Читать книгу Lives of the Engineers - Samuel Smiles - Страница 8

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The rapid increase in the coal-trade of the Tyne about the beginning of the present century had the effect of stimulating the ingenuity of mechanics, and encouraging them to devise improved methods of transporting the coal from the pits to the shipping places. From our introductory chapter, it will have been observed that the improvements which had thus far been effected were confined almost entirely to the road. The railway waggons still continued to be drawn by horses. By improving and flattening the tramway, considerable economy in horse-power had indeed been secured; but unless some more effective method of mechanical traction could be devised, it was clear that railway improvement had almost reached its limits.

Many expedients had been tried with this object. One of the earliest was that of hoisting sails upon the waggons, and driving them along the waggon-way, as a ship is driven through the water by the wind. This method seems to have been employed by Sir Humphrey Mackworth, an ingenious coal-miner at Neath in Glamorganshire, about the end of the seventeenth century.

After having been lost sight of for more than a century, the same plan of impelling carriages was revived by Richard Lovell Edgworth, with the addition of a portable railway, since revived also, in Boydell’s patent. But although Mr. Edgworth devoted himself to the subject for many years, he failed in securing the adoption of his sailing carriage. It is indeed quite clear that a power so uncertain as wind could never be relied on for ordinary traffic, and Mr. Edgworth’s project was consequently left to repose in the limbo of the Patent Office, with thousands of other equally useless though ingenious contrivances.

A much more favourite scheme was the application of steam power for the purpose of carriage traction. Savery, the inventor of the working steam-engine, was the first to propose its employment to propel vehicles along the common roads; and in 1759 Dr. Robison, then a young man studying at Glasgow College, threw out the same idea to his friend James Watt; but the scheme was not matured.

The first locomotive steam-carriage was built at Paris by the French engineer Cugnot, a native of Lorraine. It is said to have been invented for the purpose of dragging cannon into the field independent of horses. The original model of this machine was made in 1763. Count Saxe was so much pleased with it, that on his recommendation a full-sized engine was constructed at the cost of the French monarch; and in 1769 it was tried in the presence of the Duc de Choiseul, Minister of War, General Gribeauval, and other officers. At one of the experiments it ran with such force as to knock down a wall in its way. But the new vehicle, loaded with four persons, could not travel faster than two and a half miles an hour. The boiler was insufficient in size, and it could only work for about fifteen minutes; after which it was necessary to wait until the steam had again risen to a sufficient pressure. To remedy this defect, Cugnot constructed a new machine in 1770, the working of which was more satisfactory. It was composed of two parts—the fore part consisting of a small steam-engine, formed of a round copper boiler, with a furnace inside, provided with two small chimneys and two single-acting brass steam cylinders, whose pistons acted alternately upon the single driving-wheel. The hinder part consisted merely of a rude carriage on two wheels to carry the load, furnished with a seat in front for the conductor. This engine was tried in the streets of Paris; but when passing near where the Madeleine now stands, it overbalanced itself on turning a corner, and fell over with a crash; after which, its employment being thought dangerous, it was locked up in the arsenal to prevent further mischief. The machine is, however, still to be seen in the collection of the Conservatoire des Arts et Métiers at Paris. It has very much the look of a long brewer’s cart, with the addition of the circular boiler hung on at one end. Rough though it looks, it was a highly creditable piece of work, considering the period at which it was executed; and as the first actual machine constructed for the purpose of travelling on ordinary roads by the power of steam, it is certainly a most curious and interesting mechanical relic, well worthy of preservation.

But though Cugnot’s road locomotive remained locked up from public sight, the subject was not dead; for we find inventors employing themselves from time to time in attempting to solve the problem of steam locomotion in places far remote from Paris. The idea had taken root in the minds of inventors, and was striving to grow into a reality. Thus Oliver Evans, the American, invented a steam carriage in 1772 to travel on common roads; in 1787 he obtained from the State of Maryland an exclusive right to make and use steam-carriages, but his invention never came into use. Then, in 1784, William Symington, one of the early inventors of the steamboat, was similarly occupied in Scotland in endeavouring to develop the latent powers of the steam-carriage. He had a working model of one constructed, which he exhibited in 1786 to the professors of Edinburgh College; but the state of the Scotch roads was then so bad that he found it impracticable to proceed further with his scheme, which he shortly after abandoned in favour of steam navigation.

The same year in which Symington was occupied upon his steam-carriage, William Murdock, the friend and assistant of Watt, constructed his model of a locomotive at the opposite end of the island—at Redruth in Cornwall. His model was of small dimensions, standing little more than a foot high; and it was until recently in the possession of the son of the inventor, at whose house we saw it a few years ago. The annexed section will give an idea of the arrangements of this machine.

It acted on the high-pressure principle, and, like Cugnot’s engine, ran upon three wheels, the boiler being heated by a spirit-lamp. Small though the machine was, it went so fast on one occasion that it fairly outran its inventor. It seems that one night after returning from his duties at the Redruth mine, Murdock determined to try the working of his model locomotive. For this purpose he had recourse to the walk leading to the church, about a mile from the town. It was rather narrow, and was bounded on each side by high hedges. The night was dark, and Murdock set out alone to try his experiment. Having lit his lamp, the water boiled speedily, and off started the engine with the inventor after it. He soon heard distant shouts of terror. It was too dark to perceive objects; but he found, on following up the machine, that the cries proceeded from the worthy pastor of the parish, who, going towards the town, was met on this lonely road by the hissing and fiery little monster, which he subsequently declared he had taken to be the Evil One in propriá personâ. No further steps were, however, taken by Murdock to embody his idea of a locomotive carriage in a more practical form.

The idea was next taken up by Murdock’s pupil, Richard Trevithick, who resolved on building a steam-carriage adapted for common roads as well as railways. He took out a patent to secure the right of his invention in 1802. Andrew Vivian, his cousin, joined with him in the patent—Vivian finding the money, and Trevithick the brains. The steam-carriage built on this patent presented the appearance of an ordinary stage-coach on four wheels. The engine had one horizontal cylinder, which, together with the boiler and the furnace-box, was placed in the rear of the hind axle. The motion of the piston was transmitted to a separate crank-axle, from which, through the medium of spur-gear, the axle of the driving-wheel (which was mounted with a fly-wheel) derived its motion. The steam-cocks and the force-pump, as also the bellows used for the purpose of quickening combustion in the furnace, were worked off the same crank-axle.

John Petherick, of Camborne, has related that he remembers this first English steam-coach passing along the principal street of his native town. Considerable difficulty was experienced in keeping up the pressure of steam; but when there was pressure enough, Trevithick would call upon the people to “jump up,” so as to create a load upon the engine. It was soon covered with men attracted by the novelty, nor did their number seem to make any difference in the speed of the engine so long as there was steam enough; but it was constantly running short, and the horizontal bellows failed to keep it up.

This road-locomotive of Trevithick’s was one of the first high-pressure working engines constructed on the principle of moving a piston by the elasticity of steam against the pressure only of the atmosphere. Such an engine had been described by Leopold, though in his apparatus it was proposed that the pressure should act only on one side of the piston. In Trevithick’s engine the piston was not only raised, but was also depressed by the action of the steam, being in this respect an entirely original invention, and of great merit. The steam was admitted from the boiler under the piston moving in a cylinder, impelling it upward. When the motion had reached its limit, the communication between the piston and the under side was shut off, and the steam allowed to escape into the atmosphere. A passage being then opened between the boiler and the upper side of the piston, which was pressed downwards, the steam was again allowed to escape as before. Thus the power of the engine was equal to the difference between the pressure of the atmosphere and the elasticity of the steam in the boiler.

This steam-carriage excited considerable interest in the remote district near the Land’s End where it had been erected. Being so far removed from the great movements and enterprise of the commercial world, Trevithick and Vivian determined upon exhibiting their machine in the metropolis. They accordingly set out with it to Plymouth, whence it was conveyed by sea to London.

The carriage safely reached the metropolis, and excited much public interest. It also attracted the notice of scientific men, amongst others of Mr. Davies Gilbert, President of the Royal Society, and Sir Humphry Davy, both Cornishmen like Trevithick, who went to see the private performances of the engine, and were greatly pleased with it. Writing to a Cornish friend shortly after its arrival in town, Sir Humphry said: “I shall soon hope to hear that the roads of England are the haunts of Captain Trevithick’s dragons—a characteristic name.” The machine was afterwards publicly exhibited in an enclosed piece of ground near Euston Square, where the London and North-Western Station now stands, and it dragged behind it a wheel-carriage full of passengers. On the second day of the performance, crowds flocked to see it; but Trevithick, in one of his odd freaks, shut up the place, and shortly after removed the engine. It is, however, probable that the inventor came to the conclusion that the state of the roads at that time was such as to preclude its coming into general use for purposes of ordinary traffic.

While the steam-carriage was being exhibited, a gentleman was laying heavy wagers as to the weight which could be hauled by a single horse on the Wandsworth and Croydon iron tramway; and the number and weight of waggons drawn by the horse were something surprising. Trevithick very probably put the two things together—the steam-horse and the iron-way—and kept the performance in mind when he proceeded to construct his second or railway locomotive. The idea was not, however, entirely new to him; for, although his first engine had been constructed with a view to its employment upon common roads, the specification of his patent distinctly alludes to the application of his engine to travelling on railroads. Having been employed at the iron-works of Pen-y-darran, in South Wales, to erect a forge engine for the Company, a convenient opportunity presented itself, on the completion of this work, for carrying out his design of a locomotive to haul the minerals along the Pen-y-darran tramway. Such an engine was erected by him in 1803, in the blacksmiths’ shop at the Company’s works, and it was finished and ready for trial before the end of the year.

The boiler of this second engine was cylindrical in form, flat at the ends, and made of wrought iron. The furnace and flue were inside the boiler, within which the single cylinder, eight inches in diameter and four feet six inches stroke, was placed horizontally. As in the first engine, the motion of the wheels was produced by spur gear, to which was also added a fly-wheel on one side, to secure a rotatory motion in the crank at the end of each stroke of the piston in the single cylinder. The waste steam was thrown into the chimney through a tube inserted into it at right angles; but it will be obvious that this arrangement was not calculated to produce any result in the way of a steam-blast in the chimney. In fact, the waste steam seems to have been turned into the chimney in order to get rid of the nuisance caused by throwing the jet directly into the air. Trevithick was here hovering on the verge of a great discovery; but that he was not aware of the action of the blast in contributing to increase the draught and thus quicken combustion, is clear from the fact that he employed bellows for this special purpose; and at a much later date (1815) he took out a patent which included a method of urging the fire by means of fanners. [70]

At the first trial of this engine it succeeded in dragging after it several waggons, containing ten tons of bar-iron, at the rate of about five miles an hour. Rees Jones, who worked at the fitting of the engine, and remembers its performances, says, “She was used for bringing down metal from the furnaces to the Old Forge. She worked very well; but frequently, from her weight, broke the tram-plates and the hooks between the trams. After working for some time in this way, she took a load of iron from Pen-y-darran down the Basin-road, upon which road she was intended to work. On the journey she broke a great many of the tram-plates, and before reaching the basin ran off the road, and had to be brought back to Pen-y-darran by horses. The engine was never after used as a locomotive.” [71]

It seems to have been felt that unless the road were entirely reconstructed so as to bear the heavy weight of the locomotive—so much greater than that of the tram-waggons, to carry which the original rails had been laid down—the regular employment of Trevithick’s high-pressure tram-engine was altogether impracticable; and as the owners of the works were not prepared to incur so serious a cost, it was determined to take the locomotive off the road, and employ it as an engine for other purposes. It was accordingly dismounted, and used for some time after as a pumping-engine, for which purpose it was found well adapted. Trevithick himself seems from this time to have taken no further steps to bring the locomotive into general use. We find him, shortly after, engaged upon schemes of a more promising character, abandoning the engine to other mechanical inventors, though little improvement was made in it for several years. An imaginary difficulty seems to have tended, amongst other obstacles, to prevent its adoption; viz., the idea that, if a heavy weight were placed behind the engine, the “grip” or “bite” of its smooth wheels upon the equally smooth iron rail, must necessarily be so slight that they would whirl round upon it, and, consequently, that the machine would not make progress. Hence Trevithick, in his patent, provided that the periphery of the driving-wheels should be made rough by the projection of bolts or cross-grooves, so that the adhesion of the wheels to the road might be secured.

Following up the presumed necessity for a more effectual adhesion between the wheels and the rails, Mr. Blenkinsop of Leeds, in 1811, took out a patent for a racked or tooth-rail laid along one side of the road, into which the toothed-wheel of his locomotive worked as pinions work into a rack. The boiler of his engine was supported by a carriage with four wheels without teeth, and rested immediately upon the axles. These wheels were entirely independent of the working parts of the engine, and therefore merely supported its weight upon the rails, the progress being effected by means of the cogged-wheel working into the cogged-rail. The engine had two cylinders, instead of one as in Trevithick’s engine. The invention of the double cylinder was due to Matthew Murray, of Leeds, one of the best mechanical engineers of his time; Mr. Blenkinsop, who was not a mechanic, having consulted him as to all the practical arrangements. The connecting-rods gave the motion to two pinions by cranks at right angles to each other; these pinions communicating the motion to the wheel which worked into the cogged-rail.

Mr. Blenkinsop’s engines began running on the railway from the Middleton Collieries to Leeds, about 3½ miles, on the 12th of August, 1812. They continued for many years to be one of the principal curiosities of the place, and were visited by strangers from all parts. In 1816, the Grand Duke Nicholas (afterwards Emperor) of Russia observed the working of Blenkinsop’s locomotive with curious interest and admiration. An engine dragged as many as thirty coal-waggons at a speed of about 3¼ miles per hour. These engines continued for many years to be thus employed in the haulage of coal, and furnished the first instance of the regular employment of locomotive power for commercial purposes.

The Messrs. Chapman, of Newcastle, in 1812, endeavoured to overcome the same fictitious difficulty of the want of adhesion between the wheel and the rail, by patenting a locomotive to work along the road by means of a chain stretched from one end of it to the other. This chain was passed once round a grooved barrel-wheel under the centre of the engine: so that, when the wheel turned, the locomotive, as it were, dragged itself along the railway. An engine, constructed after this plan, was tried on the Heaton Railway, near Newcastle; but it was so clumsy in its action, there was so great a loss of power by friction, and it was found to be so expensive and difficult to keep in repair, that it was soon abandoned. Another remarkable expedient was adopted by Mr. Brunton, of the Butterley Works, Derbyshire, who, in 1813, patented his Mechanical Traveller, to go upon legs working alternately like those of a horse. [73] But this engine never got beyond the experimental state, for, at its very first trial, the driver, to make sure of a good start, overloaded the safety-valve, when the boiler burst and killed a number of the bystanders, wounding many more. These, and other contrivances with the same object, projected about the same time, show that invention was actively at work, and that many minds were anxiously labouring to solve the important problem of locomotive traction upon railways.

But the difficulties contended with by these early inventors, and the step-by-step progress which they made, will probably be best illustrated by the experiments conducted by Mr. Blackett, of Wylam, which are all the more worthy of notice, as the persevering efforts of this gentleman in a great measure paved the way for the labours of George Stephenson, who, shortly after, took up the question of steam locomotion, and brought it to a successful issue.

The Wylam waggon-way is one of the oldest in the north of England. Down to the year 1807 it was formed of wooden spars or rails, laid down between the colliery at Wylam—where old Robert Stephenson had worked—and the village of Lemington, some four miles down the Tyne, where the coals were loaded into keels or barges, and floated down past Newcastle, to be shipped for London. Each chaldron-waggon had a man in charge of it, and was originally drawn by one horse. The rate at which the waggons were hauled was so slow that only two journeys were performed by each man and horse in one day, and three on the day following. This primitive waggon-way passed, as before stated, close in front of the cottage in which George Stephenson was born; and one of the earliest sights which met his infant eyes was this wooden tramroad worked by horses.

Mr. Blackett was the first colliery owner in the North who took an active interest in the locomotive. Having formed the acquaintance of Trevithick in London, and inspected the performances of his engine, he determined to repeat the Pen-y-darran experiment upon the Wylam waggon-way. He accordingly obtained from Trevithick, in October, 1804, a plan of his engine, provided with “friction-wheels,” and employed Mr. John Whinfield, of Pipewellgate, Gateshead, to construct it at his foundry there. The engine was constructed under the superintendence of one John Steele, an ingenious mechanic who had been in Wales, and worked under Trevithick in fitting the engine at Pen-y-darran. When the Gateshead locomotive was finished, a temporary way was laid down in the works, on which it was run backwards and forwards many times. For some reason, however—it is said because the engine was deemed too light for drawing the coal-trains—it never left the works, but was dismounted from the wheels, and set to blow the cupola of the foundry, in which service it long continued to be employed.