THRESHING MACHINERY 211 



tact with the beater. The beater (Fig. 159) is a fan-like 

 device which tends to carry the straw away from the 

 cylinder and forms a stream of straw to pass over the 

 straw rack. Some makers make use of two beaters, one 

 above the straw and one below, in an effort to separate 

 the grain and chaff from the straw. The beater must 



FIG. 159 THE BEATER 



run at high enough speed to enable the centrifugal force 

 to prevent the straw from wrapping around it. 



289. The checkboard. The purpose of the checkboard 

 is to stop the kernels which may be thrown from the 

 beater. It is usually constructed of sheet iron and al- 

 lowed to drag over the stream of straw. 



290. Straw rack. The straw rack is for the purpose of 

 carrying the straw away from the cylinder and shaking 



FIG. 160 ONE TYPE OF STRAW RACK 



the grain down on the grain conveyor below. Straw 

 racks are of three types: (a) endless apron or raddle 

 type, (b) oscillating racks, (c) vibrating racks. 



The endless apron or raddle rack consists of a web 

 with thumpers underneath to shake the grain to the bot- 

 tom. It is usually made in sections with an opening 

 between which permits the grain and chaff to fall 



