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The Great War (1914-1918) Forum

Remembered Today:

Shrapnel shell fuse. How should it work?


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Hi guys,

It occured to me that, although I've seen many ww1 18 pounder shrapnel shell fuses, I don't really understand what was supposed to be going on inside the fuse - in order to make the shell detonate at the desired time.

I tried googling for a simple explanation - and came across this


The fuse consisted of two different primer charges separated by two channels containing gunpowder. The connection between the two channels (and thus the speed of ignition) could be adjusted by rotating the bottom portion of the fuse. The first primer was activated by the acceleration of the shell as it was fired. The acceleration drove a plunger against a stiff spring into a gliding metal or aluminum cup containing the primer, which exploded on contact.

However, this still leaves me a little confused.

Does it mean:

1.a. That the gunpowder in the first primer is ignited (by acceleration) and actually burning as the shell flies through the air &

1.b. That the length of that first primer 'burn' has been manually adjusted by the gunner prior to loading &

1.cc. That the 2nd primer charge (and therefore ejection of the shrapnel balls) is set off once the first primer has completed its burn...or alternatively

2. The gunner's adjustment (& hence timing control) is to the distance that the plunger needs to travel in order to set off the 2nd primer charge ?

Thanks for any enlightenment.


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I think explanation 1 is more or less correct - the first primer detonates on acceleration, fires the gunpowder delay which burns in flight, and then detonates the second primer to fire the ejector charge. There may be 'reserved' terminology I should've used, but that's the essence of it.



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Yes it is your number 1.

It is difficult to describe without a fuze in front of one, but here goes!

The fuze has an annular channel filled with gunpowder with a flash hole connecting it to a lower adjustable channel also filled with gun powder. When the fuze is set by the gunners the adjustable ring is turned, moving it relative to the position of the flash hole and thus changing the time before the before the upper ring flashes through to the lower ring.

When the shell is fired the ignition pellet sets back, igniting the gunpowder in the upper channel. At the set time the gunpowder flashes though to the lower and in turn sets off the powder train down the centre of the shell, igniting the gunpowder ejection charge at the base which pushes the ejection plate and shrapnel balls through the front of the shell body, blowing off the fuze and adaptor ring at the same time. That is a rather simplified version but I hope it explains things a little more clearly.

Drawing of No.80 Mark IX T & P attached.




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Many thanks for your illustration above

I now know that what I picked up 5 years ago, in a field just above Geogheghan's Bluff, Helles,

is properly called a 'Bottom Composition Ring'



All the best


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If this fuse was attached to a shrapnel shell, and the timer fuse failed, what was the effect when the shell hit the ground and the percussion fuse was activated?


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I realise that, but since there was nowhere for the shrapnel balls to go did the case fracture, or get blown backwards in the direction it had just come from, or.....


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