Simplifying Force-pump Calculations.
Page 10
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THE TWO accompanying illustrations show the two sides of a " hydrocalculator " compiled and protected by Mr. E. E. G. Nicholson, who superintends the publicity department of Leyland Motors; Ltd., the instrument being issued by that company for the use of fire-brigades and others who require a ready means IA ascertaining (I) the output of water in gallons per minute delivered through a nozzle, (2) the water horse-power, or (3) the nozzle equivalents should the rate of output of one nozzle be required to be maintained through two or more nozzles. On the "title" side of the instrument (which is made of varnished card) is a part-sectional representation in colour of a Rees roturbo pump indicating the suction, the direction of flow of the water, and the delivery. The calculator is a means of obtaining comparative results without reference to complicated " formulae or recourse to arithmetical sums. Should it be required to ascertain the output in gallons per minute, the arrow on the inner scale (the circumference of which is shown in our .diagram by the tip of the arrow, this scale rotating in reference to the outer scale of figures) is set to the known pressure in lb. at nozzle (scale D) and then_ against the nozzle diameter shown on scale A the output in gallons is shown on scale E. Thus if the nozzle pressure is 140 lb. and the nozzle diameter 14 ins., then the output is nearly 450 gallons per minute.
In order to ascertain this fact by arithmetic it would be necessary to use the following formula :--Gallons per minute x d2 x .24, where H equals the head in feet and d the diameter of the nozzle in one-eighths of an inch.
Equally, a saving in time can be effected if it is required to obtain the
water horse-power. Instead of working out the problem :— W XP X23 33,000
the arrow on the inner scale is set to the lb. pressure at the nozzle (scale C) and against, gallons per minute shown on scale E; the water horse-power can be read off on scale B.
To obtain nozzle equivalents the nozzle diameter on scale A is set, opposite the worded fraction on the outer scale (scale )), the denominator of which fraction is the same as the number of smaller nozzles required. The nearest diameter on scale A. to the point, marked "one nozzle equals 's is the size of the smaller nozzles required.
We understand that complimentary copies of these calculators are being distributed to fire-brigades for their use. Certainly it is a most valuable instrument and one which will be appreciated.