49° 



ENGINEERING ON THE FARM 



of wind wheels. The following basis for calculation may be 



used: A io-foot wheel in a 1 6-mile wind at 60 revolutions 



per minute will develop .12 horse power. To find the power 



which will be developed by a 14-foot wheel in a 20-mile wind 



at 40 revolutions per minute, proceed as follows : 



196..20 60 . 



.i2X-^X^X — = -44 horse power 

 100 16 40 



This method of calculating is amply conservative for the 



poorer types of wind wheels. The better types will develop 



up to 50 per cent more than these figures would indicate. 



Fig. 380. Pelton water wheel, used on high heads of small volume 



Water motors. Where flowing water is available in 

 such quantity that dry or cold weather does not materially 

 obstruct the flow, it may be economically used for power. 

 The expense of dam, spillway, water wheel, and power house 

 is usually considerably more than is required to install any 

 other power plant. The operating cost thereafter is small. 



It is important that the proper type of wheel be selected, 

 and this is most safely handled by an engineer who is familiar 



