THE POWER BEHIND THE ENGINE 



Belts transfer this motion to the machinery of factory or 



mill. 



173. Turbines. The most efficient form of water motor is 



the turbine, a strong metal wheel shaped somewhat like a pin 



wheel, inclosed in a heavy metal case. 



Water is conveyed from a reservoir or dam through a pipe 



(penstock) to the turbine case, in which is placed the heavy 



"metal turbine wheel (Fig. 122). The force of the water causes 

 rotation of the turbine and of the shaft which 

 is rigidly fastened to it. The water which 

 flows into the turbine case causes rotation 

 of the wheel, escapes from the case through 

 openings, and flows into the tail water. 



The power which a turbine can furnish 

 depends upon the quantity of water and 

 the height of the fall, and also upon the 

 turbine wheel itself. One of the largest 

 turbines known has a horse power of about 

 10,000; that is, it is equivalent, approxi- 

 mately, to 10,000 horses. 



1 74. How much is a Stream Worth ? 

 The work which a stream can perform 

 may be easily calculated. Suppose, for 

 example, that 50,000 pounds of water fall 

 over a 22-foot dam every second ; the power 

 = _^^__ r _____. of such a stream would be 1,100,000 foot 

 pounds per second or 2000 H.P. Natur- 



FIG. 122. -A turbine at y a t f th j g power wou ld be lost 



Niagara Falls. 3 ' 



to use by friction within the machinery and 

 by leakage, so that the power of a turbine run by a 2000 H.P. 

 stream would be less than that value. 



Of course, the horse power to be obtained from a stream 

 determines the size of the paddle wheel or turbine which can 



I Water 



