Page:EB1922 - Volume 31.djvu/1258

supporting the rear end of the main girder travel ; this is an improve- ment on the method of supporting it with jacks and circular castings (see fig. 47). This gun has a complete electric power plant, fur- nished by a 25-K.W. petrol engine and dynamo. The same mount- ing is used for the i6-m. 25-cal. howitzer.

The simple steel platform used with the American 14-in. gun is in marked contrast to the elaborate platform, consisting of a ring of caissons sunk in the earth, used by the Germans for their 15-in. gun. It is stated that the American platform answers its purpose well. It remains stable, and, even if it does not maintain its level accurately, the resulting error is eliminated by the reciprocating sight. If it be possible to lay a platform for a super-heavy gun in 8 hours, instead of the 3 weeks required for the German pattern, and to mount the un on it in one hour instead of 24, then this enables the gun to open re from any desired point on the railway, or close to it, quickly enough for all practical purposes of land warfare, though hardly quickly enough for emergencies that might arise in coast defence. So far as land warfare is concerned, it would seem that the intro- duction of an 8-hour platform will render it superfluous to build all- round railway mountings for anything heavier than the n-in. or 28o-mm. guns. For even if it were possible to produce an all-round- fire railway mounting for a 14-in. gun, such that it could fire from any point on the open line without a platform, it would probably take 2 hours to fix and bed the outriggers, and the gain in time would hardly compensate for the increased cost and complication of the mounting as compared to the simple American type.

In the design for fixed mountings proper that is, mountings and emplacements deliberately prepared in peace-time with the aid of concrete and armour the conditions of the World War brought about little change. The types described and illustrated at 20.226 are still maintained in principle, improvements having been made in details only. A very general review, therefore, will suffice here.

FIG. 47. U.S. 14-in. gun, on railway mounting. Firing position

Disappearing mountings are now no longer made, though some remain in service in America. These give the best possible protection against hostile fire, but naturally involve a very complicated mount- ing; and further, should the lowering and raising arrangements go out of order, the gun is rendered useless. High-angle mountings are still utilized in some places, mounted in deep pits for protection. They are largely used by the United States.

The utility or otherwise of cupola mountings in land fortifications is a question which the experience of the World War has made more controversial than ever. The answer lies, however, in tactical, not technical, considerations.

Coast-defence guns in permanent emplacements are now usually mounted on pedestals en barbette, as shown in figs. 84-87 at 20.229, 230. These mountings give all-round fire with breastwork pro- tection as high as the gun level and armour in the form of a thick gun-shield above that level. All barbette pedestal mountings are generally similar in design. The emplacement is prepared by em- bedding anchoring plates in the concrete foundation and to these a coned pedestal is bolted down. Arrangements are made for levelling the pedestal as required. The pedestal supports the superstructure consisting in intermediate carriage, cradle, gun and gears. The intermediate carriage is capable of revolution in a horizontal plane about the centre of the pedestal and means are usually fitted to pre- vent it lifting on firing. Fixed to the pedestal is a graduated arc, correctly oriented, and to the intermediate carriage a pointer to indicate the training or traverse of the gun. The cradle carries the gun and recoil system, and is supported by trunnions on the inter- mediate carriage; the gun and cradle are elevated about the trunnion axis by elevating gear, whilst both the elevating system and the sights the latter usually being fitted to each side of the mounting- are provided with scales to indicate the corresponding range.

With medium and heavy guns a platform is suspended on the intermediate carriage for convenience in loading and laying. All are provided with shields which cover the upper portion of the mounting and traverse with it. The intermediate carriage fits in or on the pedestal, and to lessen the friction consequent on traversing various devices are employed.,

With light mountings, the lower portion of the intermediate carriage is formed with a stem projecting downwards into the pedestal; hardened steel studs let into the bottom of the stem and the recess in the pedestal support the whole weight of the super- structure. With medium mountings, the intermediate carriage is supported on a ring of hardened steel balls carried in a recess at the top of a pivot fixed into the pedestal.

The intermediate carriage of a heavy mounting is supported on a live roller ring; the rollers take the load on their circumference, not on their axles, and can move independently of the mounting. The rollers are kept equidistant by being mounted on axles between con- centric rings, and are arranged to run between upper and lower roller paths; they are coned to give circular rolling motion without skid- ding, and are flanged to fit over the roller paths. The intermediate carriage is centred and steadied by a pivot fixed to the centre of the pedestal. The hardened studs give a form of point contact, the ball race gives circular line contact, and the roller ring circular ring con- tact. Thus the area in contact is kept at a minimum consistent with the weight of the superstructure for the mounting to be traversed with the greatest possible ease.

So far aS circumstances permit, the same principles of support are employed in the semi-fixed and railway-pivot mountings dealt with above. How far improvements in railway-pivot mountings will enable guns fired from them to rival the accuracy of guns fired from the fixed and bedded mountings hitherto used in coast defence is an open question. All mountings (except the lightest which can be easily moved by hand) are provided with traversing gear.

Prior to the World War fixed mountings were designed to permit of a maximum elevation of about 20; but they are now being de- signed to give elevation up to about 40 degrees. This necessitates a taller intermediate carriage and longer arcs on the cradle. To reduce the work of elevating the heavier guns the trunnions are mounted in ball or roller bearings. With ball-bearings, which give a point contact, the bearings are supported on springs to support the trunnions only when elevating; on firing, the spring supports give and allow the trunnions to bear upon the intermediate carriage, thus relieving the balls from the firing stresses. In the design of elevating (and also traversing) gear provision is made for relieving the mech- anism of shock strains.

The ring type of cradle, being suitable for short recoil, is in general use. _The recoil system is usually carried underneath the cradle and consists in a buffer of the valve-key type and springs or compressed air for recuperation. Springs are now being superseded except for light mountings, and the pneumatic recuperator is coming into general use with the increased elevations for which mountings are being designed. With very heavy guns a slipper is employed to sup- port the gun in the cradle, recoil with it, and connect with the recoil system. Hand-loading obtains with light and medium guns, but with heavy guns machinery is employed with hand-gear as a standby in case of breakdown. (X.)

(VII.) NAVAL ORDNANCE AND GUNNERY The many lessons learnt from the World War as to the results obtainable by naval artillery, and the multitude of improve- ments in material and in the methods of using it, were in 1921 still in process of digestion by the leading naval Powers. In so far as they reflected upon the design of future warships, from the point of view of naval ordnance, these lessons were still kept as closely guarded secrets in official quarters. The chief factors can, however, be stated in general terms.

The outstanding factor is the long range at which the naval actions of the war were fought by all types of ships. This was due primarily to the great destructive power of modern shells, and partly also to the increased range of the torpedo. It is true for all types of ships, from the capital ship to the destroyer and submarine. In each type the tendency has been to increase the size of the gun armament and to demonstrate the paramount importance of carrying guns of the largest possible calibre. This general increase in the size of the guns has been com- mon to all navies. The British navy will, however, be taken here as typical of the changes that had already taken place before 1921 and of the further developments in progress.

Before the war, 10,000 to 12,000 yd. was considered to be the probable fighting range between squadrons of heavy ships, and it was not thought likely that these ranges would be greatly exceeded. It had now been proved that 12,000 yd. was about the minimum range at which any heavy ship action had been fought during the war, while the maximum range extended to 20,000 yd. and even beyond that. This range approaches the limits of vision at sea, except under abnormal conditions of visibility. If we take into account the use of aircraft for observing, there appears to be no likelihood of the range being reduced