SAGEBIEN WHEEL 



433 



Sagebien wheel may be adopted. This wheel (Fig. 190) has buckets formed 

 by a series of flat vanes, which are tangential to a circle concentric with 

 the wheel itself. The buckets are open top and bottom, and are of com- 

 paratively great depth. The water. enters the buckets with a velocity 

 sensibly the same as that in the approach channel, the vane angles being 

 determined as indicated in the figure, so that the vanes enter the water 

 without shock. 



A circular casing is provided in which the wheel works with little 

 clearance, and which connects the head and tail-race. Then, neglecting 

 leakage between this casing and the vanes, each bucket retains its supply, 

 until it passes its lowest point of the wheel, after which communication is 



FIG. 190. Sagebien Wheel. 



made with the tail-race, and the level in the bucket falls to that of the 

 tail-race water. For maximum efficiency the wheel should be designed so 

 that the level in the bucket on reaching the bottom of the wheel is the 

 same as that in the tail-race. 



If v r represents the relative velocity of water and bucket at entrance, the 

 water will rise initially to a height in the bucket above that in the head- 



v 2 

 race, this height being given by ~- t and the depth of bucket should be 



* 9 



such that in time of flood this does not cause flow to take place over the 

 inner end of the buckets. 



In this wheel the velocity of rotation is proportional to the flow, and the 

 wheel is thus capable of dealing with large quantities of water. It is 

 however, unfitted for driving a variable load, since an increase in load, by 

 H.A. F F 



