ALLIED BOMBS AND FUZES

DESIGNATION

PRINCIPAL MARKING

(A) No. 28 Mark I

(A) No. 28

(B) No. 28 Mark II

Mark I

CLASSIFICATION

Mechanical Tail Impact

(B) No. 28

TYPE OF MISSILE

(A) H.E. - G.P. Bombs

Mark II

(B) G.P. & S.A.P. Bombs

MARKINGS AND

BOMBS USED IN:

SUBSIDIARY

(A) In the tail of:

MARKINGS:

250 lb. G.P. Mark IV

500 lb. G.P. Mark IV

(B) In the tail of:

250 lb. & 500 lb. G.P. Mark IV

250 lb. & 500 lb. S.A.P. Mark V

OPERATION

As the arming vanes (See Remarks) rotate, this motion is transmitted to the fork screwed into the striker by means of the arming vane spindle. After the fork has unscrewed, the striker is free to move but is held position by the creep spring. On impact, the striker overcomes the inertia of the creep spring and moves forward, piercing the primer.

Data

No. 28 Mark I and No. 28 Mark II

1

COLOR

2

OVERALL LENGTH

4.0 inches (less booster)

3

OVERALL WIDTH

1.9 inches

4

MATERIAL OF CONSTRUCTION

5

DESCRIPTION

The fuze consists of a body threaded externally with the 1.1 inch standard thread and the upper part knurled to facilitate handling. The striker, threaded at one end, is prevented from rotating by a set screw in body of fuze which rides in a groove in the side. To prevent the striker from moving when in the unarmed position, the upper part of its body is against a shoulder of the fuze body and a threaded fork screws down on the shoulder of the fuze body from the other direction. A creep spring, fitted between the striker and the end of the fuze body is held in position by a washer, the washer being retained by spinning over the end of the fuze body. In the No. 28 Mark II fuze, the creep spring is held in position by a thread holder which screw into the lower end of the body. The locking device consists of a spring collar around the body with projections on its under side which engages in indentations in the body. A projecting lug is formed on the lower edge of the col-lar. When the fuze is screwed into the bomb, this lug engages one of the holes in the face of the exploder container. The body of the fuze can then be screwed home independently of the spring collar and is kept from working loose by engage-ment of the projections on the collar in the body indentations.

Safety Devices:– During transit the fork is prevented form rotating by a safety plate which passes through it and engages slots in the pistol body. A pressed cap, fitting over the end of the pistol body, prevents entry of dirt and moisture. The in the carrier, the arming vanes (See Remarks) are prevented from rotating by the fuzing wire.

6

POSITION AND METHOD OF FIXING IN BOMB

Screwed by hand into exploder tube adapter in base of bomb and secured by a spring locking collar.

7

FUZES LIKELY TO BE FOUND WITH

Nose: No. 27 Mark I

8

COMPONENTS OF EXPLOSIVE TRAIN

Individual exploder tube at base plate, containing detonator and exploder.

9

ARMING TIME

10

REMARKS

1. The No. 28 fuze is similar in principle to the No. 5B fuze except that it is fitted with a locking device and is not fitted with an arming vane.

2. These fuze are not fitted with arming vanes as the vane are a part of the tail unit of the bomb. In place of the vanes, these fuzes are fitted with a fork which screws on the striker thread. When engaged and rotated by the corresponding fork on the arming vane spindle in the tail unit, it unscrews and the striker is free to function on impact.