82 SCIENCE OF SUCCESSFUL THRESHING. 



much or too little, rotate the eccentric hub on the shaft, until 

 the required lead is obtained at both ends. The valve is now 

 set for the engine running either "over" or "under," accord- 

 ing to the end of the quadrant at which the reverse lever was 

 set. The reverse-lever may now be placed in the other end 

 of the quadrant and the valve set for the other motion. This 

 is done in the same manner, except that the dividing of the 

 lead must now be done on the eccentric-rod instead of the 

 valve-stem, so that the first setting will not be disturbed. 

 When this is done, try the other motion again, so that when 

 you are through, you know that the lead is the same for both 

 dead-centers for the engine running either over or under. 

 The draw-block should be examined to insure its not being 

 so tipped as to prevent the valve from raising from its seat 

 when necessary to let water out of the cylinder. 



With the link reverse, the lead can be as much or as little 

 as desired and need not be the same for both motions. How- 

 ever, lead equal to the thickness of a playing card will give 

 the best results for this class of engines. 



