Document J3oRrzXpra315jxK2R52dwqda

82 ROSS A. MC FARLAN D have a front to rear downward slope, of perhaps 5 to 7, although this too must remain a matter of experience.29 It should be noted, of course, that the sloping of seats or back rests may be undesirable in jobs requiring special sitting positions or postures. 4. Sources of Anthropometric Data It has been emphasized in this discussion that it is often necessary to measure directly the population that will operate a given machine or perform a certain task because anthropometric differences among various industrial groups may be. quite marked. Unfortunately, relatively few anthropometric studies have been made of specific occupational groups. In many instances, therefore, surveys of this nature must be undertaken before the workers' equipment can be truly "humanengineered." In some cases, where less precise descriptive material may be suffi cient, a rough approximation of human dimensions for a given group may be obtained by consulting published anthropometric data on different series of indi viduals, especially if use is made of the concept of correlations between the various body dimensions (see page 68). Much of the existing data for American males has been taken on military populations. Newman and White, working with the United States Army Quartermaster Corps, have published the results of a com prehensive survey of 24,000 men in their "Reference Anthropometry of Army Men."14 For the Air Force, two publications offer valuable data, "Human Body Size in Military Aircraft and Personal Equipment"17 and the comprehensive" "Anthropometry of Flying Personnel."18 . For the general civilian population, Hooton has presented data on 8 body measurements especially pertinent to seat design for 1,900 males and 1,900 females )| in his A, Survey in SeatingStudies on the body dimensions of women .are reported by O'Brien and Shelton in a United States Government publication, "Women's Measurements for Garment and Pattern Construction."88 In this rpport, medians, means, standard deviations, and coefficients of variation for 59 measure- ments of over 10,000 women are given, together with tables of partial correlations of the various dimensions. Comprehensive anthropometric data directly pertinent. to the design of desks, chairs, and'other equipment for school children of all.. ages are available in The Functional BodV M'easuremeftts'"ef'`' School Age.? Children;84 FoFspecific industrial occupational groups,' 'data:i>dfi tire dimensions df 'l commercial truck and bus drivers may be found in Human Body Size and Capa bilities in the Design and Operation of Vehicular Equipment.11 ....... At'airtimes','"however,'"it should be"feifie''b'eT,ed'`tlitttiiiriS^sllii(1i'3ts`,iii,eferabl'e7" and sometimes mandatory, to measure the working population directly before applying the data to the design and layout of industrial equipment. " R. O'Brien and W. C. Shelton. Women's measurements for garment and pattern con struction, Misc. Publication No. 454, Bur. Home Economics, U, S. Dept, of Agriculture, Wash ington, 1941. "W. E. Martin and F. P. Thieme, The Functional Body Measurement!! oj School. Age Children. National School Service Institute, Chicago, 1954. HUMAN ENGINEERING AND INDUSTRIAL SAFETY 83 in. Equipment Design in Relation to Human Capabilities ^'-lif'Mtich of the equipment within the working area can be divided into two Jufain''glasses: displays and controls. Controls are those devices that govern the *``'-^atron of the machines, and the problems that are associated with them are m gpentally those of the physiology and psychology of bodily movements.. days are those devices that tell how the machines are functioning. Display SStgmo ^ms are primarily concerned with the normal functioning of man's senses. Misdirect the input of the machines; displays show the output.85 A. VISUAL DISPLAYS |cidents may occur because a worker has not clearly perceived the location rement of the indicators, meters, or dials that relate to the functioning of his j(ent. Very often one finds that special safety precautions have been taken igard to one aspect of the working situation while little consideration has cuigiveh to other components of the job. Tasks may become uncomfortable and srayii |||hce inefficient when an individual is required to perform a number of successively or simultaneously, even though any single element of the job is ^jfsj^qVexecute. The extent to which an employee receives clear and unambiguous iffi^foliriatfion concerning all aspects of his job governs the way in which he exerts mmjJjS'Sjeliffi'Dntrolling movements as the operation requires over long periods of time. feresentation of Information"48 by Baker and Grether illustrates many of r^l']f!h^pfe,rbfd?sign OfdlsplayrdisCiTSsed'below.' 1. The Visual Field gider to obtain the maximum information from the surroundings and edisplays, controls, and moving parts or materials within the immediate Rlllpea, a field of vision with the minimum of substructions is necessary, "r.field of each eye, that is, the monocular .field, ordinarily subtends a jangle of about 160, and a vertical angle of about 145. In practice, ;e.size of the monocular field varies with the-level of illumination, the |I|j>'lor of the object viewed, and the age and condition of the viewer. The ^^wrer-described-in-a-j;ev.iew..iby.-.Hall..and-Greehba;umv.?2i.0.wihg-to the Jlge overlapping of the monocular fields the total field observed when lesSiare used subtends an angle approximately 200 in the horizontal axis; JHpifiVyi . rnr, eyes does not, of course, influence the extent of^he-vertical axis. ^|,Sifet'*'dffiii!si.ap.ply..when the eyes are fixed in their central position, asawhen looking 4A< .t ,|pKead. Extreme movements of the eyes to one side and then to the other, HmL ' ilfead in its normal position, will enable a man to scan the surroundings to SggBgJavita, ed., Human engineering in equipment design. Electrical Manujacturing. pSPiprint. Gage Publishing Co., New York, 1956. C. H. Best and N. B. Taylor", the Medical Practice. 2nd ed., Williams and Wilkins, Baltimore,*1940. PfgF^^^^^pfeHall and L. J. Greenbaum, Jr., Areas of vision and cockpit visibility, Trans. Am. m&mol- Otolaryngol., 55th Annual Meeting, 74-88 (1950). c ,