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Aviation History
1914
1914 - 1156.PDF
I/OGHTJ advantage that, should it miss its target it will not explode and thus cause damage to friendly troops on striking the ground. As, however, the Krupp shells are the most successful, a fuller description of one of these may be given in order that an idea may be obtained of what our aviators at the front have to contend with. ^ v\ I'I 'ii C5 +'W 'TV Fig. 7.—The anti-aircraft shell manufactured the Krupp firm of Essen. by The Krupp shell (Fig. 7) is divided into two parts. The front portion, B, which has very thick walls, is screwed into the rear part, Bi, which has comparatively thin walls, and is locked in position by means of the set screw, b. The internal hollow spaces of the two parts of the shell are separated by the thick floor of the front part. The small space in front is fitted at the top with a screw thread for the reception of the percussion cap, A, which is held in position by the set screw, a. Contained in the hollow space below the percussion cap is the explosive charge, S. The large hollow space in the rear portion of the shell is filled with the smoke producing material which gives out a thick easily visible smoke, but does not develop any high pressure gases which might adversely affect the path of the shell. The flames produced are allowed to escape through the openings, bi. Ignition of the smoke charge is effected by the igniter, L. When the shell is fired, the shock causes the detonator, which is ordinarily kept from contact with the striking needle by means of a spring, to fly back on to the needle, and the heat thereby generated causes a small flame, which is led through small openings to the smoke charge in the rear of the shell. The smoke of this charge is, as we have already pointed out, allowed to escape through the openings, bi, and forms an easily visible trail behind the shell, the path of which may thus be followed by the gun crew. The smoke charge is placed behind the explosive charge in order to keep the centre of gravity of the shell sufficiently far forward to ensure a good flight path. The fuse must be exceedingly sensitive in order to operate on the slight shock caused by the shell hitting the envelope of an airship, and at the same time it must not be brought into action by the rotation of the shell or by the air resistance. The percussion fuse consists of a main body, 1, NOVEMBER 2J> 1914. which receives all the other parts. In the upper part are situated the bearers for the check pieces, 3, and the screw thread which receives the fuse cover, 2. In the lower part is the cavity for the two pawls, 5, the passage for the needle piece, 7, and a screw thread for the reception of the case containing the detonating charge, 8. Two horizontal passages take the pivots, 4, and a vertical passage accommodates the check pin, 10. The fuse cover, 2, serves as a guide for the cap, 9, and closes the top of the fuse. The five check pieces, 3, are made of brass and pivot round pins secured in the main body of the fuse. The two steel pawls, 5, are held on the two bolts, 4, and rest their upper ends on the hammer and their lower ends grip the needle piece, holding it in position against the action of the spring, 6. The case, 8, contains the ignition cap, the explosion cap, and' the ignition charge. The hammer, 9, which is made of aluminium, is mushroom shaped at the top, and carries a collar with two flanges. The check pin, 10, is forced upwards by the action of the spring, 11, and prevents the first check piece, a, from swinging outwards during transport. The check pieces are so arranged that the centrifugal force caused by the rotation of the shell causes them to swing outwards one by one, thus insuring that the fuse shall not be brought into action until the shell has reached a point some distance away from the gun. The hammer is locked in position by the upper flange on the collar, which is pre vented from moving upwards by engaging in a circular recess in the base of the fuse cover, and the check pieces, 3, prevent the hammer from moving downwards. The two steel pawls are pivoted round the bolts, 4, and lower arms are made heavier than the upper ones. The centrifugal force set up by the rotation of the shell causes the upper arms of the pawls to press inwards on the lower flange of the collar. The coil spring presses the flange on the needle piece against the claws of the lower arms of the pawls. The friction of the upper arms of the pawls against the upper flange of the collar, and the pressure of the coil spring is, however, only just sufficient to prevent the hammer from being forced back by the air resistance on the nose of the shell, and thus prevents a premature firing of the shell while passing through the air. When the shell is fired the check pin, 10, overcomes, on account of its inertia, the action of the check spring, 11, and by moving back allows the check piece, «, to swing outwards on account of the centrifugal force. The with drawal of the check pin has released the first check piece, a. The second check piece, b, is kept in its place until the check piece, a, has swung fully out, and it is not until then that the next is released, and so on for the whole set of check pins. As soon as the last check piece has swung out the hammer is free and the percussion fuse ready for action. When the shell strikes the hammer is forced back and the lower flange of the collar no longer prevents the upper arms of the pawls from moving inwards, or, in other words, the lower arms of the pawls from swinging outwards, which they do on account of the centrifugal force. In moving outwards the claws on the lower arms of the pawls release the needle piece which is then forced by the spring down against the percussion cap, thus starting the explosion. A certain amount of danger exists of course in case the shell misses the airship, as it will explode on returning to the ground, but as the charge is comparatively small the damage done is in most cases inconsiderable. 1156
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