Document J3MpwVoy7nqQVw1J0mmpM06ve

HUMAN ENGINEERING AND INDUSTRIAL SAFETY 77 dimensions such as height or weight can permit general predictions for groups of ngSj who will use the machine, although they may be inaccurate as far as jgmliyiduals are concerned. In vehicle cabs, for example, where seat adjustability jrMenlj, the correlations of body dimensions indicate that tall, long-legged -75" R -I05*R ho adjust their seats in rearward positions will in general also have STqndingly longer arms and will be capable of the increased reaches required heir rearward seat locations. In like manner men with shorter legs who are imjjSiprward positions will not need to reach as far with their shorter arms.18 .pjpfere it is possible to run experimental tests with a mock-up of the working B^nnwhich the more important items are completely adjustable, a simpler, ^practical, procedure may be used to determine design dimensions com- |Mtib'/e-with functional arm reach. Selected individuals of the 5th, 50th, and 95th l^^ntiles in their body dimensions are used as test subjects in different design s'The specific measurements most pertinent to this purpose are anterior ||j|nKad|i, normal sitting eye height, shoulder breadth, and weight. All subjects gBMlcrae''dressed in the heaviest clothing normally worn, which may reduce Ibjpiiinifuparm reach by as much as 1 inch. If possible, all controls or materials ^j^irlKejpocated in positions where they can be easily reached by all workers 4- 20 30 40 HORIZONTAL DISTANCE (IN.) FROM VERTICAL THROUGH SEAT REFERENCE PONT 0* i'^^milfgiven size range without moving from their normal position. Consideragiven not merely to the maximum and normal boundaries of reach airdStion and distance of reach as well, in order to insure the swiftest and Possible obstructions to free arm movement, to the sides wtiwr '*ront, a'S0 8^ou^ k considered. Those controls' or materials used pffiEn^or those of a critical nature, should naturally be given priority in their ^Sjonfifeis empirical technique is applicable not only to problems of arm TRi m situations in which some aspect of dynamic dimensions is in- l^py'^-Figure 6, for example, shows the nine adjustments used in one mock-up tjffi^^ovdeiejrnine the dimensions and spatial arrangements of truck cabs.-26 In those industrial tasks in which the workers' legs perform / 'functions, there will be no anthropometric problem other than that "''^M^^lsufficient room for comfort and to avoid. cramping or crowding. '* ^^Sl^|:a_matter_oLs)mple. .clearances based pmstatiSShuman (.dimensions fifi?afle^Pllowances to permit changes of leg positions. Where foot controls, pSis-'or treadles, must be operated, however, additional considerations ^ -MtI;"-although the\.yj uaurev ggevnuewraliljyj Uofi aa simpler uoirdei^/`tUhiaianu aarice tuhijousoec 8Ef"""vis*tpfgfjdcation of -hand controls. In few industrial tasks are the legs Figure 5. Maximum reach distances shown in vertical (upper) and horizontal (lower) jjs planes. Degrees refer to angles to the right or left of the midline of the body, and inches refer m to distances above or below the seat reference point. The reference point is established at the intersection of the upper level of the seat cushion with the small lower cushions of the back pad. These reach dimensions were attained by 97 per cent of a XI. S. Navy group, but they will: not necessarily be applicable to other groups differing in body size. (From King et al!) 76 '<* ,ltf^e more *^an two or three pedals. Since these can usually be ^touifftont of the operator, on or about floor level, the basic anthro- *8 8imP1y one f forward leg reach, a functionb'fTeg length. The Providing for variations in workers' leg length is through ,the 1 KeiSHart and J. W. Dunlap, Human Factors in the Design oj Vehicle Cab Areas. U^pL^41,ll|ifearch Center, Purdue University, 1955. 1 egwftZ&h.