FARM MOTORS 



371 



engine, and especially the factor of economy, are suggestive 

 causes. 



The tractor has been regarded as unwieldy in small fields, 

 but this difficulty has been largely overcome by using the 

 proper system in laying out the lands. One convenient sys- 

 tem is to lay out the fields in lands of such widths as to lose 

 little time in turning at the ends. A strip is left at each side 

 of the field of a width equal to the turning strip at the ends, 

 and sides and ends are turned last by plowing around the 

 entire field. 



The tractor was first introduced for plowing, as this 

 requires more power than any other kind of farm work ; but it 

 is also now being generally used in seeding and harvesting. 

 In many instances several 

 of these operations are 

 carried on at the same 

 time. 



A gas tractor consists 

 of an engine, the transmis- 

 sion, and the truck. These 

 parts will now be discussed 

 under separate heads. 



The Engine. The trac- 

 tor engine does not differ 



Fig. 237. 



The motor of an oil-burning 

 tractor. 



materially from any other 

 internal - combustion en- 

 gine. No one type of engine has been generally adopted 

 for traction purposes. However, nearly all are of the four- 

 stroke cycle type. The differences in these motors lie in the 

 number of cylinders, the speed of the engine, and the method 

 of governing. 



The single-cylinder engine has a decided advantage in 

 simplicity. It is easier to manage a one-cylinder than a two- 



