DATA:

BOMBS USED IN

FUNCTIONING

ARMED CONDITION

FUZES USED WITH

ARMING TIME

VANE SPAN

MAX. BODY DIAMETER

OVERALL LENGTH

MATERIAL

Aluminum alloy body with zinc or cadmium plated steel striker.

GENERAL:

The M144 is similar to the M146 described on page 183, except for the following:

Direct drive, instead of gear reduction arming, results in ejection of the safety block after approximately 6-9 turns of the arming vane. The direct drive involves the removal of the stationary gear from the arming hub, the movable gear from the arming sleeve and the idler gear from the pin. The arming sleeve stop plate fixed to the bottom of the arming sleeve has a fork which engages the pinion gear pin and prevents the arming sleeve from rotating. This change was made to ensure that the safety block is ejected in less than the mechanical functioning time of the fuze.

In addition, the M144 incorporates a clock mechanism which runs 3 time as fast as the M146 clock mechanism. This results in a minimum setting of 1.6 seconds (instead of 5), a maximum setting of 30.6 seconds (instead of 92), and a slider arming time of 1.5 ± .5 seconds (instead of 4.5 ± 1.5). Because of the shorter running time the clockwork is more accurate in the M144.

OPERATION:

Upon release of the bomb the arming wire is withdrawn from the fuze, the vanes are free to rotate and the arming pin jumps out. 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 stop plate attached to it engages the idler gear pin. However, the arming sleeve moves down due to rotation of the arming hub, and after approximately 6 to 9 vane revolutions the arming sleeve has withdrawn far enough for the safety collar to be thrown clear by centrifugal force. The timing disc, meanwhile, has been rotated by the spring-driven clockwork. After 1.5 ± .5 seconds of rotation, the timing disc cam, located below the timing disc (and turning with it), frees the crank-shaped end of the arming stem. Balance of operation same as M146 fuze, page 183.

This fuze is not procured for Navy use.