Naval Gun Mountings

Protection is given by a shield carried on the mounting or by placing the gun in an armoured gun house. In the case of turret mountings, fixed armour surrounds the revolving structure ex tending below the water line ; and the roof and sides of the turret above this armour are made of armour plate. The functions of a gun mounting are (I) to absorb the recoil and replace the gun in the firing position without incurring undue stresses on the deck structure. (2) To enable the gun to be rapidly and accurately laid and trained (i.e., directed in the vertical and horizontal planes) through a wide arc whether the target be in view at the gun position or not. This demands very sensitive control for aline ment, effected at the gun either directly through telescopic sights or indirectly as signalled from a control position. (3) To permit of rapid loading and a high rate of fire.

(I) Recoil Arrangements.—Guns are generally carried in a cradle in which they are free to recoil, the cradle being pivoted or supported by trunnions in the mounting. In the case of heavy guns the cradle is replaced by a carriage and slide. The carriage may be regarded as part of the gun to which it is rigidly attached, and the slide is pivoted to enable the gun to be laid, and forms a path on which the carriage can travel during recoil. The gun or carriage is attached to a piston which works in a cylinder at tached to the cradle or slide. In some cases the piston is con nected to the cradle and the cylinder is secured to, and recoils with, the gun. For heavy guns two pistons and cylinders may be employed. The energy of the recoil is absorbed mainly by the resistance offered to the passage of liquid from one side to the other of the piston, either through tapered grooves in the recoil cylinder or through a valve or orifice in the piston. In a 16 in.

gun the initial velocity of recoil is 21 fs. and the recoiling mass (approximately no tons) is brought to rest in the short travel of 3.8 feet. Efficient buffering is arranged at the end of recoil to bring the gun quietly to rest before it is returned to the firing position either by springs, or by air compressed during the recoil action, and contained in a separate compartment fixed to the cradle. In "recuperator" mountings, the run out is effected by the pressure of air contained in a communicating cylinder or reser voir, acting on the liquid in a "run out" cylinder through a valve which controls the speed of run out. Suitable arrangements are made by a liquid seal to prevent any air from passing into the run out cylinder. In power-worked mountings the gun may be

run out by hydraulic pressure acting on a ram or piston attached to the slide. It will be noted that the system of overcoming the recoil is hydraulic, whereas the counter-recoil may be mechan ical (i.e., springs), pneumatic, hydraulic or a combination of these systems. The primitive expedient of arranging for the gun to recoil up an inclined plane and to run out by gravity is no longer used.

(2) Training and Elevating Arrangements.

The training of a gun is effected by rotating the entire mounting about its vertical axis. In a hand-worked deck mounting which is sup ported on a live roller ring or pivoted on ball-bearings, this is carried out by worm gear fitted in the mounting which engages in a rack secured to the deck. In the case of light guns, this gear is usually arranged to disconnect, so as to allow the mounting to be trained from a shoulder piece in smooth weather. A turret mounting generally carries with it a hanging chamber and ammu nition trunk. Moreover it must be supported on a live roller ring which travels on a fixed roller path built into the ship and the turret is rotated by a hydraulic engine which works a driving pinion gearing into a vertical rack fixed to the hull. The great weight of the revolving structure, which may exceed ',coo tons in triple gun turrets, entails very powerful machinery to obtain the necessary nicety in movement required for accurate training, one minute of arc being of importance at long range.

In double or triple gun turrets, though the guns cannot .be trained independently, the elevation or laying is generally inde pendent. It is effected by moving the gun slide in the vertical. plane by one or two hydraulically operated rams, connected to the slide and working in cylinders fixed to the mounting. Another method of laying a gun commonly adopted in U.S.A. ships is by the rotation of a long screwed shaft driven by an electric motor which takes the place of the ram. Where very high angles of elevation are required involving a large movement the laying may be performed by a hydraulic swash plate engine (q.v.). Hand-worked guns are generally laid by the rotation of a pinion geared into a toothed arc attached to the cradle. In all cases the elevating gear is connected to the non-recoil portion of the mounting. In some turrets it is possible to lock the slides so that the guns are elevated together, and in other mountings (known as "twin" mountings) independent elevation is not possible.