Medium Tank M4A6

The Medium Tank M4A6 was the final production version of the Sherman, and used the composite hull introduced late in the production of the M4 and a modified version of the Wright Cyclone engine that could use diesel fuel.

The Wright G200 Cyclone was developed as an air-cooled petrol powered aircraft engine, but Caterpillar managed to convert it into a diesel engine, keeping the cylinders, crankshaft and supercharger from the original design and pistons, cylinder heads, fuel injection and lubrication systems of their own design. In 1942 the Ordnance Department approved the production of 28 of these Caterpillar D200A engines, and 20 were allocated for installation in the M4E1, a test version of the Sherman that used the standard M4A4 hull. The first four M4E1s were ready in December 1942-May 1943, and underwent tests at Caterpillar, General Motors and Fort Knox. A number of changes were needed, some to the engine and some to the M4 clutch and gear train, but the engine was considered to be very promising, and on 28 January 1943 an order for 1000 D200A engines was placed (with the new designation Ordnance Engine RD1820). 775 of these engines were allocated for use in the Medium Tank M4A6, the production version of the M4E1.

The M4A6 was largely based on the late production M4A4, but used a composite hull similar to the one used on late production M4. This had a cast front section and welded middle and rear. All of the production vehicles used the single piece sharp nose. All had extra armour on the side to protect the ammo storage racks. Some had pistol ports.

The M4A6 entered production at the Detroit Tank Arsenal, and the first was completed on 28 October 1943. Only 75 of the original 775 were completed before the order was cancelled in February 1944. The US Army had decided to concentrate on petrol powered tanks, as did the British, so there was no longer a need for the diesel powered M4A6.

Ten of the production M4A6s underwent tests at Fort Knox, starting in March 1944, after production had already been cancelled. In these tests the M4A6 demonstrated a better fuel efficiency, range and general performance than any other standard M4. The remaining tanks went to training units, or to the 777th Tank Battalion at Fort Knox. The M4A6 was declared to be Limited Standard on 3 May 1945.

Stats (late production)
Production:
Hull Length: 238.5in
Hull Width: 103in
Height: 108in
Crew: 5
Weight: 70,000lb combat loaded
Engine: Ordnance Engine RD-1820 9 cylinder air cooled radial
Hp: 450hp at 2,000rpm
Max Speed: 25mph sustained, 30mph max
Max Range: 120 miles cruising range, roads
Armament: 75mm Gun M3 and .30in coaxial MG in turret, .50in MG in AA mount on turret roof, 0.30in MG in hill front, 2in Mortar M3 (smoke) in turret

Armour

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