CHAPTER XII. 

 SETTING THE VALVE. 



When the engine is turned so that the crank arm, 

 piston stem and cylinder are lying in line, as when the 

 piston is at the end of its stroke, the engine will not 

 turn when the steam is admitted behind the piston, 

 as it is pushing directly against the shaft. The 

 engine is then said to be on a dead center. Obviously 

 there are two dead centers corresponding to the two 

 extreme positions of the crank. 



In order to set the valve it is often necessary to 

 place the engine on its dead center. A method of 

 doing this is explained as follows: 



When the crosshead is very near the end of its 

 throw, make a mark b, on one of the guides opposite 

 the outer edge of the crosshead. Now turn the engine 



in the direction of the arrow until the outer edge of 

 the crosshead again comes in register with the mark. 



