THRESHING MACHINERY 2O/ 



tions. These operations and the parts that are called upon 

 to perform them in most machines may be enumerated as 

 follows : 



First, shelling the grain from the head. The parts 

 which do the shelling or the threshing are the cylinder and 

 the concaves with their teeth. Fig. 157 shows these parts. 



Second, separating the straw from the grain and chaff. 

 The parts which perform this operation are the grate, the 

 beater, the checkboard, and the straw rack, or raddle. 



FIG. 157 THE CYLINDER AND CONCAVE 



Third, separating the grain from the chaff and dirt, per- 

 formed by the shoe, fan, windboard, screens, and tailings 

 elevator. 



Fourth, delivering the grain to one place and the straw 

 to another, which is accomplished by the grain elevator 

 and the stacker or straw carrier. 



Other attachments, as the self-feeder and weigher, are 

 often provided. / 



These parts will now be discussed somewhat in detail. 



284. Cylinder. The cylinder is usually made by at- 

 taching parallel bars to the outer edge of spiders mounted 

 on the cylinder shaft. The whole is made very rigid by 



