The firing trial of the first new 110½ ton breech loading gun approved for H.M.'s ships Benbow, Renown, and Sanspareil was commenced recently at the Woolwich proof butts, under the direction of Colonel Maitland, the superintendent of the Royal Gun Factories. We give herewith a section showing the construction of this gun (vide Fig. 8). It very nearly corresponds to the section given of it when designed in 1884, in a paper read by Colonel Maitland at the United Service Institution, of which we gave a long account in the Engineer of June 27, 1884.
The following figures are authoritative: Length over all, 524 in.; length of bore, 487.5 in. (30 calibers). The breech engages in the breech piece, leaving the A tube with its full strength for tangential strain (vide Fig.). The A tube is in a single piece instead of two lengths, as in the case of the Italia guns. It is supplied to Elswick from Whitworth's works, one of the few in England where such a tube could be made. There are four layers of metal hoops over the breech. Copper and bronze are used to give longitudinal strength. The obturation is a modification of the De Bange system, proposed by Vavasseur.
THE NEW 110½ TON ELSWICK GUNS FOR H.M.S. BENBOW.
The maximum firing charge is 900 lb. of cocoa powder. The projectile weighs 1,800 lb. The estimated muzzle velocity is 2,216 ft. per second. The capacity of the chamber is 28,610 cubic inches, and that of the bore 112,595 cubic inches. The estimated total energy is 61,200 ft. tons. It will be a few days probably before the full powers of the gun are tested, but the above are confidently expected to be attained, judging from the results with the 100 ton guns supplied to Italy. On January 7 last we gave those of the new Krupp 119 ton gun. It had fired a projectile with a velocity of almost 1,900 ft. with a charge of less than 864.67 lb., with moderate pressure. The estimated maximum for this gun was a velocity of 2,017 ft. with a projectile weighing 1,632 lb., giving a total energy of 46,061 ft. tons, or 13,000 ft. tons less than the Elswick gun, comparing the estimated results.
The proof of the Elswick gun is mounted on a carriage turned out by the Royal Carriage Department, under Colonel Close. This carriage is made on bogies so as to run on rails passing easily round curves of 50 ft. radius. The gun is fired on an inclined length of rails, the recoil presses of the carriage first receiving the shock and reducing the recoil. The carriage is made to lift into the government barge, so as to go easily to Shoeburyness or elsewhere. It can be altered so as to provide for turning, and it allows the piece to be fired at angles of elevation up to 24 deg. The cheeks of the carriage are made to open and close, so as to take the 12 in. gun and larger pieces. The steel castings for it are supplied from the Stanners Close Steel Works.
The first round was fired at about noon. The charge was only 598 lb., consisting of four charges of 112 lb. and one of 130 lb. of Waltham Abbey brown prism No. 1 powder. The proof shot weighs, like the service projectile, 1,800 lb. Thus fired, the gun recoiled nearly 4 ft. on the press, and the carriage ran back on the rails about 50 ft. The projectile had a velocity of 1,685 ft. per second, and entered about 52 ft. into the butt. We cannot yet give the pressure, but unquestionably it was a low one. The charges as the firing continues will be increased in successive rounds up to the full 900 lb. charge.
Figs. 1 and 2 show the mounting of the 110½ ton gun in the barbette towers of the Benbow. The gun is held down on the bed by steel bands and recoils in its bed on the slide (vide Fig. 2). The latter is hinged or pivoted in front and is elevated by elevating ram, shown in Fig. 2. When the slide is fully down, the gun is in the loading position. The ammunition lift brings up the projectile and charge, which latter is subdivided, like those employed in the German guns, in succession to the breech, the hydraulic rammer forcing them home.
The simplicity of the arrangement is apparent. The recoil always acts parallel to the slide. This is much better than allowing its direction to be affected by elevation, and the distributed hold of the steel bands is preferable to the single attachment at trunnions. Theoretically, the recoil is not so perfectly met as in some of the earlier Elswick designs, in which the presses were brought opposite to the trunnions, so that they acted symmetrically on each side of the center of resistance. The barbette tower is covered by a steel plate, shown in Fig. 1, fitting close to the gun slide, so that the only opening is that behind the breech when the gun is in the forward position, and this is closed as it recoils.
The only man of the detachment even partly exposed is the number one, while laying the gun, and in that position he is nearly covered by the gun and fittings. Common shell, shrapnel shell, and steel armor-piercing projectiles, have been approved for the 110½ ton gun. The common shell is shown in Fig. 3. Like the common shell for all the larger natures of new type guns, it is made of steel. It has been found necessary to support the core used in casting these projectiles at both ends. Consequently, there is a screw plug at the base as well as at the apex. The hole at the base is used as a filling hole for the insertion of the bursting charge, which consists of 179 lb. of powder, the total weight of the filled shell being 1,800 lb.
The apex has a screw plug of larger diameter than that of the fuse. This is shown in Fig. 4. The fuse is a direct action one. The needle, B, is held in the center of a copper disk, C C, and is safe against explosion until it is actually brought into contact with an object, when it is forced down, igniting a patch of cap composition and the magazine at A, and so firing the bursting charge of the shell below. E E E are each priming charges of seven grains of pistol powder, made up in shalloon bags to insure the ignition of the bursting charge, which is in a bag of serge and shalloon beneath.
The use of this fuse involves the curious question of the physical conditions now existing in the discharge of our projectiles by slow burning powder. The forward movement of the shell is now so gradual that the inertia of a pellet is only sufficient to shear a wire of one-tenth the strength of that which might formerly have been sheared by a similar pellet in an old type gun with quick burning powder. Consequently, in many cases, it is found better not to depend on a suspending wire thus sheared, but to adopt direct action. The fuse in question would, we believe, act even on graze, at any angle over 10°. Probably at less angles than 10° it would not explode against water, which would be an advantage in firing at ships.
Shells so gently put in motion, and having no windage, might be made, it might naturally be supposed, singularly thin, and the adoption of steel in place of iron calls for some explanation. The reason is that it has been found that common shells break up against masonry, instead of penetrating it, when fired from these large high velocity guns.
The shrapnel shell is shown at Fig. 5. Like the common shell, it is made of steel, and is of the general form of the pattern of General Boxer, with wooden head, central tube, and bursting charge in the base. It contains 2,300 four ounce sand shots and an 8 lb. bursting charge. It weighs 1,800 lb. The fuse is time and percussion. It is shown in Figs. 6 and 6A. It closely resembles the original Armstrong time and percussion pattern.
The action is as follows: The ignition pellet, A, which is ordinarily held by a safety pin, is, after the withdrawal of the latter, only held by a fine, suspending wire, which is sheared by the inertia of the pellet on discharge, a needle lighting a percussion patch of composition and the composition ring, B B, which burns round at a given rate until it reaches the communication passage, C, when it flashes through the percussion pellet, E, and ignites the magazine, D, and so ignites the primer shown in Fig. 6, flashes down the central tube of the shell, and explodes the bursting charge in the base, Fig. 5. The length of time during which the fuse burns depends on how far the composition ring is turned round, and what length it consequently has to burn before it reaches the communication passage, C. If the fuse should be set too long, or from any other cause the shell strikes before the fuse fires the charge, the percussion action fires the shell on graze by the following arrangement: The heavy metal piece containing the magazine, D, constitutes a striker, which is held in place by a plain ball, G, near the axis of the fuse and by a safety pellet, H. On first movement in the gun, this latter by inertia shears a suspending wire and leaves the ball free to escape above it, which it does by centrifugal force, leaving the magazine striker, D, free to fire itself by momentum on the needle shown above it, on impact.
There is a second safety arrangement, not shown in the figure, consisting of a cross pin, held by a weak spiral spring, which is compressed by centrifugal force during flight, leaving the magazine pellet free to act, as above described, on impact.
The armor-piercing projectile is shown in Fig. 7. It is to be made of forged steel, and supplied by Elswick. In appearance it very closely resembles those fired from the 100 ton gun at Spezia, but if it is made on the Firmini system, it will differ from it in the composition of its metal, inasmuch as it will contain a large proportion of chromium, probably from 1 to 2 per cent., whereas an analysis of Krupp's shell gives none. In fact, as Krupp's agent at Spezia predicted, the analysis is less instructive than we could wish. - The Engineer.