Steam-pow′er Me′ter.
A device for ascertaining the amount of work done by a steam-engine. Fig. 5711 is that of Messrs. Ashton & Storey, of Manchester, England. It consists of a double-acting indicator cylinder, having its ends connected with those of the engine-cylinder by pipes g g. The indicator piston-rod a carries a wheel b with a plain rim and a long pinion e gearing with the spur-wheel d. At the upper end of this rod is a helical spring, which resists either the upward or downward movement of the indicator piston. The wheel d is fixed on the lower end of a spindle having a worm at its upper end, which communicates motion to the train actuating the dial. The wheels e f are of the same diameter, and on the same horizontal shaft: the first has a smooth face, which is, by means of a spring, pressed against the rim of the wheel b; the other f is grooved and connected by a band with the crosshead or other convenient reciprocating part of the engine, causing its partial rotation in one direction; its motion is reversed by a spring, thus causing an alternating reciprocating movement of the two wheels e f when the engine is in operation. The tension of the spring at the head of the rod a is so adjusted that when the pressures on each side of the piston are equal, the wheel b is at the center of the wheel e; an excess of pressure on either side causes it to rise or fall by an amount proportionate to this excess. The principle of operation is as follows: If the wheel f be connected with the cross-head of the engine, so that its periphery and that of e move an equal distance and at an equal velocity with the cross-head, and a steam pressure of 50 pounds per inch suffices to move the wheel b to a point midway between the center and the circumference of the wheel e, the periphery of the wheel b will move with half the velocity of the engine-piston, and so on in proportion to its greater or less distance from the center of e, dependent on the effective pressure. The relation between this motion and that communicated to the gearing of the indicator is such that the dials register the amount of work done in units of 1.000 foot-pounds for each circular inch in area of the piston. The absolute work of the engine in a given time is then ascertained by multiplying the square of the diameter of the piston by the number of units indicated by the dial. As at each up-stroke of the piston the wheel b will be above the center of the wheel e, and at each down-stroke an equal, or nearly equal, distance below it, it is evident, owing to the reciprocating motion of e, that of b and of the registering mechanism will be continuous in one direction. |
| Steam-power meter. |
