DATA:

BOMBS USED IN

FUNCTIONING

ARMED CONDITION

FUZES USED WITH

ARMING TIME

DIAMETER OF FUZE

LENGTH (w/booster)

SPINDLE LENGTH

MATERIAL

Three zinc alloy castings, top, middle, and base, held together by three long screws.

GENERAL:

The top section of the fuze is centrally threaded for the arming spindle, the middle section houses the clockwork and firing mechanism, and the base section is a simple flat casting added only to afford a means of screwing the plastic booster cup to the fuze. The fuze screws into the bomb with a left hand thread and is tightened with a spanner wrench which fits into the two spanner holes in the top of each fuze. Luting on the threads insures a tight, moisture-proof fit. Assembly of the fuzes in the bombs is done at the factory.

OPERATION:

"GROUND" Burst:

The release arm is prevented from moving in the unarmed position by the presence of the arming spindle. The release arm is attached to the release rod, which has a cut-away section against which the spring-loaded striker bears (see Fig. 6). When the arm-ing spindle unthreads about 3.5 turns, the pressure of the striker against the release rod causes it to rotate and move the release arm in a clockwise direction. A gear train, through which the external teeth of the release arm pass, controls the speed of the re-lease arm and in 2.5 seconds the release arm engages the stop arm. Both the stop arm and release arm are prevented from further rotation by projection on the impact detent (Fig. 5). The fuze is now fully armed (see Fig. 7). On impact, the impact detent over-comes its light coil spring due to intertia, and as it is forced down, permite both the stop arm and the release arm to be rotated further under influence of the striker spring against the cutaway release rod. The release rod thus rotates until the striker is no longer retained by the cutaway section, and the striker fires the detonator cup (see Fig. 8).

"AIR" Burst:

When the setting switch is set for "AIR" burst, the fuze operates exactly as above except that the impact detent has already been depressed by means of the spring-loa-ded plunger under the setting switch (Fig. 5). In this condition, the projection on top of the impact detent does not offer any resistance to the release arm and stop arm during their travel across the face of the mechanism. Hence, the striker to fire the detonator as soon as the release arm and stop arm have by-passed the impact detent and the release rod has rotated sufficiently to free the striker.

REMARKS:

This fuze is the only one of the three fuzes for the M83 4 lb. Frag. (Butterfly) Bomb which can be identified after it has been inserted in the bomb. Its setting switch, mark-ed "AIR-GROUND" on top of the fuze, identifies it. This fuze is a copy of the German (41) Butterfly fuze.

In present production, an all-ways action detent replaces type of detent shown in Fig. 5.