DATA:

BOMBS USED IN

M158

M159

FUNCTIONING

ARMED CONDITION

FUZES USED WITH

ARMING DATA

VANE SPAN

MAX. BODY DIAMETER

OVERALL LENGTH

M158

M159

MATERIAL

Aluminum body with steel safety blocks and striker.

GENERAL:

These fuzes are similar to the AN-M110A1 and AN-M126A1. They differ in that the M158 and M159 have a spring actuated detonator shutter which rotates into position after withdrawal of the firing pin and is locked in place by a spring-loaded detent. In addition the arming sleeve, striker, and firing pin move upward instead of downward, and the vanes rotate freely after arming. There is no safety block in the newer series and, the striker assembly which is of heavier construction, has a retaining ring instead of a retaining pin.

These two fuzes are similar in appearance, except that the M158 incorporates a booster lead in, whereas the M159 incorporates a detonator holder. The M159 also has two arming wire guides to facilitate positioning of the arming wire.

The M158 differs from AN-M110A1 in that the body and booster holder are held to-gether by a locking pin, has the detonator in the shutter, a booster lead in mounted in the lead cup disc, and a booster below the lead cup disc.

OPERATION:

When the bomb is dropped and the arming wire pulled, the vanes rotate. The arming vane, nut, outer ball race, arming hub and stationary gear rotate as a unit, but cannot move in a vertical plane because of a collar on the arming hub. The movable and sta-tionary gears mean with the pinion gear (idler gear) and since the movable gear has one more tooth that the stationary gear, for each rotation the movable gear lags one tooth, thus screwing upward (right hand threads) and toward the stationary gear. As the movable gear moves up, it lifts the striker and withdraws the firing pin from the hole in the detonator shutter. (Retaining ring in striker groove and under arming sleeve beval enables simultaneous movement upward). After approximately 440 revolutions of the vanes, the firing pin is completely withdrawn from the detonator shutter and the deto-nator shutter and the detonator shutter is swung into position lining up the detonator with the firing pin, thus arming the fuze. The detonator shutter is locked in position by a spring-loaded detent housed in the shutter which slips into a recess in the booster holder. The vanes continue to rotate, and when the movable gear reaches the out-out portion in the pinion gear the vanes rotate freely. On impact, the striker with its firing pin are forced down, compressing the firing pin spring and piercing the detonator. The detonator sets off the booster lead in and booster succesively.

REMARKS:

In the armed condition, the striker will protrude about .25 in. beyond the vane nut, but any fuze in which the gap between the underside of the striker and the face of the vane nut exceds .125 in. should be treated as armed.