achievements in building great guns, by designing and constructing the
huge breech-loaders, one of which forms the subject of our Plate XII.
These are known as the Armstrong 110–ton guns; they are formed of solid
steel throughout, and their weight is accurately 247,795 lbs., or 110
tons 12 cwts. 51 lbs. The total length of the gun is 43 ft. 8 in., and
of this 40 ft. 7 in. is occupied by the bore, along which the rifling
extends 33 ft. 1 in. The calibre of the rifled part is 16¼ in., and the
diameter of the powder chamber is somewhat greater. The regulation
charge of powder weighs 960 lbs., although the guns are tested with
still greater charges. The weight of the projectile is 1,800 lbs., and
it leaves the muzzle with a velocity of 2,128 ft. per second, which is
equivalent to a dynamical energy of 56,520 foot-tons. What this means
will perhaps be better understood, not by describing experiments such as
those on the Millwall Shield, the results of which are depicted in Figs.
95 and 96, but by stating that if the shot from the 110–ton gun
encountered a solid wall of wrought iron a yard thick, it would pass
through it. The Elswick 110–ton gun is, in fact, the most powerful piece
of ordnance that has ever been constructed. There are no trunnions to
these great guns, but they are encircled by massive rings of metal,
between which pass strong steel bands that tie the gun to its carriage,
or, rather, to the heavy steel frame on which it is mounted, and which
slides on a couple of girders. The force of the recoil acts on a
hydraulic ram that passes through the lower part of the supporting
frame. The whole working of the gun is done by hydraulic power, and,
indeed, the same method has been applied by the Elswick firm to the
handling of all heavy guns. By hydraulic power, maintained automatically
by a pumping engine exercising a pressure of from 800 lbs. to 1,000 lbs.
per square inch, are operated the whole of the movements required for
bringing the cartridge and the projectile from the magazine; for
unscrewing the breech block, withdrawing it, and moving it aside; for
pushing home the shot and the cartridge to their places in the bore; for
closing the breech and screwing up the block; for rotating the turret
within which the gun is mounted, or in other cases for ramming the piece
in or out, and for elevating or depressing it. It is, indeed, obvious
that such ponderous masses of metal as form the barrels and projectiles
of these 110–ton and other guns of the larger sizes could not be handled
to advantage by any of the ordinary mechanical appliances. But by the
application of the hydraulic principle, a very few men are able to work
the largest guns with the greatest ease, for their personal labour is
thus reduced to the mere manipulation of levers. On board ship the power
required for working large guns has lately been sometimes supplied by a
system of shafting driven by a steam engine and provided with drums and
pulleys, exactly as in an engineer’s workshop. Great care has also been
bestowed upon the mounting of the smaller guns, which are so nicely
poised on their bearings and provided with such accurately fitted racks,
pinions, etc., that a steel gun of 10 ft. in length can easily be
pointed in any direction by the touch of a child’s hand. The mechanical
arrangements are now so admirably adapted for facility of working that,
unless in the rude shocks of actual warfare the nicely adjusted
machinery is found to be liable to be thrown out of gear, these
applications of the engineer’s skill may be considered as having done
all that was required to bring our modern weapons to perfection.
[Illustration:
PLATE XII.
THE 110–TON ARMSTRONG GUN.
]
With the construction of the 110–ton we arrive at a period when
commences a new era in guns—and especially in the armament of
war-ships—necessitated by various circumstances, amongst which may be
named the invention of torpedoes and the building of swiftly moving
torpedo-boats, and of still swifter “torpedo-boat catchers or
destroyers”; so that guns that could be worked only at comparatively
long intervals were at a great disadvantage. Again, about 1880, were
published the records of a most elaborate and important series of
researches conducted by Captain Noble and Sir F. Abel, the chemist of
our War Department. They had investigated all the conditions attending
the combustion of gunpowder in confined spaces, the nature and
quantities of the products, the temperature and pressures of the
confined gases, etc. The information thus afforded was extremely
valuable; but besides this, direct experiments made with actual guns
were carried out, more particularly at Elswick, in which the speed of
the projectiles at every few inches of their travel along the bore of
the piece was ascertained, and also the pressures of the powder gases at
any point. The way in which this is done we shall explain on another
page. (_See article on Recording Instruments._)
So long as muzzle-loading was in use, guns were necessarily made short,
for had they not to be run in from the port-holes and embrasures of
forts in order to be loaded? Now there was an obvious disadvantage in
this, for the projectile left the gun before the expansive force of the
gases had been spent that could have imparted additional velocity. When
however muzzle-loading was abandoned, and especially when strong and
trustworthy steel became available for the construction of the gun
throughout, there was no reason to waste in this way the power of the
charge, so that barrels were made lighter, much longer in proportion to
the calibre, and every part accurately adapted in strength to the strain
to be resisted. For instances of increasing length, take the 38–ton
12–inch guns built up at Woolwich (of only seven pieces) for H.M.S.
_Thunderer_ (see Fig. 93), on Mr. Fraser’s plan. These had a bore equal
to only 16 times their calibre, while in the Armstrong 100–ton guns the
bore is 21 calibres long; and in the 110–ton guns the total length of
the chase is 31 times the diameter of the rifled part. It has since been
the practice to make the bore of guns from 30 to 40 calibres in length.
The effect of a longer chase used with an appropriate charge is very
clearly and instructively shown by the diagram Fig. 98, which is by
permission copied from the very comprehensive work by Messrs. E. W.
Lloyd and A. G. Hadcock, entitled _Artillery: its Progress and Present
Position_. The reader should not pass over this diagram until he has
thoroughly understood it, for it is an excellent example of the graphic
method of presenting the results of scientific investigations. At the
lower part of the diagram there are drawn to scale half-sections of a
long and of a short gun. The horizontal line above is marked in equal
parts representing feet numbered from the base of the projectiles. The
upright line on the left numbered at every fourth division is the scale
for the pressures in tons per square inch on the base of the projectile,
and these are represented by the height of the plain curves above the
horizontal line at each point in the travel of the shot. The dotted
lines represent in the same way, but _not_ on the same scale as the
former, the velocity with which the base of the projectile passes every
point in the chase. The figures 2, 4, and 6 on the upright line at the
right-hand side refer only to pressures: the velocities scale is such
that the point where the dotted meets the right-hand one is 2,680 units
above the horizontal line, as the middle upright in the same way is
1,561 high, and the heights of the dotted lines represent each on the
same scale the velocities of the bases of the projectiles at the
corresponding parts of the chases. The shorter gun has the rifled part
of the chase 15·4 calibres long; the corresponding part of the longer is
nearly 33 calibres. The short 7–inch gun has a charge of 30 lbs. of
gunpowder, and its projectile weighed 115 lbs. The longer 6–inch gun was
not charged with gunpowder, but with the more powerful modern explosive
_cordite_ (see Index), of which there was 19·5 lbs., and its projectile
weighed 100 lbs. The charges were so adjusted that the shots had the
same initial maximum pressure of 20 tons per square inch applied to
them. Now the cordite, though much more powerful than gunpowder (that
is, a given weight will produce far more gas), is slower in its
ignition, continuing longer to supply gas. The maximum pressure, 20 tons
in both cases, is suddenly attained by the gunpowder gases, when the
shot has hardly moved 6 inches onward, and the pressure declines rapidly
as the moving shot leaves more space for the gas; while the cordite
gases produce their greatest pressure more gradually at a part where the
shot is already about 20 inches on its way, and not only do their
highest pressures continue for a greater distance,—but the decline is
far less rapid than in the other case. It will be observed by the
intersection of the dotted lines, that when the shots in each case have
moved about 2 ft. their velocities are equal. They finally leave the
muzzles with the velocities marked on the diagram, and if the reader
will apply the formula given on page 174 he will obtain their respective
energies in _foot-lbs._; but for large amounts like these it is more
usual to state the energy in _foot-tons_, which of course will be
arrived at by dividing the _foot-lbs._ numbers by 2,240, and these will
work out in the one case to 4978·9 ft.-tons, and in the other to 1942·5
ft.-tons. The shot from the long gun will therefore have more than 2½
times the destructive power of the other.
[Illustration:
FIG. 98.—_Diagram of Velocities and Pressure._
]
The operations required in constructing guns are multiform, and have to
be very carefully conducted so that the workmanship shall be of the best
quality. The finest ores are selected for reduction, and the steel is
obtained by the Siemens-Martin process already described. It must be
free from sulphur and phosphorus, and contain such proportions of
carbon, silicon, and manganese as experience has shown to be best, and
its composition is ascertained by careful chemical analysis before it is
used. The fluid steel is run into large ladles lined with fire-brick,
and provided with an opening in the bottom from which the metal can be
allowed to run out into the _ingot_ moulds, the size and proportions of
these being in accordance with the object required; some admitting of as
much as 80 tons at one operation. When a barrel or hoop is required of
not less than 6 inches internal diameter the ingot is cut to the
required length and roughly bored. The ingot is then heated, a long
cylindrical steel bar is put through the hole, and under a hydraulic
press the hot metal is squeezed into greater length and less diameter.
The hole first bored through the ingot is of somewhat greater, and the
steel bar (called a mandril) of less, diameter than required in the
finished piece. Portions are cut from each end of what is now called the
_forging_ and subjected to mechanical tests: if these are satisfactory,
the forging is rough bored and turned on the outside. It is then
annealed, by being heated and allowed to cool very slowly. The next
operation is to _harden_ the metal by raising it to a certain
temperature, at which it is immersed in rape oil until cold. Then the
piece is again annealed, and fine-turned and bored. All these operations
have to be performed not only on the barrel, but also on each hoop,
before the hoops are shrunk on, and the greatest nicety of measurement
is required in each piece. Then the gun has to be turned on the outside,
the screw for the breech piece cut, the bore rifled, etc. The object of
the annealing is to relieve the metal from internal strains. It will not
be wondered at that months are required for the construction of the
larger kind of guns. Thus at Elswick a 6 in. quick firing gun, upon
which men are employed night and day, cannot be completed in less than
five months, and sixteen months are required for making a 67–ton gun.
We may take as an illustration of the progress of modern artillery one
of the products of the Elswick factory which has just been referred to,
and for which the demand from all quarters has been unprecedentedly
great, namely, the 4·7 inch gun. This weapon is mounted in various
manners according to the position it has to occupy, whether for a land
defence, or on ship-board between decks, or on the upper deck. The
arrangement shown in Fig. 99, which is reproduced from Messrs. Lloyd &
Hadcock’s work, is known as the centre pivot mounting, and is suitable
for such a position as the upper deck of a ship. The reader should
compare the proportions and mounting of this weapon with those of the
old 32–pounder sketched in Fig. 90, observing the very much greater
comparative length of the modern weapon, and the mechanism for elevating
and training it (which, however, the scale of the drawing crowds into
too small a space to show as it deserves). C is a projection from the
breech, to which is attached the piston of the recoil press; at T is the
handle for training, which actuates a worm at V; the elevation is
regulated by the turning of the four-armed wheel. The long chase of the
gun projects in front; but the mounting and the breech machinery are
protected by shields of thick steel, of which the sections of two plates
are denoted by the dark upright parts in front. These are fixed; but a
movable plate above the gun can be raised or lowered into an inclined
position, for better taking sights. In the figure this is shown as open
and in a horizontal position. This gun is provided with sights by which
it can be aimed at night; that is, the sights can be illuminated by
small electric lamps suitably placed; the wires connecting these with
voltaic battery cells carried on the mounting are indicated. The figure
represents the gun as constructed about 1893, but the improvements that
are continually being made have brought about some modifications in the
details.
[Illustration:
FIG. 99.—_Elswick 4·7 inch Q. F. Gun on Pivot Mounting._
]
Very notable among the productions of the great Elswick factory are the
_quick firing_ guns. These were at first confined to guns of small
calibre, such as the 6–pounders. They are, of course, all
breech-loaders, and the powder and shot are both contained in a single
metallic cartridge case. A more formidable weapon of the same class is
the 45–pounder rapid firing gun, which, like the rest, is constructed
entirely of steel, with a total length of 16 ft. 2½ in., a calibre of
4·724 in., and a length of bore equal to 40 diameters. The weight of
this gun is 41 cwt., and it throws a shell of 45 lbs. weight with a
12–lb. charge of gunpowder. Quick firing guns having a calibre of 6 in.
are now also made in great numbers for arming our ironclads. The breech
block in the quick firing guns turns aside on a hinge, and after the
introduction of the cartridge it is closed and screwed up to its place
by a slight turn of a handle. The piece is then pointed and trained by
aid of mechanical gearing as in the case of the heavier guns. But Mr.
Hotchkiss has introduced a simpler method of elevating and training his
3–pounder and 6–pounder quick firing guns, by attaching to the rear, and
unaffected by the recoil, a shoulder piece against which the marksman
can lean, and move the weapon as he takes his aim. Though these guns
weigh respectively 4½ cwt. and 7 cwt., they can thus be pointed with the
greatest ease. The firing is done by pulling a trigger in what seems
like the stock of a pistol. The empty cartridge case is automatically
extracted from the firing chamber by the act of opening the breech, and
it drops to the ground. Ten or twelve rounds per minute can be fired
from these guns, and Lord Armstrong has advocated the use of a number of
them for naval armament in preference to that of a few ordinary
breech-loaders of more unwieldy dimensions. He has calculated that in a
given time a far greater weight of metal can be projected from a vessel
armed with quick firing guns than from one provided only with the
heavier class of cannons.
The breech pieces in the Elswick guns are closed on the “interrupted
screw” system—that is, a very large screw thread of V-shaped section is
cut in the barrel at the breech end, and a corresponding thread on the
principal part of the breech block, which is, of course, capable of
rotating about the axis. The screw threads, however, are not continuous,
segments parallel to the axis being cut away, the spaces in the outer
thread corresponding with the projecting parts in the inner, and _vice
versâ_, so that when the block is pushed home, one very small part of a
turn suffices to engage all the threads. The screw is also made conical,
and is so cut into steps, as it were, that great resisting power is
brought into play. The Elswick guns are provided with hydraulic buffers
for checking the recoil, and the principle is applied in various
modified forms. In some cases the pistons allow for the water a passage,
which towards the end gradually diminishes. This is the arrangement for
the 3–pounder rapid firing Hotchkiss gun, and the force of the recoil is
made at the same time to compress two springs, which serve to return the
gun to the firing position. This very handy gun is said to be able to
fire twenty rounds per minute. In Mr. Vavasseur’s plan of mounting, the
recoil is checked by ports, or openings, in the piston of a hydraulic
cylinder being gradually closed, which is easily arranged by making a
spiral groove within the cylinder, which gives a small axial motion to
part of the piston.
[Illustration:
FIG. 100.—_The Moncrieff Gun raised and ready for firing._
]
[Illustration:
FIG. 101.—_Moncrieff Gun lowered for loading._
]
An extremely effective plan for the defence of coasts and harbours was
originated by Colonel Moncrieff, when about 1863 he contrived a method
of mounting large guns on the disappearing system, by which almost
complete protection against hostile fire is given to both gun and
gunners. He utilizes the recoil as a means of bringing the gun down into
a protected position the moment it has been fired, and retains this
energy by a simple arrangement until the piece has been reloaded, when
it is allowed to expend itself by again raising the gun above the
parapet into the original firing position. The configuration and action
of Colonel Moncrieff’s gun-carriage will be understood by an inspection
of the annexed illustrations, where in Fig. 100 is shown the gun raised
above the parapet and ready for firing. When the discharge takes place,
the gun, if free, would move backwards with a certain speed, but the
disposition of the mounting is such that this initial velocity receives
no _sudden_ check, the force being expended in raising a heavy
counterpoise, and at the same time the gun is permitted to descend,
while maintaining a direction parallel to its firing position. At the
end of the descent, which, it must be understood, is caused by the force
of the recoil, and not by the counterpoise, for this more than balances
the weight of the gun, the latter is retained as shown in Fig. 101 until
it has been reloaded; and when it has again to be fired, it is released
so as to allow the descent of the counterpoise to raise it once more
into position. The great advantage of this invention is the protection
afforded to the artillerymen and gun while loading; and even the aiming
can be accomplished by mirrors, so that the men are exposed to no
danger, except from “vertical fire,” which involves but little risk.
Colonel Moncrieff took out a patent for his invention in 1864, but
committed the practical working out of his idea to the firm of Sir W. G.
Armstrong & Co., in whose hands the design was ultimately transformed
from the original somewhat cumbersome arrangement of the mounting into
the compact and manageable form shown in Fig. 102, which represents a
13·9 inch 68–ton breech-loading disappearing gun on the Elswick
hydro-pneumatic mounting. The principle of hydraulic power is fully
explained in our article on that subject, and an example of its
application to cranes as devised by Sir W. Armstrong is there described.
When guns began to be made very large, and projectiles weighing several
cwts. had to be dealt with, the application of power in some form became
essential for loading, running out, elevating, training, etc.; and
though steam-power naturally was first used, hydraulic power was adopted
at Elswick, and has been there applied to the mountings of large guns
with the greatest success by Mr. G. W. Rendel. To mention the various
arrangements in which this power is applied, or to attempt any
description of the elaborate machinery by which it is regulated, would
carry us far beyond our limits. But the powerful weapon depicted in Fig.
102 is designed to be worked only by the manual effort of a few men. In
this mounting the pressure of condensed air sustains the gun in the
firing position; that pressure, acting upon the water in the recoil
presses, having previously forced up their rams so as to turn into a
nearly vertical position the strong brackets or beams on which the
trunnions are supported. The recoil is checked in the usual way by the
forcing of the water through small ports or valves as the ram descends,
but these valves are so arranged that the water is in part forced back
into the air chamber, and there recompresses the air, to restore the
power for again raising the gun. The pressure in the air chamber when
the gun is down may be about 1,400 lbs. per square inch; when it is up
this will be reduced to perhaps one half by the expansion of the air in
doing work. We have here the reaction of compressed air taking the place
of the gravity of the counterpoise originally designed. There are in
this hydro-pneumatic mounting a number of adjusting appliances, such as
forcing pumps, brakes, etc., for regulating the pressures, or quantity
of liquid, as, for instance, when lowering the gun without any recoil
action in operation. Then again, with any change in the weight of
projectile or in the powder charge, there would be a corresponding
change in the power of the recoil, and therefore the necessity for
compensatory adjustments, which are made with great readiness. The
nicety with which the parts are adapted to each other in this mounting
must be obvious, when we observe the magnitude of the mass to be moved
with the least delay, and brought to rest, quite gently and exactly, in
a new position. Details cannot here be given even of the method by which
the valves in the recoil cylinders are automatically controlled for this
purpose. Means are also supplied for setting the gun, while still in its
protected position, to the required angle of elevation or depression.
The adjustment is made by the long rods attached near the breech and set
at their lower ends to the position giving the intended angle to the
raised gun. The varied and powerful strains to which the parts of this
mechanism are subject, and which have had to be calculated and provided
for, may be inferred from the enormous recoil energy of the gun, which
under ordinary conditions amounts to no less than 730 foot-tons. The gun
is provided with ordinary, and also with reflecting, sights, so that no
one need be exposed to the enemy’s fire. Protective armour above the gun
is not required, as the pit itself being usually on some elevation is
imperceptible to the enemy, and the gun is visible but for a few
seconds, forming a quite inconspicuous object. The pit in which the gun
is mounted is commonly lined with concrete. Italy, England, Norway,
Japan and other countries have appreciated the advantages of the
disappearing system in providing the most powerful coast defences yet
devised, and a great many guns have been mounted on this principle.
[Illustration:
FIG. 102.—_68–ton Gun on Elswick Hydro-Pneumatic Mounting._
]