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Page:Popular Science Monthly Volume 18.djvu/347

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tained fitted with a governor and the necessary pulleys at a slight increase of cost. The pumping-engines have found their way into very general use on railroads, country seats, and in city buildings, and from their economy in the use of fuel and their little trouble they have in all these situations proved very satisfactory. They are made only with coal-burning furnaces, and are on this account more troublesome than they would be if using gas, but are still but little more so than an ordinary coal-stove. Replenishing of fires and oiling are the only duties to be performed, and these can be done by unskilled labor. The engine occupies about the same floor-space as a moderately large coal-stove, and is about the same height. Two sizes are made, one of six, and one of ten-inch cylinder. The former will pump five thousand gallons of water to a height of ten feet in an hour, or a smaller amount to a proportionally greater height, at an expenditure of four pounds of coal, and the latter will raise twelve thousand gallons to the same height, in the same time, with eight pounds of coal. These amounts of coal are those used when the engine is run consecutively for ten hours. If run for a shorter time, the coal consumed per hour will be somewhat greater, owing to the starting of the fire. The engines weigh considerable, the smaller size being some sixteen hundred pounds, and the larger about double. The prices do not differ materially from those of steam-engines of from one to three horse-power.

The internal construction of the engine and manner of working; are shown in the sectional view in Fig. 10. It is also of the type which repeatedly uses a given body of air, but, unlike the motor of Ericsson, the alternate heating and cooling are done in separate cylinders. The air is heated in the cylinder B and cooled in the cylinder A. The plunger C fits the cylinder A in its upper portion, but is contracted in the lower part to allow of an annular space between it and the wall of the cylinder. The power-piston D also fits its cylinder B tightly in the upper portion, but loosely in the lower heated part. A leather packing, K K, in each cylinder secures as in other engines a perfect fit of these moving parts. Between the two cylinders is placed a regenerator, H, consisting of a number of perforated plates, through which the air passes in going from one cylinder to the other. Around the lower portion of the cylinder B is a water-jacket, E, and encircling the same part of the heating cylinder B is a metal shell, F, curved inward at the base. The extension G of the cylinder B down into this shell forms a narrow annular space, through which the air entering the heater has to pass in a thin sheet, and thus becomes thoroughly heated. In action, the plunger C descends and compresses the air below it to one third its previous bulk; then by the further upward movement of the power-piston D and the completion of the down-stroke of the plunger, this air is transferred to the heater. This compressed air becoming heated expands and forces the power-piston to the end of its stroke, and entering the cylinder A carries the plunger