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United States' M6 heavy tank

Photos

M6A2 Heavy Tank:
United States' M6A2 Heavy Tank
Aberdeen Tank Museum

Design

After the invasion of the Low Countries and France in 1940 the Chief of Infantry requested two types of heavy tanks to be developed. One would be similar to the M2 Medium with 3" of armor, a hull mounted 75 mm gun, and a turret with a 37 mm or 50 mm gun. This eventually led to the M3 Medium. The second, which became the M6 Heavy, was not to be over 80 tons, have 3" of armor, a hull gun from 75 mm to 105 mm, and a 37 mm or 50 mm in the turret. Spread throughout the vehicle were to be eight machine guns.

In 1940 this was changed to have the main gun be a 76 mm and have the 37 mm coaxially mounted.

The final drive was mounted behind the engine. The transmission was connected by a flexible coupling without the use of a propeller shaft. There was a pedal that occupied the position normally occupied by the clutch petal, and this served as a transmission brake pedal.

The 3" gun was mounted with the 37 mm gun. A gyrostabilizer was provided as well.

There were 4 bogie assemblies on each side. Each had 4 bogie wheels. Two riding on the outside half of the track and 2 on the inside. Two springs were mounted on each assembly. The driving sprocket was at the rear. There was a main idler in the front and there was a nonadjustable idler between the main idler and the front bogie assembly.

Six periscopes were provided. There were 4 escape doors.

Design Changes

After over 3,500 miles of testing, in April 1942, it was decided to completely redesign the brakes and cooling system due to flaws that were found. The new brakes were similar to train engine brakes as they were hydraulically operated disc brakes applied to the differential.

Production Withdrawn

The Armored Board decided that the M6 was too heavy and unreliable so they recommended that the contracts should be cancelled. The Ordnance Department said it could modify the design of the M6 to rectify these problems but the Army Ground Forces decided it didn't want the M6. In September 1942 orders were reduced to 115, with 50 of those going to the British Army. Also, the Armored Forces felt that the M6 would take up too much shipping space as two M4 Mediums could fit in the same space a single M6 would fit.

Prototypes

Originally four prototypes were to be built, each with a different power train, but two of these required changes to the hull so only two were authorized.
Four prototypes were constructed in February 1941. They were designated the T1E1 - T1E4. The cast hulled version with a torque converter was choosen.

The engine for the prototypes was the Wright G-200 9 cylinder air cooled aircraft engine that produced 825 HP.

T1, Hydraulic Transmission

The T1 was to have the torque converter transmission (see below) but delays in producing the complex torque converter caused it to have a hydraulic transmission.

The T1 was had a turret and was armed with a 3" T9 antiaircraft gun. Coaxially it had a M5E1 37 mm gun. Two .50 cal machine guns were mounted in the hull for the assistant driver to operate. Initially the driver had two .30 cal machine guns as well. The commander had a .30 cal machine gun in his cupola.

T1E1, Gasoline Electric Transmission

The tank engine provided power to two motors that drove each track. Braking and steering changed the amount of current going to these engines which controlled the speed of the tracks. As this transmission was flexible, one track could go forward while the other went reverse allowing the tank to rotate on its own axis.

The T1E1 didn't have a formal turret installed and was never armed as it was only used to test the transmission. It could go 25 mph but only had a range of 100 miles.

British observers followed the tests as the TOG had a similar transmission.

T1E2, Torque Converter

A form of hydraulic transmission, the torque converter, applied the power to the final drive via a variable torque speed ratio. The ratio was automatically selected based upon the load placed on the engine.

Innovative Design

For 1940, the design was innovative as it had the turret and hull made from castings. There were no side doors as the hatches were in the top and escape hatches in the bottom. There was a track skirt installed on each side to protect the suspension which was unique for an United States design.

Production

In April 1942 the T1E2 was standardized as the M6 Heavy Tank.

By September 1942, orders for 5,000 M6s were placed.

On December 7, 1942, the Chief of the Armored Forces recommended that all production be stopped immediately as the M6 series was no longer needed.

  • T1: 1
  • T1E1: 1
  • T1E2: 1
    • Production: December 1941
  • T1E3: 1
  • M6: 7
    • Manufacturer: Baldwin Locomotive
    • Production: December 1942 - ?
  • M6A1: 11
  • M6A2: 18
    • Manufacturer: Baldwin Locomotive Co.
  • Total: 40
    • Manufacturer: Fisher Body Division (12), Baldwin Locomotive (28)

Variants

  • T1: Prototype. Hydraulic transmission.
  • T1E1: Prototype. Gasoline electric transmission. Became the M6A2.
  • T1E2: Prototype. Torque converter transmission. Was selected to become the M6.
  • T1E3: Prototype. Became the M6A1.
  • T1E4: Prototype, never constructed. Was to have welded hull and a cast turret. Four diesel engines were to be installed. with two torquematic transmissions.
  • M6: Had cast hull and turret. It had a torque converter transmisison.
  • M6A1: Had a cast turret and welded hull. It had a torque converter transmission.
  • M6A2: Cast hull with electric transmission.
    The 3" gun could fire a 15 lb shell at a muzzle velocity of 2,600'/sec. The 37 mm could fire a 1.91 lb shell at 2,600'/sec.
  • M6A2E1: Had 105 mm T15E1 gun installed expecting the better armament would be needed in Europe. Fifteen were to be converted, but in July 1944 it was cancelled.

Usage

Never saw service.

Specifications

  T1
Crew  
Physical Characteristics  
Weight 120,000 lb
Length  
Height  
Height - without cupola  
Width  
Width over tracks  
Ground clearance  
Ground contact length  
Ground pressure  
Turret ring diameter  
Armament (mm)  
Main  
Secondary  
MG  
Side arms  
Quantity  
Main  
Secondary  
MG  
Side arms  
Armor Thickness (mm)  
Hull Front, Upper  
Hull Front, Lower  
Hull Sides, Upper  
Hull Sides, Lower  
Hull Rear  
Hull Top  
Hull Bottom  
Turret Front  
Turret Sides  
Turret Rear  
Turret Top  
Engine (Make / Model)  
Bore / stroke  
Cooling  
Cylinders  
Capacity  
Net HP  
Power to weight ratio  
Compression ratio  
Transmission (Type) Hydraumatic
Steering  
Steering ratio  
Starter  
Electrical system  
Ignition  
Fuel (Type)  
Octane  
Quantity  
Road consumption  
Cross country consumption  
Performance  
Traverse  
Speed - Road  
Speed - Cross Country  
Range - Road 100 miles
Range - Cross Country  
Turning radius 8' 6"
Elevation limits  
Fording depth  
Trench crossing  
Vertical obstacle  
Climbing ability  
Suspension (Type)  
Wheels each side  
Return rollers each side  
Tracks (Type)  
Length  
Width  
Diameter  
Number of links  
Pitch  
Tire tread  
Track centers/tread  
  M6, T1E2
Crew Commander, driver, co-driver, gunner, loaders (2)
5, 6
Physical Characteristics  
Weight 126,500 lb
44.6 tons
45,316 kg, 45,360 kg, 57,379 kg
Length w/gun 23' 10", 24' 9", 27' 8"
8.43 m, 8.433 m, 8.44 m
Length w/o gun 24' 9"
Height 9' 10", 10' 6", 10' 7"
3.226 m, 3.23 m
Height - without cupola 9' 11"
Width 10' 2", 10' 2.5", 10' 3", 10' 7"
3.1 m, 3.1115 m, 3.23 m
Width over tracks  
Ground clearance 1' 8.5"
Ground contact length 186"
Ground pressure 12.3 psi
Turret ring diameter 69"
Armament (mm)  
Main 1: 3"
1: 3" T9 AA
1: 3" M7
1: 76 mm
1: 76.2 mm / 3"
Secondary 1: 37 mm M5E1
1: 37 mm M6, coaxial
1: 37 mm
1: 37 mm / 1.46"
MG 4: MG
3: 12.7 mm (.50 cal)
2: 12.7 mm / 0.5" MG
2: 7.62 mm (.30 cal) MG
2: 7.62 mm / 0.3" MG
2: .30 cal MG
2: .30 cal Browning MG.
MG - bow 1: .30 cal MG
2: .50 cal Browning MG
2: .50 cal MG
MG - antiaircraft 1: .50 cal Browning MG
1: .50 cal MG
MG - cupola 1: .30 cal MG
Side arms 2: .45 cal Submachine M3
Quantity  
Main 75
Secondary 202
MG .30: 7,500
.50: 5,700
Side arms .45: 1,200
Armor Thickness (mm) 25, 100, 133
1" - 3.25"
(Actual thickness to horizontal)
Hull Front, Upper 76
3", 3.25" (4")
Hull Front, Lower 2.75-4" (4")
Hull Sides, Upper 64
1.75" (1.75"), 2.5"
Hull Sides, Lower  
Hull Rear 1 5/8" (2"), 2"
Hull Top 1"
Hull Bottom 1"
Turret Front 100
3.25" (3.25"), 3.93"
Turret Sides 3.25" (3.25")
Turret Rear 3.25" (3.25")
Turret Top 1"
Engine (Make / Model) Wright G-200, Wright Whirlwind G-200
Bore / stroke  
Cooling Air
Cylinders 9, Radial 9
Capacity  
Net HP 800, 825, 925
Power to weight ratio  
Compression ratio  
Transmission (Type) Torque converter
2 forward, 1 reverse.
Steering  
Steering ratio  
Starter  
Electrical system  
Ignition  
Fuel (Type)  
Octane  
Quantity 464 gallons
Road consumption  
Cross country consumption  
Performance  
Traverse 360°, electrical
Speed - Road 22 mph
35 kph, 35.4 kph
Speed - Cross Country  
Range - Road 100 miles, 116 miles
161 km
Range - Cross Country  
Turning radius 8' 6"
Elevation limits - main -10° to +30°
Elevation limits - bow MG .30 cal: +30°
.50 cal: -10° to +60°
Fording depth 4'
Trench crossing 11', 13' 2"
Vertical obstacle 3', 3' 6"
Climbing ability 55°
Suspension (Type) HVSS with double bogies of 4 wheels each and 2 tracks each side.
Wheels each side  
Return rollers each side  
Tracks (Type) Steel rubber bushed
Length  
Width 2' 1.75"
0.654 m
Diameter  
Number of links  
Pitch 6"
Tire tread  
Track centers/tread 7' 9"
2.362 m
  M6A1, T1E3
Crew  
Physical Characteristics  
Weight 126,300 lb
Length  
Height  
Width  
Width over tracks  
Ground clearance  
Ground contact length  
Ground pressure  
Turret ring diameter  
Armament (mm)  
Main  
Secondary  
MG  
Side arms  
Quantity  
Main  
Secondary  
MG  
Side arms  
Armor Thickness (mm)  
Hull Front, Upper  
Hull Front, Lower  
Hull Sides, Upper  
Hull Sides, Lower  
Hull Rear  
Hull Top  
Hull Bottom  
Turret Front  
Turret Sides  
Turret Rear  
Turret Top  
Engine (Make / Model)  
Bore / stroke  
Cooling  
Cylinders  
Capacity  
Net HP  
Power to weight ratio  
Compression ratio  
Transmission (Type) Torque converter
Steering  
Steering ratio  
Starter  
Electrical system  
Ignition  
Fuel (Type)  
Octane  
Quantity  
Road consumption  
Cross country consumption  
Performance  
Traverse  
Speed - Road 24 mph
Speed - Cross Country  
Range - Road 116 miles
Range - Cross Country  
Turning radius 8' 6"
Elevation limits  
Fording depth  
Trench crossing  
Vertical obstacle  
Climbing ability  
Suspension (Type)  
Wheels each side  
Return rollers each side  
Tracks (Type)  
Length  
Width  
Diameter  
Number of links  
Pitch  
Tire tread  
Track centers/tread  
  M6A2, T1E1
Crew 6
Physical Characteristics  
Weight 127,000 lb
44.6 tons, 60 tons
45,316 kg
Length 23.75'
Height 9.9'
Height - without cupola  
Width 10.25'
Width over tracks  
Ground clearance 20.5"
Ground contact length 188"
Ground pressure 12.4 psi
Turret ring diameter  
Armament (mm)  
Main 1: 3" T12, L/50
1: 76.2 mm / 3"
Secondary 1: 37 mm M6, L/53
MG  
MG - bow 1: .30 cal M1919M4 MG
2: .50 cal M2 MG
MG - antiaircraft 1: .50 cal M2 MG
Side arms  
Quantity  
Main 75
Secondary 340
MG .30: 4,000
.50: 8,000
Side arms  
Armor Thickness (mm) Front: 5"
Side: 2-2.5"
Hull Front, Upper  
Hull Front, Lower  
Hull Sides, Upper  
Hull Sides, Lower  
Hull Rear  
Hull Top  
Hull Bottom  
Turret Front 3.5"
Turret Sides 3.5"
Turret Rear  
Turret Top  
Engine (Make / Model) Wright Whirlwind G200
Bore / stroke  
Cooling Air
Cylinders 9
Capacity  
Net HP 750@2,150 rpm
Power to weight ratio  
Compression ratio  
Transmission (Type) Electric, Gasoline electric
2 forward, 1 reverse
Steering Controlled differential
Steering ratio  
Starter Electrical
Electrical system 24-volt
Ignition Magneto
Fuel (Type) Gasoline
Octane  
Quantity 350 gallons
Road consumption 0.42 mpg
Cross country consumption  
Performance  
Traverse Power or manual
Speed - Road 27 mph
Speed - Cross Country  
Range - Road 120 miles, 146 miles
Range - Cross Country  
Turning radius 0
Elevation limits  
Fording depth 48"
Trench crossing 11'
Vertical obstacle 3' 6"
Climbing ability 31° (60%) slope
Suspension (Type) Horizontal volute springs
4 two-wheeled bogies
Wheels each side 4x2
Return rollers each side 3
Tracks (Type) Double, rubber block, rubber bushed, double pin shoe
Length  
Width 25.75"
Diameter  
Number of links 100
Pitch 6"
Tire tread  
Track centers/tread 7.8'

Sources:

  1. The Encyclopedia of Tanks and Armored Fighting Vehicles - The Comprehensive Guide to Over 900 Armored Fighting Vehicles From 1915 to the Present Day, General Editor: Christopher F. Foss, 2002
  2. British and American Tanks of World War Two, The Complete Illustrated History of British, American, and Commonwealth Tanks 1933-1945, Peter Chamberlain and Chris Ellis, 1969
  3. Tanks of the World, 1915-1945, Peter Chamberlain, Chris Ellis, 1972
  4. Tank Data, Aberdeen Proving Grounds Series, 1968?
  5. Airfix Magazine Guide #26 American Tanks of World War 2, Terry Gander and Peter Chamberlain, 1977
  6. Profile AFV Weapons #32 The M6 Heavy and M26 Pershing, Robert J. Icks, Colonel AUS-Retired, 1971
  7. World War I and II Tanks, George Forty, 2012
20th Century American Military History Crucial Site