Field artillery materiel

by Unknown

RECOIL MECHANISM.

The recoil system of the gun carriage consists of a recoil brake, a counter recoil mechanism and a counter recoil brake. The function of each part is apparent from its name. Various systems of checking recoil on field guns have been used, among them may be mentioned; friction devices including brakes on the wheel, inclined planes, pneumatic and hydraulic brakes. All have either been superseded by the last named or are used in connection with hydraulic brakes. The power of the brake lies in the pressure produced in the cylinder through the resistance to motion offered by the liquid flowing through apertures. By varying the size of these apertures the braking effect may be controlled so as to fulfill the conditions demanded by the service. In designing the brake, the effect of the counter recoil system, angle of fire, length of recoil, friction and pressure within the cylinder must all be considered. In howitzers which are designed to be fired at high angles of elevation, the recoil must be shortened to prevent the breech striking the ground, a condition successfully met. Since the pressure due to recoil is ultimately led into the ground through the trail and spade, consideration must be given to the problem of the moment of inertia about the trailspade. The tendency to turn over backward about the spade as the center is offset by the amount of the weight of the carriage with respect to the same point. This raises the question as to how much pressure may be allowed to act to the rear; all of which must be considered in designing the carriage. The counter recoil systems in general use are two: spring or pneumatic. The former is illustrated in our 3” and 75-mm field guns, the latter by the French 75-mm gun and 155-mm howitzer. Their purpose, of course, is to return the gun “into battery” after it has recoiled on the carriage.

The recoil mechanism is a study in itself, of which there are two schools—the advocates of the spring and of the air recuperators. Great Britain, Germany and the United States have been the advocates of spring recuperation and France of air recuperation. Great Britain and the United States were of the spring school, undoubtedly, because of the lack of a satisfactory air recuperating system; which is rather strikingly proven by the fact that both countries have adopted air recuperation since they have procured or developed satisfactory types.

Both schools have grounds for their position, however. The spring school has in its favor simplicity of design and manufacture and ease of replacement, which can be done in the field. On the other hand, spring recoils have many breakages and greater weight combined with a high replacement of weakened springs, the life varying from 3000 to 8000 rounds.

The air school has in its favor a high order of efficiency—smoother action, general all around efficiency and less weight. But the air recuperator is difficult to manufacture, costly, and when damaged must go to the rear to be repaired; which, however, it seldom needs.

In mounting the spring recuperator, the most recent practice has separated the recoil mechanism from the springs in order to distribute the piston rod pull, thus preventing whip and allowing easy access to the various parts for replacement, refilling and repairs. In order to lower the center of gravity, the gun is slung under the recoil cylinder with the two spring recuperators below and on either side.

Air recuperators are invariably located below the gun for protection and because of their large size and shape, which adapt them for attaching the elevating mechanism.

BATTERY OR FIRING POSITION

IN-BATTERY OR FIRING POSITION

HYDRO-SPRING RECOIL SYSTEM

HYDRO-PNEUMATIC RECOIL SYSTEM WITH FLUID IN DIRECT CONTACT WITH THE AIR

In either system, the recoil is taken up by means of oil or glycerine and water passing through an orifice created by a slotted piston passing over ribs of varying height, or through a valve on the pressure side of the piston, or by a solid or perforated piston passing through a perforated intermediate cylinder.

The latter type is particularly adapted to variable recoil guns as the intermediate cylinder can be rotated, thus throwing varying orifices into position for the flow of oil.

Counter recoil is accomplished by the springs or by the air pressure in the hydro-pneumatic system, in which the air pressure is sufficient to hold the gun in battery at all elevations and is built up at recoil.

In all counter recoil systems, it is necessary to insert a buffer to take up the remaining energy of the springs or air pressure so as to bring the gun into battery without appreciable jar. Numerous types have been developed and perfected.

The counter recoil brake or buffer in our 3”-gun is a slightly tapered bronze rod, tightly fitting in the cylindrical bore of the piston rod. The retardation caused by forcing the oil in the piston rod out through the small clearance between the buffer and bore of the piston rod eases the return to battery without jar to the gun, which has been forced back by the counter recoil springs.

The physical law that action and reaction are equal has a peculiar emphasis when applied to the firing of a piece of high powered artillery. The force exerted to throw a heavy projectile 7 miles or more from the muzzle of the gun is toward the breech of the weapon in its recoil. How some of these forces are handled safely and easily by mechanical means are almost beyond the mind’s grasp. Not long ago a touring car, weighing two tons, traveled at the rate of 210 miles an hour along a Florida beach. Conceive of such a car going 337 miles an hour—which is much faster than any man ever traveled; then conceive of a mechanism which would stop this car, going nearly six miles a minute, stop it in 45 inches of space and one-half a second of time without the slightest damage to the car. This is precisely the equivalent of the feat performed by the recuperator of a heavy howitzer after a shot.