The Scoop Wheel. 83 



to a height of S feet, and the two 560 tons a minute. The wheel 

 at the Hundred Foot River in Cambridgeshire discharges 

 120 tons a minute at a height of 17 feet, and 200 tons at the 

 ordinary lift of 13 feet The two Italian wheels at Adria 

 discharge 300 tons a minute each, the maximum lift being 

 10 feet. The Egyptian wheels recently erected at Atfeh, on 

 the Nile, can each discharge 254 tons a minute, or a total for 

 the eight wheels of 2030 tons. 



The speed at which wheels with flat scoops run should not 

 exceed 8 feet per second at the periphery. When this is 

 exceeded, too great an impetus is given to the water, and 

 part of it is lifted higher than necessaiy. The best results 

 are obtained with a slower rate of speed than this. The 

 slower the speed the less the water is dashed about. It is, 

 however, contended by some managers of wheels that a slow 

 speed involves additional friction from the gearing required 

 to reduce the speed of the engine to that of the wheel. In 

 the old engines the number of revolutions of the engine to 

 those of the wheel was 3 or 4 to i. This has been increased 

 to 6 or 7 to I. A high speed, it is also contended, has the 

 advantage of the head due to the velocity with which the 

 water leaves the wheel, provided the outlet channel is of 

 suitable form. Thus, with a speed of 8 feet per second, the 

 water will pass through a regular and smooth waterway into 

 an outfall, the surface of which is nearly i foot higher than 

 the water at the wheels. Wheels in England having a 

 diameter of 30 feet generally make 4 to 4-| revolutions a 

 minute, equal to a speed of 6-27 feet to 7 feet per second 

 Some of the Dutch wheels run at as low a speed as 3 '46 feet 

 per second. Four of the new wheels at Atfeh make 2 • 29 

 revolutions a minute, and the other four I'pi revolutions, 

 equal to a speed of 3*93 feet, and 2*95 feet respectively. 

 Wheels having curved scoops can be run at a higher velocity 

 than those with flat blades. Where the discharge is into a 

 tidal stream, wheels are regulated to run at varying speeds 



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