The Armored Vehicle Thread

Speaking of Ammo Storage, I heard that the M4 had a nasty tendency to cook itself before it was switched over to wet stowage..... What exactly was going on with that?

What was happening was that ammo would take a hit and the propellants would ignite and then the warheads would deflagrate. The fire was toxic, hot, and often lethal to the crew. The intense heat was causing the rounds to sometimes detonate as well as burn which would further ignite various materials, oils, and other things on the interior and the damage would basically spread from there.

This was actually a common problem and huge risk in the bulk of WWII tanks. The ammo getting hit burned into an intense fire just as often as it exploded from the heat.

edited 25th Apr '18 4:13:53 PM by TuefelHundenIV

And to varying degrees it continued into the Cold War and beyond. There's a reason why Iraqi T-55's, T-62's and T-72's got known as "jack in the box" in Desert Storm. Same thing happened, took a hit and the inside caught fire and burned up the ammo in a massive secondary that could (and often did) blow the turret clean off the now burning hulk.

Yeah the other lesson learned was to seal ammo away inside some sort of armored compartment and eventually to include blow out panels. Loose ammo and exposed ammo were the number one cause of ammo hits killing the vehicle. The jack in the box effect was typically something you see only in the buttoned up tanks as the pressure built inside and the exploding and violently burning ammo pushed the turret off the chassis sometimes in rather impressive fashion. If you watch enough modern tank hits from ATGM's and see a gout of fire shooting out of an open hatch and sometimes the gun barrel if the gun breach is open. That is ammo and propellant deflagrating and cooking off.

There is a snippet of the US test vid of the ammo compartment blow out panel test and you can see a jet of fire shooting out the side of the tank where the ammo is venting.

edited 25th Apr '18 6:22:26 PM by TuefelHundenIV

The jack in the box effect is because the shells and the propellants in the T series tanks with autoloaders are stored just below the turret ring. You can see a little bit of it in this gif.

If any of the ammo goes up it's gonna pop the turret.

This is one of the problems that led to the development of the T-14's remote turret.

edited 25th Apr '18 6:33:37 PM by LeGarcon

I can see where the old "loading the gunner" myth comes from.

Boy, you just described every Russian tank ever made since the T-62, including Armata. There are no "T series", that's the Russian designation (outside of GRAU anyways) for tanks and has been that way for almost a century.

Garcon: They put other measures into place before the T-14 to begin with. Like removing the unprotected internal stowage for spare ammo and rounds found in the older models of T-72's. Why they ever did that I will never know. The T-90 supposedly has the full range of safety features you would find on most other modern tanks to begin with. If I can find it there are a few pictures and even vids of knocked out T-90's that look like they have ongoing ammo fires but they manage to not have popped their top.

Tom: Ivan:"T is for tank comrade!"

edited 25th Apr '18 9:06:47 PM by TuefelHundenIV

Well if you can think of a better way to refer to every Russian tank design sans the 62 in a couple words you lemme know

Soviet made shit!

-sorry, misread-

edited 25th Apr '18 7:54:17 PM by Demetrios

The Sherman cooking off was an issue mostly associated with the small hatch Shermans in British service.

During the late 1942 campaign in Africa it was becoming evident how many total losses the British armored divisions where suffering against the Germans, despite the interior of the M4 being roomy enough to allow a shell to go through one side to the other without doing much damage besides to whoever was unlucky enough to be on the shell's path, there were a lot of catastrophic kills due to ammo burns and explosions.

The British and US armored divisions then found out that the British tankers were essentially packing every inch of free space with ammo on their M4s. Combined with the bursting charge of the 88mm Pz Gr 39 being decent enough to cause ammo fires more often than the 75mm Pz Gr, meant that it would take 1 to 2 penetrations to cook off a British M4.

When the US armored divisions were rolling in Tunisia with their 75mm small hatch M 4 A1s and M4s, the ammo storage issues have been solved, which meant that in order for the Germans to kill an M4 beyond recovery changed from 1-2 shots to 4-5 shots in average.

The Germans also tended to fire on a tank until it was deemed unrecoverable and most takers died gunned down outside of their tanks.

The Large hatch Shermans, mostly associated with the M 4 A 3, used wet storage and increased the survivability even further.

Ironically, despise its fame (thanks Belton Cooper your memoirs were a great contribution to WWII armored history), the M4 Sherman had the highest crew survival chance of any WWII tank, with an average of 1.2 KIA per penetration and 2 WIA.

edited 25th Apr '18 8:28:55 PM by AngelusNox

I believe those figures are from the British Army. I think the rate for American tankers was .6 killed per tank loss.

(It was lower because the Americans brought helmets).

Plus, the 2A gives Americans +10 against government jackbooted thugs, even other governments' jackbooted thugs.

Now I kind of want to see an upgraded Sherman. Should be easy enough to put applique ablative armor blocks on the exterior, maybe a remote-controlled gun mount for the commander's Ma Deuce. GPS and Onstar for when you need to call for a recovery vehicle...

Yes, I was directly quoting the Mo D tank losses report as the basis for that data, I don't remember the US one by heart.

As of a few days ago it has been one century since the first tank on tank combat occurred during the first world war. During The Second Battle of Villers-Bretonneux, 14 German A7V tanks were met by One British Male Mark IV tank ^note Male tanks had large caliber guns or cannons meant to attack hard points and bunkers while female tanks were strictly armed with machine guns and intended to support infantry and sweep trenches and hold back enemy infantry with heavy machine gun fire. and two female tanks. The end result was the two female tanks withdrew due to damage, one German A7V was knocked out of action and the rest of the German tanks put on retreat. Later on artillery would knock the Male British Mark IV out of action. Both disabled vehicles would later be retrieved by their respective sides.

edited 28th Apr '18 6:39:37 AM by TuefelHundenIV

14? As far as I was aware courtesy of the folks at The Great War, Villers-Bretonneux had only 3 A7V's, two of which showed up after the first tank on tank battle.

Is this referring to the entire offensive in that part of the Western Front?

edited 28th Apr '18 7:20:12 AM by MajorTom

The Second Battle saw the Germans field 14 of their 20 tanks. That isn't even for the entire campaign. The overall engagement front may have only encompassed a portion but the Germans deployed more than 3 in that particular battle. Given how clunky and slow the tanks were it was likely not practical for the tanks further out from the engagement of the tank on tank duel to maneuver to participate. They may not even have been aware given the limited ability of tanks to communicate in any meaningful manner and how very badly limited their overall visibility was.

edited 28th Apr '18 7:54:46 AM by TuefelHundenIV

Sooo, Garcon and I were having a tank related argument, and one thing brought to light is that there is apparently a 5% reliability gap in penetrating modern ERA of a sabot in warm weather vs cold weather, which was significant enough that the document sheet for the M829 noted it.

....

And like, why is it that the sabots work better when it is warm out? Is it that the hotter air is less dense and offers less resistance like I suspect? or is it something else, because that is honestly quite a lot of difference just for the weather.

edited 29th Apr '18 9:31:46 PM by Imca

Do you have a link to the data? Logically speaking, simple thermodynamics mean that the chemical reaction in the ERA would occur slower and with (somewhat) less force at higher temperatures, which might contribute to the difference.

I would also wonder if it's the ERA simply getting softer and thus less effective when it goes bang to counter other bangs. When the weather is really bloody hot, just about everything gets noticeably softer (or impossible to handle).

I don't see how the ERA would be affected. It's armor plate that explodes outward.

Surely it must be the round itself that's behaving weird in extreme weather.

Not sure about the material composition of ERA plates, but uranium has substantially higher specific heat capacity and heat expansion coefficient than steel, so its hardness level is less affected by the temperature. That, and the bit I mentioned earlier about the explosive content going off at slower rates at higher temperatures.

(Then again, the latter phenomenon also applies to the tank round's propellant)

edited 30th Apr '18 8:06:59 AM by eagleoftheninth

I don't think the issue with the ammo in question. Specifically because ammo is stowed in such a way that even a cold tank offers some form of protection from exposure to the elements. ERA on the other hand is constantly exposed to the elements and shifting temperature and environmental factors which can not only affect the metal but as noted above can affect explosives. ERA is still reliant on both the explosive but also the material state of the metal plates that make up the outer layers that are pushed away by the explosive.

I was thinking more how the temperature extremes would affect it's ballistics in flight.

Snipers have to account for it, surely sabot rounds would act differently as well.