M6A2 / T1E1 Heavy Tank: Electric Dream

[Zombificus 793]

Although technically never accepted for standardisation as M6A2, the T1E1 heavy tank was the most produced member of the T1/M6 family, with as many of this type built as M6s and M6A1s combined. Like the M6, it had a cast hull, and like all standard members of the T1 family, it used a cast turret armed with one 76.2mm M7 and one 37mm M6. The T1E1/M6A2's major innovation over the other types was its gas-electric transmission, which gave it full-speed reverse and likely also sped up its acceleration, a typical trait of electric transmissions. Compared to the M6A1 in game, which the wiki lists as having a top speed of 35 kph (21.9 mph) forwards and 8 kph (5 mph) backwards, the M6A2 is faster in every direction, capable of up to 43 kph (26.9 mph). Besides the improved mobility, late-production M6s were supposed to be built to a final armour specification of 127mm maximum hull thickness and up to 152.4mm on the turret where the outer and inner mantlets overlap. While it's unclear if any were actually built to this specification, some of the photos of the 90mm-armed version used in Sirchby's M6A2(90) suggestion have features of the late-production model, so the M6A2(90) was interpreted as being a final specification tank. As the M6A2(90)s were all converted from existing M6A2s, if the 90mm version was in fact final specification standard, this implies that the 76mm-armed examples they were converted from also had this armour specification. With the disclaimer that this isn't known for certain, I'd like to suggest the M6A2(76) as a more mobile and tougher successor to the M6A1 that could help plug the gap left by the uptiered Jumbos.

 

Many thanks for @Sirchby for letting me use his sources, and to @Whelmy who did the original research for the M6A2(90) suggestion. 

 

 

History:

 

Developed as part of a resurgence in US tank development in the wake of Nazi Germany's effective use of armour as part of Blitzkrieg, the T1 heavy tank program was one of a number of American designs being worked on in the 1940s. Approved for development in June 1940, following a recommendation for a 50 ton heavy tank the month before, the T1 Heavy Tank was complicated from the beginning by the question of how to propel such a massive vehicle. While the Wright G-200 engine was quickly settled upon, the choice of transmission to put this huge powerplant to use was less clear-cut. No less than three different transmission types were proposed across the inital five designs: hydramatic on the unbuilt T1 & T1E4 (unique in its quad-GM-engine powerplant); electrical on the T1E1 (M6A2); and torque converter on the T1E2 (M6) and T1E3 (M6A1). Despite being the more advanced of the built transmissions, T1E1's electric transmission was unexpectedly found by Fort Knox heavy tank crews to be the most reliable and easiest to maintain of the whole series, and more of this type were built than any other T1 series heavy: 20 completed T1E1/M6A2s vs 12 M6A1s and 8 M6s. Like the contemporaneous M3 Lee and M4 Sherman, both cast and welded hulls were trialled on the T1s and the two types formally accepted for service represented both options. Cast armour is somewhat weaker than welded RHA, but at the thicknesses used on the T1s, particularly the 95-127mm frontal plate of the final specification tanks, the difference should have been irrelevant in the field -- anything likely to penetrate a cast-hulled M6 or M6A2 would also pierce a welded-hull M6A1. 

 

Early in development, a multi-turreted design like those in vogue with European and Soviet armies in the 1930s was considered, but it was clear that the age of the multi-turreted land battleship was at an end, so the design switched to the twin mount of one 76.2mm M7 and one 37mm M6. In hindsight, this was still an impractical armament (with crew reports often negative with regards to the "superfluous" 37mm), but it was at least much closer to the needs of the time. No sooner had the 76mm prototypes been trialled in 1942 than their main gun deemed inadequate and an upgunning to 90mm recommended, with the pilot T1E1 being put to this use in early 1943. Following the theme of no armament satisfying the Ordnance Department by the time it was fitted, even the 90mm gun couldn't save the M6, its last gasp being the ludicrous M6A2E1 with the T29's turret and the T5E1 105mm gun, which was rejected by Eisenhower himself. The armour was also a point of constant revision, perhaps even more so than the gun. The initial T1 armour design dates to May to October 1940, in the tank's infancy, followed by no less than three successive upgrades: one proposed in February 1942, another in the summer of that year, and the final specification by the end of 1942. In December that year, all M6 series production had switched to this final specification, which added a full 4.3 tons of armour to the original layout, although by this time the M6 series had already been cancelled and production cut to a 40-vehicle maximum. Photo evidence suggests that at least some of the M6A2s rearmed at Fort Knox from late 1943 to early 1944 were part of this final specification, so it's very likely that some M6A2(76)s existed with the full 127mm maximum thickness between December 1942 and mid-1943. Although the M6A2 was never standardised and therefore was still technically the T1E1, the tank was usually referred to as M6A2 by its crews and in most internal communications -- in at least one report, it's even noted as "formerly T1E1" as if it had been standardised. Also notable is the fact that the M6A2's 1944 breakthrough variant was called M6A2E1, not T1E6 or T1E1-1, which strongly implies that the tank was by this point officially M6A2 regardless of its standardisation status. 

 

Ultimately, although two M6A2E1s were built (but never equipped with the additional armour package proposed for them), the entire M6 family had been dead in the water for years, this being one last desperate attempt to resurrect the project. Although the M6A2 was well liked by tankers and maintenance crews and at one point the US planned on building 115 M6A2s for themselves, with the same number of M6s and M6A1s combined going to Britain via Lend-Lease, the tank had some inescapable flaws and higher-ups were hostile to the idea of heavy tanks in general. Even the superior M26, which formed the basis for America's first two MBTs, almost never reached production at all and as a result wound up arriving in Europe too late to make any real impact. By comparison, the oversized and impractical M6 had no chance, and all but the T1E1 prototype met an ignoble end at the scrapyard. 

 

Specifications:

 

 

Length: 8.43m (gun forward)

Width: 3.12m

Height: 3.0m

Weight: 61.67 tons (original 57.37 tons + 4.3 ton armour upgrade)

Crew: 6 (Driver, Co-Driver, Commander, Gunner, 2 Loaders)

Primary Armament: 76.2mm M7 (75 rounds; 8-10 RPM)

Secondary Armament: 37mm M6 (202 rounds; 15-20 RPM)

Armament Traverse: -10 to +30 degrees elevation; 360 degree traverse at 12-17 deg/s

Tertiary Armament: 3x 12.7mm M2HB (2 in the bow, 1 in the turret AA mount)

Turret Armour: 152.4mm mantlet (50.8mm external + 101.6mm internal); 101.6mm sides and rear; 34.925-41.275mm roof

Frontal Hull Armour: 101.6mm upper plate (at 30 degrees); 95.25mm middle plate (at 45-60 degrees); 127mm lower glacis (at 0-45 degrees)

Other Hull Armour: 76.2mm sides + 25.4mm skirts; 50.8mm rear; 44.45mm frontal roof; 38.1mm hatches; 25.4mm main roof and hull floor

Engine: Wright G-200 (Model 795C9GC1) Cyclone 960hp 9-cylinder radial engine

Power/Weight: 15.57 hp/ton (960hp at 2300 rpm / 61.67 tons fully loaded)

Max Speed: 26.9 mph (43 kph) forwards and backwards

 

Its Place In War Thunder:

 

With the M4A3E2 and M4A3E2(76)W both seeing major BR increases, there is now a space for an improved heavy tank to bridge the gap between the first Jumbo and its previous neighbour at BR 4.7. The M6A2's greater top speed and full-speed reverse might be enough to justify placing it at 5.0 by themselves, but it's really the final specification tank we'd want. Not only would it bridge the gap between the M6A1 and M4A3E2 in ability, its armour would also be somewhere in between, most importantly raising the weaker parts of the M6A1's front (barely more than 80mm in places) to a 100mm+ effective thickness that matches the M6A1's best. Given that the M6A1 isn't actually all that tough, with Panzer IVs able to deal devastating blows through the weak spots in its inconsistent frontal plate with their normal rounds, the final specification upgrade would be a welcome increase in protection. The modest improvement to top speed and acceleration, meanwhile, would allow it to be even more aggressive than it currently can and help it cross between cover without its rather large flanks getting hit. The full speed reverse is also no small upgrade: the M6A1's glacial 5 mph reverse has often gotten me killed trying desperately to retreat back into cover, whereas even the T20's 11.25 mph reverse is enough to confidently play peekaboo with other tanks and win. The fact that the M6A2's reverse is full speed is just the icing on the cake, as any significant upgrade would have had a big impact on its survivability. What the M6A2 offers is a tank with all the strengths of the M6A1 -- a good gun and useable stabiliser -- and fixes to its most major flaws -- surprisingly weak hull armour and an appalling reverse. As such, I'd expect it to be a perfect BR 5.0, which would go well tabbed with the M6A1 and provide another tank to run alongside the 5.0 M4A1(76)W, or a backup to the newly 5.3 M4A3E2. Its similarities to the existing tank, mainly requiring reworking of the hull shape and armour thicknesses, should also help to get it into the game with less work than a totally new design, and modelling one of the M6A2s would make producing the 90mm version or M6A2E1 sometime down the line.

 

I hope you like this tank, and I look forwards to hearing from you in the comments!

 

More Pictures:

Spoiler

An M6 or M6A2 heavy tank with the cast hull.

 

The M6A1 with its welded hull -- note the much sharper edges compared to the M6(A2)'s rounded shape

 

An M6A2(90) at a parade event; the lifting rings on the hull MG mounts are a late production feature that points to this being a final specification tank.

 

A side view of what I believe to be the mockup for T1E1/M6A2.

 

For comparison, this is a completed M6 or M6A2 (they are externally identical)

 

The T1E1 prototype is the only surviving T1/M6 series tank in the world.

 

Sources disagree on whether this is an M6A2 or just an M6, but they look the same so the distinction isn't all that important. 

 

The pilot T1E1 (M6A2); the only of the series not to be scrapped.

 

The M6 pilot vehicle, which is externally almost the same.

 

One of the two M6A2E1 prototypes.

 

 

 

 

 

Reports on Final Armour Specification:

Spoiler

 

Primary Sources:

Royal Army Corps - Technical Situation Report No. 2, 1942
Royal Army Corps - Technical Situation Report No. 21, 1944
TM 9-721 - Heavy Tanks M6 and M6A1, 1943
Record of Army Ordnance Research and Development - Heavy Tanks and Assault Tanks, 1945

 

Secondary Sources:

Firepower - A History of the American Heavy Tank, by R.P. Hunnicutt 

https://en.wikipedia.org/wiki/M6_heavy_tank#Variants

https://www.warhistoryonline.com/world-war-ii/us-m6-heavy-tank.html

https://www.militaryfactory.com/armor/detail.asp?armor_id=557

http://afvdb.50megs.com/usa/heavytankm6.html

http://www.historyofwar.org/articles/weapons_heavy_tank_M6.html

 

Edited September 17, 2020 by Zombificus

[leroyonly 4,311]

Open for discussion. 

[Milocat 4,855]

+1, very nice find, I would definitely like to see either an early or late model of this variant.

[corevino 308]

The M6 was never my favourite but America xxxx yeah. 

1+

[Sirchby 3,711]

+1

M6A2 was the main variant used by the US for development and propaganda purpose, after all.

It should have more presence than the M6A1.

[eleks12 1,079]

+1 

[Orphican 82]

+1 This would be great in WT.

[Nostalgistic 312]

+1 by the way the T1E1 has been confirmed in Sky Guardians update.

[leroyonly 4,311]

As the T1E1 has been implemented as per Update 2.25 Sky Guardians,

 

Moved to Implemented Suggestions.