The Scoop WheeL 85 



masonry, it would bring the result more in accordance with 

 the results which have been obtained from the best con- 

 structed wheels. Signor Cuppari states that the actual dis- 

 charge of the wheels at Zuidplas, which have curved scoops, 

 is 92 per cent, of the theoretical. The author has seen these 

 wheels at work and does not consider their work as calculated 

 to give out such a good result. Taking the dimensions as 

 given above, the gross discharge of the wheel would be 5764 

 cubic feet per minute, found thus : — Diameter of the wheel 

 30 feet. Deduct half the dip of the scoops off each of the 

 radii of the wheel, leaves the mean diameter of the im- 

 mersed part of the wheel =30 — 5 feet dip = 25 feet, of 

 which the circumference is 78 • 54 feet. Area of the scoops 

 5*0 X 4*0 = 20 feet; 78*54 x 20'0 = 1570-80. Deducting 

 the area occupied by the scoops and start posts, 129*80 feet, 

 gives 1441 cubic feet for each revolution of the wheel. This 

 multiplied by four, the number of revolutions, gives the dis* 

 charge as 5764 cubic feet per minute. If the leakage be taken 

 as that due to 70 per cent, of the theoretical quantity found 

 above, say 438 feet, the net discharge would be 5326 cubic 

 feet per minute. The lift being 5 feet, the horse-power in 



water lifted— W.H. P.— would be 5326 x 5 x62'5 ^ 



33,000 ^ ^^ 



The power required, in addition to that for lifting the water, 

 in overcoming the frictional resistance of the machinery of the 

 engine and wheel, and also for useless work in lifting water 

 too high, varies considerably. Mr. Airy estimated the per- 

 centages of loss due to unnecessary lifting of the water, 

 friction, and other causes as follows : — From leakage, 8 ; 

 unnecessary lifting of the water, 19 ; friction on the gudgeon% 

 5 ; resistance from the shape of the course, 8 ; a total of 40 

 per cent To this must be added 10 to 15 per cent for the 

 friction of the gearing, making a total loss for the wheel alone 

 of 55 per cent There is no doubt that in many of the old 

 unimproved wheels the loss from the working of the engine 



