The Scoop Wheel. 8 1 



engine-house and geared to the pinion, so that the shuttle 

 may be adjusted in the engine-room, a flange with float 

 being also placed there to show the height of the water. 

 See illustration of the Podehole wheel, Plate 5. 



The diameter of the wheel is regulated by the " head and 

 dip," that is, the distance from the lowest point of the ladles 

 to the maximum height to which the water has to be lifted, 

 Sig. Cuppari quotes a formula of Mr. Forster*s for calculat- 

 ing the diameter D = 9*82 \/ 2 +/, in which i is the immer- 

 sion of the scoops, or the dip, and p the lift = 9 * 82 V H, in 

 which H = the height from the lowest point of the wheel to 

 the highest external level to which the water has to be 

 raised, the measurements being in feet. The constant in 

 the formula gives a larger diameter than is generally to be 

 found in either the Dutch wheels or those in use in the 

 Fens. A constant of 8*75 gives a result more nearly 

 approaching the Dutch and English practice. The wheels 

 at Zuidplas, which have curved scoops, have a dip of 3*28 

 feet, and a head of 11 '8 = 11 15*08, with a diameter of 

 32*80 feet, equal to about 8*5 times the square root of H. 

 The wheels at Katwijk, erected in 1880, have a head and 

 dip of 1 1 feet, and a diameter of 29 * 50 feet, equal to 8 • 92. 

 Taking twenty -five of the principal wheels in England, 

 having an average extreme head and dip of 15*0 feet, the 

 mean diameter is 34*0 feet, equal 8*77 the square root of 

 H. The new wheel at Wexford Harbour has a diameter of 

 40 feet for 14*50 feet head and dip, equal to a constant of 

 10. Wheels with curved scoops requii*e a less diameter than 

 those with flat. The Italian wheels generally have a larger 

 diameter in proportion to the lift than the Dutch or English. 

 The largest wheels in Holland do not exceed 33 feet in 

 diameter. In England the largest diameter is 50 feet, and 

 several examples of wheels 35 feet and 40 feet exist. The 

 limit for efficient working may be taken at 36 feet. It is not 

 advantageous to use scoop wheels for lifts above 12 feet. 



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