THE VALVE-GEAR- 101 



trie may be set permanently by tightening both set-screws, 

 for which there are counter-sunk depressions in the shaft. 

 It sometimes happens when the eccentric strap has been 

 set up too tightly, or has been allowed to become dry 

 and hot, that the eccentric hub rotates a little on the shaft, 

 drawing the holes and set screws slightly. 



If necessary, the depressions may be changed by slid- 

 ing the eccentric-hub to one side (after having removed 

 the eccentric-strap) , and chipping them out with a round- 

 nose chisel so that the deepest part is in the required 

 position for the set-screw. The eccentric-hub and shaft 

 should be marked (as is done at the factory), with a cold- 

 chisel, so that should the eccentric slip, the slippage can be 

 discovered and the eccentric readily re-set. 



In any style of valve-gear the "lead" is changed by 

 rotating the eccentric around the shaft. It will be seen 

 that the Woolf reverse, having but one eccentric cannot 

 be adjusted to change the lead, because if the lead be 

 increased for engine running "over," it will be decreased 

 for engine running "under," and vice versa. There is 

 therefore but one position for the eccentric. This is de- 

 termined at the factory, and on "Case" engines built since 

 1898 the main shaft is countersunk for the set screws. 



Even Cut-offs. The above is the method used in set-i 

 ting the valve on Thirty, Thirty-six, Forty-five, Sixty and 

 Seventy-five horse-power "Case" traction engines at the 

 factory, and brake and indicator tests show that these 



