GAS, OIL AND ALCOHOL ENGINES 



425 



mated to be about 3,000 F. Since cast iron melts at 

 about 2,300, a great deal of the heat of the explosion 

 must be immediately carried off by radiation through the 

 walls of the cylinder. In order to utilize all the heat left 

 in the gases after the loss by radiation is deducted, the 



cylinder would have to be so 

 long that the gases could 

 expand to atmospheric pres- 

 sure. This is a mechanical 

 impossibility. And it has 

 been decided that the most 

 practical length of cylinder is 

 such that the stroke of the 

 piston is about twice as long 

 as the diameter of the engine cylinder. Under these con- 

 ditions the pressure at release is generally about 40 pounds, 

 and the exhaust gases are still hot enough so that they pro- 

 duce a dull red flame. These two losses are the greatest; 

 and the third loss, that is, the loss past the piston rings, is 

 due to the fact that it is impossible to have a joint be- 

 tween moving parts perfectly tight. 



FIG. 312 



FIG. 313 TOO LATE IGNITION 



FIG. 314 TOO EARLY IGNITION 



