M151M123A1, M124A1, M125A1
U.S.N.B.D. - UNITED STATES - BOMBS AND FUZES; PYROTECHNICS
SECTION III - BOMB FUZES

DATA:

 

U.S. ARMY TAIL FUZES

 

 

M123, M124, M125

BOMBS USED IN

 

M123

AN-M30A1 100# G.P.

 

AN-M57A1 250# G.P.

M124

AN-M64A1 500# G.P.

(Obsolescent)

 

AN-M58A2 500# S.A.P.

 

M125

AN-M65A1 1000# G.P.

CHEMICAL TIME

 

AN-M66A1 2000# G.P.

ANTI-WITHDRAWAL

 

AN-M59A1 1000# S.A.P.

 

 

M103 2000# S.A.P.

 

FUNCTIONING

Chemical long delay fuze:

 

  delays of 1, 2, 6, 12, 24,  

 

36, 72, and 144 hours.  

ARMED CONDITION

Considered armed if drop-  

 

ped, because of glass am-  

 

poule, or after 75.6 - 190 revolutions of vanes.

FUZES USED WITH

None, though a nose anti-distrubance fuze is being developed

 

to be use with it.

ARMING TIME

75.6 - 190 revolutions.

VANE SPAN

5"

MAX. BODY DIAMETER

1.5"

OVERALL LENGTH

M123, 9.6"; M124, 12.6"; M125, 16.6"

MATERIAL

Zinc plated and dichromate coated steel.

GENERAL:

The only difference in these three fuzes is in the length of the arming stem. Larger bombs require longer arming stem so that vanes can catch the air slip from the bomb. Functioning time of these fuzes is determined as follows:

For the 1, 2, 6 and 12 hour delays, by varrying the concentration of the alcohol-acetone solution.

For the 24, 36, 72 and 144 hour delays, by varrying the thickness of the celluloid (thickness increases as delays incresse). The M19A2 detonator contains primer mixture, lead azide and tetryl.

OPERATION:

The stem case and gear system of these fuzes are identical with the fuzes in the AN-M100A2 series, except that the threads on the arming stem are right hand threads and thread downward instead of out. The pinion gear revolves around the stationary gear and in so doing rotates the movable gear, which has one more tooth than the stationary gear, one tooth per revolution. Since the arming stem is secured to the mo-vable gear sleeve, it also rotates counter-clockwise, threading down toward the glass ampoule. The arming stem exerts pressure on the ampoule cap causing the glass am-poule to break where it rests on seat disc and knife edge. Attached to the arming stem is a stem collar, which compresses a rubber washer to seal the upper part of the fuze from leakage. (334-387 revolutions of vanes to seal). In the 1, 2, 6 and 12 hour delays, the acetone or alcohol-acetone solution is freed to act on the celluloid ring retaining the locking balls. In the 24, 36, 72, and 144 hour delays, the acetone is freed to act on the celluloid disc and subsequently the celluloid ring retaining the locking balls. As the acetone or alcohol-acetone solution acts on the celluloid ring, the locking balls are for-ced out by the head of the screw which is threaded into the spring-loaded firing pin. After the predetermined delay, as effected by varying the concentration of the alcohol-acetone solution or by varying the thickness of the celluloid disc, the balls will be forc-ed clear of the screw head and the firing pin will strike the detonator.

If an attempt is made to withdraw the fuze once it has been installed, the anti-withdrawal locking ball will ride into the  the shallow part of its groove, and lock the lower fuze body to the adapter booster. Further turning of the fuze will merely unthread the upper fuze body from the lower part, allowing the spring-loaded firing pin sleeve to force the sleeve balls into the separation, driving both the sleeve and the firing pin to-ward the detonator. A separation of 3/64" of an inch activates the fuze, regardless of the length of time the acetone or alcohol-acetone solution has been acting, or if the fuze is in an unarmed condition.

REMARKS:

(a) Never attempt to withdrawn the fuze during or after installation in the bomb.

(b) If the bomb with this fuze are not dropped, they must be jettisoned over enemy territory or in the sea. They cannot be considered safe even if dropped unarmed.

(c) The fuzes should not be subjected to temperatures exceeding 120° F. (High temp. may damage celluloid ring). In the packing box are 2 vials of powder, one a green stoppered vial, the other a red stoppered vial. If temperature exceeds 150° F., powder in green stoppered vial will melt or solidify, and fuzes are not to be used for low altitude bombing. If temperature exceeds 170° F, powder in red stoppered vial will melt or solidi-fy, and fuzes must be destroyed.

(d) In assembling the detonator, care should be taken to avoid damage to the anti-withdrawal locking ball and the crimp holding this ball.

(e) Before inserting fuze in bomb, gage the adapter booster cavity with the plug gage provided in each box of fuzes. Any bomb with which difficulty is experienced in in-serting this gage, must not be fuzed with these fuzes.

(f) Later lots of these fuzes equipped with new type lock nut as shown on the M123A1 series. Later lots require 1 1/2 turns or 3/32" to activate.

M151M123A1, M124A1, M125A1