Larger No.80 fuze?

[wingsofwrath]

I was looking at the fuzes in my collection and I noticed one of the two No.80s I have looked to be somewhat larger than the other one. I measured them and one came out at 62mm in diameter and the other at 66mm.

The smaller one is what I consider to be the "standard" model - it's a ground find from France marked 1918 VSM and it came with it's original adapter (with the bottom part blown off) to which I added a cover and ring also marked 1918 VSM, so they all fit together perfectly.

The larger one only has a broad arrow and a "33" and no manufacturing marks, and while it will happily sit in a standard adapter, it looks comically oversized on an 18-pdr shrapnel and the standard fuze cover will absolutely not fit over it.
Now, I'm not sure that afore mentioned "33" is the year or lot number, because I was unable to find any proper manufacturing dates for the No.80 fuze.

So my question is this - why is this fuze so much larger than the other one? Is it just because it was made by a different manufacturer, or is it an actual reason for it? Also, does that "33" mean it was manufactured in 1933?

Thank you!

 

[Snufkin]

Perhaps the larger fuze has a grown a bit.

It looks like the lower body at least has experienced a significant energetic/heating event, from the imprint of the inside face of the base plug on the centre channel of the body. The body appears to have suffered some expansion and distortion, and thereafter has been fiddled with - the makers monogram and filling date, etc, have been filed away - a few details can just be discerned.

 

[wingsofwrath]

Well, I think you're right when it comes to this fuze having been subjected to a large force from below, which I take as the shell exploding and ejecting the fuze (most likely with the adapter, since the thread is untouched and I've seen plenty of fuzes with stripped threads) then subsequently the lower part has been ground smooth, probably so that it could be placed on a table for display, which accounts for the missing markings.

However, I think the hypothesis that the shell explosion also accounts for the larger dimension doesn't hold water, because in order for the fuze to have been deformed laterally, it must necessarily have been squashed against something and I don't see any indication of that at the front of the fuze, just a small scuff mark on the nose, probably from where it impacted the earth after it's flight. Also, while there is a moderate amount of distortion overall and one of the platters is a bit "wonky", the height of all components is identical to that of the VSM fuze, something which would not hold true if indeed the fuze was squashed.

Also, I've measured each platter individually and all of them are just slightly larger diameter that those on the VSM fuze, adding up to 4mm overall. Another thing would be that the bottom platter of the VSM fuze has a bevel and the other fuze doesn't, so in the end I guess the simple answer is that, probably, VSM was very good at machining tight tolerances and other manufacturers weren't which is why their adapters and fuzes (see my other thread on the 13-pdr dimensions in the Projectiles section) are exactly as per spec, while other manufacturers' tend to be slightly bigger.

 

[Snufkin]

for the fuze to have been deformed laterally, it must necessarily have been squashed against something

Not necessarily. This No.80 doesn't show the usual marks of functioning of a Shrapnel shell, but more those of a timed HE. So a possibility is it was a No.80/44 sitting on top of a No.44/80. The intense heating effect of an HE detonation can cause deformations without a need for a physical impact.

As for Vickers Ltd being better at machining than other makers, all manufacturers had to supply according to the specifications. Items out of spec or not to gauge were rejected.

 

[wingsofwrath]

Now it being a No.80/44 makes sense and I also thought of it, although i'm not sure how to tell a No.80/44 apart from a regular No.80 in the absence of paint and the tell-tale wooden plug.
The fuze is stuck in what I assume was it's original setting of 21 and 1/2 seconds by the fact the disc above is slightly deformed, so that could mean they were shooting at aircraft or that they were shooting at something really far away, so I wouldn't call that conclusive.

On the other hand, I'm still not convinced about the heat deformation hypothesis, because if it were heat deformed, shouldn't it be deformed in height as well? And why wouldn't it just regain it's original dimensions when it cooled, because I assume it also cooled gradually?

I absolutely agree that all manufacturers had to supply according to the specifications, but what were these specifications exactly? Was the War Office really that invested that the external dimensions of the fuze being exactly the same, or were they more interested in the fuze sitting well on the shell (which this fuze absolutely does) and functioning correctly (which, again, it clearly did) and who cares if it's a few mm larger?

In the end, I think the problem here is we have a sample size of one, so we can only speculate on wherever it's larger because it got deformed, or because it was manufactured this way, unless some other examples of larger fuzes show up and we can find a common thread - be it that they ere all fired in timed HE shells, or have very similar features that would point to a certain manufacturer making their fuzes just a tiny bit different, etc.

In the meantime, here is the fuze sitting on my 18pdr shrapnel (Mk VI - Forced Steel - Bethlehem Steel Corporation, paint by yours truly) compared to the VSM (which doesn't screw in all the way) and a No.85 and what I said about it looking comically large and the differences in machining at the lower edge which make me think this was on purpose rather than just chance deformation.

 

[Snufkin]

because if it were heat deformed, shouldn't it be deformed in height as well? And why wouldn't it just regain it's original dimensions when it cooled, because I assume it also cooled gradually?

I absolutely agree that all manufacturers had to supply according to the specifications, but what were these specifications exactly? Was the War Office really that invested that the external dimensions of the fuze being exactly the same, or were they more interested in the fuze sitting well on the shell (which this fuze absolutely does) and functioning correctly (which, again, it clearly did) and who cares if it's a few mm larger?

It wasn't just heated. It was heated and - if a No.80/44 + No.44/80 combination - subjected to an explosive shock wave, followed by the impact of the top of the 44/80 together with the 80/44 base plug acting as a high velocity metal punch. Given the structure of the No.80 body, permanent deformation is likely to be more transversal than longitudinal.

As for specifications, the Inspection Department of the Ministry of Munitions was greatly invested in accuracy of dimensions. Small variations of shape and size could significantly range. The body dimensions for the American made No.85 (image below) show tolerances to 2 thou. Such accuracy was not done for the fun of it.

 

[wingsofwrath]

No.

You CANNOT have deformation in one direction without deformation in the other direction, because that's just simple physics - if you squish something to widen it, it always, without fail, becomes shorter, because the material from the sideways expansion must come from somewhere else in the object. In order for the fuze to have become wider on the X-Y axis, it MUST have become smaller on the Z, and the fact the rings are exactly the same height as the rings from the VSM tells me this was not the case, because if your hypothesis is correct and only deformation is at play here, then the mystery fuze must have started taller than the VSM, which also means they weren't identical to begin with, so we're back to square one.

Yes, if the mystery fuze was shorter than the VSM I would have entertained this hypothesis. As it stands, I don't think that's correct.

I also think we've been going down a wrong path with this as well as ignoring one really simple explanation.
If it's not a manufacturing error and not deformation, then can we be sure it's not simply a different version? Because my VSM is a Mk.VII and made in June 1918, and we have no idea what mark the other one is because the markings have been filed off. Maybe it's an earlier version and at one point they made it smaller to save material, or maybe it's later and they decided to make it bigger because of X-Y-Z reason...

 

[Alpini]

The fuze's base is hollow so you don't have a perfect force in one direction. It's blown up like a balloon and you see this effect on so many other fuzes too. It's clearly to see that it is deformed much from a HE charged shell. Further if you want to compare the length according to you theory you need to dismantle it and measure the fuze body only (on your picture it already looks shorter). But in my opinion it's not worth the time. I guess the fuze design engineers had enough problems to solve so they did not need to create more problems by developing a No.80 with a different thread size. Having different sized fuze bodies would be the perfect poison against a good optimized mass production.

 

[wingsofwrath]

Welp, I think I cracked the mystery - Both @Snufkin and @Alpini are right in saying that this fuze is deformed, but I was also right in insisting that deformation would happen in all three dimensions.

The problem is that after the fuze got deformed, someone went in and recut the thread as well as ground down all the excess so that the bottom ring was the proper height despite it having ballooned during firing.
The thing that initially threw me for a loop is this work isn't recent, it's at least a couple of decades work, and it's very well done, so, on a fuze which isn't a ground find it looks less jarring than it should. Of course, once you look at the fuze expecting to see it, the work becomes obvious, because the inside thread is absolutely mangled, but the outside is pristine...

Well, you live and you learn, I guess. Thanks for helping me with this one and please excuse my pigheadedness...