THE VALVE-GEAR. 77 



First. See that the "reach-rod" from the "reverse-lever" 

 to the "block-guide" is of such length that the valve moves 

 the same distance during a revolution of the fly-wheel in 

 one direction as for a revolution in the opposite, direction, 

 with the reverse-lever in the end notch of the quadrant in 

 both cases. The entire distance the valve moves, which is 

 called the "valve travel," may be conveniently measured on 

 the valve stem by the tram, as illustrated in Fig. 24. To do 

 this hold one of the tram points in the punch-mark on the 

 stuffing-box and, with the other, make scratches across the 

 rod as the fly-wheel is slowly revolved. If the "valve travel" 

 be more for one motion than for the other, it shows that 

 the reach-rod is either too long or too short to give the 

 proper angularity to the block-guide, which angularity deter- 

 mines the travel of the valve. This rod can be easily ad- 

 justed to the correct length by taking the pin out of the 

 lever and turning the forked head of the rod until the 

 required length is obtained. The jam-nut should then be 

 tightened to prevent lost motion. 



Second. See that the eccentric is in the proper position, 

 which is, with it's point of greatest throw nearly opposite 

 the engine crank-pin. The movement of the valve in throw- 

 ing the lever from one end notch to the other end notch of the 

 quadrant, with the engine on its dead-center, is called the 

 "slip." When the eccentric is properly located, the slip will 

 be the same for "head" dead-center as for "crank" dead- 

 center. The "slip" must not only be alike in amount, but 



