Discoveries and Inventions of the Nineteenth Century

already experienced in designing iron structures. Under this gentleman, with the assistance of Mr. J. J. Webster in carrying out some of the details, the work has been so successfully accomplished that the “Great Wheel” of 1895 may be cited as one of the crowning mechanical triumphs of the nineteenth century. The original design has not been followed so far as regards the lower platforms for refreshment rooms, &c. Plate V., for which we are indebted to Mr. Basset, is a photographic representation of the actual structure. The wheel at Earl’s Court exceeds the Ferris wheel in diameter by 50 feet, being 300 feet across. It is supported on two towers, 175 feet high, each formed by four columns 4 feet square, built of steel plates with internal diaphragms, and surmounted by balconies that may be ascended in elevators raised by a weight of water, which, after having been discharged into a reservoir under the ground level, is again pumped up to the top of the towers. Between the balconies on each tower there is also a communication through the axle of the wheel, which, instead of being solid as at Chicago, is a tube of 7 feet diameter, and 35 feet long, made in sections, riveted together, of steel 1 inch thick, and weighing no less than 58 tons. The raising and fixing in its high place of such a mass of metal required specially ingenious devices, which have been greatly appreciated by professional engineers. But for these devices, the erection of scaffolding in the ordinary way of proceeding would have entailed an outlay simply enormous. The axle is stiffened by projecting rings, and, between pairs of these, the spoke rods are attached by pins 3 inches in diameter. The axle was the production of Messrs. Maudslay, Field & Co.; all the rest of the metal work was made at the Arrol Works at 84Glasgow, and the carriages were constructed by Brown, Marshall & Co., of Birmingham. The Earl’s Court wheel is turned by a mechanism different from that of the Chicago wheel, for whereas the latter was provided with cogs, the former has two chains, each 1,000 feet long and 8 tons weight, surrounding the periphery of the wheel on either side. The chains go over drums in the engine-shed, from which they pass underground to guide-pulleys, and as they unwind from the Great Wheel, they again go over guide-pulleys to lead them back to the drums. These chains are firmly held throughout in the jaws of V-shaped grooves, and there are arrangements for taking up the slack. The drums are actuated by wheel gearing, connected with two horizontal Robey steam engines, each of 50 horse-power, one on either side, capable of being worked singly or together. It is, however, found sufficient to use the engine of one side only, and even then to work it at but 16 horse-power, and the operation can be controlled by one man, who has also the command of a brake. Both starting and stopping are accomplished with the greatest smoothness and absence of strain or jar. There are forty carriages, each 25 feet long, 9 feet wide, and 10 feet high. Each will accommodate forty passengers, and these enter at the ends from eight platforms at different heights from the ground, so arranged as to be on the level of the eight lowest carriages while the wheel is stationary. The passengers who have had their ride leave at the other end of the carriages by eight similar platforms on the other side of the wheel. After the change of passengers in one set of eight carriages, the wheel is turned through exactly one-fifth of a revolution, which has the effect of bringing the next eight carriages to the level of the platforms, and it is again brought to a standstill whilst the change of passengers is taking place; and so on, until the whole freight of say 1,600 persons has been changed during the five stoppages in one revolution, for which about thirty-five minutes are required, and the process of emptying and filling eight carriages at once is repeated. There are first and second class carriages, the charge for the former being two shillings, and for the latter one shilling; so that, reckoning 800 passengers of each class, one turn would bring to the treasury the handsome sum of £120. The sensations experienced in a journey on the Great Wheel are, as already mentioned, comparable to those enjoyed by the aërial voyagers in a balloon, where all perception of proper motion is lost, and it is the world beneath that seems to recede and float away, presenting the while a strangely changing panorama. Many people who have never made a balloon ascent yet know the calm delight of floating in a boat without effort down some placid stream, unconscious of any motion beyond that vaguely inferred from the silent apparent gliding by of the banks. Very similar are, in part, the feelings of the passenger who is almost imperceptibly carried up into the air in a carriage of the Great Wheel, but the vertical direction of the movement, and the gradual expansion of the horizon as the vertex is approached, lend an unwonted novelty to the situation. From the Earl’s Court Wheel the view is both interesting and extensive, for on a clear day the prospect stretches as far as the Royal Castle of Windsor. The “Gigantic Wheel” at Earl’s Court was inaugurated on the 11th July, 1895, in the presence of an assemblage of 5,000 people, including many distinguished personages, who were all treated to a ride. Plate I. shows a portion of the wheel and carriages as in motion. PLATE V.GENERAL VIEW OF THE GREAT WHEEL AT EARL’S COURT. 85 Fig. 27.—Sir Joseph Whitworth. TOOLS. Of the immense variety of tools and mechanical contrivances employed in modern times, by far the greatest number are designed to impart to certain materials some definite shape. The brickmaker’s mould, the joiner’s plane, the stonemason’s chisel, the potter’s wheel, are examples of simple tools. More elaborate are the coining press, the machine for planing iron, the drilling machine, the turning lathe, the rolling mill, the Jacquard loom. But all such tools and machines have one principle in common—a principle which casual observers may easily overlook, but one which is of the highest importance, as its application constitutes the very essence of the modern process of manufacture as distinguished from the slow and laborious mode of making things by hand. The principle will be easily understood by a single example. Let it be required to draw straight lines across a sheet of paper. Few persons can take a pen or pencil, and do this with even an approach to accuracy, and at best they can do it but slowly and imperfectly. But with the aid of a ruler any number of straight lines may be drawn rapidly and surely. The former case is an instance of making by hand, the latter represents manufacturing, the ruler being the tool or machine. Let it be observed that the ruler has in itself the kind of form required—that is to say, straightness—and that in using it we copy or transfer this straightness to the mark made on the paper. This is a 86simple example of the copying principle, which is so widely applied in machines for manufacturing; for, in all of these, materials are shaped or moulded by various contrivances, so as to reproduce certain definite forms, which are in some way contained within the machine itself. This will be distinctly seen in the tools which are about to be described. Fig. 28.—Whitworth’s Screw Dies and Tap. Probably no one mechanical contrivance is so much and so variously applied as the Screw. The common screw-nail, which is so often used by carpenters for fastening pieces of metal on wood, or one piece of wood to another, is a specimen of the screw with which everybody is familiar. The projection which winds spirally round the nail is termed the thread of the screw, and the distance that the thread advances parallel to the axis in one turn is called the pitch. It is obvious that for each turn the screw makes it is advanced into the wood a depth equal to the pitch, and that there is formed in the wood a hollow screw with corresponding grooves and projections. Screws are formed on the ends of the bolts, by which various parts are fastened together, and the hollow screws which turn on the ends of the bolts are termed nuts. The screws on bolts and nuts, and other parts of machines, were formerly made with so many different pitches that, when a machine constructed by one maker had to be repaired by another, great inconvenience was found, on account of the want of uniformity in the shape and pitch of the threads. A uniform system was many years ago proposed by Sir Joseph Whitworth, and adopted by the majority of mechanical engineers, who agreed to use only a certain defined series of pitches. The same engineer also contrived a hand tool for cutting screws with greater accuracy than had formerly been attained in that process. A mechanic often finds it necessary to form a screw-thread on a bolt, and also to produce in metal a hollow screw. The reader may have observed gas-fitters and other workmen performing the first operation by an instrument having the same general appearance as Fig. 28. This contains hard steel dies, which are made to press on the bolt or pipe, so that when the guide-stock is turned by the handles, the required grooves are cut out. 87The arrangement of these dies in Sir Joseph Whitworth’s instrument is shown in Fig. 28, which represents the central part of the guide-stock; A, B, C are the steel dies retained in their places, when the instrument is in use, by a plate which can be removed when it is necessary to replace one set of dies by another, according to the pitch of thread required. The figure also shows the set of dies, A, B, C, removed from the guide-stock. D is the work, pressed up against the fixed die, A, by B and C, the pressure being applied to these last as required by turning the nut, thus drawing up the key, E, so that the inclined planes, f, g, press against similar surfaces forming the ends of the dies. For producing the hollow screws, taps are provided, which are merely well-formed screws, made of hard steel and having the threads cut into detached pieces by several longitudinal grooves, as represented in the lower part of Fig. 28. Fig. 29.—Screw-cutting Lathe. The method of forming screws by dies and taps is, however, applicable only to those of small dimensions, and even for these it is not employed where great accuracy is required. Perfect screws can only be cut with a lathe, such as that represented in Fig. 29. In this we must first call the reader’s attention to the portion of the apparatus marked A, which receives the name of the slide-rest. The invention of this contrivance by Maudsley had the effect of almost revolutionizing mechanical art, for by its aid it became possible to produce true surfaces in the lathe. Before the slide-rest was introduced, the instrument which cut the wood or metal was held in the workman’s hand, and whatever might be his skill and strength, the steadiness and precision thus obtainable were far inferior to those which could be reached by the grip of an iron hand, guided by unswerving bars. The slide-rest was contrived by Maudsley in the first instance for cutting screws, but its principle has been applied for other purposes. This principle consists in attaching the cutting tool to a slide which is incapable of any motion, except in the one direction required. Thus the slide, A, represented in Fig. 29, moves along the bed of the lathe, B, carrying the cutter with perfect steadiness in a straight line parallel to the axis of the lathe. There are also two other slides for adjusting the position of the