IO4 SCIENCE OF SUCCESSFUL THRESHING 



taken up all the lost motion, as explained, the first thing 

 to do, in setting the valve on an engine equipped with 

 the "link" reverse, is to find the correct length of the 

 eccentric-rods. To do this, take off the steam-chest cover 

 and place the reverse lever in the last notch at either 

 end of the quadrant. Now, with a scratch-awl having 

 a very fine point, make scratches on the valve seat, show- 

 ing the extreme position of the valve at each end of its 

 travel as the fly-wheel is revolved. Measure from the 

 marks to the outside edges of the steam ports, and, if there 

 be any difference, divide it up by lengthening or shorten- 

 ing the eccentric-rod, that is for the time being, moving 

 the valve. The length of the other rod is found in the 

 same way, the reverse-lever being at the opposite end of 

 the quadrant. If the engine be marked and you have the 

 "tram" for placing it on the centers, as already explained, 

 proceed to set the valve as follows: After the lengths 

 of the eccentric-rods are correctly adjusted, according to 

 the method already given, place the engine on one of its 

 dead-centers, say, the head one, and set the reverse lever 

 in the last notch at either end of the quadrant. The valve 

 should now be in such a position that the port leading to 

 the head end of the cylinder should show a "lead" equal 

 to the thickness of an ordinary playing card. The amount 

 of lead may be varied by rotating the eccentric hub around 

 the shaft. Rotating it in the direction in which the engine 

 is to run increases the lead and moving it in the opposite 



