Page:Lowell Hydraulic Experiments, 4th edition.djvu/76

 Similarly, the sum of the areas of the smallest sections between the buckets is $$0.0339 \times 0.2344 \times 36 = 0.28606\ \text{square feet.}$$

The water is admitted into the forebay $$L$$, by the pipes $$MM$$; the diaphragm $$N$$ is to diminish the agitation of the water.

101. The apparatus for gauging the water discharged by the wheel, consisted of the weir $$O$$, which had sharp edges; the depth on the weir was measured by a hook gauge, in the box $$P$$, which communicated, by a small aperture, with the surrounding water; the height of the water above the wheel was taken at a gauge in the box $$Q$$; this box was made sloping on one side, in order to permit a better view of the gauge. The zeros of both gauges were at the level of the top of the weir; consequently, the difference in the readings of the gauges gave at once the fall acting upon the wheel.

102. The apparatus for measuring the power, consisted of the Prony dynamometer $$R$$, attached to the upper part of the vertical shaft; the weights were applied by means of the bell crank $$S$$, figures 1, 2, and 5; the oscillations of the brake were diminished by the hydraulic regulator 7, and the extent of the oscillations was limited by the stops $$UU$$. The speed of the wheel was obtained by means of a counter, driven by the worm $$V$$, attached to the top of the upright shaft; this was so arranged as to strike a bell once in fifty revolutions of the wheel.

In order to diminish the passive resistances, the weight, bearing upon the step $$W$$, was counterbalanced, in part, by other weights, one of which is represented at $$y$$, figure 2; these were attached to the brakes at the points $$XX$$, by vertical cords passing over pulleys; the weight, resting on the step when the wheel was immersed, and the dynamometer attached, was found to be 170 pounds; the counterbalance was 160 pounds, leaving 10 pounds bearing upon the step. The entire apparatus for measuring the power, was in equilibrium when there were no weights in the scale.

103. In all the experiments, except experiment 10, the brake was lubricated with oil; in experiment 10 water was used for this purpose; experiments 9 and 10 were identical in all other respects. It was noticed in experiment 10 that the whole apparatus trembled very much; this must have consumed some power, which is perceptible in the coefficients of effect. Experiment 9, in which oil was used, and in which the trembling of the apparatus was very slight, gives a coefficient of effect of 0.6922; while experiment 10, in which water was used to lubricate the brake, and in which the trembling of the apparatus was very distinct, gave 0.6886 as the coefficient of effect.