AN-M120A1 and M170 (Mechanical Impact)

Bombs

AN-M120A1

M170

Functioning

Armed condition

Fuzes used with

Arming time, seconds

AN-M120A1

M170

Body diameter, inches

Over-all lenght, inches

Material

Aluminum alloy body; cadmium-plated striker and striker head

General: The Mechanical Impact Fuze M170 duplicates the AN-M120A1 in all respects except for the arming time, which is shortened to 1.5 (± 0.15) seconds in the M170.

Operation: As the parachute opens, the arming wire is withdrawn from the arming pin, which is then ejected by the arming-pin spring. Ejection of the arming pin frees the arbor, a semicircular projection on the timing shaft, to be rotated by the clockwork me-chanism. A regulator controls the oscillation of the clockwork governor, and is properly adjusted at the factory. The slider pin rides against the inside of the arbor under pres-sure of the slider spring. After the arbor has been rotated a full 160°, it clears the slider pin, allowing the slider to be forced across the fuze by the slider spring, lining up the de-tonator with the firing pin. A spring-loaded detent locks the slider in position. On impact, the striker head is forced in, driving the firing pin into the primer detonator and detonat-ing the bomb.

Remarks: The M120 and AN-M120 did not have the clockwork regulator, and had an arming time of 2.5 (± 0.25) seconds; hence, attacks had to be made at higher levels. External appearance of all designs is the same.

This fuze is replacing the AN-M104 in the parachute fragmentation bomb.

The M170 is designed to supplant the AN-M120A1 in all bombs receiving the AN-M120A1, except for the 120-pound Para.-Frag. Bomb M86, which will continue to use the older fuze.

Figure 330. Nose Fuze AN-M120A1