Page:Lowell Hydraulic Experiments, 4th edition.djvu/75

55 EXPERIMENTS ON A MODEL OF A CENTRE-VENT WATER-WHEEL, WITH STRAIGHT BUCKETS.

99. author was led to this design by the consideration of the path of the water in passing through the wheel, according to the hypothesis in art. 83. It is a wheel well suited for low falls, in which the water, over the wheel, may stand at its natural height, without requiring a vertical shaft of great length. Its simplicity and cheapness, combined with its other good qualities as a hydraulic motor, must recommend it for many such situations.

100. Plate VII., figure 1, is a general plan, and figure 2, a vertical section of the apparatus.

Figure 3 is a vertical section through the apertures in the guides and wheel; the guides and buckets are omitted to avoid confusion in the figure.

Figure 4 is a horizontal section of part of the guides and buckets, showing, also, the path of the water in experiment 8, according to the hypothesis in art. 83.

$$A$$ is the wheel; the exterior diameter is $22 7⁄8$ inches; the interior diameter is $19 1⁄2$ inches; the height between the crowns, or $$B C$$, figure 3, is $2 13⁄16$ inches; it carries thirty-six buckets, $$EE$$, figure 4, of steel, about $1⁄22$ of an inch in thickness, fastened to the wheel by means of the wooden cushions $$FF$$, figure 3; the upper cushions are screwed to the disc $$D$$, and the lower ones to the crown $$G$$. The disc $$D$$ is of cast-iron, $3⁄8$ inch thick, with a suitable hub by which it is connected with the vertical shaft.

$$HH$$ are guides of cast-iron, which direct the water into the wheel, and also support the plate $$I$$, which protects the wheel from pressure on its upper surface; the contraction of the streams entering the apertures between the guides, is diminished by the curved wooden garniture $$K$$; there are twenty-four guides. The mean shortest distance between the buckets at $$ab$$, figure 4, is 0.0339 feet; the mean shortest distance between the guides $$cd$$, figure 4, is 0.0437 feet; and the height of both is $2 13⁄16$ inches = 0.2344 feet; we have, therefore, for the sum of the areas of the smallest sections between the guides, $$0.0437 \times 0.2344 \times 24 = 0.24584\ \text{square feet.}$$