As the net power of the wheel in the last example, for Fig. 23,
was 0.468 of a horse power, then 4,125 x 0.468 = 1,930 pounds of water
raised 8 ft. per minute by the size of bucket and velocity of current in
that case. From this a deduction of 20 per cent. should be made for loss
by spill and imperfect construction, so that 1,500 pounds or 176 gallons
per minute would be the probable output--over 253,000 gallons per day;
or, for irrigating purposes, equal to a rainfall of over 11/4 inches in
depth on 50 acres in one week.
The proportion of capacity of the lifting buckets for such a wheel
becomes of as great importance as its efficiency.
If the buckets are too large, the wheel will stall, and if too small,
the wheel will not give its full duty.
For obtaining the approximate capacity of the lifting buckets, assuming
the example as above computed, a 10 foot wheel with the velocity at
periphery of 21/2 feet per second is 150 feet per minute, or five
revolutions per minute, nearly. Then 1,930 lb. per m. / 5 revolutions =
386 pounds water capacity for all of the buckets on the wheel.
If such a wheel is constructed with 16 blades and 16 buckets, one
between each blade, then 386 / 16 = 24 pounds for each bucket, or 38 /
100 of a cubic foot.
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