Combat Car M21-5

M2: General
Date of first acceptance 1940 Total acceptances 34
Manufacturer Rock Island Arsenal Crew
4 men:
  • Commander in turret
  • Gunner in turret
  • Driver in hull left front
  • Assistant driver in hull right front
M2: Dimensions
Combat weight 25,500lbs
11,600kg		 Height over AAMG mount 95"
240cm
Length 172"
437cm		 Gun overhang forward 0"
Width over idler brackets 90.6"
230cm		 Tread 72"
180cm
Ground clearance 14.5"
36.8cm		 Fire height 75"
190cm
Turret ring diameter 47.5"
121cm		 Ground pressure, zero penetration 9.4psi
.66kg/cm²
M2: Armament
Type Mount Ammunition Traverse Elevation
.50cal M2HB MG M15 or D34956 in left side of turret 1,364 rounds 360°
(manual)		 Manual
.30cal M2HB MG M18 in right side of turret 9,470 rounds 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
M2: 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 .375"
.953cm		 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°
M2: 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		 Fuel capacity 60gal
230L
Transmission Synchromesh, 5 speeds forward, 1 reverse
Steering Controlled differential, steering levers
Brakes Mechanical, external contracting
M2: Suspension
Type Road wheels Track return rollers
Vertical volute spring 2 bogies/track;
2 wheels/bogie		 3/track
Drive sprockets Idlers Shock absorbers
14-tooth front drive Trailing adjustable with volute spring at rear of track None
M2: Track
T16E1
Outside guide, double pin, rubber bushed, reversible rubber
Width 11.6"
29.5cm		 Pitch 5.5"
14cm		 Shoes/track 66 Ground contact length 117"
297cm
T16E2
Outside guide, double pin, rubber bushed, non-reversible rubber
Width 11.6"
29.5cm		 Pitch 5.5"
14cm		 Shoes/track 66 Ground contact length 117"
297cm
M2: Performance
Max level road speed 36mph
58kph		 Max trench 72"
180cm
Max grade 60% Min turning diameter 42'
13m
Max fording depth 52"
130cm		 Cruising range ~200mi, roads
~320km, roads

The combat car M2 was modified from the combat car M1 by the installation of a trailing idler and diesel engine. The trailing idler increased the ground contact area, which reduced the ground pressure of the combat car M2 to near that of the lighter M1. The diesel engine gave the combat car M2 a longer range than gasoline-powered tanks. Diesel-powered light tanks can be identified by the long air intake pipes that travel from the air cleaners on either side of the engine compartment into the rear deck. The M2 was not fitted with a cupola, but had a folding roof like that of the combat car M1. A fixed 7½lb (3.4kg) CO2 fire extinguisher protected the engine compartment, and a 4lb (1.8kg) portable CO2 was also carried. One 12-volt battery was used for the electrical system.

After the formation of the Armored Force on 10 July 1940, the combat car M2 was redesignated as light tank M1A1. The new nomenclature was approved on 22 August 1940.

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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. FM 30-40 C1 Military Intelligence Identification of United States Armored Vehicles. Washington, DC: War Department, 8 March 1942.
  3. Sola, Samuel, Vincent Bobkowski, and Kara Crocker. Weapon Mounts for Secondary Armament. Santa Monica, CA: G. O. Noville & Associates, Inc., April 1957.
  4. Chamberlain, Peter, and Chris Ellis. British and American Tanks of World War Two. Frome, England: Cassell & Co., 2000.
  5. 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.
Last updated 3 Dec 2023.
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