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132 which would be rendered useless by the effect of rotation and shock of discharge, and as the length of the straight spring is adjustable, the movement of the pellets of the balance, and therefore that of the escapement wheel and the clock train, are controlled and regulated. A horizontal hand, the position of which depends on the setting of the fuze, has on its under surface a notch into which fits the upturned end of the lever at the top of the striker. When the clock train is started the hand moves round with it, but is prevented from rising and releasing the lever by a ring attached to the conical housing of the fuze. This ring is provided with two slots into which the hand can fit; thus when the clock is working the rotation brings the hand into coincidence with the slots, and when forced up by the action of a small spring, it releases the upturned end of the lever. The striker pre- vious to firing has been held in the safe position by a collar on it which rests on a shoulder of the centrifugal bolt, but when this bolt is moved away by the rotation of the shell, the outer part of this shoulder still rests on a steel pin. When the upturned end of the lever is freed from the notch in the lower side of the hand, as previously described, it flies out and rotates the striker so that the collar clears the steel pin and allows the striker to fall and fire the detonator.

The setting of the fuze and the hand is accomplished by turning the housing with a suitable key, this housing being free to move before firing. On discharge it is very ingeniously clamped to the body of the fuze by means of steel pins in a ring in its under surface. This ring sets back and the pins are driven through the flange of the clock case, a groove being turned on its under side to thin the metal, and thus to allow of easy penetration.

The clock train, wound up like a watch, is started at the moment of firing by the setting-back of a detent.

The British fuzes described above illustrate sufficiently the general principles on which fuzes are designed to serve the various require- ments and to meet the various dangers. There are, however, many interesting devices and expedients included in the design of French, German and other fuzes which are not usually employed in Great Britain, and the fuzes described below have been selected as exam- ples of these devices and expedients. Some of these have been copied by British designers.

German Fuzes in general have some marked peculiarities. In the first place, especially in pre-war designs, there is a tendency to excessive complication, due to the desire to make one fuze answer for several functions. Ignoring the case of fuzes for universal shell, in which the complication resides rather in the shell itself than in the fuze, we find fuzes designed for time, im- pact and delay, or impact, delay and long delay, each system having its own equipment of safety devices as well as suitable setting arrangements. In some cases the channels bored into the fuze body with their cross-connecting channels and sealing de- vices are so numerous that the interior resembles a veritable rabbit warren. One example only of these complicated fuzes will be described here.

On the other hand, some of the devices employed are elegant in their simplicity, notably the interlocking shutter-leaves described in two of the examples below. Other points of special interest found in German fuzes are in time fuzes the provision of devices to lock the movable time ring by set-back; and in percussion fuzes (and the percussion element of T. and P. Fuzes) the use of pressed powder pellets or columns as a safety device to seal the working parts until the shell is clear of the gun.

The Instantaneous Fuzes, known in Germany as " sensitive " (empfindlich), are quite unlike the British No. 106. Although it appears that the unwrapping device of No. 106 and spigot fuzes originated in a German trench-mortar fuze, it does not appear in any of the in- stantaneous fuzes used with German guns and howitzers proper, all of which are characterized by a projecting striker rod. This striker rod (very long in the case of shell fitted with false cap) is only inserted at the last moment in the socket prepared for it in the fuze. These sensitive fuzes are all relatively simple and only instantaneous effect is attempted.

The Instantaneous Howitzer Fuze 16 C. (E.H.Z. 16 C., fig. 13) is fitted with a projecting striker rod so that the fuze comes in contact with the ground, etc., a moment before the shoulders of the shell do so, thus detonating the shell before it has time to bury itself. The removable rod fits into a rod which is supported by a creep-spring at its lower end and held in position up to the moment of firing by two centrifugal spring bolts. Below the point of the needle is a small detonator in a holder also kept in position by two centrifugal spring bolts. Below this again is the main detonator, to which the flash from the smaller one is communicated through a suitable channel. This main detonator communicates with the gaine by a fire-hole, but is screened from it by a centrifugal brass shutter, in which—out of line with the detonator-gaine fire-hole—is a charge of explosive.

On rotation being imparted to the projectile the striker needle is freed, as is also the detonator holder below it, and these are then only held apart by the creep-spring. The brass shutter swings outwards, bringing the explosive patch to its position under the main de- tonator. The fuze is now in all respects sensitive. On graze, the detonator holder flies forward and strikes the needle, which is solidly supported by a plate on the rod kept (by a spring) bearing against shoulders cut in the body. Alternatively, on impact, the striker rod is pushed in, driving the needle on to the detonator holder. In either case the detonator is fired and the flash, relayed by the patch in the shutter, passes to the gaine.

In the instantaneous fuze "Granatzunder 17" (Gr. Z. 17), shown in fig. 14, the body is fitted in its lower portion with a bush carrying five centrifugal segments, a split brass sleeve and ferrule, and a detona- tor holder, to the top of which a creep-spring is soldered. The upper half of the fuze contains a needle pellet and spring, the upper part of which is shaped to take the striker rod, and has projections that, by a spring, are kept bearing on shoulders formed in the body, as in E.H.Z. 16 C. On the shock of discharge the ferrule sets back, over- coming the support of the brass sleeve, and is locked in its rearward position by lugs on the sleeve which engage in an annular groove in the inner surface of the ferrule. The centrifugal segments are now free to take up rotation about their pivot pins, but as they are inter- locked, owing to their shape and position, they can only move one at a time, and thus an appreciable interval elapses before the percussion pellet is free. The extremities of the centrifugal segments (aided by the needle-pellet spring) take up the set-back of the needle pellet on shock of discharge, and the creep-spring keeps the percussion pellet away from the needle during flight. On impact the striker rod is driven in and impels the needle pellet, which, overcoming the resist- ance of its supporting spring, fires the detonator. Should the striker rod meet with insufficient resistance .to drive it in on impact, the percussion detonator will still fly forward on graze and fire its detona- tor as it impinges on the needle, the flash passing into the shell through the passage behind it.

This shutter device is also found in an interesting German base fuze (fig. 15), in combination with a detent of the same class as that of the British 101 Fuze, but reversed.

The fuze depends for its action on the inertia of a pellet which remains steady till impact, and then sets forward on to the needle. In travelling, the movable pellet is confined between the shutter and the bottom of its cavity, and set-back on discharge does not affect it. But as soon as the shutter-leaves rotate out of the way it is perfectly free, not even a creep-spring apparently being fitted. On firing the detent flattens its stirrup spring, and sets back, and thereupon, under