EXERCISE 92 (Continued) 



brake, engineering brake, fuel system, ignition system, carburetor, and starter. Give directions in writ- 

 ing for starting, stopping, oiling, cleaning, and handling an automobile. If farm tractors are used 

 in the neighborhood either bring one 

 to the school for detailed study or 

 take the class to the store or farm 

 where a tractor is and give the stu- 

 dents the opportunity to go over the 

 machine in detail and at least to 

 witness it in operation. Get cata- 

 logues of the principal types and 

 standard makes of tractors and ex- 



Inlet 

 valve 



Spark 

 plug 



Exhaust / 

 valve 





Fig. 148. Exhaust or scavenger stroke 



During the fourth stroke the exhaust valve remains open and the burned gases are 

 driven from the cylinder into the air by the return of the piston 



plain the advantages and disadvantages of each. Assign the class the problem of listing all the 

 ways in which a tractor may be profitably used on the farm the year round. 



References. Potter, A. A. Farm Motors, Chaps. V and VI (Second Edition). McGraw-Hill Book 

 Company, through whose courtesy the cuts used in this exercise were obtained. Harshfield and Ulbright. 

 Gas Engines for the Farm, pp. 6-28. John Wiley & Sons. 



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