FARM MOTORS 



391 



engine. In this case the engine is placed underneath the 

 boiler, and is styled under-mounted. This construction 

 relieves the boiler of all stress due to the transmission of 

 power and places the engine where it may be attended by 

 the engineer standing on the ground. 



The Steering Wheels. The steering wheels of the steam 

 tractor engine are generally mounted on an axle which 

 may be turned by means of a hand wheel and a worm gear. 



Fig. 252. A top-mounted steam tractor. 



By turning the hand wheel a chain attached to one end of the 

 axle is shortened, while another at the other end is lengthened. 

 In large engines the power for steering is often supplied by a 

 separate engine or is derived from the main engine by 

 friction clutches. 



The Traction Wheels. The traction wheels of a steam 

 tractor are important features of the outfit when the tractor 

 is to be used for drawing loads or machines. The supporting 

 power of the wheels depends upon the diameter of the wheel 



