192 SCIENCE OF SUCCESSFUL THRESHING 



as the condition requires. The cylinder must be run at a 

 certain slow speed as already stated, and when so speeded, 

 more concave teeth are required than if it were allowed to 

 run faster. However, since the cylinder speed must be 

 low, a sufficient number of concave teeth should be used to 

 knock the peas out of the pods. For "blanks," when less 

 than six rows of concave teeth are used, hardwood boards 

 cut to the right length and width and fitted to the concave- 

 circles are preferable to the regular iron-blanks. Since 

 peas are apt to be cracked by the corners of the iron blank- 

 concaves or grates, the ones under the beater are some- 

 times covered with sheet-iron. This should be done where 

 trouble from cracking is experienced. The kind known as 

 "cow peas" or "stock peas," a speckled or mottled variety 

 belonging to the bean family, are easily cracked. 



In general, the adjustable chaffer and shoe sieve should 

 be set only slightly more open for the common field peas or 

 for stock-peas than for wheat. The adjustable exten- 

 sion, however, should be open enough to allow unthreshed 

 pods to pass through it and be returned to the cylinder by 

 the tailing elevator. If the separator be fitted with com- 

 mon-sieves, the one and one-quarter-inch lip, E, or the two- 

 inch lip, D, should be used as a chaffer, and the three- 

 eighths-inch lip, G, should be placed in the second notch 

 and third hole in the shoe. 



For a screen, the one-sixth by three-fourths-inch woven 

 wire, W, or the three-sixteenths by three-quarter-inch ob- 

 long hole, P, is best, although the fifteen-sixty-fourths 



