Description
The fuze consists of three main parts: the body, the striker spindle, and the arming vane assembly. The striker spindle is located in the fuze body by means of a locating screw and a shear wire which prevent the spindle from rotating or moving forward until impact. The upper portion of the spindle is threaded, while a steel firing pin is screwed into the lower end. The arming vane assembly consists of a nose cap, arming vanes, and arming sleeve. The arming sleeve, internally threaded, screws onto the spindle and its length of travel is limited by a stop screw threaded into the top of the spindle. To this sleeve, the nose cap and arming vanes are attached by four short screws. The lower end of the fuze body is internally threaded to take the standard Japanese gaine or magazine.
A heavy wire eyelet is attached to the side of the fuze body and serves as a guide for the starting wire. The starting wire is soldered to the nose cap in two places and gives an initial turn to the arming assembly when the bomb is dropped. A safety fork fits into the upper portion of the fuze body, one prong of which extends up through eyelets of arming vane assembly to prevent premature vane rotation.
The threads on the striker spindle are 12 threads per inch.
A variation of this fuze has been found with a fiber nose cap. Soldered around the cap with holes located over six projections on the cap is a thin steel band to which is soldered the starting wire. The arming sleeve, striker spindle and shear wire are brass with the remainder of the fuze unpainted steel alloy. All dimensions are the same as the standard A-3(a), Type 97, Mk 2, Model 1.
The upper portion of the fuze body down to the external threads is exactly the same as the A-3(e) as regards construction and dimensions.
Functioning
On release of bomb, the arming wire pulls the starting wire through the eyelet, breaking it loose at the soldered points and simultaneously imparting an initial rotation to the arming vane assembly. In seven revolutions, the arming sleeve rises up the striker spindle to lock against the stop screw and arm the fuze. On impact, the entire assembly (vanes, nose cap, sleeve and spindle) are driven inward, shearing the shear wire, and the firing pin pierces the primer.
Hazardous Components
Standard Navy gaine.
Physical Data
Length, overall - 5.5 in (140 mm)
Width, overall - 2.2 in (56 mm)
Vane span - 3.5 in (89 mm)
See Also
Bomb, 60 kg Land, Type 97 No. 6
Bomb, 60 kg Ordinary, Type 99 No. 6
Bomb, 250 kg Ordinary, No. 25 Model 2
Bomb, 250 kg Ordinary, Type 99 No. 25 Model 1
Nose, A-3(d), Type 97 Mk 2 Model 1
Nose, A-3(e), Type 3 Nose Priming Mechanism Model 2
Nose, A-3(f), for Type 2 No. 50 Ordinary Model 1
Tail, B-2(a), for Type 99 No. 25 Ordinary
Tail, D-2(b), Aerial Burst
Tail, D-2(c), Aerial Burst
Source(s)
OP 1667, Japanese Explosive Ordnance, Volume 1 (1946)
TM-E9-1984, Enemy Bombs and Fuzes, Section VII, Japanese Fuzes (1942)
