Armor values on M4A3E2 Jumbo

[Dragoon 45]

I have been doing some research on the Jumbo and discovered that pinning down the exact armor values on the beast in question is quite problematic. I.E. in "British and American Tanks of World War II" by Chamberlain and Ellis, the authors state 12" thick applicae armor plate was attached to the bow and sides of the hull of the vehicle (the additional bow armor covers the entire front aspect of the hull except for the final drive housing at the point of the bow). This armor was applied over the base armor so armor thicknesses would be increased over the thickness of the applicae plates. Additionally the turret was a casting 6" thick on all sides and the gun mantle was 7" thick which would give the turret front in some areas an armor thickness of 13". All this narrative is in the body of the entry on the Jumbo. But then in the technical specifications the authors then state that the armor thickness on the side of the hull was only increase to a little over 3" and the bow armor was 5-6".

This leads to my question. Which armor values are correct for the Jumbo? If the armor values stated in the body of the entries on the Jumbo are correct the Jumbo would be pretty much immune to the L71 88mm PAK-43 or KwK at any range except for an extremely lucky hit at extremely close range. The additional weight added to the Jumbo would tend to support the addition of the 12" thick plate instead of just 2-3" as implied in the technical specifications.

I have researched other sources and found the same contradictions on the armor thickness.

Also I can find little evidence either way in personal narratives about the armor on the Jumbo. Accounts of their use in combat are very rare and I can find little info on how well they stood up to German fire.

[FlashfyreSP]

I'll give you what I have from "Tanks In Detail #6: Medium Tank M4 (76mm & 105mm)" by Terry J Gander:

The M4A2E2 "Jumbo" assault tank was a basic M4A3 with additional hull and turret armour. The hull was 3.94 inches (100mm) thick, and the turret was an all-new box-contoured component with frontal armour of 5.91 inches (150mm) thick. Pictures seem to indicate that the hull armour increase was only to the frontal plates, but the turret received its additional plating all around the turret sides.

Information from this site (http://www.onwar.com/tanks/usa/data/m4a3e2.htm) indicates a similar view. The armour ratings for the front hull are 114-140mm, the front superstructure 102mm, and the turret 152mm on all three facings (front, side, and rear) with a flat-plate mantlet of 178mm.

I'm not sure what edition of Chamberlain & Ellis you have, but my copy is from 1969, and it only states that,

Additional armour was added to all hull surfaces, giving a maximum thickness of 100mm. A new heavy turret was designed with frontal armour of 150mm but the 75mm gun was retained.

Your edition may have a misprint regarding the amount of armour added to the vehicle in the narrative portion.

[Goblin]

I've seen them with huge blocks (could have been 12") of concrete bolted onto the outside of the front hull. Maybe thats what they were refering to?


Goblin

[Goblin]

Caption: The extra armor welded to the glacis of this Jumbo Sherman is immediately apparent, along with the new turret and very thick gun shield. Fixtures such as headlights and sirens have been omitted from the hull front, however the bow machine gun was retained. This tank lacks the extended end connectors on its T48 tracks which helped to reduce ground pressure.

[Goblin]

WW2 Vehicles states that they added 100mm to the hull, and that the armor thickness was 4.5" to 5.5"

I don't think a WW2 land vehicle could have moved with 12" of armor, not at 20+mph anyways!


Goblin

[Alby]

I have been playing a guy who has been using these beasts
they are daggone hard to kill!!
[:@]
[:D]

[264rifle]

Steel weighs 40lb per square foot for a 1in thickness so 12in steel weighs 480lb (almost a 1/4 ton) per square foot. Even a 4X8 slab would weigh 7 1/2 tons. this sounds like a non-starter to me. The Photo is a give away too. Adding even 10in for a 12 total would have put the bow gun in a tunnel and unless the mount was moved out and the the gunner would have been working the gun in a tunnel.

Maybe we should start a thread------Mythbusters[;)]

[Dragoon 45]

According to the technical spec's I have seen the Jumbo was almost 10 tons heavier than the normal Sherman. Some of this additional weight would have been taken up by the new turret. In "Tanks of the World, 1939-1945" by Chamberlain and Ellis (2002), also authors of the first work I cited, they once again mention 12" thick rolled armor added to the bow and side plates of the hull. Then once again they contradict themselves later by stating that the armor thickness was 4 1/2 to 5 1/2 inches thick on the bow and hull side plates. The photo Goblin posted seems to disprove the 12" thick applique armor but what is the correct value? From Goblin's photo it would appear that the applique armor is much thicker than 1-2" of armor implied by the 4.5-5.5 total armor values used in the Tech Spec's. Base armor value for the front aspect of the Sherman is, depending on which source used, somewhere around 3-3.5 inches on the bow of the basic hull.

ORIGINAL: 264rifle

Steel weighs 40lb per square foot for a 1in thickness so 12in steel weighs 480lb (almost a 1/4 ton) per square foot. Even a 4X8 slab would weigh 7 1/2 tons. this sounds like a non-starter to me. The Photo is a give away too. Adding even 10in for a 12 total would have put the bow gun in a tunnel and unless the mount was moved out and the the gunner would have been working the gun in a tunnel.

Maybe we should start a thread------Mythbusters[;)]

[Dragoon 45]

My copy is the 2000 edition. I ran across the same information in "Tanks of the World, 1939-1945" by the same two authors, which is a 2002 edition. I really don't think the 12" thick applique armor is correct but from photographic evidence and also other sources I don't believe the 114-140mm hull values are correct either. I brought this subject up to illustrate that conflicting evidence is quite common out there.

ORIGINAL: FlashfyreSP

I'll give you what I have from "Tanks In Detail #6: Medium Tank M4 (76mm & 105mm)" by Terry J Gander:

The M4A2E2 "Jumbo" assault tank was a basic M4A3 with additional hull and turret armour. The hull was 3.94 inches (100mm) thick, and the turret was an all-new box-contoured component with frontal armour of 5.91 inches (150mm) thick. Pictures seem to indicate that the hull armour increase was only to the frontal plates, but the turret received its additional plating all around the turret sides.

Information from this site (http://www.onwar.com/tanks/usa/data/m4a3e2.htm) indicates a similar view. The armour ratings for the front hull are 114-140mm, the front superstructure 102mm, and the turret 152mm on all three facings (front, side, and rear) with a flat-plate mantlet of 178mm.

I'm not sure what edition of Chamberlain & Ellis you have, but my copy is from 1969, and it only states that,

Additional armour was added to all hull surfaces, giving a maximum thickness of 100mm. A new heavy turret was designed with frontal armour of 150mm but the 75mm gun was retained.

Your edition may have a misprint regarding the amount of armour added to the vehicle in the narrative portion.

[264rifle]

Two theories I have (not facts) are that this is a misprint in orginal data being repeated. 2in had an extra numeral 1 placed in front of it. This would at least jibe with the the 102mm front superstructure number( Superstructure= plate in front of driver/s). hull front being the transmision/final drive casting. Other one is that 12in represents the level of protection that the armour would be equal to if it was vertical. This would require more than 102mm of armour.

Just suggestions[;)]

[Nikademus]

must be a misprint. There's no way the Sherman could have been quick-modified to that extreme to attempt to carry such an increase in armor weight. Assuming that the suspension could even handle the increase, the tank would have bogged down with such a ground pressure increase on those narrow treads. As already mentioned, the tank would have been lucky to crawl around. Thickest armor carried was on the Jagd-Tiger which was a massive sized vehicle that barely qualified as 'mobile' More like a mobile pillbox!

Also, be wary of adding mantlet and turret front armor together. This problem cropped up originally with the Tiger I. Mantlets protect the hole cut into the turret front where the gun and support assembly are placed. Orig this was done with Tiger I and it had 200mm rating for ver 5.x? Eventually it was reduced after alot of discussion (and arguing) Lorin Bird's tank balistics paper contained good info and diagrams of the Tiger 1 mantlet and turret front proved very useful.

[Afrika Korps]

When I read it, I think they wrote 12" in the text, but they really wanted 12cm (which is 4.72 inches), a lot closer to the actual thickness.

[Nikademus]

sounds like a good explanation. typos regarding measurement designations i've seen in more than one source.