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Question; Sherman armor sloping

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So serious question here. Why did the Sherman not ever receive (to my knowledge) sloped side armor. Is there a real reason why this never happened? I mean six inches of slope (30 degrees) would have resulted in an armor benefit of around 30%.

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1 hour ago, civdiv said:

So serious question here. Why did the Sherman not ever receive (to my knowledge) sloped side armor. Is there a real reason why this never happened? I mean six inches of slope (30 degrees) would have resulted in an armor benefit of around 30%.

If I recall correctly, the armor on the sides of U.S. tanks (not just the Sherman) was not sloped so that the tanks could be loaded, fitted into place, and unloaded more efficiently on/from ships. This factor was something that land-powers like Germany and the USSR did not have to be concerned about as much.

Edited by BluecherForward
typo

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10 hours ago, BluecherForward said:

If I recall correctly, the armor on the sides of U.S. tanks (not just the Sherman) was not sloped so that the tanks could be loaded, fitted into place, and unloaded more efficiently on/from ships. This factor was something that land-powers like Germany and the USSR did not have to be concerned about as much.

I don't see why tanks with sloped armour would be any more difficult to transport by ship...

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Sloped armour reduces internal volume, which has some serious knock on effects on things like ergonomics, ammunition count and survivability.

The other question mark is whether it would have helped in any way: the frontal armour would obviously be more effective than the side armour (it would be both thicker and more angled) and when was the last time you saw the Sherman bounce anything off it's front slope?

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2 hours ago, Hapless said:

Sloped armour reduces internal volume, which has some serious knock on effects on things like ergonomics, ammunition count and survivability.

The other question mark is whether it would have helped in any way: the frontal armour would obviously be more effective than the side armour (it would be both thicker and more angled) and when was the last time you saw the Sherman bounce anything off it's front slope?

1943. It happens quite a bit in CMFI, against Panzer III/IV. Also happens with the Jumbos in CMFB, but yeah, those are mostly edge cases.

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5 hours ago, Bulletpoint said:

I don't see why tanks with sloped armour would be any more difficult to transport by ship...

Can't recall where I picked up this tidbit. I am hoping someone else is aware of this requirement and can chime in. I will do some thinking over where I read this.

The idea, as I recall, was that the development of the Sherman was heavily influenced by the ability to optimize their loading, transport, and off-loading onto/off of Liberty ships and/or LSTs, which were then also under development.

image.jpeg.539a807d1c151076448570c850f597b3.jpeg

 

Edited by BluecherForward
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2 hours ago, Hapless said:

Sloped armour reduces internal volume, which has some serious knock on effects on things like ergonomics, ammunition count and survivability.

This

Sloped armor reduces interior space which might be needed for engine, equipment, radios, ammo, crewmen whatever. If you want to have the same internal space you need to make the tank bigger which might introduce tactical and logistical disadvantages. Taken this into account its questionable if it would be a good deal for the Sherman which no matter if sloped or not never could offer sufficient flank protection against anything that Germans might fire at it without respeccing the complete vehicle design.  

Despite this depending on model and industry characteristics it might make production more complex.

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As with any design decision, there are a plethora of variables that factored into the 90 degree sponson armour:

a. The M4 was an improvement over the M3 -- which was the first Medium that the US produced in large numbers. It was relatively expedient to switch the production lines from the M3 to the M4. The M3 was built as a tall tank, with a massive drive shaft running through the bottom of the hull. One detriment was that the M4 was narrow, tall and had the aging bogie suspension. 

b. The M4 had a 3-man turret. Which means a bigger turret ring and more hull space used than a T-34/76. The US doctrine was big on ammo capacity on their tanks. With the driver & bow gunner at the front, and the drive shaft below -- where else are you going to store the ammo but the sponsons?

c. The irrelevance of sloped side armour. Keep in mind, that only the top half of the T-34 side armour is sloped. If an enemy is attacking from the side, all they have to do is take out the track. A mobility kills turns a tank into a pillbox, easy pickings for infantry, artillery, aircraft and other tanks. This is how the Germans killed T-34s in '41.

Sloped side armour is an exception, rather then the rule. It offers the disadvantages of limiting the turret ring diameter, internal volume and adds weight, for a practically irrelevant advantage. The Soviets ditched the idea, as soon as they could -- with the T-44. As did, the French -- with their 1-man and 2-man turreted tanks/cavalry vehicles.

It just doesn't make sense for a vehicle with a 3-man turret. Look at the KV and IS -- they don't have it, either.

M4A4_cutaway.svg

Note: 22 is the front propeller shaft and 20 is the turret basket.

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The US had all sorts of design concepts for improving Sherman's armor protection, including  a much lower silhouette. But they couldn't afford to interrupt tank production. Russia had the same issue, having designed  a replacement for T34 with thicker armor and torsion bar suspension, but they were simply unwilling to interrupt the T34 production line to get it into service. Both Sherman and T34 did get new turrets out of those programs. Eventually the US design concepts evolved into Pershing while the Russian 'universal tank' project became the (much modified) base for the Stalin series. We tend to forget that US active involvement in WWII occurred over a relatively short period of time. From the Operation Torch landing in NA to VE day was about 31 months.

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General McNair was in charge of tank development for the US in WW2. He was an Artillery man who thought tanks should support infantry, not engage the German tanks in battle. His plan was to have the M10, in mass, just behind the front lines. They would handle any German tanks that broke through. When the tankers and their commanders started to complain that they were getting wiped out by the German tanks and that the 75mm just bounced off, General McNair responded by telling them that mass tanks would do the trick. He would not allow the addition of the 17lb (76mm) British gun to be installed. (The British installed the 26lb gun on their own and produced the Firefly.)

McNair used all sorts of excuses to delay upgrades to the Sherman. Delayed production, the 90mm gun was too heavy, more armor was too heavy, the tanks would be too heavy to ship, etc.  It wasn't until late in the war that McNair finally relented and allowed the M4 to be built, along with it's variants.

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y'all have seen The Chieftain's video on US armor in WW2, correct?   He has some very interesting and surprising insights, much of it directly from US army archives and not just some mythology that we've all grown up with.  

 

 

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Good read: "World War II Ballistics: Armor and Gunnery" by Lorrin Rexford Bird and Roberd D. Livingston.

By taking lesser known aspects into account like the projectile diameter vs true armor thickness overmatch effect it helps to understand why high emphasis on multi-aspect/flank sloped armour protection (despite its logistical, production, ergonomical, and other/tactical concerns)  might not be the jack of all trades solution in WW2 as some seem to perceive it nowadays, especially in a late WW2 environment.

Never tested it but my inner gut feeling teels me that the mentioned overmatch effect is simulated in Combat Mission in a bilateral way thus either armor thickness or projectile diameter overmatch. 

I heard that the authors were involved in (playing) Combat Mission aswell.

Edited by Aquila-SmartWargames

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On 2/9/2020 at 3:48 PM, civdiv said:

So serious question here. Why did the Sherman not ever receive (to my knowledge) sloped side armor. Is there a real reason why this never happened? I mean six inches of slope (30 degrees) would have resulted in an armor benefit of around 30%.

You are not supposed to get shot in the side on purpose.

On 2/10/2020 at 4:33 PM, BluecherForward said:

Here's a link to that same guy doing a briefing on the Sherman tank:

I don't know how to post the whole video as danfrodo did above.

Gotcha.

The Sherman was designed with an armor basis intended to be immune to the 37mm PaK38 AT gun from all possible aspects (that being the standard issue German at gun in 1941 when the tank was designed). The side armor is thick enough to achieve this design specification without needing to be sloped in order to meet it's overall weight requirements. Later versions of the Sherman had reinforcing armor pieces welded over the ammo storage in the hull side, but generally speaking, you want that internal volume when your overall ETO command is asking for an ammo capacity of 90 rounds in each tank so you don't need to modify your design to make sloped armor. It's much easier to weld extra plates on at the factory instead of re-casting or re-welding the entire hull.

I think the biggest consideration people need to keep in mind about the Sherman is that it was effectively a pre-war design, that was modified many times, but still in 1945 it was a pre-war design. Design of the M3 medium tank was finished on February 1st, 1941, and the order to design and build the M4 medium tank was given at the same time. The only real requirements for M4 was to be shorter in height than M3, to retain the M3 hull and chassis to the utmost extent, to have armor basis to defeat the existing AT Guns fielded by the Germans and Japanese, the addition of some type of AA protection (.50 cal), and the mounting of the 75mm main armament of the M3 in a larger rotating turret.

This wasn't a tank that had a carefully considered design process stretching for a year or two, the Sherman went from T6 Prototype to M4 production tank in about five months.

Edited by General Jack Ripper

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