force of 110 to 130 lb may ordinarily be exerted. In prying with a crowbar, it may be expected that a man could ordinarily push or pull about 100 lb, lift with about 200 lb, and push downward with a force not greater than his own weight. In turning a crank, such as on a winch, about 0.1 hp may be exerted by a laborer for 8 hr. For a few minutes' duration, he may even exert as much as | hp. CHAPTER XXI CARING FOR THE INJURED It is important in a handbook of this kind that the care of injured persons should not be overlooked. Except in isolated construction and logging camps, there are few rigging jobs where medical attention cannot be obtained in a reasonably short time. Hence, this chapter will deal only with the handling and care of persons who are critically injured until such time as the doctor or ambulance arrives. Where jobs are in progress in isolated locations, a copy of the Red Cross first-aid manual should be kept handy for ready refer ence if needed. Handling Injured Persons. The first and foremost rule is "do not move a seriously injured person unless absolutely neces sary." If a man has fallen any distance, do not move him except to straighten his body out on the floor or ground in order to make him as comfortable as possible while waiting for the ambulance. Should his spine have been injured, moving him may mean instant death. In trying to get an injured man into an automobile, the sharp end of a broken rib may pierce vital organs and cause serious complications. Even moving a man with a broken leg may result in a simple fracture, which the doctor can readily set, be coming a compound fracture with the jagged end of the bone piercing and protruding through the skin. If the patient is on the floor or ground, try to make him as com fortable as possible. Offer him a cigarette, for this will usually help him to relax. Fold up a coat and place it under his head, but do not raise it any more than necessary, and cover him with a blanket. If the ground is cold, roll up a blanket and place it close beside the patient's body. Then have three or four men all kneel on one knee (say the left knee) at the other side of the patient and slide both their hands, palms upward, under his body. At a given signal all men gently lift the patient a few inches while another man unrolls the blanket under him, and he is gently lowered onto it. The blanket is then wrapped over the patient to give the necessary warmth. 280 CARING FOR THE INJURED 281 To place an injured person on a stretcher, have three or four men lift him in this manner and rest him on their knees. Another person should place the stretcher where the patient has been lying, and he is then gently lowered onto the stretcher. . To carry a severely injured person to an ambulance the "threeman carry" (Fig. 1) is used. As described in the preceding para graph, three men kneel on one knee and slip their hands, palms upward, under the victim. Then in unison they lift his body and Fig. 1. The three-man carry is used for lifting a person onto a stretcher. It can also be used for carrying a person with severe back, chest, or leg injuries. (National Safety Council.) rest it on their extended knees. At a signal they all stand upright and hold him close to their chests. Those carrying the patient should all walk in step, taking short uniform steps. If necessary to pass through a narrow aisle or doorway, walk side-step in unison. Should the patient not have any broken or dislocated bones, yet be in an out-of-the-way place, it may be necessary to carry him to the ground and thence to the ambulance. If he is not too heavy, the "fireman's carry" (Fig. 2) can be used. With the patient lying face down on the floor, kneel above his head and place your arms under his armpits and grasp him at his back (Fig. 2, Step 1). Next, raise the patient up onto his knees (Step 2), ETHYL CORPORATION DEVELOPMENT SECTION LIBRARY baton pdit: 282 HANDBOOK OF RIGGING grasp him around his waist, and raise him onto his feet. Holding his left wrist with your right hand, "duck" your head under his arm so that his head rests on your left shoulder (Step 3). Still retaining hold of his left wrist, quickly stoop and allow his body to fall across your back at your shoulders (Step 4); at the same time place your left arm around one or both of his legs at the knees. Then transfer hold of his left wrist from your right to your left hand, and stand up (Step 5). You are then free to walk or go up or down stairs carrying the patient and with your right hand free to grasp handrails, etc., to assist you in your trip. 3 45 Fio. 2. The fireman's carry allows one hand free to grasp ladder, stair railing, etc. (.National Safety Council.) In setting down the patient, the reverse procedure is followed. Kneel on your right knee, then allow him to slide off your shoulder and rest sitting on your extended left knee, and finally allow him to slip down onto the floor. For transporting a person with an injured foot or leg the "twoman two-hand cany" is used. An unconscious person having no broken bones can also be carried in this manner, as shown in Fig. 3, which is self-explanatory. For one lone rescuer to remove an injured man from a location with restricted headroom, lay the victim on his back and tie his wrists together with a handkerchief or rope. Kneel, straddling the patient; put your head between his arms with his tied wrists at the back of your neck; and crawl on your hands and knees, dragging him along as you go. To remove an injured man from a pit or a tank manhole or to lower him from some elevated location, if no other means is avail able, make use of the rescue hitch shown in Fig. 84 in Chap. II. Form a bight about 6 ft from the end of a rope, placing this bight just below the patient's seat as he lies on the floor. Cross the ropes over his abdomen, then cross them again under his back just below TWO-MAN TWO-HANDS) SEAT CARRY Fig. 3. The two-man two-handed seat cany is used for handling persons with injured feet or ankles or uninjured unconscious persons. (National Safety Council.) the shoulders, and finally pass both parts of the rope under the armpits. Then attach the short end to the hoisting rope some distance above his head, using a bowline. This will afford a reasonably comfortable sling with which a man can be hoisted out of a manhole or other small opening. Another method of removing an injured or unconscious man from a manhole or other restricted space is to lash him to the ladder that you used to reach him. The men above will then raise the ladder (with the victim) one rung at a time until he is out of the manhole. Serious Bleeding. Look at once for serious bleeding, and if observed waste no time in finding the wound from which the blood is flowing. It may even be concealed by clothing. Bright red blood coming out of the wound in pulsations with each beat of the heart indicates bleeding from an artery; dark red blood coming out in a steady flow is indicative of bleeding from a ruptured vein. ETC 02974 284 HANDBOOK OF RIGGING In all cases of arterial bleeding, pressure must be applied without- a moment's delay to the artery between the wound and the heart. When bleeding is from a vein or capillary, apply pressure on a clean handkerchief (or better yet a sterile compress, if available) placed directly on the wound. Figure 4 shows the main arteries of the hu man body and the "pressure points" where pressure must be applied to arrest bleeding in the smaller arteries beyond. Study the drawing, and mem orize the pressure points; you may find yourself in a position some day where your knowl edge of the pressure points may save a human life. Apply pressure at once with your thumb. If the wound is on the arm or leg, have some one apply a tourniquet while you still maintain pressure with your thumb. A tour niquet is made by stretching a handkerchief out by the diagonally opposite comers and wrapping it around the limb at the proper place, with a wadded-up handkerchief or Fig. 4. Pressure points, or points where pressure must be applied to arteries to stop the loss of blood in arterial bleeding. other compress placed under it and directly on the arteiy feeding the wound. Then in sert a pencil, stick, or other object in the handkerchief, and like a Spanish windlass twist it so as to tighten the tourniquet and squeeze the artery. The thumb pressure may then be released. If medical aid is delayed, loosen the tourniquet every 20 nun for a few seconds to allow circulation in the limb, even though it means the loss of a little blood. Otherwise, stagnation may cause gangrene to set in. ETC 02975 CARING FOR THE INJURED 285 Resuscitation. In a case of electric shock, do not move the victim except to free him from contact with the live conductor.. Every second counts, so begin resuscitation at once, right at that location. Victims of gas poisoning must be moved far enough to get them out of the gaseous atmosphere and into good fresh air before starting artificial respiration. If a drowning victim is brought up onto a beach, place him with his head downhill so that the water will drain from his throat and sinuses. Otherwise, the procedure is the same for all three types of respiratory cessation. 1. Lay the patient on his belly, one arm extended directly over head, the other arm bent at elbow, and with the face turned out ward and resting on hand or forearm so that the nose and mouth Fig. 5. Artificial respiration. Position in which patient should always be placed and kept until conscious. Also, first position for operator starting artificial respi ration. (Consolidated Edison Co. of New York, Inc.) are free for breathing (see Fig. 5). Have someone else loosen the victim's belt and collar, then remove false teeth, tobacco, gum, or other foreign material from his mouth. 2. Without a moment's delay kneel, straddling the patient's thighs with your knees placed at such a distance from the hip bones as will allow you to assume the position shown in Fig. 5. Place the palms of the hands on the small of the back with fingers resting on the ribs, the little fingers just touching the lowest rib, with the thumb and fingers in a natural position, and the tips of the fingers just out of sight. 3. With arms held straight, swing forward slowly so that the weight of your body is gradually brought to bear upon the patient. The shoulders should be directly over the heel of the hands at the end of the forward swing (see Fig. 6). Do not bend your elbows. This operation should take about 2 sec. 4. Now immediately swing backward so as to completely re move the pressure (see Fig. 7). ETC 02976 286 HANDBOOK OF RIGGING 5. After 2 sec, swing forward again. Thus repeat deliberately twelve to fifteen times a minute the double movement of com pression and release, a complete respiration in 4 or 5 sec. 6. Continue artificial respiration without interruption until natural breathing is restored (if necessary, 4 hr or longer) or until a physician declares the patient is dead. Fia. 6. Second position of operator giving artificial respiration. (Consolidated Edison Co. of New York, Inc.) 7. As soon as this artificial respiration has been started and while it is being continued, an assistant should loosen any tight clothing about the patient's neck, chest, or waist. Keep the patient warm. Do not give any liquids whatever by mouth until the patient is fully conscious. 8. To avoid strain on the heart when the patient revives, he should be kept lying down and not allowed to stand or sit up. If the doctor has not arrived by the time the patient has revived, Fig. 7. Third position of operator giving artificial respiration. (Consolidated Edison Co. of New, York. Inc.) he should be given a stimulant, such as one teaspoonful of aromatic spirits of ammonia in a small glass of water or a hot drink of coffee or tea, etc. The patient should be kept warm. 9. Resuscitation should be carried on at the nearest possible point to where the patient is found. He should not be removed CARING FOR THE INJURED 287 from this point until he is breathing normally of his own volition and then moved only in a lying position. Should it be necessary, due to extreme weather conditions, etc., to move the patient before he is breathing normally, resuscitation should be carried on during the time that he is being moved. 10. A brief return of natural respiration is not a certain indica tion that resuscitation may not have to be resumed. Not infre quently the patient, after a temporary recovery of respiration, stops breathing again. He must be watched, and if natural breathing stops, artificial respiration should be resumed at once. 11. In carrying out resuscitation it may be necessary to change the operator. This change must be made without losing the rhythm of respiration. By this procedure no confusion results at the time of change of operator and a regular rhythm is kept up. Continue the artificial respiration for 4 hr or until rigor mortis has set in. Breathing has been known to return after 8 hr in a case of electric shock, but in such instances the patient will give some evidence of recovery, which will cause the effort to be con tinued. Have some one send for a doctor and the police, fire department, or public utility company inhalator. Physical Shock. Any person who has received a serious injury suffers also from physical shock. An unconscious person becomes cold very rapidly, and chilling of the body means a further strain on an already weakened vitality. Experience has shown that the cold to which unconscious persons, particularly victims of electric shock, drowning, or asphyxiation, are often carelessly exposed is probably the most important cause of pneumonia. This disease is frequently the most dangerous aftereffect of even minor acci dents. As far as possible keep an injured person lying down, with the head low, while waiting for medical aid. Keep him covered with a blanket, even when performing artificial respiration. Never give an unconscious person anything to drink, as it will choke him. If he is breathing, a handkerchief wetted with aromatic spirits of ammonia may be held near but not too close to his nose. If he is conscious, hot coffee or a teaspoonful of aromatic spirits of ammonia in a small glass of water may be given the victim as a stimulant. S S E S S S S S ia j ETC 02978 CHAPTER XXII REFERENCE CODES, LAWS, AND STANDARDS Regardless of where hoisting or scaffolding jobs are to be under taken, it is important to be assured that there will be no violations of local laws or, as far as practicable, any deviation from safe practices. Therefore, it is necessary for those in charge of the work to be familiar with all state and city laws and codes and with national standards and safety requirements that apply to the work to be performed. Many of the references listed in this chapter are those which are particularly applicable in New York City. Except possibly in a very few instances the New York requirements are more stringent than those of most other cities and states. Hence, compliance with these rules should afford reasonable assurance that the work can be performed anywhere without undue criticism. Below are listed a number of codes, laws, rules, etc., which pertain to rigging operations and which should be referred to by the riggers before starting a job. This list undoubtedly is not complete, and there are probably additional local laws that may have to be complied with. American Standard Safety Code for Cranes, Derricks, and Hoists Designated ASA B30.2, 1943. Procure from American Standards Association, New York. 91 pages. Contents: Rules for design and operation of hoisting equipment. American Standard Safety Code for the Construction, Care and Use of (Wood) Ladders Designated ASA A14, 1935. Procure from American Standards Association, New York. 33 pages. Contents: Specification for construction, rules for use of ladders. American Recommended Practice for Inspection of Elevators Designated ASA A17.2, 1937. 288 etc 02979 REFERENCE CODES, LAWS, AND STANDARDS 289 Procure from American Standards Association, New York. 80 pages. Contents: Inspectors' guide. New York State Labor Law Procure from New York State Department of Labor, Albany, New York. Contents: Scaffolding; ladders, rope; budding erection, repair, and demolition; hours of labor, outside hoisting. New York State Industrial Code Bulletin 23, Rules Relating to Per sons Employed in the Erection, Repair and Demolition of Build ings and Structures Procure from New York State Department of Labor, Albany, New York. Contents: Hoists, boatswain's chairs, ladders, scaffolds, life lines, safety belts, shoring, stairs, material hoists, derricks, cranes, rope, chain, etc. New York State Industrial Code Bulletin 8, Rules Relating to Con struction, Guarding, Maintenance and Operation of Elevators, Dumb-waiters, Escalators, Hoists and Hoistways Procure from New York State Department of Labor, Albany, New York: Contents: As indicated in title. New York State Industrial Code Bulletin 19, Rules for Guarding of Dangerous Machinery, Vats, Pans and Elevated Runways Procure from New York State Department of Labor, Albany, New York. Contents: As indicated in title. Building Code of the City of New York Purchase at City Record Office, New York. Contents: Construction rules, working stresses, etc. Code of Ordinances of New York City Purchase from Banks-Baldwin Law Publishing Co., New York- The City Record dated May 16, 1936 Procure from City Record Office, New York. Contents: An ordinance to amend Article 7, Chap. 14, of the Code of Ordinances in relation to hoist and rigging license requirements. 290 HANDBOOK OF RIGGING Safety Requirements for Excavation, Building and Construction * Procure from Superintendent of Documents, Government Printing Office, Washington, D. C. Contents: U. S. Army regulations for the construction and use of scaffolds, ladders, rope, cable, chain, etc. Wood Handbook * Procure from Superintendent of Documents, Government Printing Office, Washington, D. C. 325 pages. Contents: Practical handbook on the use of wood for structural and other purposes, prepared by the Forest Products Labora tory. Guide Book for the Identification of Woods Used for Ties and Timbers * Designated Misc. R L2. Procure from Superintendent of Documents, Government Printing Office, Washington, D. C. 110 pages. Contents: As described in title. Structural Aluminum Handbook Procure from Aluminum Company of America, Pittsburgh. 106 pages. Contents: Properties of structural aluminum sections. Dowmetal Extrusions Procure from Dow Chemical Co., Midland, Mich. 132 pages. Contents: Properties of structural magnesium sections. Accident Prevention Manual for Industrial Operations Procure from National Safety Council, Chicago. 534 pages. Contents: General accident prevention, including rigging. Modem Wire Rope Digest Procure from American Chain & Cable Co. 250 pages. Contents: Wire-rope installation design. Safety Engineering Applied to Scaffolds Travelers Insurance Co. (no longer available). 350 pages. Contents: Data on scaffolds-as of 1915. Handbook of Safety in Building Construction Travelers Insurance Co. (no longer available). 204 pages. Contents: Scaffolding, hoisting, etc. as of 1927. * All Government publications listed herein sell for a nominal price. REFERENCE CODES, LAWS, AND STANDARDS 291 Safety Methods in Power System Construction Procure from Edison Electric Institute. 196 pages. Contents: Includes rigging. Crane Engineering Procure from Whiting Corp., Harvey, 111. 150 pages. Contents: Design data for traveling cranes. Safe Practices Pamphlet No. 1--Ladders Procure from National Safety Council, Chicago. Safe Practices Pamphlet No. 4--Overhead Traveling Cranes Procure from National Safety Council. Safe Practices Pamphlet No. 6--Fibre Rope Procure from National Safety Council. Safe Practices Pamphlet No. 12--Scaffolds Procure from National Safety Council. Safe Practices Pamphlet No. 26--Wire Rope Procure from National Safety Council. Safe Practices Pamphlet No. 33--Hoisting Apparatus Procure from National Safety Council. Safe Practices Pamphlet No. 70--Maintenance and Repair Men Procure from National Safety Council. Contents: Life belts, slings, ladders, manual lifting. Safe Practices Pamphlet No. 98--Use and Care of Hoisting Chain Procure from National Safety Council. Crane and Hoist Engineering Procure from Shaw Box Crane and Hoist Division, Muskegon, Mich. 221 pages. Contents: Engineering data for design and installation of cranes. Mechanical details of cranes. Roebling Handbook of Wire Rope Purchase from John A. Roebling's Sons Co., Trenton, N. J. 240 pages. Contents: Installation design, maintenance, and discarding of wire rope. Here's How Procure from American Cable Co., New York. 80 pages. Contents: Wire-rope installations. 292 HANDBOOK OF RIGGING Steel Construction Manual Procure from American Institute of Steel Construction, New York. 420 pages. Contents: Tables of properties of structural shapes, rivets, bolts, etc. Manual of Accident Prevention in Construction Procure from Associated General Contractors of America, Washington, D. C. 370 pages. Best's Safety Directory Purchase from Alfred M. Best Co., Inc., New York. Contents: Condensed catalogues of safety and fire protection equipment. Most manufacturers of cranes, rope, cable, chain, scaffolding, jacks, safety clothing, etc., have available for distribution hand books or catalogues that describe the proper use of their products. Other state regulations relative to rigging and hoisting can be obtained by writing to the following regulatory bodies. Arizona Procure from Industrial Commission of Arizona, Phoenix, Ariz. Names of publications: Cranes Ladders Safety Code for Workers in the Construction Industry California Procure from State of California Department of Industrial Rela tions, Industrial Accident Commission, San Francisco, Calif. Names of publications: Cranes Elevators Scaffolding Construction Construction--General Safety Orders Elevator Safety Orders Ladders Steam Shovels and Locomotive Cranes--Safety Orders Trench Construction--Safety Orders Colorado Procure from Bureau of Labor Statistics, Denver, Colo. REFERENCE CODES, LAWS, AND STANDARDS 293 Names of publications: Cranes Elevators Ladders Connecticut Procure from Department of Labor and Factory Inspection, Hartford, Conn. Name of publication: Elevators Illinois Procure from Division of Factory Inspection, Chicago, 111. Name of publication: Laws of the State of Illinois Enforced by the Department of Labor Indiana Procure from Administrative Building Council of Indiana, Indianapolis, Ind. Name of publication: Elevators Iowa Procure from State of Iowa, Bureau of Labor, Des Moines, Iowa. Name of publication: Passenger and Freight Elevator Law Kentucky Procure from Department of Labor, Louisville, Ky. Name of publication: Cranes Massachusetts Procure from Department of Labor and Industry, Division of Industrial Safety, Boston, Mass. Names of publications: Erection, Alteration, Inspection and Use of Buildings Rules and Regulations for the Prevention of Accidents in Building Operations. Cranes Elevator and Escalator Regulations Ladders Scaffolds Revised Rules, Regulations and Recommendations Pertaining to Structural Painting M WjWIMWIWMB ! '' irr,~ ETC 02985 ' ~r REFERENCE CODES, LAWS, AND STANDARDS Names of publications: Elevators Rules for Operation of Elevators Ohio Procure from Ohio State Department of Industrial Relations, Columbus, Ohio. Names of publications: Ladders Building and Construction Work Cranes General Safety Precautions for Travelling Cranes Elevators Scaffolding Oklahoma Procure from Department of Labor, Oklahoma City, Okla. Names of publications: Cranes Elevators Ladders Scaffolding Elevator Safety Code Pennsylvania Procure from Department of Labor and Industry, Harris burg, Pa. Names of publications: Cranes Elevators Construction Regulations for Construction and Repairs Cranes and Hoists Elevator Safety Regulations Regulations for Elevators, Escalators, Dumbwaiters and Hoists Ladders Scaffolds Tennessee ETC 02986 296 HANDBOOK OF RIGGING Utah Procure from Industrial Commissioner of Utah, Salt Lake City, Utah. Names of publications: Ladders Elevator Code Washington Procure from Department of Labor and Industry, Olympia, Wash. Names of publications: Cranes Elevators Safety Standards West Virginia Procure from Bureau of Labor, Charleston, W. Va. Name of publications: Elevators Wisconsin Procure from Industrial Commission of Wisconsin, Madison, Wis. Names of Publications: Building Code General Orders on Existing Buildings Cranes, Derricks and Hoists General Orders on Safety in Construction Elevator Code Ladders General Orders on Safety appendix HANDY REFERENCE TABLES TRIGONOMETRIC FUNCTIONS Given Required Formulas a, c a, c a, b a, b A, a A, a A, b A, b A, e A, e d, e,f d,e,f d, e,f A, B, b Area A, B, c Area B, b, c Area B, a, c Area B, a, b Area D E F sin AA = a c a cos B = c 6 = _ a2 5 Vc2 _ 2 tan A ab b b tan B = a c = Vai + 5* ~2 B = 90 -A; b = a cot A; a sin A a% cot A 2 B = 90 - A; tan A a=6 tan A; 6 C - cos A. 2 B = 90 -- A; c2 sin 2A a = c sin A; b = c cos A 4 V. D l(s - e)(s -- f) Sm 2 ~ e/ ' d 4- e 4- / _2 .E Sm 2 j(s - d)( -/) <*/ V. F l(s- d)( - e) Sm 2 ~ 297 298 Given HANDBOOK OF RIGGING TRIGONOMETRIC FUNCTIONS (Continued) Formulas - d)(s - e)(s -/) dsn E e = ----; d sin F / = --s:--in --D (e from above formula) e sin D d sin F e -- d cos F d sin F (D from above formula) TRIGONOMETRIC SOLUTIONS OF RIGHT TRIANGLES Known a, b a, c b} c A, a Ay b Ay c Required AB .a tan A -- - cot 5=7 bb sin A c cos AA -- bc cos B -- c . sin B,, = b - c 90 - A ab v'c2 - a1 - 6= a cot A 90 - A 90 -- A 6 tan A c sin A c cos A c ^d` + 6- a sin A 6 cos A APPENDIX 299 300 HANDBOOK OF RIGGING VOLUMES OF SOLID FIGURES n h| Regular prism: Volume = area of base X A is ETC 02991 APPENDIX CIRCUMFERENCES AND AREAS OF CIRCLES* 301 D ia m e te r Circum ference Area Diam eter Circum ference Area Diam eter C ircum ference Area Diam eter C ircum ference $ 3 Ha 0.04909 0.09817 Ht 0.1473 He 0.1963 Ha 0.2454 0.2945 Hi 0.3436 H Ua `Hi 0.3927 0.4418 0.4909 0.5400 'Ha Ht 'Ha 0.5890 0.6381 0.6872 0.7363 Va 'Ha Hi 'Ha 0.7854 0.8345 0.8836 0.9327 He * Ha 3Hi 0.9817 1.031 1.080 1.129 H *Ha HU 1.178 1.227 1.276 1.325 He 2 Ha 'Hi 3 Ha 1.374 1.424 1.473 1.522 H 3Ha '7At 3Ha 1.571 1.620 1.669 1.718 3Ha 'Hi 3Ha 1.767 1.816 1.865 1.914 H *Ha 2 Hi 1.963 2.013 2.062 2.111 lMa Ha 2Hi *Ha 2.160 2.209 2.258 2.307 H 4Ha 2Ht *Ha 2.356 2.405 2.454 2.503 'He *Ha 27Ai Hi 2.553 2.602 2.651 2.700 .00019 .00077 .00173 .00307 .00479 .00690 .00940 .01227 .01553 .01917 .02320 .02761 .03241 .03758 .04314 .04909 .05542 .06213 .06922 .07670 .08456 .09281 .1014 .1104 .1198 .1296 .1398 .1503 .1613 .1726 .1843 .1963 .2088 .2217 .2349 .2485 .2625 .2769 .2916 .3068 .3223 .3382 .3545 .3712 .3883 .4057 .4236 .4418 .4604 .4794 .4987 .5185 .5386 .5591 .5800 H *7Aa 2H* *Ht 'He *Ha 3 Hi 1 M H Hi H He H He H He H 'He H 'He A 'He 2 He H Hi H He H H He H 1He H 'He 7A 'He 3 He H Hi H He H Hi Ht He H `Ma H 'He 7A `Hi 2.749 2.798 2.847 2.896 0.6013 0.6230 0.6450 0.6675 2.945 2.994 3.043 3.093 0.6903 0.7135 0.7371 0.7610 3.142 3.338 3.534 3.731 0.7854 0.8866 0.9940 1.108 3.927 4.123 4.320 4.516 1.227 1.353 1.485 1.623 4.712 4.909 5.105 5.301 1.767 1.917 2.074 2.237 5.498 5.694 5.890 6.087 2.405 2.580 2.761 2.948 6.283 6.480 6.676 6.872 3.142 3.341 3.547 3.758 7.069 7.265 7.461 7.658 3.976 4.200 4.430 4.666 7.854 8.050 8.247 8.443 4.909 5.157 5.412 . 5.673 8.639 8.836 9.032 9.228 5.940 6.213 6.492 6.777 9.425 9.621 9.817 10.01 7.069 7.366 7.670 7.980 10.21 10.41 10.60 10.80 8.296 8.618 8.946 9.281 11.00 11.19 11.39 11.58 9.621 9.968 10.32 10.68 11.78 11.98 12.17 12.37 11.04 11.42 11.79 12.18 4 He a Hi 12.57 12.76 12.96 13.16 12.57 12.96 13.36 13.77 9 A H A 28.27 28.67 29.06 29.45 63.62 65.40 67.20 69:03 H 13.35 14.19 He 13.55 14.61 H 13.74 15.03 Hi 13.94 15.47 A 29.85 n 30.24 H 30.63 7A 31.02 70.88 72.76 74.66 76.59 A He H `Ha 14.14 14.33 14.53 14.73 15.90 16.35 16.80 17.26 10 H Va n 31.42 31.81 32.20 32.59 78.54 80.52 82.52 84.54 H 'He 7A 'He 14.92 15.12 15.32 15.51 17.72 18.19 18.67 19.15 A. 32.99 H 33.38 H 33.77 7A 34.16 86.59 88.66 90.76 92.89 5 Ha A He 15.71 15.90 16.10 16.30 19.63 20.13 20.63 21.14 11 H Vi H 34.56 34.95 35.34 35.74 95.03 97.21 99.40 101.6 H 16.49 21.65 He 16.69 22.17 H 16.89 22.69 Hi 17.08 23.22 H 36.13 Hi 36.52 H 36.91 A 37.31 103.9 106.1 108.4 110.8 K He -H `M 17.28 23.76 17.48 24.30 17.67 24.85 17.87 25.41 12 A M A 37.70 38.09 38.48 38.88 113.1 115.5 117.9 120.3 H `Hi 7A 'He 18.06 18.26 18.46 18.65 25.97 26.53 27.11 27.69 H 39.27 122.7 n 39.66 125.2 Hi 40.06 127.7 7A 40.45 130.2 6 M M H 18.85 28.27 19.24 29:46 19.63 30.68 20.03 31.92 13 A H n 40.84 41.23 41.63 42.02 132.7 135.3 137.9 140.5 A 20.42 33.18 H 20.81 34.47 H 21.21 35.78 A 21.60 37.12 A 42.41 M 42.80 iii 43.20 A 43.59 143.1 145.8 148.5 151.2 7 H M n 21.99 38.48 22.38 39.87 22.78 41.28 23.17 42.72 14 A M H 43.98 44.37 44.77 45.16 153.9 156.7 159.5 162.3 V4 23.56 44.18 H 23.95 45.66 H 24.35 47.17 A 24.74 48.71 A 45.55 165.1 A 45.95 168.0 44 46.34 170.9 A 46.73 173-8 8 A W 94 25.13 25.53 25.92 26.31 50.27 51.85 53.46 55.09 15 A H 47.12 47.52 47.91 48.30 176.7 179.7 182.7 185.7 M 26.70 56.75 94 27.10 58.43 94 27.49 60.13 94 27.88 61.86 A 48.69 188.7 H 49.09 191.7 n 49.48 194.8 A 49.87 197.9 * From Marks, Mechanical Engineers' Handbook, 4th ed., McGraw-Hill, 1941. ETC 02992 302 HANDBOOK OF RIGGING CIRCUMFERENCES AND AREAS OF CIRCLES (Continued) Diam eter C ircum ference Area Diam eter Area Diam eter C ircum ference Area ` Diam eter | C ircum ference eg |a o'- < 16 A M M V H n 17 V4 n V M H li 18 % V H V H Vi H 19 A V 50.27 50.66 51.05 51.44 51.84 52.23 52.62 53.01 53.41 53.80 54.19 54.59 54.98 55.37 55.76 56.16 56.55 56.94 57.33 57.73 58.12 58.90 59.30' 59.69 60.08 60.48 60.87 201.L 204.2 207.4 210.6 213.8 217.1 220.4 223.7 227.0 230.3 233.7 237.1 240.5 244.0 247.4 250.9 254.5 258.0 261.6 265.2 268.8 272.4 276.1 279.8 283.5 287.3 291.0 294.8 19 H H A 20 M H V n K 7A 21 A H n V. A Hn 22 H W .H H H X H 61.26 61.65 62.05 62.44 62.83 63.22 63.62 64.01 64.40 64.80 65.19 65.58 65.97 66.37 66.76 67.15 67.54 67.94 68.33 68.72 69.12 69.51 69.90 70.29 70.69 71.08 71.47 71.86 298.6 302.5 306.4 310.2 314.2 318.1 322.1 326.1 330.1 334.1 338.2 342.2 346.4 350.5 354.7 358.8 363.1 367.3 371.5 375.8 380.1 384.5 388.8 393.2 397.6 402.0 406.5 411.0 23 n h H A 24 H V X 25 M H 26 H ! X 27 is 16 H 29 y* Vi M 72.26 72.65 73.04 73.43 73.83 74.22 74.61 75.01 75.40 76.18 76.97 77.75 78.54 79.33 80.11 80.90 81.68 82.47 83.25 84.04 84.82 85.61 86.39 87.18 87.96 88.75 89.54 90.32 415.5 420.0 424.6 429.1 433.7 438.4 443.0 447.7 452.4 461.9 471.4 481.1 490.9 500.7 510.7 520.8 530.9 541.2 551.5 562.0 572.6 583.2 594.0 604.8 615.8 626.8 637.9 649.2 29 a v> 54 30 14 M H 31 14 It 14 32 H It X 33 14 It H 34 14 It X 35 14 It 14 91.11 91.89 92.68 93.46 94.25 95.03 95.82 96.60 97.39 98.17 98.96 99.75 100.5 101.3 102.1 102.9 103.7 104.5 105.2 106.0 106.8 107.6 108.4 109.2 110.0 110.7 111.5 112.3 660.5 672.0 683.5 695.1 706.9 718.7 730.6 742.6 754.8 767.0 779.3 791.7 804.2 816.9 829.6 842.4 855.3 868.3881.4 894.6 907.9 921.3 934.8948.4 962.1 975.9 989.8 1003.8 AREAS OF CIRCLES* Diameters in Feet and Inches, Areas in Square Feet Inches Feet 0 1 2 3 4 5 6 7 8 9 10 11 0 .0000 .0055 .0218 .0491 .0873 .1364 .1963 .2673 .3491 .4418 .5454 .6600 1 .7854 .9218 1.069 1.227 1.396 1.576 1.767 1.969 2.182 2.405 2.640 2.885 2 3.142 3.409 3.687 3.976 4.276 4.587 4.909 5.241 5.585 5.940 6.305 6.681 3 7.069 7.467 7.876 8.296 8.727 9.168 9.621 10.08 10.56 11.04 11.54 12.05 4 12.57 13.10 13.64 14.19 14.75 15.32 15.90 16.50 17.10 17.72 18.35 18.99 5 19.63 20.29 20.97 21.65 22.34 23.04 23.76 24.48 25.22 25.97 26.73 27.49 6 28.27 29.07 29.87 30.68 31.50 32.34 33.18 34.04 34.91 35.78 36.67 37.57 7 38.48 39.41 40.34 41.28 42.24 43.20 44.18 45.17 46.16 47.17 48.19 49.22 8 50.27 51.32 52.38 53.46 54.54 55.64 56.75 57.86 58.99 60.13 61.28 62.44 9 63.62 64.80 66.00 67.20 68.42 69.64 70.88 72.13 73.39 74.66 75.94 77.24 10 78.54 79.85 81.18 82.52 83.86 85.22 86.59 87.97 89.36 90.76 92.18 93.60 11 95.03 96.48 97.93 99.40 100.9 102.4 103.9 105.4 106.9 108.4 110.0 111.5 12 113.1 114.7 116.3 117.9 119.5 121.1 122.7 124.4 126.0 127.7 129.4 131.0 13 132.7 134.4 136.2 137.9 139.6 141.4 143.1 144.9 146.7 148.5 150.3 152.1 14 153.9 155.8 157.6 159.5 161.4 163.2 165.1 167.0 168.9 170.9 172.8 174.8 FROM INCHES AND FRACTIONS OF AN INCH TO DECIMALS OF A FOOT * Inches Feet Inches Feet 1 0.0833 A 0.0104 2 0.1667 H 0.0208 3 0.2500 H 0.0313 4 0-3333 V 0.0417 0.4*167 M 0.0521 6 0.5000 H 0.0625 7 0.5833 A 0.0729 8 0 6667 9 0.7500 10 0.8333 11 0.9167 Example: 5 ft 7H in. = 5.0 + 0.5833 + 0.0313 - 5.6146 ft * From Marks, Mechanical Engineers' Handbook, 4th ed., McGraw-Hill, 1941. APPENDIX NATURAL SINES AND COSINES* Natural Sines at intervals of 0. 1, or 6'. Degrees .o = (O') M *.2 .3 .4 .5 .6 .7 .8 .9 C6') (12') (180 (24') (30') (36') (420 (480 (540 303 Average differ ence 0.0000 90 0 0.0000 0017 0035 0052 0070 0087 0105 0122 0140 0157 0175 89 1 0175 0192 0209 0227 0244 0262 0279 0297 0314 0332 0349 88 2 0349 0366 0684 0401 0419 0436 0454 0471 0488 0506 0523 87 3 0523 0541 0558 0576 0593 0610 0628 0645 0663 0680 0698 86 4 0698 0715 0732 075U 0767 0785 0802 0819 0837 0854 0.0872 85 5 0.0872 0889 0906 0924 0941 0958 0976 0993 1011 1028 1045 84 6 1045 1063 1080 1097 1115 1132 1149 1167 1184 1201 1219 83 7 1219 1236 1253 1271 1288 1305 1323 134C 1357 1374 1392 82 8 1392 1409 1426 1444 1461 1478 1495 1513 153C 1547 1564 81 9 1564 1582 1599 1616 1633 1650 1668 1685 1702 1719 0.1736 80 10 0.1736 1754 1771 1788 1805 1822 1840 1857 1874 1891 1908 79 11 1908 1925 1942 1959 1977 1994 2011 202$ 2045 2062 2079 78 12 2079 2096 2113 2130 2147 2164 2181 219$ 2215 2233 225C 77 13 2250 2267 2284 2300 2317 2334 2351 236* 2385 2402 2419 76 14 2419 2436 2453 2470 2487 2504 2521 2538 2554 2571 0.2588 75 15 0.2588 2605 2622 2639 2656 2672 2689 2706 2723 2740 2756 74 16 2756 2773 2790 2807 2823 2840 2857 2874 2890 2907 2924 73 17 2924 2940 2957 2974 2990 3007 3024 304C 3057 3074 309C 72 18 3090 3107 3123 3140 3156 3173 3190 3206 3223 3239 3256 71 19 3256 3272 3289 3305 3322 3338 3355 3371 3387 3404 0.3420 70 20 0.3420 3437 3453 3469 3486 3502 351R 3535 3551 3567 3584 69 21 3584 3600 3616 3633 3649 3665 3681 3697 3714 3730 3746 68 22 3746 3762 3778 3795 3811 3827 3843 3859 3875 3891 3907 67 23 3907 3923 3939 3955 3971 3987 4003 4019 4035 4051 4067 66 24 4067 4083 4099 4115 4131 4147 4163 4179 4195 4210 0.4226 65 25 0.4226 4242 4258 4274 4289 4305 4321 4337 4352 4368 4384 64 26 4384 4399 4415 4431 4446 4462 4478 4493 4,509 4524 4540 63 27 4540 4555 4571 4586 4602 4617 4633 4648 4664 4679 4695 62 28 4695 4710 4726 4741 4756 4772 4787 4802 4818 4833 484S 61 29 4848 4863 4879 4894 4909 4924 4939 4955 4970 4985 0.5000 60 30 0.5000 5015 5030 5045 5060 5075 5090 5105 5120 5135 5150 59 31 5150 5165 5180 5195 5210 5225 5240 5255 5270 5284 5299 58 32 5299 5314 5329 5344 5358 5373 5388 5402 5417 5432 5446 57 33 5446 5461 5476 5490 5505 5519 5534 5548 5563 5577 5592 56 34 5592 5606 5621 5635 5650 5664 5678 5693 5707 5721 0.5736 ' 55 35 0.5736 5750 5764 5779 5793 5807 5821 5835 5850 5864 5878 54 36 5878 5892 5906 5920 5934 5948 5962 5976 5990 6004 6018 53 37 6018 6032 6046 6060 6074 6088 6101 bus 6129 6143 6157 52 38 6157 6170 61H4 6198 6211 6225 6239 6252 6266 6280 6293 51 39 6293 6307 6320 6334 6347 6361 6374 6388 6401 6414 0.6428 50 40 0.6428 6441 6455 6468 64R1 6494 6508 6521 B5R4 BS47 6561 49 41 6561 6574 6587 6600 6613 6626 6639 6652 6665 6678 6691 48 42 6691 6704 6717 6730 6743 6756 6769 6782 6794 6807 6820 47 43 6820 6833 6845 6858 6871 6884 6896 6909 6921 6934 6947 46 44 6947 6959 6972 6984 6997 7009 7022 7034 7046 7059 0.7071 45 45 0.7071 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 17 16 16 16 16 16 16 16 16 16 15 15 15 15 15 15 14 14 14 14 14 13 13 13 13 13 12 .9 .S .7 .6 .o .4 -3 .2 .l = (540 (480 (42') (36') (30') (240 (180 (12') (6') .o Degrees (O') Natural Cosines * From Marks, Mechanical Engineer* Handbook, 4th ed., McGraw-Hill, 1941. 304 HANDBOOK OF RIGGING NATURAL SINES AND COSINES (Continued) Natural Sines at intervals of 0.l, or 6'. Degrees .o -(O') .l (60 o 2 .3 .4 .6 .7 .8 .9 (12') (180 (240 (30') (36') (42') (48') (540 Average differ ence 0.7071 45 45 0.7071 7083 7096 7108 7120 7133 7145 7157 7169 7181 7193 44 46 7193 7206 7218 7230 7242 7254 7266 7278 7290 7302 7314 43 47 7314 7325 7337 7349 7361 7373 7385 7396 7408 7420 7431 42 48 7431 7443 7466 7478 7490 7501 7513 7524 7536 7547 41 49 7547 7559 7570 7581 7593 7604 7615 7627 7638 7649 0.7660 40 50 0.7660 7672 7683 7694 7705 7716 7727 7738 7749 7760 7771 39 51 7771 7782 7793 7804 7815 7826 7837 7848 7859 7HtW 788C 38 52 7880 7891 7902 7912 7923 7934 7944 7955 7965 7976 7986 37 53 7986 7997 8007 8018 8028 8039 8049 8059 8070 8080 809C 36 54 8090 8100 8111 8121 8131 8141 8151 8161 8171 8181 0.8192 35 55 0.8192 8202 8211 8221 8231 8241 8251 8261 8271 8281 8290 34 56 8290 8300 8310 8320 8329 8339 8348 8358 8368 8377 8387 33 57 8387 8396 8406 8415 8425 8434 8443 8453 8462 8471 8480 32 58 8480 8490 8499 8508 8517 8526 8536 8545 8554 8563 8572 31 59 8572 8581 8590 8599 8607 8616 8625 8634 8643 8652 0.8660 30 60 0.8660 8669 8678 8686 8695 8704 8712 8721 8729 8738 8746 29 61 8746 8755 8763 8771 8780 8788 8796 8805 8813 8821 8829 28 62 8829 8838 8846 8854 8862 8871) 8878 8886 8894 8902 8910 27 63 8910 8918 8926 8934 8942 8949 8957 8965 8973 8980 8988 26 64 8988 8996 9003 9011 9018 9026 9033 9041 9048 9056 0.9063 25 65 0.9063 9070 9078 9085 9092 9100 9107 9114 9121 9128 9135 24 66 9135 9143 9150 9157 9164 9171 9178 9184 9191 9198 9205 23 67 9205 9212 9219 9225 9232 9239 9245 9252 9259 9265 9272 22 68 9272 9278 9285 9291 9298 9304 9311 9317 9323 9330 9336 21 69 9336 9342 9348 9354 9361 9367 9373 9379 9385 9391 0.9397 20 70 0.9397 9403 9409 9415 9421 9426 9432 9438 9444 9449 9455 19 71 9455 9461 9466 9472 9478 9483 9489 9494 9500 9505 9511 18 72 9511 9516 9521 9527 9532 9537 9542 9548 9553 9558 9563 17 73 8563 9568 9573 9578 9583 9588 9593 9598 9603 9608 9613 16 74 9613 9617 9622 9627 9632 9636 9641 9646 9650 9655 0.9659 15 75 0.9659 9664 9668 9673 9677 9681 9686 9690 9694 9699 9703 14 76 9703 9707 9711 9715 9720 9724 9728 9732 9736 9740 9744 13 77 9744 9748 9751 9755 9759 9763 9767 9770 9774 9778 9781 12 78 9781 9785 9789 9792 9796 9799 9803 9806 9810 9813 9816 11 79 9816 9820 9823 9826 9829 9833 9836 9839 9842 9845 0.9848 10 80 0.9848 9851 9854 9857 9860 9863 9866 9869 9871 9874 9877 81 9877 9880 9882 9885 9888 9890 9893 9895 9898 9900 9903 82 9903 9905 9907 9910 9912 9914 9917 9919 9921 9923 9925 83 9925 9928 9930 9932 9934 9936 9938 9940 9942 9943 9945 84 9945 9947 9949 9951 9952 9954 9956 9957 9959 9960 0.9962 9 8 7 6 5 85 0.9962 9963 9965 9966 9968 9969 9971 9972 9973 9974 9976 4 86 9976 9977 9978 9979 9980 9981 9982 9983 9984 9985 9986 3 87 9986 9987 9988 9989 9990 9990 9991 9992 9993 9993 9994 2 88 9994 9995 9995 9996 9996 9997 9997 9997 9998 9998 0.9998 1 89 0.9998 9999 9999 9999 9999 0000 0000 0000 0000 0000 1.0000 0 90 1.0000 12 12 12 12 11 11 U 11 10 10 10 10 9 9 9 9 8 8 8 7 7 7 7 6 6 6 6 5 5 5 4 4 4 3 3 3 3 2 2 2 l l 1 0 0 .9 .8 .7 .6 .5 .4 .3 .2 .l 3 (54') (48') (42') (360 (300 (24') (180 (120 (60 .o Degrees (O') Natural Cosines APPENDIX NATURAL TANGENTS AND COTANGENTS* Natural Tangents at intervals of 0. 1, or 6'. Degrees .o =m .l (6') .2 .3 .4 .5 .6 .7 -8 .9 (12') (18') (24') (300 (36') (420 (480 (54') 305 Average differ ence 0.0000 90 0 0.0000 0017 0035 0052 0070 0087 0105 0122 0140 0157 0175 89 1 2 0175 0192 0209 0227 0244 0262 0279 0297 0314 0332 0349 88 034S 0367 0384 0402 0419 0437 0454 0472 0489 0507 0524 87 3 0524 0542 0559 0577 0594 0612 0629 0647 0664 0682 0699 86 4 0699 0717 0734 0752 0769 0787 0805 0822 0840 0857 0.0875 85 5 0.0875 0892 0910 0928 0945 0963 0981 0998 1016 1033 1051 84 6 1051 1069 1086 1104 1122 1139 1157 1175 1192 121C 1228 83 7 1228 1246 1263 1281 1299 1317 1334 1352 1370 138* 1405 82 8 1405 1423 1441 1459 1477 1495 1512 1530 154* 1566 1584 81 9 1584 1602 1620 1638 1655 1673 1691 1709 1727 1745 0.1763 80 10 0.1763 1781 1799 1817 1835 1853 1871 1890 1908 1926 1944 79 11 1944 1962 1980 1998 2016 2035 2053 2071 2089 2107 2126 78 12 2126 2144 2162 2180 2199 2217 2235 2254 2272 229T 230S 77 13 2309 2327 2345 2364 2382 2401 2419 2438 2456 2475 2493 76 14 2493 2512 2530 2549 2568 2586 2605 2623 2642 2661 0.2679 75 15 0.2679 2698 2717 2736 2754 2773 2792 2811 2830 2849 2867 74 16 2867 2886 2905 2924 2943 2962 2981 3000 3019 303* 3057 73 17 3057 3076 3096 3115 3134 3153 3172 3191 3211 3230 3249 72 18 3249 3269 3288 3307 3327 3346 3365 3385 3404 3424 3443 71 19 3443 3463 3482 3502 3522 3541 3561 3581 3600 3620 0.3640 70 20 0.3640 3659 3679 3699 3719 3739 3759 3779 3799 3819 3839 69 21 3839 3859 3879 3899 3919 3939 3959 3979 4000 4020 4040 68 22 4040 4061 4081 4101 4122 4142 4163 4183 4204 4224 4245 67 23 4245 4265 4286 4307 4327 4348 4369 4390 4411 4431 4452 66 24 4452 4473 4494 4515 4536 4557 4578 4599 4621 4642 0.4663 65 25 0.4663 4684 4706 4727 4748 4770 4791 4813 4834 4856 4877 64 26 4877 4899 4921 4942 4964 4986 5008 5029 5051 5073 5095 63 27 5095 5117 5139 5161 5184 5206 5228 5250 527? 5295 5317 62 28 5317 5340 5362 5384 .5407 5430 5452 5475 5498 5520 5543 61 29 5543 5566 5589 5612 5635 5658 5681 5704 5727 5750 0.5774 60 30 0.5774 5797 5820 5844 5867 5890 5914 5938 5961 5985 6009 59 31 6009 6032 6056 6080 6104 6128 6152 6176 6200 6224 6249 58 32 6249 6273 6297 6322 6346 6371 6395 6420 6445 6469 6494 57 33 6494 6519 6544 6569 6594 6619 6644 6669 6694 6720 6745 56 34 6745 6771 6796 6822 6847 6873 6899 6924 6950 6976 0.7002 55 35 0.7002 7028 7054 7080 7107 7133 7159 7186 7212 7239 7265 54 36 7265 7292 7319 7346 7373 7400 7427 7454 7481 7508 7536 53 37 7536 7563 7590 7618 7646 7673 7701 7729 7757 7785 7813 52 38 7813 7841 7869 7898 7926 7954 7983 8012 8040 8069 8098 51 39 8098 8127 8156 8185 8214 8243 8273 8302 8332 8361 0.8391 50 40 0.8391 8421 8451 8481 8511 8541 8571 8601 8632 8662 8693 49 41 8693 8724 8754 8785 8816 8847 8878 8910 8941 8972 9004 48 42 9004 9036 9067 9099 9131 9163 9195 9228 9260 9293 9325 47 43 9325 9358 9391 9424 9457 9490 9523 9556 9590 9623 0.9657 46 44 0.9657 9691 9725 9759 9793 9827 9861 9896 9930 9965 1.0000 45 45 1.0000 17 17 17 18 18 18 18 18 18 18 18 18 18 18 19 19 19 19 19 20 20 20 21 21 21 21 22 22 23 23 24 24 25 25 26 26 27 28 28 29 30 31 32 33 34 .9 .8 .7 .6 .5 .4 ,3 .2 .l = (54') (48') (42') (36') (30') (24') (18') (12') (') .o Degrees (O') Natural Cotangents * From Marks, Mechanical Engineers' Handbook, 4th ed., McGraw-Hill, 1941. 306 HANDBOOK OF RIGGING NATURAL TANGENTS AND COTANGENTS (Continued) Natural Tangents at intervals of 0.l, or 6'. Degrees .o = (00 .l (6') .2 .3 .4 .S .6 .7 .8 .9 (120 (iso (240 (300 (36') (420 (480 (54') A. Average differ ence 1.0000 45 45 1.0000 0035 0070 0105 0141 0176 0212 0247 0283 0319 0355 44 46 0355 0392 0428 0464 0501 0538 0575 0612 0649 0686 0724 43 47 0724 0761 0799 0837 0875 0913 0951 0990 1028 1067 1106 42 48 1106 1145 1184 1224 1263 1303 1343 1383 1423 1463 1504 41 49 1504 1544 1585 1626 1667 1708 1750 1792 1833 1875 1.1918 40 50 1.1918 1960 2002 2045 2088 2131 2174 2218 2261 2305 2349 39 51 234S 2393 2437 2482 2527 2572 2617 2662 2708 2753 2799 38 52 279S 2846 2892 2938 2985 3032 3079 3127 3175 3222 3270 37 53 327C 3319 3367 3416 3465 3514 3564 3613 3663 3713 3764 36 54 3764 3814 3865 3916 3968 4019 4071 4124 4176 4229 1.4281 35 55 1.4281 4335 4388 4442 4496 4550 4605 4659 4715 4770 4826 34 56 4826 4882 4938 4994 5051 5108 5166 5224 5282 5340 5399 33 57 5399 5468 5517 5577 5637 5697 5757 5818 5880 5941 6003 32 58 6003 6066 6128 6191 6255 6319 6383 6447 6512 6577 6643 31 59 1.6643 6709 6775 6842 6909 6977 7045 7113 7182 7251 1.7321 30 60 1.732 1.739 1.746 1.753 1.760 1.767 1.775 1.782 1.789 1.797 1.804 29 61 1.804 1.811 1.819 1.827 1.834 J .842 1.849 1.857 1.865 1.873 1.881 28 62 1.881 1.889 1.897 1.905 1.913 1.921 1.929 1.937 1.946 1.954 1.963 27 63 1.963 1.971 1.980 1.988 1.997 2.006 2.014 2.023 2.032 2.041 2.050 26 64 2.050 2.059 2.069 2.078 2.087 2.097 2.106 2.116 2.125 2.135 2.145 25 65 2.145 2.154 2.164 2.174 2.184 2.194 2.204 2.215 2.225 2.236 2.246 24 66 2.246 2.257 2.267 2.278 2.289 2.300 2.311 2.322 2.333 2.344 2.356 23 67 2.356 2.367 2.379 2.391 2.402 2.414 2.426 2.438 2.4.50 2.463 2.475 22 68 2.475 2.4K8 2.500 2.513 2.526 - .539 2.552 2.565 2.578 2.59? 2.605 21 69 2.605 2.619 2.633 2.646 2.660 2.675 2.689 2.703 2.718 2.733 2.747 20* 70 2.747 [2762 2.778 2.793 2.888 2.824 2.840 2.856 2.872 2.888 2.904 19 71 2.904 2.921 2,937 2.954 2.971 2.989 3.006 3.024 3.042 3.860 2.078 18 72 3.078 3.096 3.115 3.133 3.152 3.172 3.191 3.211 3.230 3.251 3.271 17 73 3.271 3.291 3.312 3.333 3.354 3.376 3.398 3.420 3.442 3.465 3.487 16 74 3.487 3.511 3.534 3.558 3.582 3.606 3.630 3.655 3.681 3.706 3.732 15 75 3.732 3.758 3.785 3.812 3.839 3.867 3.895 3.923 3.952 3.981 4.011 14 76 4.011 4.041 4.071 4.102 4.134 4.165 4.198 4.230 4.264 4.297 4.331 13 77 031 4.366 4.402 4.437 4.474 4.511 4.548 4.586 4.625 4.665 4.705 12 78 4.705 4.745 4.787 4.829 4.872 4.915 4.959 5.005 5.050 5.097 5.145 11 79 5.145 5.193 5.242 5.292 5.343 5.396 5.449 5.503 5.558 5.614 5.671 10 80 5.671 5.730 5.789 5.850 5.912 5.976 6.041 6.107 6.174 6.243 6.314 9 81 6.314 6.386 6.460 6.535 6.612 6.691 6.772 6.855 6.940 7.026 7.115 8 82 7.115 7.207 7.300 7.396 7.495 7.596 7.700 7.806 7,916 8.028 8.144 7 83 8.144 8.264 8.386 8.513 8.643 8.777 8.915 9.058 9.205 9.357 9.514 6 84 9.514 9.677 9.845 10.02 10.20 10.39 10.58 10.78 10.99 11.20 11.43 5 85 11.43 11.66 11.91 12.t6 12.43 12.71 13.00 13.30 13.62 13.95 14.30 4 86 14.30 14.67 15.06 15.46 15.90 16.35 16.83 17.34 17.89 18.46 19.08 3 87 19.08 19.74 20.45 21.20 22.02 22.90 23.86 24.90 26.03 27.27 28.64 2 88 28.64 30.14 31.82 33.69 35.80 38.19 40.92 44.07 47.74 52.08 57.29 1 89 57.29 63.66 71.62 81.85 95.49 114.6 143.2 191.0 286.5 573.0 oo 0 90 90 35 37 38 40 41 43 45 47 49 52 57 60 64 67 7 s 8 9 9 10 11 12 13 14 16 17 19 22 24 28 32 37 44 53 .9 .8 .7 .6 .5 .4 .3 .2 .l = (540 (480 (42') (36') (300 (24') (18') (12') (6') .o Degrees (O') Natural Cotangents APPENDIX 307 DECIMAL EQUIVALENTS OF COMMON FRACTIONS* Sths 16ths 32nds 64ths Exact decimal values 8ths 16ths 32nds 64ths Exact decimal values 4 8 16 32 0.50 1 0.01 5625 33 .51 5625 1 2 .03 125 17 34 .53 125 3 .04 6875 35 .54 6875 1 2 4 .06 25 9 18 36 .56 25 5 .07 8125 37 .57 8125 3 6 .09 375 19 38 .59 375 7 .10 9375 39 .60 9375 12 3 4 8 .12 5 5 9 .14 0625 5 10 .15 625 n .17 1875 6 12 .18 75 13 .20 3125 7 14 .21 875 15 .23 4375 10 20 40 .62 5 41 .64 0625 21 42 .65 625 43 .67 1875 11 22 44 .68 75 45 .70 3125 23 46 .71 875 47 .73 4375 24 8 16 .25 6 12 24 48 .75 17 .26 5625 49 .76 5625 9 18 .28 125 25 50 .78 125 19 .29 6875 51 .79 6875 5 13 20 .31 25 13 26 52 .81 25 21 .32 8125 53 .82 8125 11 22 .34 375 27 54 .84 375 23 .35 9375 DO .85 9375 3 6 12 24 .37 5 7 14 28 56 .87 5 25 .39 0625 57 .89 0625 13 26 .40 625 29 58 .90 625 27 .42 1875 59 .92 1875 7 14 28 .43 75 15 30 60 .93 75 29 .45 3125 61 .95 3125 15 30 .46 875 31 62 .96 875 31 .48 4375 63 .98 4375 STRENGTH OF U.S. STANDARD BOLTS FROM K TO 3 IN. DIAMETER* Diameter of bolt, in. Bottom of thread, aq in. Bolt Areas 'o jCj3j'Oai.S.> 1j |i Tensile strength, lb s? A t 12,500 lb per aq in. A t 17,500 lb per sq iu. s 5 ^> Shearing strength, lb Full bolt Bottom of thread --5 oi (t At 10,000 lb per sq i... At 7,500 lb per rq in. At 10.000 lb per sq in. S H Mns Ms H W. H H 7A 1 1W m1H ih 1M 1H 21H 2M 2H 294 3 20 18 16 14 13 12 11 10 9 8 7 7 6 6 5H 5 5 4M 4H 4 4 ZlA 0.049 0.077 0.110 0.150 0.196 0.248 0.307 0.442 0.601 0.785 0.994 1.227 1,435 1.767 2.074 2.405 2.761 3.142 3.976 4.909 5.940 7.069 0.027 0.045 0.068 0.093 0.126 0.162 0.202 0.302 0.419 0.551 0.693 0.890 1.054 1.294 1.515 1.745 2.049 2.300 3.021 3.716 4.620 5.428 270 450 680 930 1,260 1.620 2,020 3,020 4.190 5.510 6.990 8,890 10,540 12,940 15,150 17,450 20,490 23,000 30,210 37,160 46,200 54,280 340 570 850 1,170 1,570 2,030 2,520 3,770 5.240 6,890 8.660 11,120 13,180 16,170 18,940 21,800 25,610 28,750 37,770 46,450 57,750 67,850 470 790 1,190 1,630 2,200 2.840 3,530 5,290 7,340 9,640 12,130 15,570 18,450 22,640 26,510 30,520 35,860 40,500 52.870 65,040 80,840 94,990 380 580 830 1,130 1,470 1,860 2,300 3,310 4,510 5,890 7.450 9,200 11,140 13,250 15,550 18,040 20,710 23,560 29,820 36,820 44,580 53,020 490 770 1.100 1,500 1,960 2.480 3.070 4.420 6.010 7,850 9,940 12,270 14.850 17,670 20,740 24,050 27,610 31,420 39,760 49,090 59,400 70.690 200 340 510 700 940 1,220 1,510 2,270 3.150 4.130 5,200 6.670 7.910 9.700 11.360 13,080 15,370 17,250 22,660 27,870 34,650 40.710 270 450 680 930 1,260 1,620 2,020 3.020 4,190 5.510 6,930 8.900 10,540 12,940 15,150 17,440 20,490 23.000 30.210 37,160 46,200 54,280 * From Marks, Mechanical Engineers' Handbook, 4th. ed., McGraw-Hill, 1941. ETC 02998 308 HANDBOOK OF RIGGING SQUARE AND HEXAGONAL REGULAR BOLT HEADS* (All dimensions in inches.) Rough and semifinished Finished o lt diam eter Width across flats Min width across corners Height Width across fiats Min width across corners Height a Max Min Hex Square Max Min Hex Square H Ms H Ms W H yi 1 Hi 1M 1M m 2 2H 2M m 3 n Mb M H yi 4l6 m lMs 14 l'Mo Hi 2M 2H 3 3*8 3H 44 0.363 0.484 0.544 0.603 0.725 0.847 0.906 1.088 1.269 1.450 1.631 1.813 2.175 2.538 2.900 3.263 3.625 3.988 4.350 0.414 0.552 0.620 0.687 0.827 0.966 1.033 1.240 1.447 1.653 1.859 2.067 2.480 2.893 3.306 3.720 4.133 4.546 4.959 0.498 0.665 0.747 0.828 0.995 1.163 1.244 1.494 1.742 1.991 2.239 2.489 2.986 3.485 3.982 4.480 4.977 5.476 5.973 'tfu 4*4 M 464 H64 H a 2^2 2^2 1 1^2 14 l24i 13MU 2 Mb Mb H H 4I8 *8 4(8 IV* IMe 14 11 Mb lyi 2U 2H 3 3*i 3M 44 4H 0.428 0.552 0.613 0.737 0.799 0.861 0.922 1.108 1.293 1.479 1.66.5 1.850 2.222 2.593 2.964 3.335 3.707 4.078 4.449 0.488 0.629 0.699 0.840 0.911 0.982 1.051 1.263 1.474 1.686 1.898 2.109 2.533 2.956 3.379 3.802 4.226 4 649 5.072 0.588 0.758 0.842 1.012 1.097 1.182 1.266 1.521 1.775 2.031 2.286 2.540 3.051 3.560 4.070 4.579 5.090 5.599 6.108 Ms 1 27Aa H 2;^ Hi 1M iu MHs Hi 2 Mi 2M Regular nuts (rough, semifinished, and finished) have a maximum width across flats of except for D - H to Ms when the width = 1 HD -|- Ms. D is bolt diameter. Tolerance for width is --0.050Z). Thickness is yiD. * From Marks, Mechanical Engineer*' Handbook, 4th ed., McGraw-Hill, 1941. APPENDIX 309 DIMENSIONS OF STANDARD RAILS AND LIGHT RAILS* Standard and nominal weight Weight per yd. lb Area of section, sq in. Dimensions, in. abc Axis 1-4 r. r. S. in.4 in. in.* X. in. Penna. R.R. 152 A.R.E.A. 131 A.R.E.A. 112 A.S.C.E. 110 A.R.E.A. 110 A.S.C.E. 100 A.A.R.-A 100 A.A.R.-B 100 A.R.E.A. 100 A.S.C.E. 95 A.S.C.E. 90 A.A.R.-A 90 A.A.R.-B 90 A.S.C.E. 85 A.S.C.E. 80 A.A.R.-A 80 A.A.R.-B 80 A.S.C.E. 75 A.S.C.E. 70 A.A.R.-A 70 A.A.R.-B 70 A.S.C.E. 65 A.S.C.E. 60 A.A.R.-A 60 A.A.R.-B 60 A.S.C.E. 55 A.S.C.E. 50 A.S.C.E. 45 A.S.C.E. 40 A.S.C.E. 35 A.S.C.E. 30 A.S.C.E. 25 A.S.C.E. 20 A.S.C.E. 16 A.S.C.E. 14 A.S.C.E. 12 A.S.C.E. 10 A.S.C.E. 8 152 130.8 112.4 110.36 100.3 100.3 101.49 94.5 89.9 89.96 90.7 84.7 80.0 80.0 80.8 74.6 69.5 69.7 64.5 60.6 60.0 54.7 49.6 44.8 40.1 35.0 30.5 24.3 20.4 15.8 13.6 12.0 9.76 7.84 12.86 11.02 10.82 9.84 9.84 9.85 9.95 9.28 8.83 8.82 8.87 8.33 7.86 7.86 7.91 7.33 6.81 6.82 6.33 5.93 5.86 5.38 4.87 4.40 3.94 3.44 3.00 2.39 2.00 1.55 1.34 1.18 0.96 0.77 8 7 64* 6 Vi 6K SK 6 .9*IU 6 591# 5W 594 541# 5 5 Vi 4`M, 4141# 444 *K 434^ 4ZU i'A 4K 44i 4V1# 344 3i M 3X 3M 3W 2K m 2H 2H 2 1H 191# 6% 6 5M 6V4 5 Vi 5 V? 59*4 544 5M 544 5V4 594* 541# 5 444 4V1# 4i4i 444 4K 4M 4 31^ 4H 394 3'Ha 3,4 3M 3W 2H ' 2H 244 2 Vf # 2 1H lWa 3 3 22442 88.5 65.8 2.65 22.6 2.44 18.1 22442 2H 2M 22 Via 2% 2`M 294 2?1 23 Via 291# 2V4 2!4 2V\e 2i94a 291# 294 57.0 44.0 48.9 41.3 49.0 38.8 34.4 38.7 32.3 30.1 26.4 28.8 25.1 22.9 19.7 21.0 2.30 2.11 2.22 2.05 2.22 2.05 1.97 2.19 1.91 1.90 1.83 1.9! 1.78 1.77 1.70 1.75 16.8 14.6 15.0 13.7 15.1 13.3 12.2 12.5 11.4 11.1 10.1 10.2 9.4 9.1 8.2 8.2 2`4ia 2U 2 '4 2V4 2H 2V4 2 194 IK UV1# 1!4 llV4a llVi4 lHa 1 `91# 16.9 14.6 -15.4 12.0 9.9 8.1 6.6 5.2 4.1 2.5 1.9 1.2 0.76 0.66 0.40 0.26 1.63 1.57 1.62 1.50 1.43 1.36 1.29 1.23 1.16 1.02 0.99 0.89 0.75 0.75 0.65 0.58 7.4 6.6 6.5 5.7 5.0 4.3 3.6 3.0 1.8 1.4 1.0 0.73 0.63 0.46 0.32 3.5 3.2 2.98 2*9*4 2.73 2.75 2.63 2H 2.65 2*9*4 2.44 2.47 2.38 2.31 2.27 2.30 2.22 2.20 2.14 2.05 2.13 1.97 1.88 1.78 1.68 1.60 1.52 1.33 1.27 1.15 1.02 0.96 0.87 0.75 I = moment of inertia of section, r =* radius of gyration. S = section modulus, x -- dis tance from neutral axis to base. * From Marks, Mechanical Engineers' Handbook, 4th ed., McGraw-Hill, 1941. ETC 03000 310 HANDBOOK OF RIGGING WIRE AND SHEET-METAL GAUGES* (Diameters and thicknesses in decimal parts of an inch.) -4-5 as r* .S x 9 .5 ,83 35*1 5 list iSS-2.! 5 % -- 3u 3 5 i 5 X3---^0u--lal ^ :i;g* I==S V 5) X SC p S-COQ Z; x a*fl = -- 2 !) 3 W,, J 3au M 4> b **" a 0000000 00000000000 0000 000 000 0.460 0.410 0.365 0.325 0.289 0.258 0.229 0.204 0.182 0.162 0.144 0.128 0.114 0.102 0.091 0.081 0.072 0.064 0.057 0.051 0.045 0.040 0.036 0.032 0.0285 0.0253 0.0226 0.0201 0.0179 0.0159 0.0142 0.0126 0.0113 0.0100 0.0089 0.0080 0.0071 0.0063 0.0056 0.0050 0.0045 0.0040 0.0035 0.0031 0.4900 0.4615 0.4305 0.3938 0.3625 0.3310 0.3065 0.2830 0.2625 0.2437 0.2253 0.2070 0.1920 0.1770 0.1620 0.1483 0.1330 0.1205 0.L055 0.0915 0.0800 0.0720 0.0625 0.0540 0.0475 0.0410 0.0348 0.0317 0.0286 0.0258 0.0230 0.0204 0.0181 0.0173 0.0162 0.0150 0.0140 0.0132 0.0128 0.0118 0.0104 0.0095 0.0090 0.0085 0.0080 0.0075 0.0070 0.0066 0.0062 0.0060 0.0058 0.0055 0.0052 0.0050 0.0048 0.0046 0.0044 0.454 0.425 0.380 0.340 0.300 0.284 0.259 0.238 0.220 0.203 0.180 0.165 0.148 0.134 0.120 0.109 0.095 0.083 0.072 0.065 0.058 0.049 0.042 0.035 0.032 0.028 0.025 0.022 0.020 0.018 0.016 0.014 0.013 0.012 0.010 0.009 0.008 d.007 0.005 0.004 0.500 0.464 0.432 0.400 0.372 0.348 0.324 0.227 0.300 0.219 0.276 0.212 0.252 0.207 0.232 0.204 0.212 0.201 0.192 0.199 0.176 0.197 0.160 0.194 0.144 0.191 0.128 0.188 0.116 0.185 0.104 0.182 0.092 0.180 0.080 0.178 0.072 0.175 0.064 0.172 0.056 0.168 0.048 0.164 0.040 0.161 0.036 0.157 0.032 0.155 0.028 0.153 0.024 0.151 0.022 0.148 0.020 0.146 0.018 0.143 0.0164 0.139 0.0148 0.134 0.0136 0.127 0.0124 0.120 0.0116 0.115 0.0108 0.112 0.0100 0.110 0.0092 0.108 0.0084 0.106 0.0076 0.103 0.0068 0.101 0.0060 0.099 0.0052 0.097 0.0048 0.095 0.0044 0.092 0.0040 0.088 0.0036 0.085 0.0032 0.081 0.0028 0.079 0.0024 0.077 0.0020 0.075 0.0016 0.072 0.0012 0.069 0.0010 0.500 0.469 0.438 0.406 0.375 0.344 0.312 0.281 0.266 0.250 0.234 0.219 0.203 0.188 0.172 0.156 0.141 0.125 0.109 0.094 0.078 0.070 0.062 0.056 0.050 0.0438 0.0375 0.0344 0.0312 0.0281 0.0250 0.0219 0.0188 0.0172 0.0156 0.0141 0.0125 0.0109 0.0102 0.0094 0.0086 0.0078 0.0070 0.0066 0.0062 0.0059 0.0055 0.0053 0.0051 0.0049 0.0047 0.4902 0.4596 0.4289 0.3983 0.3676 0.3370 0.3064 0.2757 0.2604 0.2451 0.2298 0.2145 0.1991 0.1838 0.1685 0.1532 0.1379 0.1225 0.1072 0.0919 0.0766 0.0689 0.0613 0.0551 0.0490 0.04290.0368 0.0337 0.0306 0.0276 0.0245 0.0214 0.0184 0.0169 0.0153 0.0138 0.0123 0.0107 0.0100 0.0092 0.0084 0.0077 0.0069 0.0065 0.0061 0.0057 0.0054 . 0.0052 0.0050 0.0048 0.0040 0.6666 0.6250 0.5883 0.5416 0.5000 0.4452 0.3964 0.3532 0.3147 | 0.2804 0.2500 j 0.2225 0.1981 0.1764 I 0.1570 I 0.1398 j 0.1250 ; 0.1113 0.0991 ! 0.0882 ' 0.0785 ; 0.0699 0.0625 0.0556 0.0495 0.0440 0.0392 0.0349 0.0313 0.0278 0.0248 0.0220 0.0196 0.0175 0.0156 0.0139 0.0123 0.0110 0.0098 0.0087 0.0077 0.0069 0.0061 0.0054 0.0048 0.0043 0.0039 0.0034 0.0031 0.0027 0.0024 0.0022 0.0019 0.0017 0.0015 0.0014 0.0012 * From Marks. Mechanical Engineers' Handbook, 4th ed., McGraw-Hill, 1941. KTC 03 00 1 APPENDIX WEIGHTS OF SQUARE AND ROUND STEEL BARS* (For iron, subtract 2 per cent.) 311 Size, in. Weight, lb per Lin ft Square Round Size, Weight, lb per lin ft Square Round Size, in. Weight, lb per lin ft Square Round Size. Weight, lb per lin ft Square Round 0 He He H He H 7Ae Vi He H 'He H `Me H `Me 1 He H Hi y< Hi H 7Ae M Me H `Ha W `He `Me 2 Me w Ha H Hi H Me Me W `Me Ms `Me 0.013 0.053 0.120 0.010 0.042 0.094 3 Me H He 0.213 0.332 0.478 0.651 0.167 0.261 0.376 0.511 M Hi H Me 0.850 1.076 1.328 1.607 0.668 0.845 1.043 1.262 M Me H `Me 1.913 2.245 2.603 2.988 1.502 1.763 2.044 2.347 H `Me `Me 3.400 3.838 4.303 4.795 5.313 5.857 6.428 7.026 2.670 3.015 3.380 3.766 4 Ha W Hi 4.172 4.600 5.049 5.518 H Hi H Ha 7.650 8.301 8.978 9.682 6.008 6.519 7.051 7.604 M Hi H `Ha 10.413 8.178 11.170 8.773 11.953 9.388 12.763 10.024 H `Me 7A `Me 13.600 14.463 15.353 16.270 10.681 11.359 12.058 12.778 5 Ha Hi 17.213 13.519 18.182 14.280 19.178 15.062 20.201 15.866 M Me H Ha 21.250 16.690 22.326 17.534 23.428 18.400 24.557 19.287 25.713 20.195 26.895 21.123 28.103 22.072 29.338 23.042 H Me H `Ha n `Me H `Me 30.60 24.03 31.89 25.05 33.20 26.08 34.54 27.13 35.91 28.21 37.31 29.30 38.73 30.42 40.18 31.55 41.65 32.71 43.15 33.89 44.68 35.09 46.23 36.31 47.81 37.55 49.42 38.81 51.05 40.10 52.71 41.40 54.40 42.73 56.11 44.07 57.85 45.44 59.62 46.83 61.41 48.23 63.23 49.66 65.08 51.11 66.95 52.58 68.85 54.07 70.78 55.59 72.73 57.12 74.71 58.67 76.71 60.25 78.74 61.85 80.80 63.46 82.89 65.10 85.00 66.76 87.14 68.44 89.30 70.14 91.49 71.86 93.71 73.60 95.96 75.36 98.23 77.15 100.53 78.95 102.85 80.78 105.20 82.62 107.58 84.49 109.98 86.38 112.41 88.29 114.87 90.22 117.35 92.17 119.86 94.14 6 Me Hi M Hi H Ae H Me ' Me H `Me 7A `Me 7 Me Ha H Me H Ha Vi Me H `Me H Ha 7A `Me 8 W Ha M Ha H Me M Me H `Me n `Me H `Me 122.4 125.0 127.6 130.2 132.8 135.5 138.2 140.9 143.7 146.4 149.2 152.1 154.9 157.8 160.7 163.6 166.6 169.6 172.6 175.6 178.7 181.8 184.9 188.1 191.3 194.5 197.7 200.9 204.2 207.5 210.9 214.2 217.6 221.0 224.5 227.9 231.4 234.9 238.5 242.1 245.7 249.3 252.9 256.6 260.3 264.0 267.8 271.6 96.1 98.2 100.2 102.2 104.3 106.4 108.5 110.7 112.8 115.0 117.2 119.4 121.7 123.9 126.2 128.5 130.9 133.2 135.6 137.9 140.4 142.8 145.2 147.7 150.2 152.7 155.3 157.8 160.4 163.0 165.6 168.2 170.9 173.6 176.3 179.0 181.8 184.5 187.3 190.1 192.9 195.8 198.7 201.5 204.5 207.4 210.3 213.3 9 Me H Ha 275.4 279.2 283.1 287.0 216.3 219.3 222.4 225.4 H 290.9 228.5 Hi 294.9 231.6 n 298.8 234.7 Hi 302.8 237.8 H 306.9 Me 310.9 M 315.0 `Ha 319.1 241.0 244.2 247.4 250.6 H 'Ha `Me 323.2 327.4 331.6 335.8 253.9 257.1 260.4 263.7 10 Ha a Hi M Ha H He 340.0 344.3 348.6 352.9 357.2 361.6 366.0 370.4 267.0 270.4 273.8 277.1 280.6 284.0 287.4 290.9 H Hi H `Ha 374.9 379.3 383.8 388.4 294.4 297.9 301.5 305.0 H 392.9 `Me 397.5 H 402.1 `Me 406.7 308.6 312.2 315.8 319.5 U Me H He 411.4 416.1 420.8 425.5 323.1 326.8 330.5 334.2 H 430.3 338.0 Hi 435.1 341.7 n 439.9 345.5 7Ae 444.8 349.3 K 449.7 Me 454.6 H 459.5 `Ha 464.4 353.2 357.0 360.9 364.8 M `Me H `Me 469.4 474.4 479.5 484.5 368.7 372.6 376.6 380.5 * From Marks, Mechanical Engineer*' Handbook, 4th ed.f McGraw-Hill, 1941. ETC 03002 312 HANDBOOK OF RIGGING Nominal in ternal, in. Actual exter nal, in. STANDARD PIPE AND LINE PIPE* Diameter Ja . Circum ference li= a |l a c 0 "3 Z <s External, in. Internal, in. Transverse areas Length of pipe per sq ft of External surface, ft Internal, aq in . "a . ca "5 ? a "3 s 'Z, s? *a3v^ sj z Length of pipe contain 1cu ft, i fn tg Nom inal weight per ft, lb ao a! a t. *3 g Z M y* H 1 m 0n? 3 4 65 88 11900 111022 0.405 0.540 0.675 0.840 1.050 00.27 0.068 0.36 ,0*8 0.49 0.091 0.62 0,109 0.82 0.113 1.27 21,.1720 2.63 3.30 0.85 1.14 1.55 1.95 2.59 0.13 0.23 0.36 0.55 0.87 1.315 1.660 1.900 2.375 2.875 1.05 0.134 11.38 0.140 61 0.145 2,07 0.154 2.47 0.204 4.13 5.22 5.97 7.46 9.03 3,29 4.34 5,06 6.49 7.75 1.36 2.16 2.84 4.43 6.49 3.500 4.000 4.500 5.563 6.625 3,07 0.217 11.00 9.63 3.55 0.226 12.57 11.15 4 03 0.237 14.14 12.65 5.05 0.259 17.48 15.85 6.07 0.280 20.81 19.05 9.62 12.57 15.90 24.31 34.47 8.625 8.625 9.625 10.750 10.750 10.750 12.750 12.750 8.07 0.276 27.10 25.35 7.98 0.322 27.10 25.07 8.94 0.344 30.24 28.08 10.19 0.278 33.77 32.01 10.14 0.306 33.77 31.86 10.02 0.366 33.77 31.47 12.0012.09 0.328 40.06 37.98 0.375 40.06 37.70 58.43 58.43 72.76 90.76 90.76 90.76 127.68 127.68 00..0160 0.19 0.30 0.53 0.120.07 9.44 14.15 2513.00 7.08 10.49 1383.30 0.17 5.66 7.76 751.20 0.25 4.55 6.15 472.40 0.33 3.64 4.64 270.00 0.24 0.42 0 57 0.85 1.13 27 18 IS 14 14 0.86 1.50 2.04 3.36 4.78 0.50 2.90 0.67 0.80 22..0310 1.07 1.61 1.71 1.33 3.65 2.77 2.37 1.85 1.55 166.90 96.25 70.66 42.91 30.10 1.68 1IM 2,27 2.72 U11VU4 83.65 \iy 5.79 7.39 9.89 12.73 19.99 28.89 o 94 2.68 1.09 0.96 3.18 0.85 4.32 0.69 5.59 0.58 1.25 1.08 0.95 0.76 0.63 19.50 14.57 11.31 7.20 4.98 7.57 9.11 10.79 14.62 18.97 8 888* 51.15 50.02 62.72 81.55 80.75 7.28 0.44 8.41 0.44 10.04 0.40 190..2011 0.36 0.36 0.47 0.48 0.43 0.37 0.38 22..8828 24,69 28.55 2.29 33.91 1.76 31.20 1.78 34.24 88888 12.8878.82 11.94 0.36 0.38 114.80 0.30 0.32 113.10 14.59 0.30 0.32 1.82 40.48 1.25 43.77 1.27 49.56 888 Nom inal internal, in. Actual external, in. Approx internal diaiu, in. Nom inal thick ness, in . E x te rn a l, in. Internal, iu. M etal, sq in. E x te rn a l surface, ft Nom inal weight per ft, lb Diameter EXTRA-STRONG PIPE* Circumfer ence Transverse areas Length of pipe per sq ft of "a s a. 43 ^ ** a Id fi a SU O31 vS-m 3nt:- H M H Vi H 1 1V4 2U4 2W 3 3H 4 65 11802 0.405 0.540 0.675 0.840 1.050 0.21 0.29 0.42 0.54 0.74 1.315 1.660 1.900 2.375 2.875 0.95 1.27 1.49 1.93 2.32 3.500 4.000 4.500 5.563 6.625 2.89 3.36 3.82 4.81 5.75 8.625 7.63 10.750 9.75 12.750 11.75 0.100 0.123 0.127 0.149 0.157 0.182 0.194 00..222013 0.280 0.304 0.321 0.341 0.375 0.437 0.500 0.500 0.500 1.27 21..1720 2.64 3.30 4.13 5.22 5.97 7.46 9.03 11.00 12.57 14.14 17.48 20.81 27.10 33.77 40.06 0.64 0.92 1.32 1.70 2.31 2.99 4.00 4.69 6.07 7.27 9.09 1102..5050 15.12 18.07 23.96 30.63 36.91 0.13 0.23 0.36 0.55 0.87 0.03 0.10 0.07 0.14 00..2126 0.23 0.32 0.43 0.44 1.36 2.16 2.84 4.43 6.49 0.71 1.27 1.75 2.94 4.21 0.65 0.89 1.08 1.50 2.28 9.62 12.57 15.90 24.31 34.47 68..8567 11.45 18.19 25.98 3.05 3.71 46..1416 8.50 58.43 45.66 12.76 90.76 74.66 16.10 127.68 108.43 19.25 9.43 7.08 5.66 4.55 3.64 2.90 22..0310 1.61 1.33 1.09 0.96 0.85 0.69 0.58 0.44 0.36 0.30 18.63 12.99 9.07 7.05 5.11 0.31 0.54 0.74 1.09 1.47 4.02 3.00 2.56 1.98 1.65 2.17 2.99 3.63 5.02 7.66 1.33 10.25 11..1040 12.50 14.98 00..6769 20.78 28.57 0.50 43.34 0.40 54.73 0.33 65.41 * From Marks, Mechanical Engineers' Handbook, 4th ed., McGraw-Hill, 1941. FTC 03004 INDEX A Bending stress in wire rope, 52 A-frame derrick 239 Abaca, 11 Acceleration stress, 53 Accident prevention, 270-279 "Acco" Endweldur chain, 66 "Acco-Loc" cable eye splice, 48 Allowable wear on rope, 60 Aluminum ladders, 217 Anchor knot, 25 Anchorage of rope on drum, 55 Bends, reverse, in rope, 50 rope, 21-33 Bent, scaffold, 156 Bight of rope, 22 Blackwall hitch, 26 Bleeding, treatment for, 283, 284 "Blue Center" wire rope, 39 Blue stain, 85 Boat knot, 22 Boatswain's chair, 172, 191-199 Angle, fleet, 51 Annealing, 65, 69 Boatswain's-chair hitch, 31 Bolt rope, 12 Annual rings, 84, 91, 92, 105 Areas of plane figures, 3, 4 Artificial respiration, 285, 287 Boom, derrick, 251-253 Boom indicator, 249, 250 Bow warping, 89 Asphalt on wire rope, 39 Attachments for wire rope, 43 Automotive crane, 242 Bow knot, 32 Bowline, 24 Boxed heart, 85 . Bracing, 156-160 importance of, 222 B Braided sling, 81-83 Babbitt for cable socketing, 47 Brakes, crane, 233, 234, 244, 245 Back-handed sailor's knot, 32 Brashness, 85, 103-105, 129 Back hitch, 31 Break, cross, in wood, 85, 108 Back splice, 31 Breaking in a new rope, 57 Barrel hitch, 31 Breaking strength of rope, 55, 56 Basket guard on ladder, 175, 176, 178 Breast derrick, 240 Basket slings, 75, 82, 83 Bridge crane, 234, 235 Bastard sawn, 85 Broken wires in rope, 59, 60 Beams, calculations for metal, 224- Brown stain, 85 232 Bruise, 85 calculations for wood, 218-221 Bucket hitch, 25 location of defects in, 95 Builder's knot, 25 metal, strength and weight of, 226, Built-up scaffolding, 151-168 227 Buntline hitch, 31 wood, 96, 102 Burl, 86 Bearers, 155 Bearing pressure of rope, 50, 51 C Becket bend, 23 Cable, 34, 63 Belaying-pin hitch, 30 Cable clamp, 45 Bell-ringer's knot, 33 Cable-laid rope, 35 Belt, life, 189-192 Calculations for metal beams, 224^232 315 316 INDEX Calculations for wood beams, 218-- 221 Cantilever beams, strength of, 228 Carrick bend, 32 Carrying injured person, 281-283 Caterpillar crane, 242 Cat's paw, 26 Cells, wood, 89, 90 Chain, safe loads on, 66 Chain-hoist accident, 272, 273 Chain hoists, 257-262 Chain knot, 28 Chair, boatswain's, 172, 191-199 Check, 85, 95, 96, 131 Chemicals, effect on rope, 17, 43 Chesebro-Whitman scaffolding, 163, 166-168 Chimneys, painting and repairing, 172-188 Choker sling, 75, 82, 83 Circle, area of, 3 Circular stack scaffold, 178-184 Clamp, cable, 45 Clipped eyes, 43-45 Clove hitch, 25 Coal-unloader rope, 35 Coarse-laid rope, 36 Codes, reference, 288-296 Columns, calculations for wood, 222, 223 Comb grain, 86 Compression failure, 85, 96, 106, 107, 132 Compression wood, 85, 108, 109, 132 Condemning wire rope, 59, 60 Condemning worn chain, 21, 67, 68 Conductivity, electrical, of manila rope, 22 Cone, volume of, 5 Conifer, 85 Constructions of wire ropes, 34 Corrosion, 43 Cotton rope, 13 Cracks in chain links, 67 Crane ropes, 35 Cranes, 233-256 Crank, 8, 9 Crawler crane, 242 Critical diameter of sheave, 49 Crook warping, 89 Crosby clips, 43, 44 Cross break, 85, 108 Cross grain, 85, 98, 99, 129, 130, 206 Cross section, 86 Crossed running knot, 31 Crowbar, 8 Crown knot, 27 Cup warping, 89 Cut splice, 29 Cylinder, volume of, 5 D Decay, 86, 109-112, 211 Derrick, 233-256 Derrick ropes, 35 Design of rope installations, 43 Diagonal grain, 86, 98, 99, 101, 102, 129, 206 Diamond knot, 33 Differential chain hoist, 257, 259 Dip grain, 86, 103, 207 Displacement of rope strands, 52 Double becket hitch, 23 Double blackwall hitch, 26 Double bowknot, 32 Double bowline, 24 Double hitch, round turn and, 25 Double overhand knot, 24 Drums, 51, 55 Dry manila rope, 21 E Edge grain, 86, 87 Electrical conductivity of rope, 22 Elevator rope, 34, 35 Endless sling, 74 "Endweldur" chain, 66 Equalizing sheave, 50 Extension ladder, 212, 213 Extra-pliable rope, 37 Eyebolts, safe loads on, 70 Eye splice, 28, 48 manila Forest Products Laboratory, 208 Factor of safety, 15, 17, 56, 62, 63, 145 Failure, compression, 96, 106, 107 ETC 03006 INDEX 317 Fiber rope, 11-33 Fibers, rope, 12, 20 Figure eight knot, 22 Filler-wire rope, 35 First aid to the injured, 280-287 Fisherman's bend, 25 Fisherman's eye knot, 24 Fisherman' knot,- 23 "Fist Grip" cable clip, 45 Fork-lift industrial truck, 243 Flagpole knot, 29 "Flash-Alloy" chain, 66 Flat grain, 86, 87, 100 Flat knot, 22 Flattened-strand rope, 35 Fleet angle, 51, 52 Flemish eye splice, 28, 33 Flemish knot, 32 Fracture, 104, 105 Frequency of use of wire rope, 61 Friction of rope on drum, 55 Friction of wire rope, 53, 54 Frozen rope, 16 G Gantline, 172, 173 Gantry crane, 234, 235 Gasoline, hazard in use of, 271 Gin pole, 240, 251 Goggles, 271 Grades of steel for wire rope, 38 Grain, cross, 85, 86, 98-103, 129, 130 Grain of wood, 87 Granny knot, 23 "Green Strand" wire rope, 39 Grommet, 28 Grommet sling, 74 Grooves, sheave, 49 Guard rope, 35 Guys, 35, 253 Guyed derrick, 241, 253 H Half-hitch, 25 Halyard bend, topsail, 33 Hammerh ;d crane, 236 Hand signals for hoisting, 267, 268 Handcuffs, rope, 28 Handling injured persons, 280 Hard-laid rope, 13 Hardwood, 93 Harness, parachute, 191, 200 Harness hitch, 27 Hat, safety, 188, 270 Haulage rope, 35 Hawser bend, 23, 26 Hazard of rope failure, 62 Heart, rope, 20 wood, 85 Heartwood, 86 "Heavi-Lift" chain, 66 Heaving-line bend, 25 Hemp rope, 12 Henequen rope, 12 "Herc-Alloy" chain, 66 "Hercules" wire rope, 39 Highway guard rope, 35 Hitches, 21-33 Hoist rope, 35 Hoist signals, 267-269 Hoists, 233-256 Holes, 132 Honeycombing, 86 Hooks, hoisting, 69 worn, 259, 260 I Identification of chain manufac turers,. 13, 39, 66, 69 Identification of wood species, 114-- 127 Improved plow-steel rope, 38, 56 Inclined plane, 7 Independent wire-rope center, 37 Indicator, boom, 249, 250 Industrial truck crane, 243, 248 Injuries, treatment of, 280-287 Inspection, chain, 65, 66 manila rope, 20 wire rope, 59-63 Interlocked grain, 86 Iron chain, 66 Iron rope, 38 Irregular shapes, areas of, 3 Jacks, 263-266 Jib cranes, 237 Jute rope, 12 J 318 INDEX K Key for identification of wood species, 114^127 Killick hitch, 33 Kinks in rope, 41 Knot shortening, 24 Knots, rope, 21-33 wood, 86, 93-95, 131, 207 Ladder accident, 274-277 Ladders, 204-217 on chimneys, 174-177 Lang-lay rope, 34 Lanyard knot, 33 Lark's head with toggle, 32 Lashing, 29, 30 Lateral bracing of beams, 229 Laws relating to rigging, 288-296 Lay of rope, 20, 34 Lead for cable socketing, 47 Ledger, 155 Ledger and pole lashing, 29 Left-lay rope, 34 Lever, 8 Life belts, 189-192, 271 Life line, 189, 191 Life net, 201, 202 Life of rope, 21 Lifting, 8 Limit device, 234, 244, 254 Live timber, 87 Load brake, 234, 244, 245, 257 Loads, safe (see Safe loads) Loads lifted by men, 277, 279 Locomotive crane, 242 Long splice, 29 Low-density wood, 87 Lubber's knot, 23 Lubrication of rope, 12, 42 M Magnesium ladders, 217 Magnus hitch, 25 Manila rope, 11-33 Manila-rope accident, 273, 274 Marline spike hitch, 22 Marling hitch, 28 Material hoist tower, 166, 170 Measuring rope size, 13, 42 Mechanical load brake, 234, 244, 245 257 Mesh knot, 26 Midshipman's hitch, 26 Midshipman's knot, 24 Mild plow-steel rope, 38, 56 Mill hoist rope, 35 Mine hoist rope, 35 Modified Seale rope, 36 Moisture, effect on rope, 16 Molds, 111, 112 "Monarch Whyte Strand" wire rope, 39 " Monitor" wire rope, 39 Mooring knot, 25 Mousing, 26, 272 N Nails, holding power of, 152 Needle-beam scaffolds, 169 Net, life, 201, 202 Net splice, 26, 202 Netting knot, 26 Nonrotating rope, 35, 37 Nylon rope, 13 0 Oil-well rope, 35 Outrigger scaffold, 167, 168 calculations for, 231 Overhand knot, 22-24 Overhead crane, 233, 243, 244 Overloaded hoist hook, 69 Paint on wood, 208, 210 Painter's scaffold hitch, 31 Parachute harness, 191, 200 Patent Scaffolding Co. winch, 144- 148, 180-182 Personal hazard of rope, 62 Pillar crane, 238 Pitch, 87, 132 Pitch pocket, 87, 98, 132, 207 Pitcher knot, 28 ETC 03008 INDEX 319 Pith ray, 89, 90 Planks, scaffold, 128-137 Plant, western ocean, 28 Pliable rope, 37 Plow-steel rope, 38, 56 Pole lashing, 29 Pole scaffold, 153 Pores, 87, 89, 91, 92, 103 , Portal crane, 239 Portuguese knot, 29 Posts, calculations for, 222, 223 Power-shovel, rope for, 35 Preservative, wood, 208 Pressure, bearing, on sheave, 50, 51 Prism, 5 Property hazard of rope, 62 Pull-lift chain hoist, 257 Pull to move object, 7 Purchasing rope, 13, 38 "Purple Strand" wire rope, 39 Putlog, 155 Pyramid, 2, 5 Q Quadrilateral, area of, 3 Quarter sawed, 86 R Radial, face, 88 Ramp, 7 Rays, 88 Rectangle, area of, 3 Red heart, 88 Reef knot, 22 Reef knot on the bight, 31 Reeving, 17, 54 Reeving line bend, 23 Regular lay, 34 Regulating lashing, 30 Reserve strength of wire rope, 61 Resin ducts, 88, 90 Respiration, artificial, 285-287 Resuscitation, 285-287 Reverse rope bends, 50 Rigging, special, 57 Right-lay rope, 34 Ring, volume of, 5 Rings, annual, 84, 91, 92, 105 Rivet scaffold hitch, 30 Rocking hitch, 26 Rollers, 266 Rolling hitch, 25, 27 Rope, fiber, 11-33 wire, 34-63 Rope accident, 273, 274 Rope handcuffs, 28 Rope-yarn knot, 33 Rosette knot, 23 Rot, 86, 109-112, 211 Round turn and double hitch, 25 Running bowline, 24 Running knot, 24, 31 S Safe loads, on beams, 218-220 on chains, 66 on columns and posts, 221-223 on eyebolts, 70 on manila rope, 16, 17 on manila rope falls, 17 on scaffold planks, 133 on shackles, 71 on slings, 82, 83 on wire rope, 56 "Safe-Line" cable clamp, 45 Safety, 270-279 Safety factor, 15, 17, 56, 62, 63, 145 Safety hats, 188, 270 Safety hitch for boatswain's chair, 31 Safety shoes, 270 "Safeway" scaffolding, 162 Sailor's knot, 22 back-handed, 32 Sap, 88 Sap stains, 85, 111, 112 Sapwood, 88 Scaffold for chimney, 178-184 Scaffold hitch, 30, 31, 169 Scaffolds, 128-169, 214 Screw-geared chain hoist, 257, 258 Seale-lay rope, 35-37 Second growth, 88 Sectional ladder, 213 Seizing, 25, 41 Shakes, 88, 95, 97, 131, 207 Sheaves, 48, 49, 51 Sheepshank, 24 knotted, 33 320 INDEX Sheet bend, 23, 26, 201 double, 32 with toggle, 32 Shock stresses, 53 Shoes, safety, 270 Short splice, 28 Shortening, knot, 24 Shoulder protection, 188 Shrinkage, 109 Shroud knot, 32 Signal rope, 35 Signals, hoist, 267-269 Single bow knot, 32 Single carrick bend, 32 Single knot, 22 Single leg sling, 76 Sisal rope, 12 Skids, 266 Sling accidents, 272-274 Slings, 72-83 for handling injured man, 31 safe loads on, 82, 83 Slip knot, 24 Slippery hitch, 30 Slippery ring knot, 25 Sliver, 12 Sockets for wire rope, 45--47 Soft-laid rope, 13 Softwood, 93 Solenoid brake, 233, 234 Sound wood, 88 Spanish windlass, 30 Speed, rope, 62 Spelter for socketing, 47 Sphere, volume of, 5 Spiral grain, 86, 98-102, 129, 206 Spliced eye, 48 Splices, 21, 26, 28, 29, 31 Split, 88, 131 Springwood, 88-92, 105 Spur-geared chain hoist, 257, 258 Stack scaffold, 178-184 Stacks, painting and repairing, 172- 188 Stains, sap, 88, 111, 112 Standards, safety, 288-296 Steel, grades of, for wire rope, 38 Steering rope, 35 Step ladder, 213 Stevedore's knot, 27 Stiff-leg derrick, 241, 252, 253 Stopper knot, 33 Storage of rope, 14, 39 Strands, 12, 34, 52 Strap on a rope, 27 Strength of manila rope, 15, 16 Strength of men, 277, 279 Strength ratio, 128 Stress diagram for trolley cable, 58 Stress on slings, 58 Stress, total, on hoist rope, 54 Stresses in derricks and gin poles, 253 Studding sail hitch, 25 Swinging scaffold, 138-150, 272 Snubber, 29 Square knot, 22 Sudden stress on rope, 53 Summerwood, 89-92, 105 Surgeon's knot, 23 Suspended scaffold, 149, 150 T Tangential surface, 89, 100 Tar on wire rope, 39 Telegraph hitch, 27 Termites, 112-114 Testing of jacks, 265 Testing ladders, 207 Testing scaffold planks, 134-137 Thief knot, 23 Thrust-out scaffold, 167 "Tico Special" wire rope, 39 Tightly stretched cable, 57 Tiller rope, 35 Timber hitch, 25, 27 Topsail halyard bend, 33 Tower, material hoist, 166, 170 Tower crane, 237 Traction steel rope, 38 Transmission rope, 35 Trapezoid, area of, 3 Traveling crane, 233, 243, 244 Trestle ladder, 213, 214 Triangle, area of, 3 Trolley cable, 57 "Trouble Saver" scaffolding, 163-- 165 "Tubelox" scaffolding, 163, 166-168 Uncoiling rope, 14, 39-41 Usage of wire-rope constructions, 34 U slings, 82, 83 Varnish on wood, 208, 210 Vertical grain, 86 Volumes of solid figures, 5, 6 Wall crane, 236 Wall knot, 27 Wane, 89, 132 Warping, 89, 114, 115, 129 Warrington lay, 35 Waterproof rope, 20 Weak point on rope, 62 Wear, allowable, on wire rope, 60 Weaver's knot, 23, 26 Wedge socket, 45, 46 Yacht rope, 12 Yale & Towne chain, 66 Yarns, 12, 20 Yarn knot, 33 "Yellow Strand" wire rope, 39 Zinc for socketing, 47 Zone line, 110 ETC 03011