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| M6 Heavy Tank. |
The Heavy Tank M6 was an American heavy tank designed during
World War II. The tank was produced in small numbers and never saw combat.
Because of limited budgets for tank development in the
interwar years, at the outbreak of World War II the US Army possessed few
tanks, though it had been keeping track of the use of tanks in Europe and Asia.
Successful employment of armored units in 1939 - 1940, mostly by the Germans,
gave momentum to a number of US tank programs, including a heavy tank program.
The United States possessed a massive industrial infrastructure and large
numbers of engineers that would allow for mass production of tanks.
Following the Chief of Infantry recommendation from 20 May
1940, the US Army Ordnance Corps started to work on a 50-ton heavy tank design.
Initially a multi-turreted design was proposed, with two main turrets armed
with low-velocity T6 75 mm (2.95 inch) guns, one secondary turret with a 37 mm gun,
and a coaxial .30 caliber (7.62 mm) machinegun, and another secondary turret
with a 20 mm gun and a coaxial .30 caliber machine gun. Four .30 caliber
machine guns were to be installed in ball mounts, two in the glacis (front)
plate and two in the rear corners of the hull. The project was approved on 11
June 1940 and the vehicle received the designation Heavy Tank T1. The design
was somewhat similar in concept to multi-turreted breakthrough tanks developed
in Europe in the 1920s and throughout the 1930s, such as the 1925 British
Vickers A1E1 Independent or the Soviet T-35 of the early 1930s. Disadvantages
of these "land dreadnoughts," namely their excessive size, difficulty
in coordinating actions of the crew, and high production costs, led to abandonment
of the concept in Europe.
By October, the US developers reached the same conclusion as
their European counterparts. The armament was changed to a single
vertically-stabilized 3 inch (76.2 mm) gun and a coaxial 37 mm gun in a single
three-man turret with both manual and electric traverse. The turret had a
commander's cupola identical to that of the M3 Medium Tank. Additional armament
consisted of two .50 caliber machine guns in a bow mount (operated by the
assistant driver), two .30 caliber machine guns in the front plate (fired
electrically by the driver), one .30 caliber in the commander's cupola and one
.50 caliber in a rotor mount for anti-aircraft use in the right rear of the
turret roof (operated by the loader). The crew consisted of commander (seated in
the turret left), gunner to the right of the gun, gun loader (turret), driver
and assistant driver in the front left and right of the hull respectively, and
another crewman in the hull to pass ammunition to the turret.
One of the main challenges was developing a powerpack for
such a heavy vehicle. The Wright G-200 air-cooled radial gasoline engine was
selected by a committee formed by the Society of Automotive Engineers, but no
suitable transmission was available. The committee recommended developing a hydramatic
transmission, while a possibility of using a torque converter or an electric
transmission was also to be checked.
In 1941-1942 three prototypes were built by the Baldwin
Locomotive Works, one with electric transmission and two with torque converter
transmission. Variants with hydramatic transmission were never completed. The
prototypes also differed in hull assembly method - one had welded hull and two
cast hull. On 26 May 1942 two variants with torque converter transmission were
standardized as M6 and M6A1. Standardization of the electric transmission
equipped T1E1 as M6A2 was never approved, but manufacturing of the vehicle was
nevertheless recommended. It was proposed by the Ordnance Corps that 115 T1E1s
would be built for the US Army for "extended service tests," between
that and Services of Supply instruction to increase production with the balance
going to aid US allies, this would mean 50 M6s and 65 M6A1s built for the
British. The production started in December 1942.
Some minor changes were introduced in the production
vehicles: the cupola was replaced by a double-door hatch with a ring mount, the
machine gun in a rotor mount and the left front machine gun were removed.
However by the time the M6 was ready for production, the
Armored Corps had lost interest in the project. The advantages the M6 offered
over medium tanks - its much thicker armor and slightly more powerful gun -
were offset partly by the shortcomings of the design - such as very high
silhouette, awkward internal layout and reliability problems - and partly by
logistical concerns due to its weight.
In early 1942 the Ordnance Department set a production
target of 250 a month with Fisher as a second contractor to meet a planned
expansion in the size of the army. However by September the focus had changed
with tank production scaled back and more aircraft for the USAAF. Under this
new "Army Supply Program," the M6 production was cut from 5,000 to a
little over 100.
By the end of 1942, the Armored Corps were of the opinion
that the new M4 Sherman gave adequate solution for the present and the near
future, while being reliable, cheap and much easier to transport and they had
no need for a heavy tank. In 1943 the production target was reduced again, down
to 40, being an economic cut-off.
Production M6 and pilot M6A1 examples were evaluated at Fort
Knox in the early part of 1943. The reports were critical of the awkward and
inefficient crew stations and the superfluous 37mm gun.
The Ordnance had expected the 75 mm gun to be lacking and
The T1E1 prototype was tested with a T7 90 mm gun and was found to be a
satisfactory gun platform, although poor turret layout was noted again. By this
point the M6 had been cancelled.
In August 1944 the Ordnance Corps recommended modifying the
T1E1s to build 15 specially armored and armed tanks to meet a need for
attacking heavily fortified areas. These 77-ton vehicles - designated M6A2E1 -
with thicker (equivalent to 7.5-inch (190 mm) vertical protection) glacis armor
and a turret developed for the T29 Heavy Tank, armed with a T5E1 105 mm gun but
no increase in engine power. Ordnance believed they could be delivered by
November. The proposal was put to the supreme commander in Europe General
Eisenhower who rejected them as impracticable. Two tanks were used to test the
T29 turret and gun but their armor was not modified.
However, by late 1942 main development effort shifted to
other projects, one of which eventually resulted in the M26 Pershing.
On 14 December 1944 the M6 was declared obsolete. Only forty
units were produced and they never left US soil. Several toured the United
States for propaganda purposes, where they gave performance displays (such as
car crushing) at War Bond drives and the like. All were eventually scrapped
except for a single T1E1 which was put on display at the United States Army
Ordnance Museum, Aberdeen, Maryland.
The British used the suspension of the M6 in the first of
their two A33 Heavy Assault Tank ("Excelsior") prototypes.
Specifications
Type: Heavy tank
Place of origin:
United States
In service:
trials only
Used by: United
States Army
Wars: World War
II
Designer: U.S.
Army Ordnance Corps
Manufacturer:
Baldwin Locomotive
Number built: 40
Variants
T1: Cast hull,
hydramatic transmission. Never built.
T1E1: Cast hull,
General Electric electrical transmission. Standardization proposed as M6A2 but
not accepted. 20 units built.
T1E2 / M6: Cast
hull, torque converter transmission. 8 units built.
Weight: 126,500 lb (57.4 tons) combat loaded
Length: 27 ft 8 in (8.43 m) gun forward
Width: 10 ft 3 in (3.12 m) over track armor
Height: 9 ft 10 in (3.0 m) to turret roof
Crew: 6 (commander, gunner, driver, assistant driver, loader,
assistant loader)
Armor: 25–83 mm
Main armament:
1 × 3in (76.2 mm) gun M7 (75
rounds)
1 × 37 mm (1.46 in) gun M6 (202
rounds)
Secondary armament:
2 × .50 cal (12.7mm) Browning M2HB
machine guns, hull (6,900 rounds)
2 × .30 Browning M1919A4 machine
guns, one fixed (bow), one flexible AA (5,500 rounds)
Engine: 1,823 in3 (29.88 L) Wright G-200 9-cylinder gasoline; 825
hp at 2,300 rpm
Power/weight: 15.7 hp/ton
Transmission: Timken mechanical model 16001, three speeds (two
forward, one reverse); rear drive sprocket
Suspension: Horizontal volute spring
Ground clearance: 20.5 in (52 cm)
Fuel capacity: 477 US gallons (1,810 L)
Operational range: 100 miles (160 km)
Speed: 22 mph (35 km/h)
T1E3 / M6A1: Welded
hull, cast turret, torque converter transmission. 12 units built.
T1E4: Welded
hull, hydramatic transmission. Four GM engines. Cancelled 1942. Never built.
M6A2E1: Uparmored T1E1 fitted with a new turret with a T5E1 105 mm
gun. Used for testing T29 heavy tank project armament system.
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| T1E1 Heavy Tank prototype. |
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| Front view of Heavy Tank M6, with several early M3 Light Tanks in the background. |
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| A U.S. Army M6 Heavy Tank in December 1941. Original caption: "Delivery of the first heavy tanks. This is the new 57-ton tank, known as the M1 in the initial demonstration. Notice that the gun turrets are on the top, making it possible for the tank to take advantage of irregular land, sheltering the lower part and shooting from revolving turrets on top. In the turret are 3-inch guns and a 37mm anti-aircraft gun." |
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| M6A1 Heavy Tank. Note its angular welded hull, as opposed to rounded cast hulls of M6 and T1E1. |
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| T1E1 Heavy Tank. |
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| The M6A2E1 was a modified M6A2 with a new heavy turret and the T15E1 105mm Gun, in anticipation of demands for assault tanks from the European theater. Aberdeen Proving Ground, 7 June 1945. |
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| The M6 heavy tank was nothing if not imposing, as this view illustrates. The smooth lines of the cast hull are apparent here. Hidden behind the 3" gun is the coaxial 37mm gun, which was the main armament of the M2 medium tank produced three years previously. A .50 cal. machine gun is partially hidden by the open turret hatch, and two more .50 cal. machine guns were mounted in the right bow. Just behind the pistol port for the assistant driver is an antenna mount. |
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| The position of the M6 Heavy Tank's weapons are illustrated in this picture. No coaxial machine gun was mounted, meaning that the tank commander had to expose himself to provide machine gun fire to the vehicle's sides or rear. |
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| Although externally identical to the M6, the T1E1 Heavy Tank was driven by an electric drive system instead of a more conventional transmission. This vehicle is fitted with the center guide T31 tracks. These were made from a set of the outside guide tracks where the center guide replaced the center connector, and the outside guides were removed by flame cutting. Note the partially-open driver's visor on this tank. |
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| M6 Heavy Tank during a public demonstration. |
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| Heavy Tank M6 or M6A1, circa 1942. This tank was never put into full production, only forty M6 Heavy Tanks were built. |
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| M6 Heavy Tank. |
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| Upper rear view of an M6 Heavy Tank. |
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| M6 Heavy Tank crushing a vehicle during a demonstration. |
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| M6 Heavy Tank and M3 Light Tank. |
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| M6 (T1E2) Heavy Tank. |
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| M6A1 (T1E3) Heavy Tank. |
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| In early 1944 the T1E1 Heavy Tank was fitted with an experimental mounting of the 90mm Gun T7 using a turret based on that of the Heavy Tank M26 with the hull stowage rearranged for 90mm ammunition. Project was cancelled in March 1944. |
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| M6 Heavy Tanks, Aberdeen Proving Ground, Maryland. |
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| M6 Heavy Tank (probably same vehicle as seen in the previous photo), Aberdeen Proving Ground, Maryland, July 1974. |
