Over-all length (with gaine): 4 3/8 inches.

Over-all length (without gaine): 3 7/8 inches.

Maximum diameter: 1 5/8 inches.

Threaded length: 5/16 inch.

Number of threads: 4, right-hand.

Construction: The fuze resembles in appearance a large-sized type 88 short-delay fuze. It has an aluminum striker head, a brass three-piece body, and a brass gaine. It has the following safety features: a heavy creep spring, hourglass shaped centrifugal detents under the striker, a centrifugal shutter, which is held in place until after set-back by an arming collar-latch spring arrangement, and a safety fork, which also prevents the arming collar from moving down until the fork has been removed.

Settings of instantaneous or short delay are accomplished by means of a sliding delay carrier, which has both an open channel and a powder delay channel. This delay carrier can be moved horizontally in its housing, so that either the instantaneous or short-delay is aligned with the firing train, by pushing on the proper setting pin with any sharp instru-ment. The delay carrier is held in place by friction and by centrifugal force after the pro-jectile has been fired.

Operation: Set-back forces the striker down on the hourglass detents, holding them in place, and also forces the arming collar down, compressing its spring, so that the latch springs are engaged. As set-back decreases, the striker is forced up by its spring, re-leasing the detents, which move out against their springs because of centrifugal force. The arming collar springs also forces the arming collar up, carrying the latch springs with it. This allows centrifugal force to move the shutter out, thus clearing the flash channel. On impact, the striker is driven into the primer, which flashes either into the delay ele-ment or into the instantaneous channel, depending on the setting, and from there to the detonator. The detonator initiates the gaine.

Figure 324 – Type 90 Instantaneous-Short-Delay Fuze.