ENERGY LOSSES FOR MOTORS 



581 



several cylinders. The pistons of the four-cylinder engine 

 are connected with the drive shaft in such a manner that, while 

 one piston is performing the first stroke, another is performing 

 the second stroke, the third piston the third stroke, and the 

 fourth the fourth stroke. Thus we 

 see that some one of the pistons is at 

 work every instant. This produces 

 a steady motion. In the six-cylinder, 

 eight-cylinder, and twelve-cylinder en- 

 gines the power is still more nearly 

 constant (Fig. 371). 



VII. ENERGY LOSSES AND COST OF 

 FUEL FOR DIFFERENT MOTORS 



fOUff C YL/A/af?3 



S/X CYLINDERS 



fICH T CTL INDR S 



TWEL Kf CYLINDERS 



In actual practice the efficiency of FlG> SJI.HOW several 

 power plants of the same general type cylinders produce a con- 



.-. i , , f f ! stant, steady power. 



varies so greatly and the cost of fuel 



varies so much in different parts of the country that only 

 average efficiencies and relative cost can be given. Never- 

 theless, as a closing section in the study of motors it is in- 

 teresting to note, as far as we can do so, the average efficiency 



FIG. 372. Losses of energy in a steam power plant. 



and relative cost of fuel for the different kinds of motors in 

 common use. 



700. Sources of Energy Loss. The sources of loss usually 

 occurring in the different power plants are shown in the 



