THE STEAM TRACTOR 61 



the grade, and the higher the wheel the less it will be 

 affected in passing over soft ground or rough roads. In order 

 to compromise, designers have had to sacrifice something of 

 both advantages. 



The drive wheels on steam plowing tractors are not so ex- 

 treme in variation as on gas tractors, since the engines are more 

 nearly uniform in size and weight. The wheels are usually 

 from 24 to 36 inches wide and 6 to 8 feet in diameter, with 

 extension rims 10 or 12 inches wide. The built-up type of 

 wheel is most common, with steel tires, to which are attached 

 either round or flat steel spokes, which in turn are fastened to 

 a cast iron hub. 



Steering Wheels 



The front wheels are usually of the built-up type, but are 

 more often made with cast iron rims than the rear wheels. A 

 flange or collar around the middle of the wheel prevents 

 it from lateral slippage. Steering is done by guiding the 

 front wheels, which are rotated with the axle by means of 

 a chain winding shaft, worm gear, and hand wheel. At 

 some additional cost a steam steering apparatus may be 

 attached to certain engines whereby the heavy work of 

 steering is performed by power and the wheels can be kept 

 more rigidly in line. 



Lubrication 



It is evident that different parts of the steam engine will 

 require different methods of lubrication. Steam cylinder oil 

 is a rather heavy liquid with a considerable percentage of 

 animal or vegetable fat mixed with mineral oil in order to 

 make it capable of emulsifying or mixing with the steam. It 

 is commonly fed into the steam pipe outside of the throttle 

 valve, and sometimes between the throttle and the cylinder as 

 well. It may be delivered by a mechanically driven oil 



