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in the interior faces of the links ; the links are kept at a proper distance apart by bolts. The links are capable of being lifted up by means of the lever g, and connecting piece f. When the slide-valve is out

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of gear, the eccentric-rods are in the position shown in the diagram, the line of valve-rod bisecting the angle formed by the eccentric-rods. In this case, if the engine is in motion, as just in pulling up at a station, the eccentric-rods merely make the link oscillate or vibrate in the centre, of the valve-spindle, in and out alternately, as shown by the arrows

But if the valve is required to make the engine go ahead, or forward, the link is raised up by means of the handle g, until the forward eccentric-rod b is in a line with the valve-rod; and by this means the throw of the eccentric will be communicated to the valve-rod, and the engine will go forward. To reverse the engine, all that is necessary is to lower the links until the upper eccentric-rod c is placed in a line with the valve-rod, when the engine moves backward.

Having sufficiently, for the elementary purposes of our treatise, given the details of the locomotive, we now proceed to give illustrations of engines, showing the connexion of the various parts. The first we give is the longitudinal section of a “fast passenger-engine,” constructed by Mr. Hackworth; and for the drawing of which, and description, we are indebted to Mr. W. Johnson, fig. 153. She has been expressly designed for fast passenger trains, having driving-wheels 6 feet 5 inches diameter, with leading and hind wheels

of 4 feet diameter. Her weight, in working order, is 23 tons 15 cwt., and this is distributed in the following manner : on leading wheels, 8 tons 6 cwt. ; drivers, 11 tons 4 cwt. ; and hind wheels, 4 tons 5 cwt. The crank axle, A, is carried in bearings in the inner frame, whilst those of the leading and hind wheels, B and c, are in the outer frame ; the length from centre to centre of the latter pairs being 13 feet 6 inches; these proportions having been laid down with a strict reference to the stability of the leading wheels, without an undue detraction from the tractive adhesion of the drivers. The barrel, D, of the boiler presents the novelty of welded longitudinal seams : it is composed of five

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fig. 153.

plates, turned into rings, each being welded longitudinally, whilst their transverse junctions one with another are riveted in the ordinary way. The junctions, E E, of the two ends, with fire-box and smoke-box, are formed by angles or flanges welded on, instead of by separate angle irons riveted : these were turned and faced in the lathe to a true surface, for the bearing against the fire-box at one end, and the cylinder foundation-plate at the other, thus affording great accuracy in these details. The original idea of welding the boiler-plates is claimed by Mr. Hackworth, who, it appears, had actually made a boiler on this principle long prior to the date of the construction of the “farmer's engine" by Mr. Willis. The example of construction now before us is a very beautiful one ; indeed, it is unrivalled as a specimen of this class of workmanship. The lagging, or cleading, of the boiler is covered with sheet iron, giving the surface a smooth appear

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The plate, F, forming the back corners of the fire-box, is 14 inches broad, and was originally made in three pieces for the convenience of setting; but, after the completion of the process, they were welded together, so as to form a single plate. The grate bars, GG, are arranged longitudinally, and are carried on two transverse bearers, supported on projections on a pair of longitudinal shafts, H h, at the bottom of the fire-box, and worked by a lever, I, standing up from the foot-plate, so that the driver may drop the whole set of bars instantaneously into the ash-box, J. The latter

may also be dropped independently of the bars, by releasing the suspending bars, K k, on each side.

The fire-door, L, is provided with a regulator for the admission of air into the fire-box at pleasure, the baffle-plate being perforated with small apertures for its dissemination in the interior.

The boiler tubes, M, are of brass, 2 inches in external diameter, and are 221 in number. At the smoke-box end of the tubes a baffle-plate is also fixed opposite the tube ends ; it is perforated with holes 1 inch diameter, the under sides of which correspond with the bottom line of the tubes, so that the hotter portion of the vapour is retained at the upper side, inducing a superior evaporative action. This addition does not interfere in any way with the cleaning of the tubes, as it may be removed with great facility. The dome, or steam chest, n, is formed out of a single plate, welded longitudinally, the flange for riveting it to the boiler being worked out of the same plate. The upper flange at o is welded on internally, being turned and faced to form a steam-tight joint with the convex cover, which is similarly formed, and is removable for obtaining access to the boiler.

The pistons also involve some novelties both in design and construction : they are made entirely of wrought-iron, with the rods forged on them; so that whilst there is thus a gain in lightness and strength, the dangers resulting from occasional looseness are completely removed. The inner framing, Q, consists of two wrought-iron slabs extending the whole length of the boiler's barrel, and attached at one end to the fire-box by inch angular plates riveted on. The peculiar advantage of this arrangement of frame is, that it yields to the expansion and contraction of the boiler, preserving a constantly uniform length between the cylinder and crank axle, and obviating the very common tendency to work loose, and cause leakage. The frame-plates extend from the centre of the crank axle, so as to counteract the effect of the strain of the engine at the most effective point; and a stiff connexion is formed with the barrel of the boiler by a strong central transverse plate, riveted on by means of stirrup angle-irons. At the smoke-box end, a foot, or flange, is formed on each frame-plate, for abutting against the tube-plate, to which it is riveted and bolted, the connexions being passed through the cylinder flanges.

The outer framing consists of a wrought-iron slab, 9 inches deep and 1 inch thick, extending the whole length between the buffer bars, the axle guards being forged with it in one piece. The transverse junctionplate, s, forms a very important feature of the engine ; it is riveted to the boiler by double angle-irons, and extends across and between the inner and outer frame-plates, forming an effective fixed point for the pressure of the

working gear.

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The piston-rod motion consists of a pair of slide-bars, Tt, attached at one end to protecting flanges cast on the cylinder cover, and at the other to the transverse junction-plate, s. The cross-heads, or motion-blocks, u, each consists of a malleable iron double eye-piece, with a box at the inner end, into which the piston-rod is keyed ; and on the upper and lower sides of the double eye are bolted the brass slides, with protecting flanges to guide them on the motion-bars.

The connecting-rods, v, are of a plain rectangular section, and are attached to the cross-heads by a steel pin passing through them and through the double eyes, secured by a nut on the outside. The feed-pumps are placed in a line parallel to the piston-rods. The rams are of malleable iron, passed through and secured by a nut to the cross-head pin. The pumps are of brass ; they are attached to the inner frame and transverse junction-plate.

It is an ascertained fact that, in too many cases, very little regard is paid to the obtainment of a sufficient area in the valve-cases for the admission of feed-water to the boiler. Owing to the contraction of this space,

the valves are made of small size, and thus a great rise is absolutely necessary to admit a due supply of water; and this, coupled with their great rapidity of action, is frequently the occasion of great inconvenience in point of derangement and wear. Where the contraction exists in excess, the defect is heightened by the absorption of power in forcing the feed through the passages. In the " Sanspareil,” the valves and valve-boxes, w,

are made very large, so as only to require [th inch lift of valve.

The eccentric sheaves are made with the smaller divisions of wroughtiron, having pins forged upon them, to connect them with the larger or prominent eccentric sides, which are of cast-iron. The eccentric rods and straps are of wrought-iron, and the rods are forged on the front halves of the straps, the latter being lined with brass. The back halves have an oilvase, x, forged on each, with a syphon-pipe on each side the bolt, for lubricating the sheave. The slide-spindles are guided in brass bearings, in a bracket, y, fixed to the transverse junction-plate; and the bottom of this bracket, at 2, forms a bearing for one end of the reversing weigh-bar.

The ordinary link motion is adopted for the slide and reversing gear, the lifting links for reversing being placed inside the motion links, and connected with the forward eccentric pins; and the levers on the reversing weigh-bar are forged on.

The fire-box is at cc, the smoke-tubes at dd, the balanced spring safety-valve at a ad'; b the steam-whistle; ss the smoke-box; h the blast

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pipe; m the chimney; ee the regulator; c the regulator-handle; n the pipe

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