Modern shipbuilding and the men engaged in it

by David Pollock

The shell plating, as has already been said, is about the only feature for which inventors and manufacturers of hydraulic riveters have now any serious difficulty in making provision. But many minds are exercised with the problem, and doubtless at no very distant date the present obstacles will be surmounted. One aspect of the question—and one which certain classes are apt to overlook—is that which regards the mutual adaptation of means to the end desired. Shipbuilders have often under consideration the practicability of so modifying structural features and methods of work as that inventors of mechanical riveters will be met half-way in supplying the much-felt desideratum. Referring to this subject, Mr Henry H. West, chief surveyor to the Underwriters Registry for Iron Vessels, in a paper on “Riveting of Iron Ships,” read before the Institution of Naval Architects at its last meeting, said:—

“May I urge upon shipbuilders the importance of endeavouring to extend the application of power riveting to the shell plating of iron vessels. By this means we shall both increase the frictional resistance, and also, by more completely filling the rivet holes, vastly improve the rigidity of the riveted joints. The difficulty of completely and exactly filling the counter-sink of a counter-sunk hole with a machine-closed rivet suggested to my friend Mr Kirk the idea of entering the rivet from the outside, both the rivet and the counter-sink being made to gauge, and then closing up with a machine snap-point on the inside of the ship. What progress he has made in this direction I do not know, but the difficulty does not appear to be an insuperable one. If however, we are prepared to sacrifice a fair appearance to utilitarian simplicity, there seems no sufficient reason why, above water, all the rivets should not be closed up with snap heads and points, both inside and outside. In whatever way it is accomplished, I look to the use of machine riveting as one very great step in advance in the future improvement of the riveted joints of iron ships; and if the weight of iron vessels is to be reduced in any important degree, or if the dimensions and proportions of large merchant steamers are to increase in the future as they have done in the past, I feel sure that one of the first steps must be the reconsideration of our butt fastenings.”

The increased engine power now demanded in steamships undoubtedly points to the further adoption of mechanical riveting—if vessels are to successfully withstand the enormous strain and vibrations to which they are thereby subject. While several have already shown drawings of the shell difficulty having been met, Mr Tweddell, whose experience in common with that of his manufacturers and co-patentees, Messrs Fielding & Platt, of Gloucester, may justly be considered greatest in this branch of engineering, has never illustrated this. It may be mentioned, however, that excellent flush riveting is constantly done by the Tweddell hydraulic riveters, and that the same plan suggested by Mr Kirk of entering rivets with prepared counter-sunk heads from one side, and snap pointing them by machine on the other has been long in use by Messrs Fielding & Platt. In conjunction with Mr Tweddell, this firm have also designed several efficient arrangements to ensure the machine being kept in position until the unfinished head of the rivet is formed. Judging from these facts, there seems good reason to hope that the production of riveting machines required to overtake the remaining features will not be very long delayed.

To show that where the exigencies of the times necessitate them, expedients involving inventive skill and industrial intrepidity are never quite wanting, it may be related that several years ago, during a prolonged strike of riveters, the principal of the firm of Messrs A. M‘Millan & Son, Dumbarton, introduced a portable riveting machine for the shells of ships. The machine, although improvised, as it were, to meet an emergency, fulfilled all that was expected of it, and won the approval of Lloyd’s Surveyors for the Clyde district, as well as of a special deputation selected by the Committee of Lloyd’s in London from among the chief surveyors of the United Kingdom. Their verdict on the performances of the machine after due inspection was that it “thoroughly fills the holes and countersinks, and produces a smoother and better clench than can usually be obtained by hand labour.” From this it will be seen that in the yard of Messrs M‘Millan the matter of machine riveting has received early and earnest consideration. Indeed, the extent to which hydraulic riveting is presently employed by this firm so well represents the development and progress made in this direction throughout other yards that the system adopted in their establishment may be described somewhat in detail.

The hydraulic plant and numerous different classes of portable riveters are on the Tweddell system. The hydraulic power required to work the various machines is furnished by a pair of vertical steam engines, geared to a set of two-throw pumps, which force the water at a pressure of 1,500-lb. per square inch into an accumulator. This latter feature, as is well known, serves to store up the power in a considerable amount ready to meet the sudden demands of one or more of the riveters without calling on the pumps. As is the case in all machinery on this system, the accumulator is loaded to a pressure of 1,500-lb. per square inch. The means employed for the transmission of the water-power, from the service of main pipes laid as required throughout the yard, are flexible copper pipes, admitting of being led almost in any direction, however irregular, without being impaired or rendered inefficient. When the plant was laid down about four years ago, Messrs M‘Millan determined to err if anything on the side of prudence, and they laid all their mains of double the required size, so that they could, if the high pressure was found objectionable, return to the lower pressures sometimes employed; they have, however, never found it advisable to do so.

In this yard can be seen portable riveters suspended over a vessel’s deck between 40 and 50 feet above ground, capable of reaching and clenching rivets in stringers at a distance of 4 feet 6 inches from edge of plate. The power brought into play in closing some of these rivets is very great—from 20 to 30 tons—and yet this is conveyed by a small tube of only half-inch outside diameter in some cases through a distance of many hundred feet. The portable riveter here indicated is suspended on a light and handy carriage, which can travel the upper deck from stem to stern, being made purposely low so as to clear poop and bridge deck beams if such should be fitted. With this machine Messrs M‘Millan have closed from 400 to 450 rivets per day of nine hours in stringers 3 feet 6 inches wide. They have also effected some very heavy work in attaching the sheer strake to the gunwale bar, the rate of progress being correspondingly satisfactory. The same features in the Alaska, built by Messrs John Elder & Co., were similarly operated upon by another of Mr Tweddell’s riveters, whose complete system has been adopted in this large establishment also. By an elongation of the suspending arm Messrs M‘Millan hope to execute, besides the stringers, most of the deck work, such as ties, diagonals, hatch coamings, &c., in one traverse of the carriage. Moreover, a second carriage with riveter may be doing simultaneously the same work on the other side of the vessel. Indeed, it only requires a further development of such work to make the riveting of complete iron decks practicable, and—with the rate of wages, for hand riveted work, usually prevailing—profitable also.

FIG. 22.

TWEDDELL PORTABLE FRAME AND BEAM RIVETER.

The riveting of the frames and beams is the simplest of all the work overtaken by the hydraulic riveters, and it is here the system is seen to most advantage. In any yard furnished with these machines rivets are closed at a greatly accelerated rate compared with work done by hand. Tweddell machines have been known to close, in beams, 1,800 to 1,900 rivets per machine per day of 9½ hours. In frames the average rate at which rivets are closed is about 1,400 per day. The cost for this section of riveted work has been computed to be about one-half of that by hand, and the quality of the work is everywhere acknowledged to be better. With the same number of men the work is accomplished in something like one-third of the time. The modus operandi in overtaking this feature of the work may be briefly described. For the riveting of the frames, in almost every case, two cranes of any convenient construction are fixed at the head of the berth in which the vessel is to be built; the frames are laid across the keel as in hand work, and rest on trestles, where the portable riveter, carried on the before-mentioned cranes, rivets them up. As the riveting in each frame is completed it is drawn down the keel by steam or hand power, and set up in place. The riveting of the beams is a still more simple operation, the beam to be riveted being placed under a gantry somewhat longer than the beam itself, and upon which the portable riveter travels. The suspending gear in this and other of the Tweddell machines combines the functions of hydraulic lifts for raising or lowering the riveter, and of conveying the necessary hydraulic pressure to the riveter. The beam is supported on trestles, and the riveter, having the facilities for travel and exact adjustment just described, accomplishes the surprising work before mentioned.