WATER WHEELS AND WINDMILLS 



203 



wheel is 10 feet in diameter, and develops 10,500 horse 

 power. 



The energy of the turbine wheel is transmitted by a 

 shaft to an electric dynamo or other 

 machinery. There are turbine wheels 

 which transmit for use 90 per cent of 

 the energy of the falling water. 



The diagrams illustrate the parts of a 

 turbine and one installed. 



136. Value of a Stream or Waterfall. 

 - Before any kind of water wheel is 

 installed the quantity of water and the 

 distance it can be made to fall are 

 ascertained in order to determine the 

 kind and size of wheel to use. A small 

 wheel cannot transform all the energy of 



a large supply of water, and a large 



. , 11 u -*u TURBINE AT NIAGARA 



wheel cannot develop much power with FALLS 



a small quantity of water. 



The quantity of water delivered by a stream can be 

 determined as follows: Measure the width of the stream 

 and the depth at intervals of 5 or 10 feet and take the 

 average depth. Measure the speed of flow of the water 

 by placing a float in the middle of the stream and 

 see how far it moves in a minute. For example, sup- 

 pose the stream is 50 feet wide; if the depths are 4, 6, 

 9, 7, and 5 feet, the average depth would be (4 + 6 + 9 

 + 7 + 5) -=- 5 = 65 f ee t- Suppose the stream flows 4 

 feet per second. The quantity of water that would flow 

 over a dam in a second would be 50 X 6^ X 4 f eet > or 

 1240 cubic feet. A cubic foot of water weighs 62.5 

 pounds. So the weight of water flowing over the dam 

 per second would be 1240 X 62.5 pounds, or 77,500 



