1248

THEORY AND PRACTICE OF ENGINEERING.

Book II.

of tho cylinder in feet multiplied by the velocity in feet, with the addition of one-tenth forwaste, gives the quantity of steam; and this again divided by the volume of steam give*the quantity of water required per minute for steam : the proportions of the boiler marthen be determined; at the common pressure of two pounds per circular inch on thevalve, the divisor will be 1497. The water for injection o o

must be 24 times that required for steam; and the dia-meter of the injection-pipe made one-36th that of thecylinder. The effective power of such an engine is foundby multiplying the effective pressure on the piston by thesquare of its diameter in inches, and that product by thevelocity in feet per minute:the quantity of pounds raisedone foot high per minutebeing obtained, and dividedby 33000, gives the horse-power, and each horse-powerrequires a supply, of 9'2 lbs.of coal per hour ; but whenthe engine is less than tenhorse, the quantity requiredis increased: such an engineis applicable to all purposes,and when steam is made toact expansively, the power isobtained with less fuel; whenso applied, a fly-wheel equal-ises its motion. Fig. 1961.shows the steam shut off, andthe passage to the condenserstill open. Fig. 1960. repre-sents its state when steam islet on at the bottom: theletters refer to correspondingportions of fig. 1962.

One of the earliest engineswith a double-action wasmade by Mr. Watt, in 1782,and some years afterwardstwo of fifty-horse power eachwere put up at the AlbionMills, Blackfriars, whichjointly drove 20 pair of mill-stones, of which 12 or more,

■with all the machinery fordressing the flour, were generally kept

Fig. 1960

Fig. 1961

Fig. 1962. D0VBLE-ACT1NG CONDENSING ENGINE.

In this engine (fig. 1963.), A

at work.

the cylinder, 34 inches in diameter; B, the piston, which has an 8-feet stroke; C, thepiston-rod; D, the stuffing-box, or cover of the cylinder; E, the steam-case or jacket,of the cylinder, from which a siphon empties the water, and which is supplied bya pipe; G, the upper steam nozzle and valve or regulator box and regulator; H,the upper exhaustion nozzle and valves; I, the perpendicular steam-pipe; J, the educ-tion-pipe ; K, the lower steam nozzle and valve; L, the lower exhaustion nozzle andvalves; M, the condenser, immersed in a cistern of cold water, the injectionco^k being always open during the woiking of the engine; O, the blow-valve;P, the air-pump; Q, the lower valve and air-pump ; R, the bucket and rod of theair-pump ; S, the upper valve of the air-pump; T, the hot water pump, with thebucket and rod ; U, the cold water pump ; V, the pump for supplying the boiler ; \Y, thegovernor, turned by a belt from the shaft of the fly-wheel; X, the lever and rod, whichconnects the governor with the throttle valve t ; Y, the working gear of the nozzle valves ;Z, the plug-tree which drives the working gear; a, the main lever or working beam; 6,its main gudgeon; c, the perpendicular links of the parallel motion; d, the parallelbars ; e , the regulating radii; f the small perpendicular links ; g , the secondary parallelmotion for the air-pump; A, the connecting rod; i, the planet-wheel fixed to the con-necting rod; j , the iron wheel; k, the shaft of the fly-wheel,‘on which the iron wheel isfixed ; l , the connecting link, which retains the planet-wheel in its orbit; w> the fly-wheel;n, the boiler; o, the tube through the boiler and the tube round it; p, the grate; q, thefeeding mouth ; r, the damper; 5 , the chimney; t, the feed-pipe; «, the gauge pipes, withthe cocks; r, the safetv-valve.