Railway Artillery - Design
The various types of railway artillery may be classified to advantage by the characteristics of three chief factors in design traverse, recoil, and anchorage. Before going into the details of these classifications it should be emphasized that a very large number of the mounts were designed and constructed under the greatest possible pressure, so far as time was concerned, and from whatever materials happened to be available. In consequence, many features found in them were the result of this pressure, and in many cases were inherently undesirable.
Traverse is obtained in railway mounts by one of three methods. These are: (1) By moving the mount along a curved track or epi (nontraversing mount); (2) by rotating the railway carriage about a real or imaginary vertical axis (car traverse) ; and (3) by rotating a top carriage rotable with respect to the car (top carriage traverse).
On the nontraversing mount no provision is made either on the gun carriage or the railway car body for traversing the gun; it can be pointed in azimuth only by moving the entire mount along a curved track. The most striking examples of this typpe are the so-called Schneider mounts on which the gun is either supported on the side girders of the car or on a gun carriage that is capable of linear motion only, and that in a direction parallel to the side girders.
The nontraversing mount distinctive feature is the provision which is made for traversing the entire car body. The gun is supported in the car body, either directly on rigid trunnions, or through a cradle or top carriage without traverse, and it can be moved in azimuth only to the extent that it is possible to traverse the car body. As a rule this traverse is obtained by a slight movement of the car body on the trucks, giving a few degrees on each side of the center line. Other mounts of this type, however, were provided with an elaborate center plate with traversing rollers and are capable of large traverse or even of all round fire. The latter type, and sometimes the former as well, required an elaborate foundation and were generally provided with a large center pin which takes the horizontal component of the shock of recoil.
The Top Carriage Traversing Mounts distinctive feature is the provision of a top carriage rotable with respect to the car body. The amount of traverse varies on the different designs in use from 10 to 360 degrees. In each of these designs, with the single exception of the American 16-inch howitzer, model 1918 M1, either a more or less elaborate firing platform or some arrangement of outriggers is required.
The nontraversing mounts were all, to a certain extent, improvisations. The French termed them "affuts de circonstance. " It is the concensus of opinion that, where time and facilities permit, a small amount of traverse at least should be given, so that the gun may be trained closely in azimuth. The distinction between the other two types seems to be more essentially on the basis of caliber and muzzle energy. The top carriage type traverse is easily applied with the smaller guns while the car-body traverse is reserved for the heavier and higher powered ones.
Recoil was taken up on railway artillery by allowing the displacement of the mount or some portion thereof and retarding this motion, Characteristic provisions are made for bringing the moving part back to its original position. Such artillery may be classified in accordance with the extent of this recoiling portion into the following well-marked systems: Cradle recoil, top carriage recoil, sliding mount recoil, and rolling mount recoil. The means of retardation and of return to battery are various but each is more or less characteristic of one of these types.
Cradle Recoil characteristic is that the gun only recoils, moving backward along the Une of fire, in a sleeve or cradle. The gun is retarded and brought to rest by means of hydraulic buffers, or dashpots, attached to the cradle, and with pistons which are rigidly attached to the gun. Return to battery is obtained by helical steel springs, or by the pressure of air in a pneumatic recuperator cylinder, in which increased compression is produced by the recoil. The cradle is provided with trunnions and the cradle and gun are swung in the trunnion bearings of the carriage.
Top-Carriage Recoil characteristic is that the gun is carried in a top carriage, supported by wheels on fixed rails. The gun and carriage recoil together in a fixed direction along, these rails. Recoil is restrained by hydraulic buffers and return to battery is obtained either by gravity, through the use of inclined rails, up which the gun recoils, by springs, or on some improvised mounts, by rubber bands. An air recuperator might equally well be used, but no example of such a combination is known.
Sliding Recoil characteristics are that the gun, car body, and trucks recoil together, the car body sliding on a special set of girders incorporated in the track. The car body is provided with wooden crossbeams or "sleepers" which are jacked down on the track girders in such a way that about one-half the weight of the mount is transferred to them from the truck. The resulting friction thus created absorbs the energy of recoil and brings the mount to rest. This recoil varies from 1 to 2 meters. All of these mounts, with two exceptions the American Army 14-inch design and Italian 381-millimeter were of the nontraversing type and must be fired from a previously prepared curved firing track or epi. Counter-recoil, or the return of the gun to firing position, is obtained by jacking up the sleepers, thus returning all of the weight to the trucks and rolling the entire mount forward by the amount of the recoil. This is usually accomplished by gear trains and handwheels through which two or more pairs of wheels may be driven and exact adjustment of the mount on the track obtained. In the heavier mounts an electric motor drive is employed, and in other cases a gasoline winch has been used with success. Even with the heaviest guns ordinary car pushers, applied in sufficient number, have served as an emeigency method of moving the gun back into battery.
Cradle recoil with air recuperation is probably the highest development in recoil systems. Top-carriage recoil was devised in the 1880s for coast defense guns operated at low angles of elevation. It is not well suited to firing at high elevations. This system is found only on rail- road mounts which have been improvised from available coast defense materiel, and there seems no great reason why it would be considered for new design.
The sliding recoil system is worthy of considerable consideration. Improvised originally to provide for heavy guns, a mount which could be manufactured in a minimum of time, it has shown a ruggedness and convenience in service that have recommended it very highly. There are certain limitations on the use of this type of mount. Time of operation and lack of traverse make it unsuited to small guns. The enormous trunnion forces which must be taken care of likewise make it unsuited for the very largest howitzers firing at high angles.
The cradle-rolling recoil combination is, like the sliding system, unsuited to small guns, because of the lack of traverse and time of operation, but it represents a very satisfactory system for the heaviest type of guns.
Railway mounts may be classified according to the character of the structure required to transmit the force of recoil from the gun to the earth, as follows: 1. Mounts requiring no structure whatever. 2. Moimts requiring a track platform; ie a structure built above and more or less without disturbing the track; 3. Mounts requiring a groimd platform; i. e., a structure fitting into and under the track. Mounts Requiring no Structure The only mounts of this type are those with the combination of cradle and rolling recoil mechanism, which fire directly from standard track. They were provided with car-body traverse, giving a small movement in azi- muth, and must be fired from a curved track or epi to get greater traverse. The British 12-inch and 14-inch rifle mounts, the American 14-inch naval mount, Mark I (for firing at angles under 15 degrees) and Mark II (for elevations as great as 40 degrees), the 16-inch howitzer, model 1918 M1 (American), and German 38-centimeter are examples.
Mounts Requiring a Track Platform In mounts of this type a part of the vertical component of the force of recoil is taken by girders, pads, or floats placed on the ground or on top of the ties, and the horizontal component either by friction, or through rail clamps, guys, or struts. The Schneider sliding mounts are examples of the type in which the horizontal component is absorbed by friction. This type can have only very limited car traverse (a maximum of 5 degrees), sinc« a greater traverse will result in an abnormal displacement of the track. The 194 and 240 milUmeter Schneider mounts and the British 12-inch howitzers and 9.2-inch guns belong to the class employing rail clamps or guys. They had top-carriage or cradle recoil and in some cases afforded all-round fire. The American 8-inch gun and French 240-millimeter gun belonged to the class using struts as well as track platforms and both permit of all-round fire.
Mounts Requirino a Ground Platform The characteristics of this type is that an extensive anchorage, the installation of which involves tearing up the track, must be constructed before firing can take place. This foundation may consist simply of very heavy timber pads and floats, as with the St. Chamond 340 and 400 millimeter and the American 16-inch mounts, or it may be a very elaborate and specially constructed steel or concrete base, as with the Batignolles, and the German 280 and 380 millimeter mounts.
Two points are intimately connected with the type of anchorage employed, viz: (1) The time necessary to get into action and withdraw the moimt from position, and (2) the amoimt of traverse allowed. The former is important in effecting a surprise and in withdrawing to avoid enemy counterfire. It varies from almost nothing on the first type, after the epi is constructed, to perhaps an hour on the best of the second type, and then up to three or four days on the very elaborate mounts of the ground platform type.
As to traverse, the first type permits any desired amount, limited only by the extent of the curve, and is suited to the largest calibers; the second likewise permits of a traverse limited only by the extent of the curve for heavy guns with sUding recoil and all-round fire for the lighter and medium guns. The third type usually permits of only limited traverse (10 to 15 degrees) for the heaviest guns and all-round fire for medium calibers. It might be added that rail clamps and guys are devices adopted with the lighter guns and are to be considered improvisations; struts have proved more efficient.
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