INDUSTRIAL LABOUR 401 



In referring to this result Lazare Carnot ( x ) gives the speed as 

 97 metres, which is, of course, an error. Coulomb ( 2 | considered 

 that a continuous effort of 12 kg. was impossible, and that no 

 more than 7 kg. could be expected. The crank handle used in 

 his experiments, described a circle of 2-3 metres in circumference 

 and the speed was 20 revolutions per minute. He found the 

 output for 6 hours to be : 



7 x 2-30 X 20 X 60 x 6 = 116,000 kilogrammetres, 

 at the average speed of 



2-30 X 20 



= 0-7 / m. per second. 

 oO 



A workman rarely exceeds a speed of 0-80 m. In regard to the 

 duration Navier was able to extend it to 8 hours. Taking an 

 effort of 8 kilogrammes and a speed of 0-75m., the work done was : 



. 8 x 0-75 x 3,600 X 8 = 172,800 kilogrammetres. 



Christian's ( 3 ) experiments are more instructive because they 

 lasted three months without interruption. 



The speed was -5 m. per second, the effort 14 kg., and the effec- 

 tive working day was seven hours. The total work done was 

 therefore : 



14 x--5 X 3,600 X 7 = 176,400 kilogrammetres, 

 which is nearly the same as Navier 's result. 



To the above useful work must be added the energy expended 

 in bending the upper portion of the body. The moment of 

 inertia I., is about -86. This bending corresponds to an angular 

 displacement of 65 per half turn of the handle, i.e., 130 per 

 revolution, the speed of revolution being 20 turns per minute, 

 i.e., a revolution per 3 seconds. The angular displacement per 

 second is 130 = 43. By the method of computation described 

 above ( 272), the work done per revolution of the crank handle 

 would be 



* x ' 86 ; TS^-* ( Wo = ' 368 kgm ' 



In 8 hours, the 20 X 60 X 8 revolutions will give muscular 

 work amounting to 



9,600 X 0-368 = 3,533 kilogrammetres approximately. 



Certain authorities have given much higher values which are 

 not justified. 



307. Vertical Haulage of Ropes. The Pile Driver. If a force 

 P is applied to one end of a rope, passing over a fixed pulley, in 



f 1 ) L. Carnot Essai sur les Machines, 1786. 



( 2 ) Loc. cit. Bull. Soc. Ing. Civ. Feb., 1885. 



( 8 ) Christian, M6canique Industrielle, 1822, vol. i., 114. 



