BOMBS USED IN:

FUNCTIONING

FUZES USED WITH

MAX. BODY DIAMETER

OVERALL LENGTH

COLOR

DESCRIPTION:

The fuze consists of a body into which is screwed a striker housing and a magzine containing gunpowder and housing a percussion cap. Inside the striker housing is a spring-loaded striker retained in the cocked position by three retaining balls located in holes in the striker housing. These balls engage a sloping shoulder on the striker and the tapered internal surface of a sleeve surrounding the striker housing. The sleeve is held against axial movement, while the striker is in the cocked position, by three larger balls which are located in three further holes in the striker housing, these larger balls engaging the parallel portion of a cone-ended arming pin secured to a boss in the end of a vacuum bellows. The nonpointed end of the striker has a hole into which the point-ed end of the arming pin can enter.

One end of the vacuum bellows, together with a stop plate, forms the closed end of a cylinder which passes over the striker housing and abuts against a washer located in a cup. An arming spring is compressed between the cylinder and the fuze body. Inside the vacuum bellows is a spring which controls the expansion or contraction of the bel-lows by atmospheric pressure.

The cylinder, when the fuze is unarmed, is held down towards the magazine by an arming screw which is screwed through an arming vane support carried by a thin outer cover attached to the fuze body by screws.

The arming screw supports an arming vane so mounted on the arming screw that it is permitted approximately half an inch of free travel before it locks against the head of the arming screw. Two stop pins, one projecting from the arming vane support and the other from the hub of the arming vane, prevent the arming vane from binding against the arming vane support.

The arming vane is protected against damage, premature rotation, and freezing by an arming vane cober which is bedded against the outer cover of the fuze. The arming vane cover is fitted over three clips riveted to the outer cover. A vane stop, riveted to the inside of the arming vane cover, prevents premature rotation of the arming vane due to vibration. A lug is provided on the arming vane cover for attachment to the fuze setting control link of a bomb carrier.

The outer cover has four vent holes to permit air to escape from inside the cover, thereby relieving excess pressure which builds up inside the fuze while the fuzed wea-pon is failling, after the arming screw has fallen away. The vent holes are covered by white adhesive tape on which in black letters is the following instruction: "TO BE REMO-VED AFTER FLARE IS FIXED ON CARRIER".

A safety pin is housed in the fuze body and is loacted between the striker and the percussion cap so that, should the striker be prematurely released, the safety pin will prevent its firing the cap. The safety pin is held in place by a shear wire located in a groove round the fuze body and in a slot in the head of the pin. A spring, housed in the body, is compressed beneath the head of the safety pin. A clip is mounted on the shear wire and can slide along the wire.

OPERATION:

When the fuzed weapon is dropped from the plane, the arming vane cover is pulled clear leaving the arming vane exposed, and the shear wire is broken, allowing the spring to eject the safety pin. The arming vane the rotates freely on the arming screw until it becomes locked on the head of the arming screw, after which the screw rotates with the vanes until they both fall away from the fuze. The cylinder, together with the va-cuum bellows, will then have been moved by the arming spring so that the stop plate rests against the inner end of the setting screw. This movement of the cylinder with-draws the arming pin so that the balls engaged by the pin rest against the cone-shap-ed end of the pin.

As the weapin continues to fall, atmospheric pressure increases, and the vacuum bellows contracts, thus compressing the spring in the bellows and withdrawing the arm-ing pin. When the weapon reaches a region of the predetermined barometric pressure, the arming pin will have moved to a position such that the balls are pressed inside the striker housing by the sleeve. This permits the sleeve to be sequezed, by the action of the striker spring, away from the magazine end of the fuze until the balls engaging the striker are freed and fall away. The striker is released and is forced by its spring against the percussion cap which fires the gunpowder in the magazine.

REMARKS:

1. The No. 867 Mk I is a TAIL fuze. Instead of an arming vane, it incorporates a "T" bar which engages an arming fork on a standard type British Tail Unit.

2. The No. 860 Mk I differs from the Mk II in that the zinc colored section of the fuze is of greater diameter than the rest of the body.

3. The No. 885 Mk I is the same as the No. 867 Mk I except that it incorporates a 2-second delay.

4. The No. 896 fuze is the same as the No. 860 Mk II except that a delay element has been introduced between the cap and the magazone. The fuze is designated either A2, A3, or A4, the figure in each case indicating length of deleay in seconds.

5. No. 886 fuze incorporates a shear wire to prevent arming at low speeds. Like No. 867 Mk. I with 1 second delay.