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131 fuze


Well-Known Member
Premium Member
Attached is a picture of a 131 fuze. VERY sensitive, nearly all the ones you see are minus the gain.



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Can anyone post a diagram of this fuze?

Isn't this the one from the 1 Pounder Mark III that was desigened to detonate on Airship fabric?

If it is the one i'm thinking of, it would be interesting to see a diagram of the internal operation.
Yes you're correct Falcon.
Also used in the Mk V, the 1.5 pounder COW and the Crayford.
Diagram attached.


  • 131 Fuze.jpg
    131 Fuze.jpg
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Thanks Dave, it's a bit clearer now. However, I can't quite tell what the "ste back ring" does, it appears to be pushed fowards when the centrifugal bolts are spun outwards.
I'm thinking the set back ring might act as a delay, slowing the side pressure from the centrifugal bolts, to let the detents retract before the centrifugal bolts can put too much side pressure on them to jam them in a nonretracted position.
This was by all accounts a very sensitive fuze, which is not surprising as it was to be used against fabric. My interpretation of the design, is that on firing the set back ring, would by virtue of acceleration acting upon it, set back and lock the centrifugal bolts place. The centrifugal bolts would in turn lock the needle plug in place. The detents, oblivious as to what was occurring elsewhere in the fuze would set back and lock themselves. This partial state of safety would continue until such time as the centrifugal force imparted to the centrifugal bolts was sufficient to overcome the force imparted by the set back ring, i.e. the projectile had all but finished accelerating and should be a healthy distance from the muzzle of the weapon..

I would be interested to know how the pressure plates faired, as notwithstanding the air holes around the top of the fuze nose, there must have been considerable air pressure acting upon them. This would have been especially so in the bore, on firing. I wouldnt be at all surprised if some were badly distorted.

John, yes it is a delay, but to ensure that the fuze was well and truly bore safe.


Tim. G.
Complex little things these fuzes!!

Just a tip for anyone who has one of these and is tempted to unscrew the large screws that are by the centrifugal bolts.......don't, speaking from experience they are really difficult to bet back in. The screws are sloped on top to follow the profile of the fuze and the metal that the fuze is made out of is some sort of poor quality alloy (mazac someone told me) which is brittle. I got the screw back in without damage but it took about an hour!!