Изображения страниц
PDF
EPUB

CHAP. XII.

FURTHER IMPROVEMENTS IN THE LOCOMOTIVE.

MR. STEPHENSON's experiments on fire-damp, and his labours in connection with the invention of the safety lamp, occupied but a small portion of his time, which was mainly devoted to the engineering business of the colliery. He was also giving daily attention to the improvement of his locomotive, which every day's observation and experience satisfied him was still far from being perfect.

At that time, railways were almost exclusively confined to the colliery districts, and attracted the notice of few persons except those immediately connected with the coal trade. Nor were the colliery proprietors generally favourable to locomotive traction. There were great doubts as to its economy. Mr. Blackett's engines at Wylam were still supposed to be working at a loss; the locomotives tried at Coxlodge and Heaton, proving failures, had been abandoned; and the colliery owners, seeing the various locomotive speculations prove abortive, ceased to encourage further experiments.

Stephenson alone remained in the field after all the other improvers and inventors of the locomotive had abandoned it in despair. He continued to entertain confident expectations of its eventual success. He even went so far as to say that it would yet supersede every other tractive power. Many looked upon him as an enthusiast, which zo doubt he was, but upon sufficient grounds. As for his ng engine, it was by most persons regarded as a curious toy; and many, shaking their heads, predicted for it “a terrible blow up some day.” Nevertheless, it was daily performing its work with regularity, dragging the coal waggons between the colliery and the staiths, and saying the labour of many men and horses. There was not, however, so marked a saving in the expense of working when compared with the cost of horse traction, as to induce the northern colliery masters to adopt it as a substitute for horses. How it could be improved and rendered more efficient as well as economical, was never out of Mr. Stephenson's mind. He was quite conscious of the imperfections both of the road and of the engine; and he gave himself no rest until he had brought the efficiency of both up to a higher point. He worked his way step by step, slowly but surely: every step was in advance of the one preceding, and thus inch by inch was gained and made good as a basis for further improvements.

[graphic]

At an early period of his labours, or about the time when he had completed his second locomotive, he began to direct his particular attention to the state of the road; as he perceived that the extended use of the locomotive must necessarily depend in a great measure upon the perfection, solidity, continuity, and smoothness of the way along which the engine travelled. Even at that early period, he was in the habit of regarding the road and the locomotive as one machine, speaking of the rail and the wheel as “ man and wife.”

All railways were at that time laid in a careless and loose manner, and great inequalities of level were allowed to occur without much attention being paid to repairs; the result was that great loss of power was caused, and also great wear and tear of machinery, by the frequent jolts and blows of the wheels against the rails. His first object therefore was, to remove the inequalities produced by the imperfect junction between rail and rail. At that time (1816) the rails were CHAP. x11.) IMPROVEMENT OF THE RAILROAD.

137

made of cast iron, each rail being about three feet long; and sufficient care was not taken to maintain the points of junction on the same level. The chairs, or cast-iron pedestals into which the rails were inserted, were flat at the bottom; so that, whenever any disturbance took place in the stone blocks or sleepers supporting them, the flat base of the chair upon which the rails rested, being tilted by unequal subsidence, the end of one rail became depressed, whilst that of the other was elevated. Hence constant jolts and shocks, the reaction of which very often caused the fracture of the rails, and occasionally threw the engine off the road.

To remedy this imperfection, Mr. Stephenson devised a new chair, with an entirely new mode of fixing the rails therein. Instead of adopting the butt joint which had hitherto been used in all cast-iron rails, he adopted the half-lap joint, by which means the rails extended a certain distance over each other at the ends, somewhat like a scarf joint. These ends, instead of resting upon the flat chair, were made to rest upon the apex of a curve forming the bottom of the chair. The supports were extended from three feet to three feet nine inches or four feet apart. These rails were accordingly substituted for the old cast-iron plates on the Killingworth Colliery Railway, and they were found to be a very great improvement upon the previous system, adding both to the efficiency of the horse power (still used on the railway) and to the smooth action of the locomotive engine, but more particularly increasing the efficiency of the latter.

This improved form of the rail and chair was embodied in a patent taken out in the joint names of Mr. Losh, of Newcastle, iron-founder, and of Mr. Stephenson, bearing date the 30th of September 1816.* Mr. Losh, being a wealthy, enterprising iron-manufacturer, and having confidence in George Stephenson and his improvements, found the money for the purpose of taking out the patent, which, in those days, was a very costly as well as troublesome affair.

* A grant unto William Losh, of the town and county of Newcastle-uponTyne, iron-founder, and George Stephenson, of Killingworth, in the county of Northumberland, engineer, for their invented new method or new methods of facilitating the conveyance of carriages, and all manner of goods and materials along railways and tramways, by certain inventions and improvements in the construction of the machine, carriages, carriage-wheels, railways and tramways employed for that purpose. - 30th Sept. 1816. Patent Record Office, Number 4067.

The specification of the same patent also described various important improvements on all locomotives previously constructed. The wheels of the engine were improved, being altered from cast to malleable iron, in whole or in part, by which they were made lighter as well as more durable and safe. Thus the road was rendered smoother, and the wheels of the locomotive were made stronger. But the most ingenious and original contrivance embodied in this patent was the substitute for springs which was devised by Mr. Stephenson. He contrived an arrangement by which the steam generated in the boiler was made to perform this important office! The means by which this was effected were so strikingly characteristic of true mechanical genius, that we would particularly call the reader's attention to this ingenious device, which was the more remarkable, as it was contrived long before the possibility of steam locomotion had become an object of parliamentary inquiry or even of public interest.

It has already been observed that up to, and indeed for some time after the period of which we speak, there was no such class of skilled mechanics, nor were there any such machinery and tools in use as are now at the disposal of inventors and manufacturers. The same difficulty had been experienced by Watt many years before, in the course of his improvements in the steam-engine; and on the occasion of

[ocr errors][merged small][merged small]

the construction of his first condensing engine at Soho, Mr. Smeaton, although satisfied of its great superiority over Newcomen's, expressed strong doubts as to the practicability of getting the different parts executed with the requisite precision ; and he consequently argued that, in its improved form, this powerful machine would never be generally introduced. Such was the low state of the mechanical arts in those days. Although skilled workmen were in course of gradual training in a few of the larger manufacturing towns, they did not, at the date of Stephenson's patent, exist in any considerable numbers, nor was there then any class of mechanics capable of constructing springs of sufficient strength and elasticity to support a locomotive engine ten tons in weight.

The rails then used being extremely light, the road soon became worn down by the traffic, and, from the inequalities of the way, the whole weight of the engine, instead of being uniformly distributed over the four wheels, was occasionally thrown almost diagonally upon two. Hence frequent jerks of the locomotive, and increased stress upon the slender road, which occasioned numerous breakages of the rails and chairs, and consequent interruptions to the safe working of the railway.

In order to avoid the dangers arising from this cause, Mr. Stephenson contrived his Steam Springs. He so arranged the boiler of his new patent locomotive that it was supported upon the frame of the engine by four cylinders, which opened into the interior of the boiler. These cylinders were occupied by pistons with rods, which passed downwards and pressed upon the upper side of the axles. The cylinders opening into the interior of the boiler, allowed the pressure of steam to be applied to the upper side of the piston ; and that pressure being nearly equivalent to one-fourth of the weight of the engine, each axle, whatever might be its position, had at

« ПредыдущаяПродолжить »