580 



HYDRAULICS AND ITS APPLICATIONS 



exit are equal. If any variation is made from this^ design, it is better to 

 increase the angle of egress, since this reduces the loss due to lifting the 

 water above head-race level. While increasing the loss at entrance due 

 to shock, and to driving the water back from the floats, this is in general 

 less serious than the former source of loss. In some cases the angle of 

 egress is made equal to twice the angle of ingress. The floats are found 



FIG. 266. Scoop Wheel with movable breast. 



to give better results when flat than when curved, and are arranged to 

 make an angle of from 20 to 40 with the radial line. Since any 

 variation in the head or tail-race level militates against efficient working 

 it is advisable to regulate the supply level at the wheel by means of an 

 adjustable sluice, so as to keep this constant. As usually constructed 

 the diameter of the wheel lies between 9 V H and 10 V H, where H i 

 the lift in feet. The peripheral speed is usually about 8 feet per second. 

 Fig. 266 shows one of a set of six wheels installed in 1901 at Schelling 



