used in the U. S. service, one for the 4¹⁄₂-inch rifle, another on which
the 30-pounder Parrott is mounted, and a third for the 8-inch howitzer,
being the old 12-pounder, 18-pounder, and 24-pounder siege-carriages
modified; these are all constructed in the same manner, and differ only
in their dimensions. Siege-carriages are similar to the field-carriage
in construction (see FIELD-CARRIAGE), the principal difference being in
the manner in which they are joined to the limbers. Projecting upwards
from the limber and in rear of the axle-tree is placed a pintle, which
enters a hole made in the trail from the under side, and a lashing chain
and hook keep the two parts together when once in position; the weight
of the stock bearing on the rear of the limber relieves the horses of
the weight of the pole, which is long and heavy. On the upper surface of
the cheeks near the rear ends are placed two projecting bolts, which
with the curve of the cheeks form resting-places for the trunnions, when
the piece is in position for transportation. They are called traveling
trunnion-beds. When the piece is in this position the breech rests upon
the bolster, which is a curved block of wood bolted to the upper side of
the stock.
_Sea-Coast Carriages_ are divided into barbette front-pintle and
barbette centre-pintle carriages, casemate, and flank-defense carriages;
depending upon the part of the work in which they are mounted. The
casemate-carriage differs from the barbette in being much lower.
Sea-coast carriages are now chiefly made of wrought iron. All are
composed of two principal parts, viz.: the gun-carriage and chassis. The
gun-carriage is composed of two cheeks, held together by two plates of
boiler-iron, called the front and rear transoms respectively. Each cheek
is formed of two pieces of boiler-iron cut to a triangular shape,
separated at the edges by interposing the vertical portion or web of a
T-shaped bar. The horizontal branches project over each side to form a
double rim, which gives stiffness to the cheeks. Flat bars of iron are
also placed between the plates at suitable intervals to stiffen the
cheeks in the direction in which the weight and recoil of the piece bear
upon them. All these parts are held together by screw-bolts. The motion
to and from battery is regulated in the 8- and 10-inch carriages by a
pair of eccentric truck-wheels, called manœuvring-wheels, which work on
an axle-tree placed underneath and a little in front of the centre of
the trunnions. When it becomes necessary to check the recoil of the
gun-carriage, the wheels are thrown out of gear by means of a handspike
inserted in the socket attached to the end of the axle-tree, and the
carriage moved on sliding friction. When the gun is to be moved into
battery, the wheels are thrown into gear in a similar manner, and the
front of the carriage moves on rolling friction. The manœuvring-wheels
mentioned above are fixed on the projecting ends of the axle-tree, the
axis of the wheel being eccentric with the axis of the axle-tree. These
eccentrics are so arranged that when the centres of the wheels are at
their lowest points, the surfaces of the wheels bear on the rails of the
chassis, and raise the gun-carriage from it; and when the centres are at
their highest points, the surfaces of the wheels do not touch the rails,
and the gun-carriage is in contact with them. In case there is no socket
connected with the end of the axle-tree, the wheel is thrown into or out
of gear, that is, made to bear on the rail of the chassis, or relieved
from it, by turning the axle-tree with a wrench placed on the hexagonal
end. In the 15-inch carriage there are two pairs of manœuvring-wheels,
one pair being placed in front as above described, and the other pair
near the rear end of the carriage. In all sea-coast carriages except the
flank casemate the elevation and depression are given by a lever, the
point of which works in a ratchet cut in the breech of the piece. The
fulcrum (ratchet-post) is made of cast iron and rests on the rear
transom of the gun-carriage. It has several notches for adjusting the
position of the elevating bar. The chassis is a movable railway on which
the gun-carriage moves to and from battery. It is composed of two
wrought-iron rails inclined 3° to the horizon, and united by transoms as
in the gun-carriage. In addition to the transoms, there are several
diagonal braces to give stiffness to the chassis. For the 10-inch and
smaller carriages, the chassis-rails are single beams of rolled iron, 15
inches deep; for all calibers above, the rails are made of long
rectangular pieces of boiler-plate and T-iron, in a manner similar to
that of the cheeks of the gun-carriage. In order to move the carriage
horizontally in the operation of aiming the piece, the chassis is
supported on traverse wheels, which roll on circular plates of iron,
fastened to a bed of solid masonry, called the traverse circles. The
motion of the gun-carriage is checked front and rear, by pieces of iron
bolted to the top of the rails, called hurters and counter-hurters; and
it is prevented from slipping off sideways by friction rollers and
guides, which are bolted to the cheeks and transoms. In a late
modification of the 15-inch carriage, the front eccentric axle is
replaced by an ordinary one, dispensing with axle-pawls and
friction-bands, the handspike pawls are made double instead of single,
with a spring to keep them out of the ratchets, the front set of
transoms and diagonal braces are removed from the chassis, and pneumatic
or hydraulic buffers to check the recoil are put in with thick braces.
When the rear manœuvring-wheels are out of gear, the top carriage
touches the rails of the chassis and moves on sliding friction, and when
they are in gear the front wheels are also made to touch the rails and
the top carriage moves on rolling friction. To prevent the rear
manœuvring-wheels from working out of gear while the gun is being run
from battery, or jumping in gear when the gun is fired, pawls are
provided for locking the rear axle. When no pawls are provided for
locking the eccentric axle, it is often necessary for one cannoneer to
remain embarred in the axle-socket to prevent the axle from flying out
of gear. The 15-inch carriage allows an elevation of about 32° and a
depression of about 6°, unless when fitted with pneumatic buffers, when
no more than 25° elevation can be given. With the hydraulic buffer which
passes along the centre of the chassis and is little used in the U. S.
service the elevation is still further diminished. The 10-inch rifle and
13-inch smooth-bore are used with the 13-inch carriage, and the 12-inch
rifle and 15-inch smooth-bore on the 15-inch carriage; the 20-inch gun
has a separate carriage. The flank-casemate carriage is adapted to the
mounting of the 24-pounder iron howitzer in the flanks of casemate
batteries. Several modifications have been introduced into the carriages
for the experimental rifled guns. For the largest calibers the
chassis-rails are deeper in rear than in front. The pintle, set in a
heavy flanged block of cast iron, is in front of the chassis, to which
it is attached by a strap or heavy plate of iron. The top carriage is
manœuvred by chain-gearing worked by a capstan near the rear of the
chassis. The elevation is given by a wheel with projecting spokes on the
side of the top carriage, which is geared to work a toothed arc attached
to the breech of the gun, the reading being given by a pointer on a
dial-plate above the wheel. Rubber buffers are placed at the rear
transom of the chassis to assist the cylinders to take up the recoil.
Friction-plates attached by india-rubber ends to the rear transom take
the place of cylinders in certain smaller carriages. In some cases the
traverse-wheels are made to relieve the pintle of part of the strain by
grooving them to run on heavy traverse-rails and inclining them towards
the pintle.
_Mortar-Beds._--Mortars are fired from a bed; in the U. S. service there
are three kinds of mortar-beds in use in the siege service; the 8-inch,
10-inch, and the Coehorn; the first two differ only in dimensions. They
are made of wrought iron and put together after the manner of the
sea-coast gun-carriage. The different parts are the cheeks, which, like
those of the gun-carriage, are triangular in shape, and two transoms
connecting the cheeks together. At the end of each cheek are
projections, called front and rear notches, underneath which the
cannoneers embar with their handspikes to move the bed on the platform;
there are also two front and two rear manœuvring-bolts for the same
purpose. The elevation and depression are given as in the gun-carriage
by embarring with the iron elevating bar through the fulcrum into the
ratchets on the breech of the mortar. The Coehorn-bed is made of a block
of oak wood, in one piece, or two pieces joined together with bolts. A
recess for the trunnions and part of the breech is made in the top of
the bed, and the trunnions are kept in their places by plates of iron
bolted down over them. Two iron handles are bolted to the bed on each
side, by which four men can carry the bed with the mortar in its place,
the entire weight being only 296 pounds. Sea-coast mortar-beds are
similar to those for siege purposes, but they have eccentric
truck-wheels for manœuvring the mortar-bed on the platform and the
manœuvring-bolts are omitted. The 13-inch sea-coast mortar is now
mounted upon a centre pintle-carriage. The usual bed, now become the top
carriage, is placed upon a chassis resting on a platform. The top
carriage has a crane attached to the left cheek, and to the inside of
the right cheek is attached a pawl worked from the front, for locking
the eccentric axle in and out of gear, and the carriage is strengthened
by an additional rear transom about 5 inches wide, the pipe being
omitted. The chassis has the usual appliance for throwing this class of
carriages into gear, and in addition an eccentric axle placed at right
angles to and supported by a double front transom, and carrying a
traverse wheel, by means of which motion is communicated to the
chassis. The chassis is otherwise transomed and braced in accordance
with the system. Heretofore nearly all sea-coast carriages were made of
wood, but in consequence of the great difficulty of preserving this
material from decay, especially when exposed to the dampness of
casemates, they have nearly all been replaced by wrought iron. The
carriages principally employed for the transportation of ammunition,
implements, and materials for repairs, are caissons, mortar-wagons,
forges, and battery-wagons.
_The Caisson._--Caissons are used for conveying ammunition for a
field-battery; all are similar in form. It is a four-wheeled carriage,
consisting of two parts, one of which is a limber similar to that of the
gun-carriage, and connected in a similar way by a wooden stock and
lunette. On the axle-body of the rear part and parallel to the stock are
placed three rails, upon which are fastened two ammunition-chests, one
behind the other, and similar to the one on the limber; so that the
caisson has three ammunition-chests, which will seat 9 cannoneers. The
interior compartments of the ammunition-chests vary according to the
nature of the ammunition with which they are loaded. In rear of the last
chest is placed a spare-wheel axle of iron, with a chain and toggle at
the end of it. On the rear end of the middle rail is placed a carriage
hook similar to a pintle-hook, to which the lunette of a gun-carriage
whose limber has become disabled may be attached, and the gun carried
off the field. The caisson has the same turning capacity and mobility as
the gun-carriage, so that it can follow the piece in all its manœuvres,
if necessary. It also carries a spare-wheel, spare-pole, etc. The
principal parts of the caisson are: stock, or middle-rail; it has an
iron lunette on its front end; side-rails, front foot-board, rear
foot-board, middle-chest, rear-chest, spare-wheel axle; it has a body,
two ribs, and a chain and toggle to secure the wheel; there are also two
stays for the axle; lock-chains, fastened to lock-chain bridles under
the front ends of the side-rails, and held up by lock-chain hooks
fastened to the outside of the side-rails; spare-pole, spare-pole key,
key-plate, chain, and pin; the key-plate is fastened to the under side
of the lunette; the key is attached to the left side of the stock by a
chain and eye-pin; carriage-hook, for attaching a carriage that has lost
its limber; wheel-guard plates, spare-pole ring, held by the axle-strap;
ring-bolt for spare hand-spike, key-plate and key, on the right side of
the middle-rail; key-plate, chain, and key for the shovel-handle, on the
inside of the right side-rail; middle assembling-bar, of iron; it has
two ears in the middle to serve as stay-plates for the middle-chests,
and a slot for the axe on the right of the middle-rail; rear
assembling-bar; it supports the spare-wheel axle, and has a slot for the
pickaxe on the left of the middle-rail. Axle, the axle-body, being
notched to receive the middle-rail and tenoned to fit into the notches
in the side-rails; staples for tool-handles; they are driven into the
top of the axle-body in front of the iron axle-tree, one for the
shovel-handle near the right side-rail, the other for the handle of the
pickaxe on the left of the middle-rail. Wheels of all artillery
carriages are similarly constructed; they differ, however, in the size
and strength of certain parts, depending on the size of the carriage to
which they are attached. The principal parts are: the nave, the
nave-bands, the nave-box, the spokes, the felloes, and the tire. The
nave constitutes the central portion of the wheel, and distributes the
pressure of the axle-arm to the spokes. It is generally made of a single
piece of wood, and strengthened by four iron bands called the
nave-bands. It is also pierced with a conical hole for the axle-arm; and
to diminish wear and friction, it is lined with a box of brass or cast
iron, called the nave-box. The spokes serve to transmit the pressure of
the load to the rim of the wheel. In all artillery carriages there are
seven felloes and fourteen spokes. The felloes are the wooden segments
which form the rim, and are joined together at their ends by wooden
pins, or dowels. The tire is a strong band of iron, shrunk tightly
around the felloes, to hold them together, and protect the rim from
wearing away by contact with the ground.
_Mortar-wagons_ are designed for the transportation of siege-mortars and
their beds, or of guns or large shot, and shells. A limber similar to
the one for siege-gun carriages is used with it. The body consists of a
platform of rails and transoms resting on an axle-tree. The stock is
formed by prolonging the two middle-rails. The side-rails projecting to
the rear form supports for the pivots of a windlass-roller. This roller
is used to load guns and mortars on the wagon by drawing them up the
stock. A muzzle-bolster on the stock near the limber, and a
breech-hurter near the hind part of the wagon, are provided and used
when long pieces are transported on it. Mortars are usually carried
mounted on their beds.
The _traveling-forge_ is a complete blacksmith’s establishment, which
accompanies a battery for the purpose of making repairs and shoeing
horses. It consists of a body, upon which is constructed the
bellows-house, etc., and the limber, which supports the stock in
transportation. The body is composed of two rails, a stock, and an
axle-tree. The bellows-house is divided into the bellows-room and
iron-room. Attached to the back of the house is the coal-box, and in
front of it is the fireplace. From the upper and front part of the
bellows an air-pipe proceeds in a downward direction to the air-box,
which is placed behind the fireplace. The vise is permanently attached
to the stock, and the anvil, when in use, is supported on a stone or log
of wood, and when transported is carried on the hearth of the
fireplace. The remaining tools are carried in the limber-chest. When in
working order the point of the stock is supported by a prop.
Nomenclature of the traveling-forge body: Lunette, prop, vise, stock,
wheel-guard plates, stock-stirrup, fireplace, back of fireplace,
air-back, wind-pipe, bellows, ribs, hinges, hook, fulcrum, hook and
staple, roof of bellows-house, bows, studs, girders, end-boards,
bottom-boards, side-rail, lock-chain hook, coal-box, lid or roof,
handles, hinges, turnbuckle, and hasp. A new pattern of field-forge has
been proposed by Col. Laidley, U. S. Ordnance Corps.
The _battery-wagon_ is employed to transport the tools and materials for
repairs. Among the tools are those for carriage-makers, saddlers,
armorers, and laboratorians’ use, scythes and sickles for cutting
forage, and spare implements for the service of the piece. The body of
the battery-wagon is a large, rectangular box, covered with a roof of
painted canvas; and to the back part is attached a rack for carrying
forage. The bottom of the body is formed of one middle- and two
side-rails, resting on a stock and axle-tree, as in the traveling-forge.
The tools and materials of the battery-wagon are carefully packed in the
manner prescribed by the Ordnance Manual, in order that no difficulty
may be experienced in finding a particular article when wanted. The
smaller articles are carried in boxes properly lettered and numbered.
The traveling-forge and battery-wagon are not confined to the service of
field-batteries, but are used with siege and sea-coast carriages as
occasion may require. Nomenclature of the battery-wagon body: Lunette,
stock, wheel-guard plate, lock-chain, lock-chain bridle, lock-chain
hook, studs, side-rails, upper rails, hinges, bows, cover-boards,
cover-strap and turnbuckle, hasp, side-boards, stays, bottom-rails,
bottom-boards, cross-bars, forage-rack, including chains, sides, and
bars.
=Ordnance, Construction of.= The present condition of gun construction
is mainly experimental. Iron in one form or another is the only material
used for heavy artillery, but the particular form in which it is to be
used, whether as cast, wrought, or steel, or whether in bars, coils, or
ingots, or in combination,--as, for instance, steel or wrought iron
interior and cast iron or wire-wrapped or hooped exterior,--is still
undecided, and it is left for experiments which are still in progress,
or to be made hereafter, to decide which is best. In the United States,
cast iron is used for smooth-bore guns, and also for rifle guns, but as
its use for the latter has not proved satisfactory, experiments are now
being made with wrought iron lined and with wire-wrapped and other
built-up guns, with fair prospect of success. In England, modern gun
construction at one period inclined to the use of a steel or wrought
iron interior tube, strengthened by an exterior casting of iron, which
is the system of Palliser and Parsons. But the preference for the
inventions of Sir William Armstrong, improved by those of Fraser, have
resulted in the exclusive use, in that country at present, of the system
of these two inventors. This method of gun construction is, in brief, a
steel core (or body of the gun) strengthened by three or more exterior
tubes of coiled wrought iron. This system is at present popularly known
as the “Woolwich,” but sometimes called the “Elswick,” from the place
where Sir William Armstrong’s works are now located. In Germany and
Russia, and some other European nations, the Krupp system of heavy
forgings of steel ingots is preferred. This last is by far the most
expensive, and does not always produce the most durable guns. The
question of breech- or muzzle-loading is still an undecided one. (See
BREECH-LOADING and BREECH-MECHANISM.) The Germans prefer the first
named, as do the French, Austrians, and Russians, for large calibers and
for most small guns, while the English, after several years’ trial of
the first, have of late abandoned its use and returned to the
muzzle-loader, though the question has again been recently agitated. In
the United States, experiments still going on have not yet demonstrated
which principle is the best suited to the gun construction used in
America. The advantages of loading at the breech with heavy guns are
numerous and great; but the serious mechanical difficulties (see
BREECH-MECHANISM) of perfecting the movable breech attachment have
militated against its adoption, especially in a country committed like
the United States to the use of cast iron. During the half-decade
(1855-60), and the succeeding decade (1860-70), enormous strides were
made in gun construction and in that of carriages and projectiles, and
the manufacture of gunpowder.
_Cast Metal Guns._--The principles which govern the construction of
homogeneous cast metal guns as established by long practice will be
considered under the following heads:
_Exterior Form._--The exterior of cannon is generally divided into five
principal parts, viz.: the breech, the first reinforce, the second
reinforce, the chase, and the swell of the muzzle.
The _breech_ (see BREECH) is the thickness of metal in the prolongation
of the axis of the bore, and should be at least equal to one and a
quarter times the diameter of the bore; a less thickness has been found
insufficient for heavy iron guns.
The _first reinforce_ (see REINFORCE) extends from the base-ring to the
seat of the ball, and is the thickest part of the piece, for the reason
that the pressure of the powder is found to be greatest before the
projectile is moved far from its place. In shape this reinforce was
formerly made slightly conical, under the impression that the pressure
was greater at the vent than at the seat of the projectile; but it is
now made cylindrical throughout. The thickness of bronze cannon at the
seat of the charge is less than for iron guns.
The _second reinforce_ (see REINFORCE) connects the first reinforce with
the chase. It is made considerably thicker than is necessary to resist
the action of the powder, in order to serve as a proper point of support
for the trunnions, and to compensate for certain defects of metal liable
to occur in the vicinity of the trunnions of all cast cannon, arising
from the crystalline arrangement and unequal cooling of the different
parts.
_The Chase_ (see CHASE).--From the extremity of the second reinforce
cannon taper more or less rapidly to the vicinity of the muzzle; this
part called the chase constitutes the largest portion of the piece in
front of the trunnions. The thickness of metal in the chase should be
sufficient to resist the striking of the ball against the side of the
bore. This injury being greater in bronze and soft iron guns, their
taper is less than in cast-iron cannon. In the construction of bronze
guns, the thickness of metal at the neck or thinnest part is about
five-elevenths of that at the first reinforce. All projections on the
surface of cannon not absolutely necessary for the service of the piece
are omitted in cannon of _late models_. This omission simplifies their
construction, renders them easier to clean, and obviates certain
injurious strains that would otherwise arise from unequal cooling in
fabrication.
_Swell of the Muzzle._--The enlargement called swell of the muzzle was
generally regarded as necessary, inasmuch as the metal situated
immediately at the muzzle is supported only in rear, and it was thought
necessary to increase its thickness in order to enable it to resist the
action of the projectile at this point. At present, however, the
tendency is to reduce the size of the swell of the muzzle and to omit it
entirely on all sea-coast cannon.
_Interior Form of Cannon._--The interior of a cannon may be divided into
three distinct parts, viz.: the vent, or channel which communicates with
the charge; the seat of the charge or chamber, if its diameter be
different from the rest of the bore, and the cylinder, or that portion
of the bore passed over by the projectile (see appropriate headings).