The table above shows the result of a recent test of a pair of there engines, guaranteed to develop 700 indicated horse-power per hour. rpon starting the engines it was found that it would not, at least for some time. pract icable to load Them to more than about 300 horsepower it was then concluded to dis connect one of the pair and test the other, the builders of the engines waiving the right to steam of 110 lbs. pressure. and using but lbs.: two boilers only were used. While the engine was run only through the ordinary working lionrs 10i—all the coal tied (lur ing the 24 hours was charged against it : this in cluded coal for banking fires, getting up steam in the morning, etc. The test was (.1)1161mi:it for 4 days 90 hours—a large number of diagrams being taken from which to compute the power.
The Friek-Corlis En gine.—Pig. 74 (from Cao: sier's .1Iagazihe) represents a tandem-compound CI•rli.s engine built by the Frick Co., engineer., Waynesboro, The valve-gear is of the Corliss type, with con stant lever-disengaging mo tion. (tile gi3vernor trols steam-valves on high and low pn•ssnre cyl inders. The wrist - plate motion is driven by two eccentrics, making, inde pendent actuation forsteatu and exhaust valves, and is known as the long-range ent-otT. The engine is de signed for electrie railway and cable work the variation of the loads is very great. The low-press ure cylinder is 44 in. diam eter. highiwessiire in. din:actor, tly-wheel 27i ft, diameter, 0 Ft. face. weight 50 tons, Connection is had between the high and low pressure cylinders by means of a reeeiver-pipe, which connects with a flat passage secured on the side of the low-pressure cylinder leading to the steam chest. The engine illustrated has a nominal capacity of 750 horse-power.
The itc11x Balanced Compound-Engine, made by the Wells Engine Co., of New York. is shown in Fig. 75, It is claimed for this engine that it has a natural balance in weight of the two pistons. and their connections, at all angles of the cranks and at all speeds ; also a balance of steam pressures. Equal weight being attached to opposite sides of the crank-shaft moving in opposite directions (in the same plane), the thrust of one is perfectly counteracted by that of the other. Steam is admitted simultaneously to the bottom of the high-pressure and to the top of the low-pressure cylinders, and vice versa, The force on one cylinder-head is counter acted by an equal force on the other. Hence there can be no strains transmitted to the frame,
and thence to the main bearing-boxes. The ascending steam force on the small piston is equaled by a descending steam force on the large piston, which transfers the fulcrum from the main boxes to the crank-shaft, concentrating the whole force in the shaft for useful effect. As clearly shown in the cut, there are three connecting-rods, one transmitting the pressure from the high-pressure cylinder, and the other two connecting with the two piston-rods of the larger cylinder.
Repeater for Compound Engines.—F. W. Dean, of Cambridge, Mass., has recently invented a repeater for use in connection with compound engines for the purpose of superheating the exhaust steam from the high-pressure cylinder before it enters the low-pressure cylinder. Fig. 76 shows a vertical section elevation, and Fig. 77 a sectional plan. The cylinder A is of cast iron, and is provided at the center with an inwardly projecting T-shaped annular rib, A'.
On one side is formed a passage, B, communicating with the exhaust-pipe B' of the high pressure cylinder, and a passage C opening into the pipe through which the steam passes to the low-pressure cylinder after having been reheated. The ends of the cylinders are closed by the heads A' and into its under side are screwed two drain-pipes a. A copper or steel cylinder I) has its ends closed by heads which serve as tube-sheets to support the series of tubes b, which are inserted in the usual way—that is, by expanding their ends. Live steam enters through the pipe E and passes out through the pipe F. The construction of the cylinders A and D and the heads is such that the exhaust steam from the high-pressure cylinder surrounds the cylinder D at the left of the partition-rib Al, passes through the tubes, sur rounds the right-hand half of the inner cylinder, and then passes through the pipe C' to the valve-chest of the low-pressure cylinder. In the mean time the interior of the cylinder D has been filled with live steam from the boiler which surrounds all the small pipes. imparting a portion of its heat to them and to the shell of the inner cylinder, which is taken up and ab sorbed by the exhaust steam.
Joy's Valre-Gear.—IL has constantly been an object with inventors to get rid of the com plications of the two eccentrics, link, etc., required for an expansion and reversing gear.