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The Medium Tank M3A4 used a multi-bank Chrysler engine, designed to overcome a potential shortage of tank engines in 1941-42.
During 1941 the biggest bottleneck in tank production was the supply of suitable engines. The standard M3 used a Wright Continental air cooled radial engine that was also in demand in the aircraft industry. A series of attempts were made to find alternative engines. In June 1941 Chrysler were asked to design a tank engine that could be put into production using existing machine tools. When faced with a similar request General Motors combined two diesel truck engines. Chrysler used a similar concept, but on a larger scale. They combined five six-cylinder car engines in a star configuration to produce a 30-cylinder engine capable of producing 425hp at 2,850rpm or 370hp at 2,400rpm.
This A57 multibank engine was the biggest to be installed in the M3 medium tank family. The engine compartment had to be lengthened, making the entire tank noticeably longer. The three suspension bogies were moved further apart to compensate, and the larger gap between the bogies is one identification feature of the M3A4. The compartment also had to be made taller, with a bulge in the floor to carry the cooling fan and a bulge in the top to cover the radiator (just behind the rear of the turret). The standard M3 had two fuel tanks in the engine compartment, but these had to be removed. The two tanks in the sponsons (above the tracks) were expanded to compensate.
The pilot M3A4, powered by an experimental engine, went to the Aberdeen Proving Grounds in February 1942. After 42 hours of road tests a production engine was installed, and tests continued with this, and a third engine, until October 1942. This prolonged testing programme meant that the multibank engine was thoroughly reliable by the time it entered production.
Production of the M3A4 began at the Detroit Tank Arsenal in June 1942, quite late in the lifespan of the M3. A total of 109 M3A4s were built before production moved over the M4A4, which used the same engine, in August 1942. The US Army didn't consider the multibank engine suitable for combat in the M4, and so the vast majority of M4A4s went to Britain, where they were known as the Sherman V, and proved to be reliable.
Because the M3A4 entered production so late it had most of the features introduced during the production run of the standard M3. The side doors of the original design were removed. Three ventilators were installed to cope with the gases produced by the guns. The heavy model bogie assembly introduced to reduce suspension failures was used. Most got the long barrelled 75mm gun M3.
Stats
Production: 109
Hull Length: 242mm with M2 gun, 261in with M3 gun
Hull Width: 104in
Height: 123in
Crew: 6 or 7
Weight: 64,000lb combat loaded
Engine: Chrysler A57 30 cylinder multibank liquid cooled
Hp: 370hp at 2,400rpm
Max Speed: 20mph sustained, 25mph max
Max Range: 100 miles cruising range, roads
Armament: 75mm Gun M2 or M3 in front right of hull, 37mm Gun M5 or M6 in turret; three .30in machine guns - one in turret cupola, one coaxial in turret, one in hull front
Armour
| Armour | Front |
Side |
Rear |
Top/ Bottom |
Turret |
2.0 |
2.0 |
2.0 |
0.875 |
Hull |
2.0 |
1.5 |
1.5 |
1.0 |