INDUSTRIAL LABOUR 433 



30 kg., and carrying a load of earth weighing 70 kg., over hard, 

 dry ground. He found that the tractive effort, F, was 2-5 kg., 

 whence we get the equation F = -025 X P (load). Vauban, in 

 his " Instructions " ( l ) laid down that a man could transport 

 14-8 cubic metres of earth a distance of 29-3 metres, making 500 

 trips in all. A total distance traversed (loaded and empty) of 

 14-6 kilometres, approximately. 

 The work done in the loaded trips was therefore : 



14600 X 2-5 -f 70 x I 4 ' 600 = 97,900 kgm. 



The tractive effort exerted in the return journeys was only : 



30 X 25 -- ! 



TOST 



The work done was :- 



14,600 X -75 + 7Q x 1 4 > 6QQ = 82,300 kgm. 

 lo 



Coulomb found that the supporting effort was only 19% of 

 the total load, i.e., 19 kg. on the loaded journey and 5-5 kg. on 

 the return journey. (These figures are twice as favourable as 

 those obtained by Imbert.) 



The mean effort, per trip, was therefore : 



19 + 5 ' 5 = 12-25 kg. 

 2 



Adding the weight of the man, the supplementary work is : 

 12-25 X 14,600 X 2 

 16 



The summation of all these quantities gives a total daily work 

 of : 202,730 kilogrammetres. 



330. The Two- Wheeled Barrow. Gilbreth ( 2 ) observes that 

 the two-wheeled barrow (fig. 293) causes less fatigue than the 

 single-wheeled barrow because the load is better balanced in 

 the former case. He found that the maximum economical 

 load was 490 kg. The author considers, however, that such a 

 heavy load entails excessive fatigue. 



Guenyveau ( 3 ) found that a tractive effort of 3 kg. was required 

 to transport a load of 70 kg. on a two-wheeled barrow itself weigh- 

 ing 30 kg. A total gross load of 100 kg. The effort needed to 

 propel the same barrow empty was -9 kg. ; 18 kilometres per day 

 was covered. 



(*) Vauban, Instructions, or the Directeur General des Fortifications. 

 ( 2 ) Gilbreth, Motion Study, p. 57 (G. Routledge & Sons, 19l'l). 

 ( 8 ) Guenyveau, Essai sur la Science des Machines. 



