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Stephenson to state that it appears he was much indebted to Timothy Hackworth for a variety of sound practical information; indeed, Hackworth was the only person at this period who had any thing like a practical knowledge of the whole bearings of the case.
In offering the above reward for the best locomotive, the directors made the following stipulations: "the engine was to consume its own smoke; to be capable of drawing after it three times its own weight at ten miles an hour, and have not exceeding 50 lbs. pressure upon the square inch on the boiler; two safety-valves, one locked up; engine and boiler to be supported on springs, and rest on six wheels if it should exceed four and a half tons; height to top of chimney not more than fifteen feet; weight, including water in boiler, not to exceed six tons, but preferred if of less weight; boiler, &c. proved to bear three times its working pressure, and pressure-gauge provided; cost of machine to be not more than 5501." The following is a description of the public trial of the competing engines: The "Rocket," constructed by George Stephenson, and of which we give a representation in fig. 141, weighed 4 tons 5 cwt., and the tender, with water
and coke, 3 tons 4 cwt. 2 lbs. ; it had two loaded carriages attached, weighing 9 tons 10 cwt. 3 qrs. 20 lbs., thus making the whole weight to be moved equal to 17 tons. The velocity attained by this engine was 14 miles an hour, with an evaporation of 114 gallons per hour, and consumption of coke equal to 217 lbs. per hour. The greatest velocity attained was at the rate of 24 miles per hour. The "Sanspareil," by Timothy Hackworth, and of which we give a representation in fig. 142, was the next engine tried, although from its not having been made in strict accordance with the specified rules, it was scarcely competent to enter the lists of competition. The weight of the engine was 4 tons 15 cwt. 2 qrs.; the tender and water and fuel being 3 tons 6 cwt. 3 qrs. ; the loaded carriages, three in number, attached to it being equal to 10 tons 19 cwt. 3 qrs.; the whole weight to be moved being equal to 19 tons 2 cwt. The engine in her eighth trip became disabled through the feed-pump becoming disordered in its action, the level of the water in the boiler got low
therefore, and the leaden plug, which was used as a safety-valve, getting melted, an end was thus put to the experiment. Her rate of speed was however satisfactory, being equal to conveying 19 tons at fifteen miles per
hour. The greatest velocity attained was 22 miles per hour. The consumption of fuel was very great in this engine, being equal to 692 lbs. per hour; this was in consequence of the great draught induced by the steamblast in the chimney.
The third engine, the "Novelty," by Messrs. Braithewaite and Erricson, and of which we gave a representation in fig. 143, carried its own water and fuel, and weighed 3 tons 1 cwt. The weight of the tank, water, and fuel, being 16 cwt. 14 lbs.; the two loaded carriages being 6 tons 17 cwt.; the total weight being 10 tons 14 cwt. 14 lbs. In consequence of successive accidents in the working arrangements of this engine, it was withdrawn from competition; its performances, however, were very satisfactory so far as they went.
Another engine, named the "Perseverance," constructed by Mr. Burstall, was also entered for competition; but being unsuited to the railway, was at once withdrawn. The judges on this interesting occasion were Mr. Nicholas Wood, Mr. Rastrick, and Mr. Kennedy. The prize was awarded to Mr. Stephenson for his engine the "Rocket.'
The "Rocket" undoubtedly owed its efficiency, at least in an economical point of view, from the construction of the boiler, and the large amount of surface which was presented to the action of the heated air. This was obtained by introducing twenty-five copper tubes, three inches diameter, into the interior of the boiler, at its lowest diameter; these tubes opened at one end into the space below the chimney, and at the other into what is now termed the fire-box; by this arrangement, the flame and heated air passed through the tubes, which were surrounded by the water in the boiler. The furnace or fire-place was an external box, about three feet deep and two wide; the furnace was provided with an external casing; into the space thus formed the water from the boiler passed: a large additional amount of heating-surface was also thus obtained. The boiler or fluetubes-" which has since proved to be the main-stay of the modern locomotive"- —was the invention of Mr. Henry Booth, the secretary of the railway; a gentleman " to whom railways are indebted for much of their practical efficiency." From the invention not having been patented, Mr. Booth did not receive the great pecuniary advantages which might otherwise have resulted from this highly valuable improvement. We understand, however, that he received a pecuniary reward from the directors of the railway on account of it. As will be seen on inspection of the diagram, the cylinders were placed outside the boiler, near the fire-box, and inclined at an angle; and the piston-rod of which is connected with the drivingwheel by means of a connecting-rod.
In the "Sanspareil" of Hackworth, the cylinders were inverted and placed vertically; the piston-rod cross-head worked between parallel guides; and to the cross-head was attached the connecting-rod which communicated motion to the hind wheels; the fore and hind wheels were coupled by a connecting-rod. The boiler was cylindrical, with the flue returned to the front, where it entered the chimney; the flue was of course entirely surrounded with water.
The "Novelty" possessed some arrangements of considerable merit, the most distinguished feature being the construction of the boiler and fire-place. This will be seen by an inspection of the diagram in fig 144: is the furnace placed inside the boiler, and surrounded with water; fuel is supplied to the fire-place c by the tube or funnel e, passing through the dome of the boiler, and covered with a lid or cap. Air is forced into the fire, to maintain combustion, by a small pair of fanners worked by the engine, through the pipe b communicating with the ash-pit c. The heated air is forced along the series of pipes fg to the chimney h, the steam space being at ii. By this arrangement a large amount of heated surface is obtained; the fireplace not only being surrounded with water, but the long range of pipes fg. The peculiar arrangements of the engine will be seen by the diagram in fig. 143. Mr. Stephenson not only obtained the prize, but the appointment of engine-manufacturer to the company. The attention of the firm was now devoted to the perfecting of the mechanism of the locomotive. "Each engine that issued
month by month from the factory was an improvement on its predecessors, and the fourteen and twenty miles of the 'Rocket' were raised to sixty and seventy miles; and the Newcastle factory became the largest and most famous in the world." Other manufacturers entered the field of competition, and the vast amount of ingenuity and practical experience brought
to bear on the mechanism of the locomotive by such eminent firms as those of Hawthorn and Company; Sharp, Roberts, and Company; Bury, Curtis, and Kennedy; and last, though not by any means least, of Timothy Hackworth, soon resulted in bringing the locomotive engine to its present high state of perfection.
We now proceed to give illustrations of locomotive engines, showing the majority of the improved arrangements as now introduced. It is impossible to notice the whole details so fully as we should wish in a short treatise like the present; we hope, however, that the illustrations we give will enable the reader pretty closely to understand the arrangements and operation of this beautiful machine.
For the purposes of description, we shall divide the locomotive into two parts: the fire-box, smoke-box, and boiler; and the moving parts of the engine which give motion to the whole.
The fire-box, as may be seen by inspection of the longitudinal sections of engines hereafter given, at cccc, fig. 147, is enclosed on all sides except the bottom; at this part the fire-bars are placed on which the fuel rests; and at the side next the funnel or chimney, this side is pierced with holes, into which are passed the smoke-tubes dd. To prevent the dispersion of the red-hot ashes from the fire, a plate-iron tray or receptacle is placed beneath the fire-bars. Fire-boxes are of two kinds, square and round, as in figs. 153, 155. The round top is recommended by some, as being best calculated to withstand the pressure of the steam. In both methods of construction, however, it is imperatively essential to strengthen the parts by numerous stays or bolts. The fire-box door (see longitudinal sections) is double, to prevent loss of heat; and the outer and inner boxes, between which the water of the boiler is allowed to flow, are here joined. The fire-bars are placed loosely in a frame, so as easily to be lifted out when
required to be renewed. In some instances the fire-bar frame is suspended by catches; when these are withdrawn, the fire-bars and fuel above them are precipitated into the ash-tray.
The smoke-tubes are generally made of brass, but malleable iron ones are now becoming largely used. The number of tubes in each engine varies from 96 or thereabouts to 134. Great care is necessary to fit the tubes into the fire-box end, and also that of the smoke-box. They must be fitted water-tight. The diameter of the tubes is generally about one inch and a half. The communication between the fire-box at one end and the smokebox ss, figs. 153, 155, is kept up entirely by means of the smoke-tubes dd. This is formed of plates of iron of the same shape externally as the fire-box. Access is had to the interior of the smoke-box by a door at the front of the engine; this is made in various ways: in some instances it is hinged at bottom and opens downwards; in others it is in two leaves, like ordinary folding-doors. The smoke-tubes pass through the side of the smoke-box nearest the fire-box. The cylinders are in many instances placed inside the smoke-box; by this arrangement, the loss by radiation and condensation of steam is avoided. The steam, after working the cylinder, is ejected up the chimney through the blast-pipe h fig. 153, and ee fig. 155. The diameter of chimney is about 13 inches, and the height is limited to about 7 feet above the boiler, to allow it to pass under the railway bridges.
The fire is moderated by a damper placed in the chimney; this is generally made of the "throttle-valve" species, being a plain disc, a a fig. 145, turning on an axis d somewhat out of the centre; it is provided with
an aperture through which the end of the blast-pipe passes, when the damper is wholly shut, the end of the blast-pipe projecting above it; the damper is moved by the lever e, actuated on by a long lever under the control of the engine-man. This lever is furnished with three slots, which take into a rest; according as the lever rests on either of the slots, so is the opening of the damper regulated. The upper orifice of the chimney is sometimes covered with a wire-netting; this is in order to arrest the sparks. This contrivance is, however, fast falling into disuse, and a perforated iron plate is placed below the blast in the smoke-box. In American locomotives, where wood is extensively used for firing, a "spark-arrester" is adopted; this gives a degree of size to the chimney unusual in locomotives in this country. This will be described hereafter.
The water is supplied to the boiler by means of a small force-pump,