THE INTERNAL -COMBUSTION TRACTOR 103 



is rotated about a pedestal which supports the frame. In 

 another type the axle remains stationary. The wheels turn 

 about short axes, being mounted on independent knuckles, 

 as in an automobile. A single wheel in front is sometimes 

 directed by means of a spur pinion and a segment of spur gear. 

 The upright shaft carrying this pinion may be operated from 

 the platform through a steering wheel and cable, or a line shaft 

 with a bevel or spiral gear may take the place of the cable. 

 In one friction-drive tractor a pair of friction disks are con- 

 nected by a horizontal shaft and bevel pinions to an upright 

 shaft which in turn acts upon the ordinary chain and drum. 

 By bringing one or the other disk in contact with the rim of 

 the adjacent flywheel, the power of the engine can be used for 

 steering. In another case the steering is done almost auto- 

 matically hi plowing by a long triangular frame which extends 

 forward of the front axle, carrying at the end of the frame a 

 wheel which hugs the wall of the previous furrow. Cables 

 extending from the hand steering wheel to the wheel on the 

 triangular frame enable one to steer by hand for turning and 

 for other kinds of work. 



HITCH 



The drawbar to which the plows are attached is usually 

 supported by a strong truss riveted to the tractor frame. On 

 most plowing tractors a plow beam, made of two pieces of angle 

 or flat steel, extends across the rear, being punched at intervals 

 to allow the insertion of a pin and clevis. In some tractors 

 this crossbar is merely to hold in place a swinging drawbar 

 which is attached at a point near or in advance of the rear 

 axle. This places the load nearer the center of the engine, 

 and makes turning much easier. Frequently the tractor is 

 equipped with an eyebolt and spring to absorb the jar on 

 starting. Since a variation in the point of hitch may either 

 increase or decrease the draft, it has been found advisable on 

 some tractors to provide some means of adjusting the height 



