« ПредыдущаяПродолжить »
I said to my friends, there was no limit to the speed of such an engine, if the works could be made to stand it.”
Mr. Stephenson had, however, many serious difficulties to encounter before he could get fairly to work with the erection of his locomotive. His chief difficulty was in finding mechanics sufficiently skilled in the knowledge of machinery, and in the use of tools, to follow his instructions and embody his designs in a practical shape. Skilled mechanics were few in number in those days, and were for the most part confined to Birmingham, Manchester, Leeds, and London. The tools in use about the collieries were rude and clumsy; and there were then no such facilities as now exist for turning out machinery of an entirely new character. Mr. Stephenson was thus under the necessity of working with such men and tools as were at his command; and he had in a great measure to train and instruct his workmen himself. The engine was built in the workshops at the West Moor, the leading mechanic being John Thirlwall, the colliery blacksmith, an excellent workman in his way, though quite new to the work now entrusted to him.
In this first locomotive constructed at Killingworth, Mr. Stephenson to some extent followed the plan of Blenkinsop's engine. The boiler was cylindrical, eight feet in length and thirty-four inches in diameter, with an internal fue tube twenty inches wide passing through the boiler. The engine had two vertical cylinders of eight inches diameter and two feet stroke let into the boiler, working the propelling gear with cross heads and connecting rods. The power of the two cylinders was continued by means of spurwheels, which communicated the motive power to the wheels supporting the engine on the rail, instead of, as in Blenkinsop's engine, to cogwheels which acted on the cogged rail independent of the four supporting wheels. This adoption of spur gear was the chief peculiarity of the new engine; it worked upon what is termed the second motion. The chimney was of wrought iron, around which was a chamber extending back to the feedpumps, for the purpose of heating the water previous to its injection into the boiler. The engine had no springs whatever, and was mounted on a wooden frame supported on four wheels. In order, however, to neutralise as much as possible the jolts and shocks which such an engine would necessarily encounter from the obstacles and inequalities of the then very imperfect plateway, the water-barrel which served for a tender, was fixed to the end of a lever and weighted, the other end of the lever being connected with the frame of the locomotive carriage. By this means the weight of the two was more equally distributed, though the contrivance did not by any means compensate for the total absence of springs.
The wheels of the new locomotive were all smooth, and it was the first engine that had been so constructed. From the first, Mr. Stephenson was convinced that the adhesion between a smooth wheel and an edgerail would be as efficient as Mr. Blackett had proved it to be between the wheel and the tramroad. And, although everyone at that time argued that the adhesion upon a tramrail was by no means a criterion of what the adhesion would be upon an edgerail, Mr. Stephenson felt confident that there was no essential difference between the one and the other. Before, however, constructing the smooth wheels for his locomotive, he had the adhesion between the wheels of a carriage, properly loaded, and the rails, tested and satisfactorily proved by experiment. He made a number of workmen mount upon the wheels of a waggon moderately loaded, resting their entire weight upon the spokes on one side, and found that the waggon could thus be easily propelled forward without the wheels slipping. He then determined to fix smooth wheels upon his locomotive, in the firm belief that the weight of the engine would of itself give sufficient adhesion for the purposes of traction.
The engine was, after much labour and anxiety, and frequent alterations of parts, at length brought to completion, having been about ten months in hand. It was first placed upon the Killingworth Railway on the 25th of July, 1814; and its powers were tried on the same day. On an ascending gradient of 1 in 450, the engine succeeded in drawing after it eight loaded carriages of thirty tons' weight at about four miles an hour; and for some time after it continued regularly at work. It was indeed the most successful working engine that had yet been constructed.
Although a considerable advance upon all previous locomotives, “ Blutcher" (as the engine was popularly called) was nevertheless a somewhat cumbrous and clumsy machine. The parts were huddled together. The boiler constituted the principal feature; and being the foundation of the other parts, it was made to do duty not only as a generator of steam, but also as a basis for the fixings of the machinery and for the bearings of the wheels and axles. The want of springs was seriously felt; and the progress of the engine was a succession of jolts, causing considerable derangement to the machinery. The mode of communicating the motive power to the wheels by means of the spur gear also caused frequent jerks, each cylinder alternately propelling or becoming propelled by the other, as the pressure of the one upon the wheels became greater or less than the pressure of the other, and, when the teeth of the cogwheel became at all worn, a rattling noise was produced during the travelling of the engine.
As the principal test of the success of the locomotive was its economy as compared with horse power, careful calculations were made with the view of ascertaining this important point. The result was, that it was found the working of the engine was at first barely economical; and at the end of the to be as nearly as possible upon a par in point of cost. The fate of the locomotive in a great measure depended on this very engine. Its speed was not beyond that of a horse's walk, and the heating surface presented to the fire being comparatively small, sufficient steam could not be raised to enable it to accomplish more on an average than about three miles an hour. The result was anything but decisive; and the locomotive might have been condemned as useless, had not Mr. Stephenson at this juncture applied the steam-blast, and at once more than doubled the power of the engine.
Although Trevithick, in the engine constructed by him in 1804, allowed the waste steam to escape into the chimney, there was no object in the arrangement except to get rid of a nuisance and to avoid the unsightliness of the escaped steam blowing off in jets into the open air. The exit pipe adopted by Mr. Trevithick, as we have already observed, was not contrived with the view of producing any effect; nor does any seem to have been produced, for it is certain that he afterwards abandoned the arrangement. It is remarkable that a man so ingenious as Trevithick should not have discerned its advantages; but it is clear that he could not have done so, for as late as 1815, after George Stephenson had discovered and successfully adopted the steam blast, Trevithick took out a patent, the principal object of which was to“ produce a current of air in the manner of a winnowing machine, to blow the fire.” “Flat plates or leaves," revolving in a case, were the means adopted by him for this purpose ; and in the same patent he proposed to “place in the flue a screw or set of vanes, somewhat similar to a smoke-jack," which were “to revolve by connection with the steam-engine, for the purpose of creating an artificial draft in the chimney.” This contrivance was, however, a useless one, as Mr. Stephenson's mode of applying the blast already threw it far into the shade is a means of stimulating combustion by artificial means.
It is remarkable how little Trevithick really accomplished for railway progress, notwithstanding his ingenuity and skill as an inventor and mechanician. Instructed by Murdock and assisted by Vivian, he was enabled to erect his first steam-carriage, after which he constructed his first railway locomotive. But Trevithick was one of those men who are satisfied with making a beginning. He was not endowed with the gift of continuance — the quality of perseverance. With half the cleverness, and double the application, he might have successfully worked out the problem of railway locomotion, and kept ahead of all competitors.
George Stephenson was a man of an entirely different fibre. His patience was never baffled by failure ; his faith was never shaken by opposition. When he became fully possessed by a conviction, he held to it with dogged tenacity, and braved the shafts of ridicule, the arguments of opponents, and the shrugs and the sneers of the utterly indifferent. Above all, he was an accurate and careful observer; and the improvements which he was enabled to effect in the locomotive were mainly due to the care with which he noted facts, and the patient reflection which he bestowed upon them, with the object of turning them to useful account.
Thus, his adoption of the steam blast in the chimney was in no way the issue of accident; but it was an invention the result of careful observation and patient reflection. In his first locomotive the eduction steam was allowed to escape into the open atmosphere, with a hissing blast, which was the terror of horses and cattle, and was generally complained of as a nuisance. A neighbouring squire even threatened an action against the colliery lessees if it were not put an end to. But Mr. Stephenson's attention had already been drawn to the circumstance of the much greater velocity with which the steam issued from the exit pipe, compared with