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Nose, A-7(a), for Type 2 Bomb

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1397-139

Description

Aluminum body and arming vane, brass arming spindle, striker and primer carrier. Firing pin is steel.

Threads into an adapter on the bomb body, tightened with a spanner wrench.  

The fuze body is of one piece construction. It is closed at the forward end by a threaded closing disk. The after end is threaded externally to screw into the bomb and internally to receive the gaine. The base of the body is pierced centrally by a flash hole.

A single arming vane is held in the safe position against the fuze body by a safety pin which fits through a brass nub protruding from the fuze body. The arming vane is hinged to a brass arming spindle. The spindle threads through the fuze body and extends through the striker body.

The all-ways action unit is housed within the fuze body, the cavity of which is tapered so that the diameter at the base is smaller than at the nose. The outer ends of the striker and primer carrier assembly are domed. The striker body is of solid brass construction with a sharp steel firing pin in the base. A hole is drilled through the body to receive the arming spindle. The primer carrier is made of brass and consists of a barrel threaded at one end to receive a male base plug containing the primer. In the outer diameter of the plug are drilled four flash holes. The inner diameter of the barrel is large enough to accommodate the striker body. A light spring holds the two apart.

Since this fuze is designed not to fire when the bomb strikes on its nose, UXB's may be found without in any way having failed to function as designed. Because the creep spring is quite weak, a highly sensitive and dangerous UXB can be expected.

Functioning

The safety pin is withdrawn from the arming vane before the bomb is thrown from the plane. The vane rotates causing the arming spindle to thread out of the fuze body and fall free. On impact with a solid object, the striker and primer are cammed together overcoming the force of the spring. The flash from the primer passes through the flash holes, ignites the relay which in turn sets off the gaine.

Hazardous Components

Primer and gaine. Gaine incorporates a black powder relay.

Physical Data

Length, overall (with gaine) - 2.125 in (54 mm)

Width, overall - 1.75 in (44.5 mm)

See Also

Japanese Bomb Fuzes

Source(s)

TM 9-1985-4, Japanese Explosive Ordnance (Bombs, Bomb Fuzes, Land Mines, Grenades, Firing Devices and Sabotage Devices) (1953)

OP 1667, Japanese Explosive Ordnance, Volume 1 (1946)

TM-E9-1984, Enemy Bombs and Fuzes, Section VII, Japanese Fuzes (1942)