4IO FARM MOTORS 



be toward the explosion end. All rings should be cres- 

 cent-shaped. This causes an equal pressure all around. 

 The connecting rod. The connecting rod (Fig. 293) 



FIG. 293 CONNECTING ROD 



should be of forged steel and of the right weight to carry 

 the load. A simple bearing is sufficient at the wrist pin, 

 but at the crank end the boxings should be held in place 

 by means of two bolts. All parts should be in perfect 

 alignment. 



Crank shaft (Fig. 294). It is essential that the crank 

 shaft be heavy enough to withstand the sudden shocks 

 which come to it from the explosions, and it should also 

 carry the heavy flywheels without springing. The bear- 

 ings should be long and in perfect alignment. Their line 

 of centers must be exactly at right angles with the cylin- 

 der. A good way to detect a weak crank shaft is to 

 notice whether the flywheels wobble at each explosion 

 of the engine. 



Flywheels (Fig. 295). These are necessarily heavy 

 and massive, but not necessarily ungainly in appear- 

 ance. Loganecker says : 

 "At a medium speed, 

 which may be based on 

 about 225 revolutions for 

 25 H.P. to 375 for 2 H.P., 

 100 pounds to the horse 

 power will not be very far 

 Fir 204 TRANK SHAFT out of the way. The di- 



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