FARM MOTORS 387 



stop in line with the connecting rod, or be on dead center, in 

 such a way that the engine cannot be started by the applica- 

 tion of steam. 



The two-cylinder engines give a steadier motion but are not 

 usually as economical in the use of steam as the single- 

 cylinder engines, and are more expensive. 



The Fly Wheel. All steam engines and especially single- 

 cylinder engines must be provided with a fly wheel to carry 

 the engine over dead center, when the steam cannot act effec- 

 tively upon the piston. It is customary to make this fly 

 wheel in the form of a pulley, from which the belt 

 may be run to other machines as desired. 



The Governor. The purpose of the governor is 

 to maintain a uniform speed. The usual construc- 

 tion of a governor is similar to that shown in the 

 accompanying illustration. The fly balls are 

 thrown outward by centrifugal force as they are 

 rotated, thus gradually closing the valve through 

 which the steam must pass. Governors may be 

 adjusted for different speeds. Fig. 249. 



A common 



Lubrication. One important fea- type of gov- 

 ernor. 

 ture of the operation of the steam 



engine is the lubrication of the piston, which 

 is usually accomplished by admitting oil with 

 the steam. The two devices in common use 

 for feeding the oil uniformly are the oil pump 

 and the lubricator. The oil pump is driven 

 by the engine and is simply a small pump 

 sight- feed lubri- connected with a suitable reservoir for the oil. 

 It can be adjusted to feed oil at any specified 

 rate. The best kinds have a sight-feed device, which en- 

 ables the engineer to see the rate at which the pump is feed- 

 ing the oil. 



