Other tests, which it is unnecessary to tabulate here, showed that by changing the position and contact of the gears, this loss at times might be fully 10 per cent.
In these tests, the velocity of the external surface of the wheel was from 68 to 70 per cent. of the theoretical velocity of the water. From the shape of the bucket, it is difficult to ascertain the velocity at the point of maximum discharge, but it appears to have been about 58 per cent, of the theoretical velocity. Emerson's test shows .6345 per cent. with half-water. Fig. 11 shows the Victor wheel on a horizontal shaft.
The Hercules Wheel.—This wheel in case is very similar in external appearance to the Victor, but has a cylinder gate, rising to admit the water, and the buckets arc provided with interior flanges, which tend to confine the water at partial gate, and keep it from spreading to waste over the surface of the wheel. In this wheel, the buckets are cast singly. The bases of the separate buckets fit together and form the base of the wheel, and are bolted to an iron or steel ring which surrounds them. This wheel is so constructed as to give the highest efficiency at three-fourth gate, or seven-eighth water, and should be run so in prac tical use, leaving the other quarter gate to be opened in case of high water, when the waste can be afforded.
Numerous tests in the writer's possession show from 80 to 84 per cent. efficiency at seven-eighth water, and when it is considered that the apparent loss of 15 per cent, in cludes all the power required to overcome the xis iacrtia of the wheel, the step and bearing friction, and such small amount of slip of water as may be actually wasted, it will be seen that not much more than 85 per cent. should be expected from a wheel in practical use.
The accompanying record of tests of a 23-in. Hercules wheel, made a few years since at tile Holyoke testing flume, is in sonic respects very valuable. IL does not show quite so high a percentage of effect as some of these wheels have since done, but it shows a high average per cent. down to nearly half w: or less than half gate, with the highest results at about seven-eighth water, leaving the other 4 in. of gate, equal to 10 horse-power, to be used in ease of back water. from floods in the river, it is the record of the last series of three clays'
successive tests, which varied but a small fraction of 1 per cent. in their results.
The water was measured over a 12-ft. weir. and a uniform gate leak " of 56'23 cub, ft. per minute is in all eases deducted from the quantity of water.
The circle of the friction pulley was 20 ft., which, multiplied by the weight. and revolu tions per minute, gives the horse-power. It will be seen that the highest results obtained from this wheel were at a velocity of 152 revolutions per minute. This gives a velocity of external circumference, at entrance of water, of 06 per cent, of the theoretical velocity under the head, and as the buckets are so formed as to discharge the water in as centrifugal a direction as possible, the velocity at point of maximum discharge appears, like that. of the Victor, to be about per cent. of theoretical. As the water enters this wheel through con verging chutes, it probably reaches the wheel at a higher velocity than the 60 per cent. noted by the revolutions.
The _Wel Wheel, represented in Fig. 12, is of the horizontal-shaft type, and embodies the latest improvements in the double-discharge construction. The water is divided equally at the center, and passes laterally and parallel with the shaft in opposite directions, discharging downwards on each side of the wheel through curved pipes. This casing is made as narrow through the central portion as possible. for the purpose of obtaining the shortest distance between the journals, bringing them as near to the wheel as the discharge space will admit. These wheels may be used for various purposes, particularly where a lame amount of power is transmitted from a main horizontal of shafting, and from the pulleys of which direct connection can be made to one or more pulleys on the horizontal water-wheel shaft.. Many applications of double-discharge wheels have been made to electric lighting, electric power, and other uses, directly from pulleys on the water-wheel shaft to the pulleys on the dynamo, the saw arbor, or the pumping machinery.