M2 Medium Tank - Design

Design

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 redesignated 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, and rubber-bushed and rubber-shoed track proved durable on roads. The initial M2 model was powered by an aircooled Wright R-975 radial engine. 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.

The M2 had a high superstructure, with a sponson-mounted machine gun in each corner. In addition, two more machine guns were fixed in the glacis plate and fired by the driver. Surmounting the superstructure was a small revolving turret armed with a 37 mm Gun M3 and a coaxial machine gun. The 37 mm gun could penetrate 46 mm of face-hardened armor sloped 30° at a range of 500 yards (457 meters), and 40 mm at 1,000 yards (914 meters). This armament configuration was a hybrid between the sponson-mounted weapons of the Mark VIII Liberty tank of World War I vintage, and the combination of turreted cannon, coaxial machine gun and glacis-mounted machine gun that was almost universal in World War II medium tanks. (Two additional .30-caliber machine guns could be mounted on pintles on either side of the turret for anti-aircraft use, bringing the total to nine—surely a record for any tank brought into service by any army.) The crew consisted of the tank commander, a driver and four gunners. The vehicle provided internal stowage for 200 rounds of 37 mm ammunition and up to 12,250 rounds of .30-caliber.

Bullet deflector plates were installed over the rear fenders. The idea behind these plates was that the tank could drive over a trench, and the rear sponson machine guns could then fire onto the plates; the bullets would deflect into the trench or the area directly behind the tank. Like the sponson machine guns themselves, the deflector plates turned out to be useless in modern warfare.