THE CYLINDER, CONCAVES AND BEATER. 135 



up the straw, thereby consuming much power, increasing 

 the difficulties of separation and making the sieves handle a 

 large amount of chaff. This same condition exists when 

 all of the teeth are more or less bent. The cylinder may be 

 moved endwise, as already explained, to give the proper 

 spaces between the teeth, but the teeth must be kept straight. 



Special Cylinders. To do good work in rice a special 

 cylinder and concave are required with a wider spacing of the 

 teeth than the regular ones. This gives more clearance be- 

 tween the cylinder and concave teeth and, together with a 

 reduced speed, prevents the cylinder from cracking the rice. 

 A special cylinder and concaves are also made for threshing 

 peas and beans. Either of these special cylinders may be 

 put in any Case separator by making the complete change 

 in cylinder, concaves and' concave circles. Further informa- 

 tion regarding threshing rice, peas, beans, etc., is given else- 

 where in this book. 



Balancing Cylinders. On account of the high speed at 

 which cylinders run, they must be accurately balanced or 

 they will not run smoothly. It is essential in balancing a cyl- 

 inder that the weights used for this purpose be placed where 

 the deficiency of weight exists. The shop practice is to rest 

 the journals of a cylinder on level ways and put weights 

 under center bands until the cylinder will stand at any 

 point on the ways. The cylinder is then put in a frame 

 having narrow, loosely fitting wooden boxes and run at 

 about 1 200 revolutions per minute. The parts of the jour- 



