other end of which is fixed to the spindle supporting a pointer, reading angles of elevation on the drum R. As the gun elevates the tape is paid out, the slack being taken in and the pointer revolved by the action of a clock spring.[1] The mounting carries an automatic sight (see Sights, Gun Sights).
| |
| Fig. 87. | Fig. 86. |
| Fig. 86.—British Mark II. Barbette Mounting for 6″ B.L. Gun. Fig. 87—Longitudinal Section of Part of Cradle of Gun shown in fig. 13, through Axis of Buffer. | |
The British 12-pr. Q.F. Gun. — A typical mounting for guns of class (c) is the British pedestal mounting for the 12-pr. Q.F. gun. This mounting consists of a cradle, a pivot, a pedestal and holdfast. The cradle is a gunmetal casting, provided with trunnions that rest in bearings on the pivot; the gun recoils in the upper portion of the cradle and the lower part of the latter is bored at the rear for an hydraulic buffer and at the front for a running-out spring. The pivot is of steel, is fork-shaped at the top end, where are the trunnion bearings for the cradle; its lower end is conical and fits into bushes in the pedestal, where it is free to revolve but is prevented from lifting by a holding-down screw.[2] The pedestal is bolted down to the platform. The gun has a shoulder-piece and it can be trained and elevated by the layer. It has also an automatic sight.
A typical Krupp mounting of this kind is shown in fig. 88, Plate VI., which represents an 8·8-cm. (3·4″) automatic gun firing, it is stated, 40 aimed rounds in the minute.
The United States 12″ Mortar.—A typical mounting for pieces of class (d) is afforded by the United States mounting, model of 1896, for the 12″ B.L. mortar. The piece is mounted in a top carriage or saddle consisting of two arms connected by a heavy web. This saddle is hinged on a heavy bolt and is connected to the front of the turntable (fig. 89). The saddle inclines to the rear and upwards at an angle of 45°, the upper ends forming trunnion bearings: it is supported at a point about one-third of its length from the bolt or fulcrum by five columns of double springs arranged in a row, side by side. The recoil is checked by two hydraulic cylinders, one on each side, the pistons of which are attached to the saddle near the trunnions of the piece. When the mortar is fired the saddle revolves about its fulcrum to the rear and downwards, carrying the mortar and compressing the spring columns until the action is stopped by the hydraulic buffers; the springs then assert themselves and return the piece to the firing position. The mortar must always be brought horizontal for loading.
The fighting units of coast artillery in the British service are the fire command, the battery command and the group. The limits of a fire command are governed by the possibility of efficient surveillance and control that can be exercised by an individual, and these limits vary much from time to time. Usually a number of forts or emplacements are included in a fire command. The fire command is broken up into battery commands, in every one of which it must be possible for its commander actually to take charge of the guns therein contained in all phases of action. The battery command is divided up into gun groups, each consisting of one or more pieces of like calibre, nature and shooting qualities. As a rule a fire commander is a field officer, a battery commander a major or a captain, a gun group commander a subaltern or senior N.C. officer. In connexion with coast artillery range-finders (q.v.) and electric lights (see Coast Defence) are installed and electric communications established for the chain of command. (J. R. J. J.)
V. Naval Guns and Gunnery
In dealing with naval guns and gunnery, we shall take the British navy as the basis. At the close of the 19th and at the beginning of the 20th century it appeared that a type of British battleship (see Ship) had been evolved which was stable as regards disposition of armament, and that further advance would consist merely in greater efficiency of individual guns, in improvements of armour rendering possible the protection of greater areas, and in changes of engine and boiler design resulting in higher speeds. The “Majestic,” “Glory,” “Exmouth,” “London” and “Bulwark” classes differed from each other only in such details, all of them subordinate to the main raison d’être of the battleship, i.e. the number and nature of the guns which she carries.
The strength and disposition of the armaments of the ships of these classes were identical except in small details (see fig. 90). In every case the main armament consisted of a pair of 12-in. guns forward and a pair aft, each pair enclosed in a hooded barbette, which was more commonly designated a turret. The turrets were on the midship line, and the guns in each commanded an arc of fire of 240°, i.e. from right ahead to 30° abaft the beam on either side in the case of the fore turret, and from
