EMPLOYMENT: Used in 5-cm H.E. shell. (See fig. 575.)

DATA:

Overall length: 1.719 inches.

Maximum diameter: 1.312 inches.

Threaded length: 0.312 inch.

Number of threads: 5 RH.

CONSTRUCTION: This is a detonating type with a direct action in which the needle is supported by a shutter.

The direct action mechanism consists of an aluminum needle supported over the detona-tor by the shutter, which engages under the enlarged head on the needle. An aluminum striker is positioned in front of the needle in a recess in the cap of the fuze. The recess is closed against air pressure by an aluminum disc.

The shutter slides in a diametrical groove in the front of the body where it is retained in the safe position by means of two centrifugal steel bolts. The bolts are housed in holes in the body within an expanding spring ring and engage in slots in the shutter. The shut-ter has two holes formed in it, one on each side of its center. One of these holes has formed in the inner side of its periphery, a recess which expands to the center of the shutter and receives the needle. The dimensions of the recess prevents the head of the needle passing it but the hole will permit this movement when the sutter is in the armed position. With the shutter in the unarmed position, the second hole conicides with a channel in the body which houses a shell ball.

The brass magainze of the fuze is fitted to the underside of the body means of an alumi-num screwed plug. The magazine is fitted with a brass detonator containing 0.33 gram of lead azide with calcium silicide over a filling of 48 grams PETN.

ACTION: On acceleration, the ball is held in then channel by set-back. During flight, the ball is cuased to move forward by creep action combined with the effort of the slope of the channel and centrifugal force until it enters the hold in the shutter. The rotation of the shell also causes the spring ring to expand and the bolts to disengage the shutter which, with the ball as a displaced weight, slides across the body and ceases to support the needle at the head. The needle is then held off the detonator by creep action. On impact, the needle is driven in and pierces the detonator.

REMARKS: Sometime marked A.Z. 39ZN.

Figure 575 – A.Z. 39