Position and method of fixing in bomb: Screwed into the modified nose of the type 1 Army bombs. (Right-hand thread.) Antiwithdrawal locking device is fitted to prevent re-moval.

Components of explosive train: Primer, powder train relay, gaine, and booster.

Fuzes likely to be found with: E-1 (a).

Delay times: 2 hours to 24 hours (may be shorter or longer).

Threads: 2 31/32 inches in diameter, 12 thread per inch.

Description: The fuze consists of the fuze body, a nose cap which will not usually be found on a UXB, and a collar which joins the booster to the body. An antiwithdrawal de-tent prevents the fuze form being unscrewed by hand. An arming spindle is hollowed out to house a copper tank filled with acetone. The arming spindle is held in place by two spring-loaded detents. A screw-driver slot in the top of the spindle allows it to be turned from the safe position (+) to the armed position (–) marked in red meaning "firing point". The rotation of the spindle is regulated by the length of the grooves into which the spring-loaded detents are fitted. When in the armed position, the four cut-away seg-ments of the spindle are in line with the raised portions of the inertia weight, thus allow-ing the latter to move up on impact. The inertia weight is held by two shear wires which are sheared on impact. Two spring-loaded detents hold the inertia weight in position be-fore impact. On impact, the inertia weight moves up toward the top of the fuze, and is locked in this position by these detents. This insures that the firing pin is in line with the primer. When the inertia weight moves up to the armed position, the safety detents re-mains behind, leaving the firing pin held only by the striker release pin bearing against the soluble plug. When this plug dissolves, the pin moves up, freeing the striker and allowing it to be pushed into the detonator by the spring behind the striker. A rubber sealing ring keeps the solvent from running throughout the fuze after the acetone tank is pierced.

Figure 108 – C-3 (a) Bomb Fuze.

Operation: Nose cap is removed. The arming spindle is turned to the firing point (–). This turns the spindle so that the inertia weight is free to move ahead on im-pact. The spindle is locked in position by spring detents. The nose cap may be replaced. On impact, the inertia weight shears the shear wires and moves ahead. The striker is lined up with the primer and is moved away from the stop pin. The acetone tank is pierced and the inertia weight is locked in the armed position by detents. After the acetone has softened the soluble plug, the striker release plunger moves out under spring action releasing the cocked striker which fires the primer.

Remarks: (a) Once the arming spindle is turned through 45° to the firing point, it cannot be turned back to safe. The spring-loaded detents prevent this. Also, af-ter impact, the inertia weight has moved on to the spindle and will prevent rota-tion.

(b) If the cap is found on a UXB, the fuze may have been armed and the cap may have been replaced.

(c) The antiwithdrawal detent will usually prevent the fuze from being removed from the bomb. If the fuze is removed, the booster and gaine may be set off if the fuze operates later. Therefore, unscrew the booster and gaine immediately after withdrawing the fuze.

Note. – Actual time test run by Allied forces on the C-3 (a) types A, B, C, and D gave the following average delays:

Type A

Type B

Type C

Type D

These tests were run under field conditions which whould closely approximate actual dropping of the bomb.

Figure 109 – C-3 (a) Bomb Fuze.