Tail Fuzes No. 859 Mk I and No. 854 Mk I (Service)

Description: The Fuze No. 859, which is of the all-ways action type, has a bakelite body, waisted to form two chamfered flanges. It is threaded at its lower end to permit it to be screwed into the fuze adapter. The fuze body houses a hollow cylinder, at the lower end of which a detonator is located over a flash hole in the body of the fuze. The firing pin is positioned in the cylinder, and is split at its lower end to form a double stri-ker. The striker is held away from the detonator by a light creep spring, which also is housed in the hollow cylinder.

The upper end of the striker terminates in an enlarged head having a seating for a lead ball. The ball is held in position by the concave under-surface of a bakelite closure disc which is screwed into the top of the fuze body. Just below the striker head, the stem of the striker is drilled to receive a safety pin, which extends through the fuze body and has an enlarged head housed in the waist of the body. A short length of webbing tape, which is wound around the waist of the fuze body, is secured to the head of the safety pin. A lead sleeve, curved to fit into the waist of the fuze body, is secured over the free end of the wepping tape.

A bakelite safety cap is fitted over the fuze body, and has a fabric drogue attached to its by adhesive tape.

Operation: When the bomb is released from the Small Bomb Container, the safety cap of the fuze is drawn off by the action of air resistance on the fabric drogue. The lead sleeve on the webbing tape attached to the safety pin causes the free end of the tape to clear the waisted portion of the fuze body and to be caught in the air stream, thus withdrawing the safety pin. The fuze is now armed, with the lead ball and the striker held away from the detonator only by the creep spring.

On impact with the target, the momentum of the lead ball and the striker overcomes the resistance of the creep spring and cause the striker point to pierce and fire the de-tonator. The flash from the detonator passes through the flash hole in the fuze body, ini-tiating the action of the bomb.

If the bomb falls on the side, the ball, striker, and cylinder move sideways as an as-sembly, the ball riding up the curved surface of the closure disc and the cylinder riding up the curved surface of the body. The striker thus operates and fires the detonator.

Tail impact of the bomb would cause the hollow cylinder to move down against the creep spring and impinge the detonator on the striker.

Remarks: The Fuze No. 854 Mk I is identical to the No. 859 Mk I except that the method of arming differs slightly. In the No. 854 Mk I, both the safety cap and safety pin are spring-loaded. The safety cap holds the safety pin in place and is itself retained by an arming fork which engages the cap and the fuze body. The arming fork is withdrawn as the bomb is released from the Small Bomb Container, allowing the safety cap and safety pin to be ejected by their springs. The fuze is now armed. On impact with the tar-get, its action is identical to that of the Fuze No. 859 Mk I.

The Fuze No. 854 Mk I has a long tubular burster screwed and cemented to its lower portion. This burster tube contains a powder pellet and about 2 oz. gunpowder. It is approximately 5½ in. long, and the tubular portion is 0.9 in in diameter.

Figure 164 - Tail Fuze No. 854 Mk I