SPECIFICATIONS 



313 



increased to an undetermined extent, hence possibly 250 pounds 

 of resistance per ton of tractor weight would be none too much 

 to allow on the level in order to estimate the horsepower re- 

 quired to move a tractor over an ordinary road. Each per cent, 

 of grade adds 20 pounds per ton to the resistance. For example : 

 A tractor weighs 8 tons and moves at 2.5 miles per hour up a 

 4 per cent, grade. What power does it take to move it? 



(8 x 250) x (8 x 4 x 20) = 2640 pounds. 

 2640x2.5 ,_, 

 -375 =l7 - 6h 'P- 



EFFECT OF VELOCITY ON DRAFT 



Relative draft of a stage coach and passengers on Holyhead 

 Turnpike, in England, at different speeds of travel. Based 

 on table of dynamometer tests reported by Trautwine: 



