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.