BOMBS USED IN

FUNCTIONING

ARMED CONDITION

FUZES USED WITH

ARMING TIME

MAX. BODY DIAMETER

OVERALL LENGTH

COLOR

DELAY TIMES

DESCRIPTION:

This fuze is a fatigue type long delay fuze with delay times designed to vary from ½ min. to 6 hrs. at 50° F. The designed delay time is set during the manufacture of the fuze and cannot later be altered. The nominal delay time cannot be ascertained from the external appearance of the fuze. At higher or lower temperatures, the delay times will vary considerably from those designed at 50° F. At below freezing temperatures the fuze has been known to delay 26 hrs. befor functioning.

The fuze consists of a brass body, bored entrally to house a striker guide spring, located between a shoulder at the top of the striker guide and the top of the shutter holder.

The shutter holder is of machined brass and is threaded into the bottom of the fuze body. It contains a spring-loaded detonator shutter.

The striker guide contains a striker pellet under double spring load from the two stri-ker springs. An annular groove in the pellet is engaged by three retaining balls, located in holes in the striker guide and prevented from moving outward by the walls of the shutter holder. Beneath the striker pellet, and loosely fitted to it, is a striker block and striker. A lead delay wire passes through the striker block and the striker guide. A hori-zontal channel bored in the top of the striker guide contains two spring-loaded locking detents. In the unarmed position, these detents bear against the walls of the fuze body.

The striker guide is held compressed against its spring by an arming pin and by the vertical arming detent. The vertical arming detent, in turn, is held in position by the end of the horizontal arming detent. The horizontal arming detent contains an inertia pin which engages a hole in the top of the fuze body, preventing the horizontal detent from moving.

Safety during shipment and storage is provided by a threaded safety screw in the top of the fuze body, preventing accidental removal of the arming pin. In addition, the end of the striker in the unarmed position fits into a blind hole in the detonator shutter, holding the detonator out of alignment.

OPERATION:

The safety screw is removed manually when the bomb is loaded into its cluster, and the arming pin is withdrawn by the parachute shrouds as the parachute opens. The striker guide now is held depressed against its spring only by the series of arming de-tents.

On impact, the inertia pin in the horizontal arming detent moves downward against its spring, and the horizontal detent is allowed to be forced over by the vertical arming detent, which is pushed upward by the striker guide and spring. When the striker guide riese, the two locking detents are forced into the enlarged recess in the top of the fuze body, firmly locking the striker guide in the raised position.

Simulatenously, the retaining balls are freed, and the spring-loaded striker pellet is forced against the striker block. The striker has been removed from the detonator shut-ter, which is now caused by its spring to align the detonator with the striker.

The entire force of the twin striker springs now bears against the delay wire, which eventually shears and allows the striker to pierce the detonator, initiating the bomb.

REMARKS:

1. Two additional fuzes designed for this bomb, and identical in external appearance, are under development by the British. Designated No. 881 and No. 883, the former in-corporates and anti-disturbance feature with the long delay functioning, and the latter is anti-disturbance only.

2. No. 880 Mk I: This is an earlier model of the No. 880 fuze and is identical to the Mk. II, except that the arrangement of the shutter holder is slightly different.