Old military technology: the Welin breech block

[RamblinRover]

This will likely be of particular interest to ttyymmnn, Skyfire, and some of the others of you particularly into military history. Some may already be familiar.

As it happens, there is an inherent difficulty with the breech of an artillery piece, particularly naval artillery, in that a breech which locks into place is subject to the whimsy of some type of lock mechanism not to blow off the back of the gun - and with wear and stretching and whatever, it won't always be as tight as it needs to be. It also may take up unnecessarily large amounts of space around the breech.

On an artillery piece on the field, nobody cares if the breechlock takes up a lot of space. In a tank, they care more, but most tanks don't have an 8"+ gun.

There is another reason you didn't normally see an army-style breech block at sea, and it's a big one. The easiest way to seal a gun with no cartridge casing to hold the pressure (read: historically any large-bore naval gun) is with an obturator - something that must be held into the bore that will (like a bullet) expand under pressure or deform under pressure from the breech to seal and prevent gases escaping to the rear. You can see the obturator on the breech plug in the main picture.

If, unlike a land-based artillery with a breech block and lock, you treat the naval gun as being like a pipe shotgun and screw the breech in, "squishing" the obturator, you need (a) enough room to retract the plug, and (b) enough time to unscrew the breech through however many turns it might take for a thread to clear.

Clearly, what is needed is something with the advantages of both threads and a lock.

The Welin breech allows a breech plug which locks in place with 75% of the hold of a full thread, with a short plug and only turning a couple of degrees.
https://en.wikipedia.org/wiki/Welin_breech_block
It does this by having stepped threads, which is a little like using a nut of the wrong size on a bolt as a lazy substitute for a washer.

The older de Bange system is a big improvement over just screwing a plug in all the way, but does not take advantage of the fact that different diameters of thread can pass each other, and only locks with about 50% of the circumference, which means that the plug has to be longer to get the same strength.

[Albino Kangaroo]

@ramblinrover Good read. By the bottom of the post the top pic makes the most sense.

[Skyfire77]

@ramblinrover There's something viscerally fascinating to me about the massive engineering that goes into devices that are meant to contain very high pressure, but still need to be accessible, like big guns, pressure vessels and autoclaves .

[ttyymmnn]

@ramblinrover

Interesting. I don't pretend to know much of anything about guns, big or little. But I do enjoy reading about interesting ways to solve problems.

I was living in Norfolk, VA when 47 sailors were killed in an explosion inside one of the turrets on USS Iowa. Iowa was based in Norfolk at the time, so the news was all over it. I can't even imagine how much work it must have been to man those guns.

[Chariotoflove]

@ramblinrover Very nice. A good bite-sized read.

[RamblinRover]

@ttyymmnn What set me off on actually reading up on this stuff was reading on the gun complement of CV3 Saratoga (which my great-grandfather was on), and reading in the description of one of the guns the term "Welin breech".

The gun in question was a large bore one - the old 8 inch (one of the quirks of Saratoga: initial armament somewhat as a light cruiser).

https://en.wikipedia.org/wiki/8-inch/55-caliber_gun

Funny sentence regarding Saratoga: "In theory the guns could fire to both sides, but it is probable that firing them to port would have damaged the flight deck"

[ttyymmnn]

@ramblinrover I'm more for airplanes than ships, but it seems that in the older carriers they envisioned them more like gunboats that could launch planes, and armed them accordingly. Later, the deck guns became smaller. You might be able to comment on that.

[RamblinRover]

@skyfire77 The Welin article doesn't go into that much detail on the obturator, but the de Bange article does. Basically a squishy pad is behind the metal disc, so after the domed metal disc is tightened in place and has its edge under pressure all around, the gun fires, which depresses the metal disc in the middle, causing the softer pad to kind of reactively increase the pressure at the edge all around as it's displaced with nowhere to go. Weird stuff.

Almost as weird as the initial fire delay design on the Thompson submachine gun: it was designed to slow its rate of fire by a weird property of dissimilar metals basically fusing together for an instant under pressure contra the expectations of newtonian friction. When the pressure dropped off to a point, the parts would unstick enough to cycle. In practice, the weight of the parts meant there was no real difference between that the the delay of the operation from dynamic characteristics in simple blowback.

[RamblinRover]

@ttyymmnn Chiefly, it was that the Langley was too small and kind of useless, but the Lexington and Saratoga ran a little bit too far the other way - there was a concern about being left behind in development, so they went in for the biggest hulls possible to divert to carrier use that they could. Much better to have a slightly awkward carrier while what was actually required in a carrier design could be determined by testing doctrine, than to have a carrier which was unfit for purpose. They cut back on the plans for armor belting, and decked out the hulls with tall and very long hanger decks, and that was that.

Most of the things that were positioned to make the two ships good if slightly obsolescent cruisers were good for carrier use, such as their speed and capacity for damage control.

However, with RADAR and spotting plane fleet doctrines still on the horizon (ha ha), there was a legitimate concern that a carrier without a full modern carrier group might have to lash out in its own defense - particularly at night. Hence keeping a kind of impressive and out of place complement of guns. "Eh, we were building a cruiser, they made us build a table on top of the cruiser, let's finish building a cruiser because why the hell not."

The Japanese of course refined the repurposed-other-kind-of-hull game in building Shinano - when they realized the battleship war was lost and that their carriers needed more protection and resilience, they converted the sister ship of Yamato and Musashi into the largest carrier of the war.
Well, when I say "refined", I mean they did it crazier.

[RamblinRover]

@ttyymmnn Another note on the "damag(ing) the flight deck" line: it is very much the case that testing of military systems at the time would reveal just how much things could take near the muzzle blast of a gun more than theory. There is no assurance that the deck would have been good for it, unless actually tested. I've been reading a book called Can Openers about the US development of tank destroyers, and with the light tank destroyers in particular, there are things like needing to reinforce the hood of the vehicle, because the blast keeps deforming it or need better muzzle brake because the shock is shattering the dash instruments.

Or, in the case of one tank destroyer prototype, the fact that firing the gun sideways was lifting the near corner 14"+ off the ground. WHEEEE

[ttyymmnn]

@ramblinrover said in Old military technology: the Welin breech block:

to reinforce the hood of the vehicle, because the blast keeps deforming it or need better muzzle brake because the shock is shattering the dash instruments.

This reminds me of the constant problem of jets injecting muzzle gas, and how they had to design around that. If you look carefully at one of the pictures of the Cutlass I posted today, you'll see a rail affixed to the underside of the fuselage below the pilot to deflect shell casings from getting sucked into the engines. It's amazing how much you learn empirically, especially when it's all new technology.

Thanks for the long replies.

[BicycleBuck]

@ttyymmnn

Here’s a brief overview of the 5-inch guns on the USS Kidd.

We stayed overnight on the Kidd twice with the Scouts. Lots of fun to be that close to history!

[ttyymmnn]

@bicyclebuck I had to go look up "sound powered phone." I've heard that for years but never really understood what they were talking about.

[BicycleBuck]

@ttyymmnn

They mention the crew and their placement in the magazine and “family” rooms. What they don’t talk about in the video was the procedure for passing the shells and powder up through the floor into the turret. He did say that a burley guy was needed, but they needed even more of them in the two decks below!

[gmporschenut also a fan of hondas]

@ttyymmnn

craziest job is still the primer man @5:45 who has to hide in a pocket at the bottom of the turret. and next to the breach when the gun is elevated.

[BicycleBuck]

@gmporschenut-also-a-fan-of-hondas

That was excellent! The 5” guns on the Kidd don’t have all machinery. Everything is small enough to be passed by hand. If you ever visit the ship, take a look down the hole in the turret floor. That’s where everything is passed when arming the guns.

[gmporschenut also a fan of hondas]

@ttyymmnn When they were built the plans were still for the fleet to engage in line of sight/edge of the horizon battle, and the carriers aircraft unable to fully defend. So the guns were defensive. also with the washington naval treaty probably wanted to slip in as many of the largest guns they could.

[ttyymmnn]

@gmporschenut-also-a-fan-of-hondas

It's very interesting, and something I had never really delved into. I was fiddling around a bit with the timeline this morning. Billy Mitchell and his bombers sank the Ostfriesland all the way back in 1921, Lexington and Saratoga are launched in 1925, still 15 years before WWI. Battle of Coral Sea, the first naval battle between fleets that never see each other (unless you count Taranto), isn't until 1942.

So there is a 15-year period in which both naval and aviation doctrine changed radically, driven in large part by the extremely rapid increase in the potency and capability of naval aviation.

Here's a shot from Wiki of Lexington's guns in action.

[ttyymmnn]

@gmporschenut-also-a-fan-of-hondas That's a fascinating video. I was reading about the Iowa turret explosion yesterday, and the second investigation into that disaster found that an over-ram of the powder bags can cause detonation and was the most likely cause of the explosion. Watching this video, you can see that the speed and power of the ram is directly controlled by the operator and how far forward he pushes the lever. It would be very easy to shove that handle too far forward. In that accident, I bet those guys in the gun house were vaporized.

[RamblinRover]

@ttyymmnn It's funny how despite this not being a #planelopnik topic, it was spurred by a #planelopnik topic and ended up coming back around to it anyway.

[ttyymmnn]

@ramblinrover said in Old military technology: the Welin breech block:

@ttyymmnn It's funny how despite this not being a #planelopnik topic, it was spurred by a #planelopnik topic and ended up coming back around to it anyway.

Some of the best conversations on Oppo start one place and go in entirely different directions. I posted about the Cutlass yesterday, and mentioned that it was the inspiration for the 55 Bel Air hood ornament. That spawned an entirely different and interesting discussion about hood ornaments.

It's like somebody once said, Oppo is like a bunch of guys standing around in a garage shooting the shit. The conversation goes in all sorts of ways because everybody brings a little something different to the discussion.

[gmporschenut also a fan of hondas]

@ttyymmnn IT shoots a 2k lb shell at rifle velocity speeds. If there was one way to go, its probably the fastest way to go.

[gmporschenut also a fan of hondas]

@ttyymmnn https://www.youtube.com/channel/UC4mftUX7apmV1vsVXZh7RTw
This guys youtube channel is a deep rabbit hole. I think it was on one of the 2hr q&a videos. in terms of naval bomber aircraft in the 20s they were really limited in payload. Some could carry a single 500lb, but that was edge of performance and substantially limited range.
it wasn't really til 1929 that they saw, "hey we've been limiting the use".
There was a fascinating video by i think Military Aviation History where it was brought up could ww2 inthe pacific could have happend 5 years earlier, when the japanese air arm was much less capable.
https://www.youtube.com/channel/UCmpahmxWXajV0-tuMMzSzAg also another rabbit hole