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M1
M1A1
M1A1E1

Combat Car M11-7

M1: General
Date of first acceptance 1935 Total acceptances 89
Manufacturer Rock Island Arsenal Crew
4 men:
  • Commander in turret
  • Gunner in turret
  • Driver in hull left front
  • Assistant driver in hull right front
M1: Dimensions
Combat weight 18,790lbs
8,523kg		 Height over AAMG mount 89"
226cm
Length 163"
414cm		 Gun overhang forward 0"
Width over side stowage 94"
240cm		 Tread 72"
180cm
Ground clearance 15"
38cm		 Fire height 73"
185cm
Turret ring diameter 47.5"
121cm		 Ground pressure, zero penetration 9.4psi
.66kg/cm²
M1: Armament
Type Mount Ammunition Traverse Elevation
.50cal M2HB MG
--OR--
.30cal M2HB MG		 M15 in left side of turret 1,100 rounds .50cal 360°
(manual)		 Manual
.30cal M2HB MG M16 or M18 in right side of turret 6,700 rounds .30cal 360°
(manual)		 Manual
.30cal M2HB MG
--OR--
.30cal M1919A4 MG		 AA bracket mount M19 or M20 behind turret 360°
(manual)		 Manual
.30cal M2HB MG
--OR--
.30cal M1919A4 MG		 M2HB: Ball mount M8 in right bow
M1919A4: Ball mount M10 or M13 in right bow		 M13:
31°
(17° left and 14° right;
manual)		 M13:
+24° to -14°
(manual)
Aiming equipment
Telescopic sight M5 or M1918A2 in mount M15 or M18
M1: Armor
Assembly
Riveting
Hull
Rolled face-hardened steel
Location Thickness Angle from vertical
Upper front .625"
1.6cm		 17°
Middle front .625"
1.6cm		 69°
Lower front .625"
1.6cm		 21°
Sides .5"
1.3cm		 0°
Rear .25"
.64cm		 0°
Top .25"
.64cm		 90°
Floor .25"
.64cm		 90°
Turret
Rolled face-hardened steel
Location Thickness Angle from vertical
Front .625"
1.6cm		 30°
Sides .625"
1.6cm		 0°
Rear .625"
1.6cm		 0°
Top .25"
.64cm		 90°
M1: Automotive
Engine Continental R-670-3, -3C, -5; or W-670-7 or -8; 7 cylinder, 4 cycle, static radial gasoline
Horsepower Net: R-670-3, -5, W-670-7: 250@2,400rpm
R-670-3C, W-670-8: 235@2,400rpm
Gross: R-670-3, -5, W-670-7: 262@2,400rpm
R-670-3C, W-670-8: 248@2,400rpm		 Torque Net: R-670-3, -5, W-670-7: 584 ft-lb@1,800rpm
Gross: R-670-3, -5, W-670-7: 590 ft-lb@1,700rpm		 Fuel capacity 50gal
190L
Transmission Sliding, constant mesh, 5 speeds forward, 1 reverse
Steering Controlled differential, steering levers
Brakes Mechanical, external contracting
M1: Suspension
Type Road wheels Track return rollers
Vertical volute spring 2 bogies/track;
2 wheels/bogie		 2/track
Drive sprockets Idlers Shock absorbers
14-tooth front drive Adjustable at rear of track None
M1: Track
T16E1
Outside guide, double pin, rubber bushed, reversible rubber
Width 11.6"
29.5cm		 Pitch 5.5"
14cm		 Shoes/track 62 Ground contact length 86"
220cm
T16E2
Outside guide, double pin, rubber bushed, non-reversible rubber
Width 11.6"
29.5cm		 Pitch 5.5"
14cm		 Shoes/track 62 Ground contact length 86"
220cm
M1: Performance
Max level road speed 45mph
72kph		 Max trench 48"
120cm
Max grade 60% Max vertical obstacle 24"
61cm
Min turning diameter 42'
13m		 Max fording depth 43"
110cm
Cruising range ~120mi, roads
~190km, roads

The first 58 M1 combat cars had a flat-faced, D-shaped turret. The rest were fitted with an octagonal turret assembled from eight flat armor plates. The roof of the turrets was made up of three pieces that could be folded in such a way as to provide a forward-facing shield with vision slots. Early vehicles had a rounded engine cover, which was replaced later by an angular, flat-sided engine cover. Later combat cars also had their constant mesh transmission replaced by a synchromesh model. Three M1s were fitted with the Guiberson T-1020 diesel engine of the combat car M1A1E1 in 1937.

The term combat car came into use as a way around the 1920 National Defense Act, which assigned tanks to the infantry. Cavalry therefore was forced to invent a separate nomenclature for their tanks: "combat cars." The combat car M1 was renamed light tank M1A2 on 22 August 1940; with the creation of the Armored Force on 10 July 1940, all tanks now belonged to this organization, and separate names were no longer required.

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Combat Car M1A11-3,5,7

M1A1: General
Date of first acceptance 1938 Total acceptances 17
Manufacturer Rock Island Arsenal Crew
4 men:
  • Commander in turret
  • Gunner in turret
  • Driver in hull left front
  • Assistant driver in hull right front
M1A1: Dimensions
Combat weight ~19,000lbs
~8,600kg		 Height over AAMG mount 89"
226cm
Length 174.5"
443.2cm		 Gun overhang forward 0"
Width over side stowage 94"
240cm		 Tread 72"
180cm
Ground clearance 15"
38cm		 Fire height 73"
185cm
Turret ring diameter 47.5"
121cm		 Ground pressure, zero penetration 9.4psi
.66kg/cm²
M1A1: Armament
Type Mount Ammunition Traverse Elevation
.50cal M2HB MG
--OR--
.30cal M2HB MG		 M15 in left side of turret 1,364 rounds .50cal 360°
(manual)		 Manual
.30cal M2HB MG M18 in right side of turret 9,470 rounds .30cal 360°
(manual)		 Manual
.30cal M1919A4 MG AA bracket mount M20 behind turret 360°
(manual)		 Manual
.30cal M1919A4 MG Ball mount M13 in right bow 31°
(17° left and 14° right;
manual)		 +24° to -14°
(manual)
Aiming equipment
Telescopic sight M5 or M1918A2 in mount M15 or M18
M1A1: Armor
Assembly
Riveting
Hull
Rolled face-hardened steel
Location Thickness Angle from vertical
Upper front .625"
1.6cm		 17°
Middle front .625"
1.6cm		 69°
Lower front .625"
1.6cm		 21°
Sides .5"
1.3cm		 0°
Upper rear .375"
.953cm		 0°
Lower rear .375"
.953cm		 19°
Top .25"
.64cm		 90°
Floor .25"
.64cm		 90°
Turret
Rolled face-hardened steel
Location Thickness Angle from vertical
Front .625"
1.6cm		 30°
Sides .625"
1.6cm		 0°
Rear .625"
1.6cm		 0°
Top .25"
.64cm		 90°
M1A1: Automotive
Engine Continental W-670-7; 7 cylinder, 4 cycle, static radial gasoline
Horsepower Net: 250@2,400rpm
Gross: 262@2,400rpm		 Torque Net: 584 ft-lb@1,800rpm
Gross: 590 ft-lb@1,700rpm		 Fuel capacity 60gal
227L
Transmission Sliding, constant mesh, 5 speeds forward, 1 reverse
Steering Controlled differential, steering levers
Brakes Mechanical, external contracting
M1A1: Suspension
Type Road wheels Track return rollers
Vertical volute spring 2 bogies/track;
2 wheels/bogie		 2/track
Drive sprockets Idlers Shock absorbers
14-tooth front drive Adjustable at rear of track None
M1A1: Track
T16E1
Outside guide, double pin, rubber bushed, reversible rubber
Width 11.6"
29.5cm		 Pitch 5.5"
14cm		 Shoes/track 67 Ground contact length 97"
246cm
T16E2
Outside guide, double pin, rubber bushed, non-reversible rubber
Width 11.6"
29.5cm		 Pitch 5.5"
14cm		 Shoes/track 67 Ground contact length 97"
246cm
M1A1: Performance
Max level road speed 36mph
58kph		 Max trench 60"
152cm
Max grade 60% Max vertical obstacle 24"
61cm
Min turning diameter 42'
13m		 Max fording depth 43"
110cm
Cruising range ~110mi, roads
~180km, roads

The combat car M1A1 had its rear hull redesigned to improve engine accessibility and fuel capacity. The idler was moved backwards and the rear bogie was moved 11" (28cm) to the rear. All M1A1s were fitted with the octagonal turret. Combat cars M1A1 were also renamed light tanks M1A2 with the creation of the Armored Force.

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Combat Car M1A1E11,5

M1A1E1: General
Date of first acceptance 1938 Total acceptances 7
Manufacturer Rock Island Arsenal Crew
4 men:
  • Commander in turret
  • Gunner in turret
  • Driver in hull left front
  • Assistant driver in hull right front
M1A1E1: Dimensions
Height over AAMG mount 89"
226cm		 Length 174.5"
443.2cm
Gun overhang forward 0" Width over side stowage 94"
240cm
Tread 72"
180cm		 Ground clearance 15"
38cm
Fire height 73"
185cm		 Turret ring diameter 47.5"
121cm
M1A1E1: Armament
Type Mount Ammunition Traverse Elevation
.50cal M2HB MG
--OR--
.30cal M2HB MG		 M15 in left side of turret 1,364 rounds .50cal 360°
(manual)		 Manual
.30cal M2HB MG M18 in right side of turret 9,470 rounds .30cal 360°
(manual)		 Manual
.30cal M1919A4 MG AA bracket mount M20 behind turret 360°
(manual)		 Manual
.30cal M1919A4 MG Ball mount M13 in right bow 31°
(17° left and 14° right;
manual)		 +24° to -14°
(manual)
Aiming equipment
Telescopic sight M5 or M1918A2 in mount M15 or M18
M1A1E1: Armor
Assembly
Riveting
Hull
Rolled face-hardened steel
Location Thickness Angle from vertical
Upper front .625"
1.6cm		 17°
Middle front .625"
1.6cm		 69°
Lower front .625"
1.6cm		 21°
Sides .5"
1.3cm		 0°
Upper rear .375"
.953cm		 0°
Lower rear .375"
.953cm		 19°
Top .25"
.64cm		 90°
Floor .25"
.64cm		 90°
Turret
Rolled face-hardened steel
Location Thickness Angle from vertical
Front .625"
1.6cm		 30°
Sides .625"
1.6cm		 0°
Rear .625"
1.6cm		 0°
Top .25"
.64cm		 90°
M1A1E1: Automotive
Engine Guiberson T-1020-4; 9 cylinder, 4 cycle, radial diesel
Horsepower Net: 220@2,200rpm
Gross: 245@2,200rpm		 Torque Net: 580 ft-lb@1,400rpm
Gross: 645 ft-lb@1,300rpm
Transmission Sliding, constant mesh, 5 speeds forward, 1 reverse
Steering Controlled differential, steering levers
Brakes Mechanical, external contracting
M1A1E1: Suspension
Type Road wheels Track return rollers
Vertical volute spring 2 bogies/track;
2 wheels/bogie		 2/track
Drive sprockets Idlers Shock absorbers
14-tooth front drive Adjustable at rear of track None
M1A1E1: Track
T16E1
Outside guide, double pin, rubber bushed, reversible rubber
Width 11.6"
29.5cm		 Pitch 5.5"
14cm		 Shoes/track 67 Ground contact length 97"
246cm
T16E2
Outside guide, double pin, rubber bushed, non-reversible rubber
Width 11.6"
29.5cm		 Pitch 5.5"
14cm		 Shoes/track 67 Ground contact length 97"
246cm
M1A1E1: Performance
Max trench 60"
152cm		 Max grade 60%
Max vertical obstacle 24"
61cm		 Min turning diameter 42'
13m
Max fording depth 43"
110cm

The combat car M1A1E1 was an M1A1 powered by the Guiberson diesel engine.

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References

  1. Hunnicutt, R.P. Stuart: A History of the American Light Tank, volume 1. Navato, CA: Presidio Press, 1992. Reprinted with permission from Stuart, R.P. Hunnicutt ©1992, available from Presidio Press, 505B San Martin Drive, Suite 160, Navato, CA 94945.
  2. Chamberlain, Peter, and Chris Ellis. British and American Tanks of World War Two. Frome, England: Cassell & Co., 2000.
  3. AGF Board No. 2. Development of Armored Vehicles, volume 1: Tanks. 1947.
  4. FM 30-40 C1 Military Intelligence Identification of United States Armored Vehicles. Washington, DC: War Department, 8 March 1942.
  5. Sola, Samuel, Vincent Bobkowski, and Kara Crocker. Weapon Mounts for Secondary Armament. Santa Monica, CA: G. O. Noville & Associates, Inc., April 1957.
  6. Nenninger, Timothy K. "Organizational Milestones in the Development of American Armor, 1920-1940." Camp Colt to Desert Storm: The History of U.S. Armored Forces. Eds. George F. Hofmann, Donn A. Starry. USA: University Press of Kentucky, 1999.
  7. Kirk, William. "Light Tanks." TANKS! 21 Jun 2000. 7 Dec 2000 <http://mailer.fsu.edu/~akirk/tanks/UnitedStates/lighttanks/​LightTanks.html>. TANKS!
Last updated 24 Nov 2023.
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© Copyright 2000-23 Chris Conners