Water Power for the Farm and Country Home

by David R. Cooper

At the downstream end of the forebay the diverting embankment approaches a steep bank. At this point Mr. Miner built a small power house. Under the power house is the wheel-box, which consists of a box-like compartment having one side open to the forebay. This opening is covered with a coarse screen to prevent leaves or other debris from entering the wheel, but the water flows through it readily. In the wheel-box a waterwheel, of the type known as a turbine, was placed. This revolves on a vertical shaft, or axle, which is guided by bearings in a metal case surrounding the wheel and resting on the bottom of the box-like compartment. The wheel-case is open at the bottom to allow the free escape of the water after it has passed through the wheel. The construction of the turbines is such that the pressure of the water on the curved vanes causes the wheel to revolve, just as the pressure of wind causes a windmill to revolve. The water must have a free escape from the opening in the bottom of the wheel-case and wheel-pit and to provide for this a channel, called a “tail-race,” was excavated to carry the water back to the creek. Natural conditions were favorable here and a tail-race joining the main channel about 100 feet below the power house was constructed with little difficulty. At the point where the tail-race joins the creek the elevation is two feet lower than the power house, so that there is little tendency for water to back up from the creek into the tail-race. There is a certain amount of back-water during freshets but the increased height of the water in the forebay at such times partially offsets it.

Interior of E. B. Miner’s Power House

The vertical shaft of the turbine extends up through and about two feet above the floor near one end of the power house, where it is supported on ball-bearings which enable it to be revolved with very little friction.

At the other end of the [power house], which is twelve feet by sixteen feet in plan and seven feet high to the eaves, was placed an electric generator, or dynamo, rated at 12½ kilowatts, which is equivalent to about 17 horsepower. This machine is intended to operate at about 1100 revolutions per minute. The waterwheel, under the pressure of about six feet, would not revolve at such a high rate of speed. It was, therefore, impracticable to connect the generator shaft directly to the waterwheel shaft and it became necessary to magnify the revolutions by connecting the two shafts by belt, using different-sized pulleys. A large wooden pulley, seventy-six inches in diameter, was keyed on the end of the waterwheel shaft. A much smaller pulley, about eight inches in diameter, was placed on the driving shaft of the generator. A leather belt connects the two, and since the wheel shaft is vertical and the generator shaft is horizontal, it is necessary to pass the belt over an intermediate pulley, or “idler.” This idler is set with its axis at an angle with both the horizontal and vertical, so that the transition of the belt from the horizontal to vertical is made gradually. Since the driving pulley on the generator shaft is so much smaller than the pulley on the wheel shaft, there are about nine revolutions of the generator shaft for every revolution of the wheel shaft.

The amount of power which this equipment will generate depends to a considerable extent upon the amount of water flowing. Oriskany creek at this point has a tributary drainage area of about fourteen square miles, and the flow required to drive the turbine to full capacity is about 2900 cubic feet per minute. This volume is probably available during most of the year, but is not available in the driest seasons, at which times the flow is probably reduced to about 600 cubic feet per minute. The waterwheel probably has an efficiency of about eighty per cent, that is, it will probably develop about eighty per cent of the theoretical energy of the falling water. The remainder is lost in friction in the wheel-box at the entrance to the wheel and in the velocity still remaining in the water after it leaves the wheel. Five per cent of the power generated on the wheel shaft is probably lost by friction of the belting, so that, at rated load, about seventy-six per cent of the theoretical power of the water is probably delivered to the shaft of the generator.

Mr. Miner realized that there would be times when he would not require all or any of the power which would be produced. At the same time the pond formed by the dam was not large enough to store any considerable amount of water, and he had all the power he would require at any one time, so it was not considered necessary to provide storage batteries to store the electricity. On the other hand he did not wish to be compelled to turn the water on and off at frequent intervals, as would be necessary unless some auxiliary regulating apparatus were provided. Therefore, it was decided to provide for the plant to run continuously and to devise some means to consume the electric current when not in use. A series of resistance coils were mounted on a frame in the power house, and connected with the generator. When the demand for electric current is less than the capacity of the generator, a small electric device automatically throws one or more of these coils into the circuit, and the surplus current is converted into heat by the resistance of the coils. By means of this arrangement it was planned to run the plant continuously, so that whenever electric current was wanted it could be had simply by turning a switch at the house or barns.

The power plant, including the dam and all the features thus far described, was completed and in operation before Christmas of the year in which the construction was begun.

We have thus far seen how Mr. Miner developed his water power and transformed it into electricity. It remains to see how he gets it to his house and farm buildings, and how he uses it after he gets it there.

The power house is situated about 1700 feet from the house, where the electric current was most wanted. This necessitated the construction of a transmission line. For this purpose a double line of bare aluminum wire was stretched on a row of poles about twenty feet high and about one hundred feet apart. The poles are provided with ordinary crossarms at the top on which are mounted the insulators carrying the wires. As the transmission line leaves the power house it crosses a highway and runs in a perfectly straight line to the house. Over the highway insulated wires were used as a safety precaution, but bare aluminum wire was used for the remainder because it was cheaper.