398 



THE HUMAN MOTOR 



incline, the deposit of the load, and the return empty-handed. 

 He took as his standard the results obtained by timing the very 

 best men. He found that hardly one man in five could attain 

 to such a standard. Hence he emphasised the need for the selec- 

 tion of workmen. The leading features of Taylor's system are 

 therefore time measurement and selection. 



304. Classification of Manual Operations. We shall, provi- 

 sionally, adopt the following order and sub-division : 



(1) Operations in which the weight of the human body is alone 

 employed. 



(2) Operations in which the muscles of the arms are used. 



(3) Operations employing the muscles of the legs. 



(4) Miscellaneous operations. 



If we had full knowledge of all the factors which enter into 

 such operations we might survey the various occupations of in- 

 dustry seriatim. We could also draw a distinction between the 

 exercise of force and speed. This being impossible, we are con- 

 strained to adopt a classification in accordance with those factors 

 with which we are familiar. 



(a.) Work done by the Weight of the body. 

 A form of treadmill, an illustration of 

 which was given in fig. 216, and which is 

 shown, diagramatically, in fig. 274, is still 

 employed in some stone quarries for raising 

 stone from pits (vide para. 233). The 

 weight of the man who climbs the wheel 

 is the power P. The leverage is the 

 radius R of the wheel if the power is exerted 

 on the level of the axis at A. If exerted 

 at a point B below that axis the leverage 

 is represented by the distance /. Let the 

 resistance be Q, then the motor moment P X 

 R or P x I = the resistant moment Q X r, 

 r being the radius of the barrel on which 

 the rope is coiled. 



Whence : 



-tA 



FIG. 274. 

 Diagram of a treadmill. 



or = 



The work done per rotation is 2:rR x P. For ^revolutions 

 in a day, the expression will be : 



T = 27rRn X P. 



Replacing P by its value, it will be written : 

 T = 2-nRn X Q X r - or 2wra x Q. 



