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.
[Illustration: 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.
[Illustration: FIG. 4.]
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.
[Illustration: FIG. 5.]
[Illustration: FIG. 6.]
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.
[Illustration: FIG. 3.]
[Illustration: FIG. 7.]
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.
[Illustration: FIG. 6A.]
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_.
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