The machines in use at the present day for preparing the separate and multitudinous pieces of material which go to form the hull structure of iron and steel vessels are both numerous and highly efficient. This work of preparing material, it may be shortly stated, mainly consists of shearing and planing the edges of plates and bars—these as supplied by the manufacturers being, of course, only approximately near the final form and dimensions—rolling and flattening or giving uniform curvature to plates; bending angle or other bars, such as are used for deck beams; and punching the holes through plates and bars for the reception of rivets. In this list regard is not had to the operations concerned with material in the heated state, the features requiring to be thus manipulated being mainly the frames of the vessel; the work being effected without the aid of any special machine tools. A small proportion of the plating also requires to be operated upon in this state, and for this purpose machine tools are sometimes brought into requisition, some notice of which will be taken further on.
While most of the machines have been introduced for a period exceeding that with which our review is more directly concerned, improved types have been made, and entirely new machines brought into requisition during recent times. The universal adoption of piece-work in almost all the departments of construction has demanded a more economical type of machine than formerly. In this way punching machines, which play so important a part in shipyards, have risen from a working speed of about fourteen rivet holes per minute to thirty and even—in the case of frame punching—to as high as forty per minute. Other machines have had a corresponding increase in speed; in several of the best appointed yards the general increase being about sixty per cent.
The introduction of the double bottom for water ballast in ships, brought about a great increase in the amount of necessary punching caused by the numerous man-holes required through the floors and longitudinals. These man-holes, oval in shape as shown by Fig. 1—of say 18-ins. by 12-ins.—had to be punched all round by the rivet-punch, and the edges afterwards dressed by hand with a chisel. To economise work in this connection, need was felt for a machine which would be capable of punching a man-hole of the ordinary size out of the thickest plate at one operation. In 1879, at the request of one of the prominent Clyde firms, Messrs Craig & Donald, the well-known machine-tool makers of Johnstone, introduced a man-hole punching machine which cut holes 18-ins. by 12-ins. at the rate of seven per minute, in such a way that no after-dressing with chisels was required. This machine, an ordinary eccentric motion one driven by its own engine, although tested and found capable of cutting an 18-in. by 12-in. hole through a plate 1-in. thick, was superseded in the yard for which it was made, by another, designed to meet the requirements of the heaviest type of vessels built on the cellular principle. This machine—also made by Messrs Craig & Donald, and five or six of which are now at work in yards on the Clyde and at Barrow—was capable of piercing a hole 30-ins. by 21-ins. through a plate ¾-ins. thick, at one operation, and was actuated by hydraulic power. The ordinary eccentric machine, driven by engine attached, is still in favour for lighter work, and machines of this type are at work in several of the East Coast yards capable of punching holes up to 21-ins. by 15-ins. through plates ¾-ins. thick.
Reverting to the subject of the proportion of material requiring to be heated before manipulation, it is noteworthy that the employment of mild steel is a source of economy in this connection as well as in the many others already noticed. The superior homogeneity and great ductility of the material favours cold-bending when such an operation would be fatal to iron. Not only does an economy in labour result, but incidentally there is a further advantage. Cold-bending distresses steel less than hot-bending, and the special precautions so often taken, in the way of annealing, to toughen steel which has been operated upon when hot, are thus obviated.
A certain proportion of the bottom plates in a ship—e.g., those adjoining the keel—and a few at the stern and elsewhere, have quick bends and twists which are much more difficult to treat than the easy and generally uniform curvatures on the plates of the bilge. The latter are effected in great measure by the “bending rolls” with the plates perfectly cold, but the former have to be made with the plate in the heated state. Hydraulic presses have been used for this purpose for some years, a certain proportion of the work done being the manipulation of plates while cold. With steel as the material to be operated upon, these machines are being more and more utilised in this direction, and their presence in the shipyard, as in boiler works, is sure to become more and more prevalent. The operations of the shipyard, in short, have been gaining in exactitude every year, and have borrowed both in the matters of methods and of appliances from the marine boiler works, where machine tools are more conspicuously a feature. Machine tools for riveting, now playing so important a part in shipyards, first had their utility approved in boiler shops, and the introduction of improved types of drilling machines is largely the reflected successes attending them there.
From the foregoing imperfect sketch of the principal directions in which machine tools used in preparing material for the constructive stage have been improved or recently introduced, it will be gathered that hydraulic power in lieu of steam has taken a prominent place in shipyards. That this is so to a remarkable extent will sufficiently appear from what follows regarding the appliances used in the work of binding the structure of vessels. It may, however, be premised that in several establishments hydraulic pressure has now displaced steam power in almost all the machine-tools used in the iron departments. This is so in the case of the Naval Dockyards of Toulon and Brest, in France, and of the Spanish naval establishments at Ferrol, Cadiz, &c.; the machinery in the former of which was fully described in June, 1878, before the Institution of Mechanical Engineers, by M. Marc Berrier-Fontaine, of the French Navy. The plant and machinery are by Mr Ralph H. Tweddell, C.E., of Delahay Street, London, whose numerous inventions and great experience in this special branch of engineering are well worthy of recognition. The machines comprise those for punching, shearing, angle cutting, plate bending, and riveting, and the author referred to is high in his praise of the superior efficiency and economy of the hydraulic system, as exemplified in practice. One or two of the leading advantages of the system may be here summarised. Hydraulic machines do not consume any power at all during the interval between employment, and the power can be applied at any moment without preparatory consumption, and stopped equally quick. No shafting or belting is required, and the wear and tear of continuous motion, as in steam machines, is thus obviated. The power exerted is much more gradual than that of steam, performing the work more thoroughly, and with less liability to strain or otherwise damage the material operated upon, or the tool itself.
Although hydraulic machinery was successfully introduced by Sir William Armstrong so long ago as 1836, and has since been applied by him and others in almost every direction the application of hydraulic power to machines for constructive purposes is of comparatively modern date. Its early employment as the motive power for machine-tools was in the case of machines which were “stationary” or “fixed” in position when in use. Machines for riveting purposes in boiler shops and locomotive works were the first tools of any note to which hydraulic power transmitted from a distance was applied, but even this dates back only to about 1865. In that year Mr R. H. Tweddell, already referred to, designed hydraulic plant, consisting of pumps, an accumulator, and a riveting machine, which were first used by Messrs Thompson, Boyd & Co., Newcastle-on-Tyne, with satisfactory results. The work was done perfectly, and at about one-seventh of the cost of hand work, and the same power was utilized in actuating hydraulic presses for such purposes as setting or “joggling” angle or tee irons. Excellence and economy of work were thus secured; and in a comparatively short time above 100 machines were at work in various dockyards and large works.
Although patent designs for portable hydraulic riveters existed before 1871, it was not till that year that any form of portable riveters was applied in practice with any degree of success. Previous to that year the frames of ships had been riveted by Mr Tweddell’s stationary hydraulic machines, but a portable riveter invented by that gentleman in 1871 was then tried, when it was thoroughly demonstrated that during a working day of 10 hours the machine was capable of closing 1,000 rivets. Not much encouragement, however, was received from shipbuilders at the time, owing chiefly to the fact that the wages for riveting labour was not then a very urgent question. On a modification of the general plan of working, these machines being proposed by their inventor in 1876, they received more cordial recognition from shipbuilders thereafter. It is only, however, within the past five years or so that portable riveters have been so extensively introduced into shipbuilding yards. The success which has attended them during the period leaves no reasonable doubt as to their ultimate place in every well-appointed shipbuilding establishment. Already the majority of Clyde shipyards—including all the larger ones—and most of the yards in the Tyne and Wear districts, are furnished with hydraulic riveting machines and plant, overtaking work constantly, efficiently, and with greatly reduced expense, that is matter of envy in yards not similarly favoured. In most of the larger Clyde yards the Tweddell machinery and plant are employed; but in some cases machines introduced by Mr William Arrol, Dalmarnock Ironworks, Glasgow—chiefly for riveting the frames, beams, &c.—are used. The Arrol machines work on a similar principle to those of Mr Tweddell, whose system is practically the only one in use on the Tyne and the Wear, and at Barrow.
The prime cost of furnishing a complete hydraulic plant is of course considerable, and such as might perhaps appear an outlay not speedily enough recouped. In view, however, of the uncertain and oftentimes harassing conditions—not to speak of the pecuniary loss—under which the riveting department of shipbuilding work is conducted in the ordinary way, shipbuilders are constrained to acknowledge the economic advantages of the hydraulic system. Neither expense nor trouble have been spared in several yards to extend the hydraulic system into every feature where hydraulic work is practicable. The only feature now for which the machines presently in use are not available is the shell plating, and perhaps the decks, where such are entirely laid with plates. Indeed, it may fairly be said that hydraulic riveters have virtually supplanted manual riveting in nine-tenths of the structural features of a vessel. The percentage of rivets closed by machinery to the total number of rivets employed in a vessel’s structure has been computed to be about fifty per cent. In one of the yards fitted with the Tweddell system the following comprise the list of structural features for which the hydraulic riveters are daily employed:—Double bottom, including the thousands of detached pieces of plates and angles of which the bracket floor style of bottom is composed; side bars attaching frames to double bottom, frames and reverse frames, beams, stiffening bars, gunwale bars, keelsons, and keels.