Page:Popular Science Monthly Volume 18.djvu/235

Rh introduction of water under pressure into buildings in cities and towns, be used in very many places. As, however, the supply that most waterworks are capable of furnishing is not at any time greatly in excess of the demand, wheels adapted for use upon house-pipes have to be, first of all, economical of water. They should also be constructed so that they are not liable to injury by water freezing in them, and be of low first cost. Several different wheels, designed to meet these requirements, are now made, and have been more or less widely introduced. One of the best of these, and one which has met with considerable favor in the market, is that shown in Fig. 2, the invention of Mr. O. J. Backus. It is exceedingly simple in construction, and has proved very satisfactory in use. It consists of a light but strong wheel, carrying buckets or vanes upon its rim, against which a jet of water impinges. The wheel is inclosed in an iron casing in which it revolves freely, the only points at which there is any friction being the bearings of the shaft. The manner of using the water constitutes the special feature of the motor, and is one that peculiarly adapts it to use on service-pipes, as it reduces the consumption to a minimum. In the wheels used in manufacturing, whether of the turbine or other pattern, motion is imparted by the continuous pressure of a considerable body of water. In this the motion is due to the successive impacts of a small jet having a high velocity, which allows of considerable work being performed with comparatively little water, as the striking force of the jet is utilized. In the smaller sizes of these motors, those capable of running a sewing-machine, the water jet is but one sixteenth of an inch in diameter, while in the largest machines it does not exceed half an inch. A steady and uniform motion of the wheel is attained by placing the buckets very close together, so that the impulses follow each other in rapid succession. The water enters the wheel-casing at one side and escapes at the bottom, traversing but one quarter of it. As there is nothing to impede its flow, none can remain in the wheel and freeze in cold weather. The motors are manufactured in sizes varying from seven to forty-five inches' diameter of wheel, and from about one eighth to eight horsepower. The power obtained depends of course upon the pressure of the water, but they are designed to run at any pressure above fifteen pounds per square inch. This is easily obtained, as at most places where there are water-works there is a pressure of from twenty to forty pounds, and at some a much higher one. The manner of applying the motor to a sewing-machine is shown in Fig. 3. Perfect control over the supply of water is given by a valve operated by a treadle, which enables the operator to stop and start the machine as readily and quickly as by the ordinary foot-power. This method of regulating the speed of the machine has the great advantage that only the amount of power required is at any time used, thus saving the water to the utmost.