FARM MOTORS 373 



The clutch is a vital part of the tractor and should be 

 located as close to the engine as possible. The higher the 

 speed at which the clutch rotates the smaller force it will have 

 to transmit. 



The Gearing. The gears are an important part of the 

 tractor. They should (1) be of liberal dimensions and of 

 great strength; (2) be constructed of such materials as to 

 resist wear to the greatest advantage; (3) be adequately lubri- 

 cated and protected from dirt and grit. 



Change of Speed. Change of speed is especially desirable 

 with light tractors and is quite necessary where the land is 

 rolling. The load which any tractor will draw is limited by 

 the load it is able to draw up the steepest incline. If a 

 reduction of speed be made for inclines or hills a larger load 

 may be carried continuously. 



A reverse in direction of travel or a change of speed is 

 accomplished in two general ways : by sliding gears, which is 

 the accepted method now used in automobiles; and by plane- 

 tary gears. The former is the simpler method but is not so 

 convenient of operation. 

 Planetary gears take 

 their name from the 

 gears, being fitted to a re- 

 volving frame or spider. 



The Trucks. One of 



, , . Fig. 239. The truck for a gas tractor. 



the mOSt important partS showing frame, gearing, and steering and 



of the modern tractor is ( 



the truck, which consists of the frame and the steering and 

 drive wheels. The frame is the backbone of the tractor, 

 and to it are attached the bearings that carry the main axle 

 and the shafts which support the gears. 



The Steering Wheels. Two methods of constructing the 

 axle of the steering wheels are in common use. In one the 



