SOME COMMON MECHANICAL MOTORS 



561 



power at Niagara Falls as well as that of the Mississippi 

 River at Keokuk, Iowa, (Fig. 345) is developed by means of 

 turbine wheels. At Niagara they operate under a "head" 

 of about 170 ft. and at Keokuk with a "head" of about 30 

 ft. At the present time 500,000 horse-power is developed 

 at Niagara Falls and 150,000 horse-power at Keokuk (Fig. 346). 

 The turbine wheel is placed at the bottom of a cylindrical 

 well or pit. The water at the bottom of the well is under 



FIG. 349. One of the turbine wheels in the Keokuk power plant. It 

 hangs on the bottom of a steel shaft over two feet in diameter and turns one 

 of the 10,000'h.p. generators shown in Fig. 346. 



high pressure and is forced horizontally through spaces be- 

 tween fixed or stationary vanes set at a certain angle (Figs. 

 347 and 348). The water strikes against the vanes or blades 

 of the movable wheel causing it to rotate (Fig. 349). After 

 its energy is expended upon the vanes of the movable wheel, 

 the water drops into the outlet, or TAILRACE. A shaft which 

 revolves with the wheel extends upward above the surface 

 of the water where it runs a dynamo or other machinery. 



