M155 (Nose Clockwork Aerial Burst)

Bombs

Functioning

Armed condition

Fuzes used with

Arming time

Vane span, inches

Body diameter, inches

Over-all lenght, inches

Material

Aluminum alloy body with zinc- or cadmium-plated steel striker

General: The Nose Clockwork Aerial Burst Fuze M155 is the same as the M111A2, ex-cept that the gear-reduction system has been eliminated. A spinner device is incorpora-ted to force the safety block to rotate with the arming vane. Elimination of the gear-re-duction system has been accomplished by removing system has been accomplished by removing the stationary gear from the arming hub, and pinning the pinion gear in place so that it cannot rotate.

Operation: The vanes are positively attached to the arming hub and rotate as one unit. The arming sleeve, which is threaded to the arming hub, is prevented from rotating, since the movable gear which is attached to it, meshes with the bound pinion gear. How-ever, the arming sleeve moves down as a result of rotation of the arming hub, and after approximately six to nine vane revolutions the arming sleeve has withdrawn far enough for the safety block to be thrown clear by centrifugal force. The remainder of the opera-tion is like the Nose Clockwork Aerial Burst Fuze M111A2.

Remarks: The M155 replaces the M111A2 in the Fragmentation Clusters M26, M27, M28, and M29, since slusters fuzed with the M111A2 sometimes failed to open with low fuze settings. The cluster flight is not always stable enough to permit arming of the Fuze M111A2 before the set time expires. Elimination of the gear-reduction system obviates this difficulty. The spinner insures ejection of the safety block at completion of arming.