THE VALVE-GEAR IO5 



direction decreases the lead. When you have obtained 

 the desired lead, place the engine on the other dead-center 

 and see if the lead be the same. If it be not, the valve- 

 stem should be lengthened or shortened (by means of 

 adjusting nuts), until it is the same. If, after dividing 

 the lead, there be too 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," according 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 rising 

 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. 

 However, lead equal to the thickness of a playing card will 

 give the best results for this class of engines. 



