M2 Medium Tank

Medium Tank M2
The M2A1 Medium at Aberdeen Proving Grounds in 2008
Type	Medium tank
Place of origin	United States
Production history
Manufacturer	Rock Island Arsenal
No. built	18 M2s, 94 M2A1s
Variants	M2, M2A1
Specifications
Weight	41,000 lb (18.7 metric tons)
Length	5.38 m (17.7 ft)
Width	2.59 m (8 ft 6 in)
Height	2.82 m (9 ft 3 in)
Crew	6 (Commander, driver, (4x) gunners)
Armor	M2 6.4–32 mm (0.25–1.26 in);         M2A1 6.4–51 mm (0.25–2.01 in)
Main armament	1× 37 mm Gun M3 200 rounds
Secondary armament	7× (maximum 9) .30-06 Browning M1919 machine guns 12,250 rounds
Engine	Wright R975 EC2 air-cooled radial gasoline 400/340 hp (298/253 kW)
Suspension	Vertical Volute Spring Suspension (VVSS)
Fuel capacity	473 liters (125 U.S. gal)
Operational range	210 km (130 mi)
Speed	42 km/h (26 mph)

The Medium Tank M2 was a United States Army tank that was first produced in 1939 by the Rock Island Arsenal, just prior to the commencement of the Second World War in Europe. Production was 18 M2 tanks, and 94 slightly improved M2A1 tanks, for a total of 112. Events in Western Europe rapidly demonstrated that the M2 was obsolete, and it was never used overseas in combat; it was, however, used for training purposes throughout the war.

The M2's features included an unusually large number of machine guns, bullet deflector plates, and sloped armor on the hull front (glacis plate). The main armament was a 37 mm (1.5 in) gun, with 32 mm (1.3 in) armor; the M2A1 had a 51 mm (2.0 in) gun mantlet. Some features of the M2 series, especially the suspension and powertrain, provided the basis for later, important U.S. tank designs including the M3 Lee, M4 Sherman and other armored fighting vehicles.

Rock Island Arsenal started work on a new medium tank, based on the design of the M2 Light Tank. Initially designated the T5, the redesigned model (with a 350 hp R-975 radial engine) was re-designated as the M2 Medium Tank in June, 1939. After the first 18 units had been produced at Rock Island Arsenal and evaluated by the Army, the upgraded M2A1 specification was approved with a redesigned turret and a more powerful engine.

The medium tank M2 was a larger development of the M2 Light Tank. Many components were common or used a similar design, including the vertical volute spring suspension which would be used in later tanks as well. Twin-wheeled bogies were mounted externally, which saved internal space compared to other suspension designs. The rubber-bushed and rubber-shod track proved durable on roads. The initial M2 model was powered by an air-cooled Wright R-975 radial engine, originally designed for aircraft. For the M2A1, this engine was supercharged to provide an extra 50 hp (37 kW) for a total of 400 horsepower (300 kW), and designated as the R-975 C1 radial engine. These track and suspension designs, with slight modifications, were later used on the M3 and M4 medium tanks.