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Old 02-08-2019, 03:41 AM
dragoon500ly dragoon500ly is offline
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Default Part Forty-seven, the Medium Tank M-3 Series

The events in Europe in the late Spring of 1940 emphasized the urgent necessity to rebuild the U.S. Armed Forces. The success of the German “Blitzkrieg” underlined the requirement that the new forces be reorganized, but they must be armed with equipment second to none. The first move towards this reorganization was the formation of the separate Armored Force combining the tank elements that previously belonged to the Cavalry and the Infantry. A key item in its equipment was the Medium Tank M-2A1 but reports from observers in Europe indicated that its 37mm gun and light armor was already inadequate for a modern medium tank. The success of the 75mm short barreled cannon of the Panzer Mark IV clearly showed the need for a weapon at least as powerful for the new medium tank.

In June of 1940, new requirements was issued by the Ordnance Corps. This was standardized in July 1940 as the Medium Tank M-3. So urgent was the world situation that it was standardized and ordered into production long before the design was complete.

at Dunkirk. There was now a vital need to equip its armored units as quickly as possible. A British Tank Mission was dispatched to the U.S. to arrange for the purchase of armored vehicles. At first, it was hoped that the production of British designs in American factories would be possible. It was quickly realized that this would cause a dispersion of effort and an inefficient use of the available resources. The British were informed that only designs acceptable to the U.S. would be produced, but some modifications would be permitted on vehicles under British contracts. On this understanding, the British placed orders for the new M-3 with a modified crew compartment and a new turret.
During the summer of 1940, a great deal of change took place in the design of the M-3. The original concept was to thicken the armor and install a 75mm gun in the right front sponson on the M-2A1. A meeting of the various manufacturers along with representatives of the Armored Force met in Aberdeen Proving Grounds in August, 1940 to view a full size wooden mockup of the new tanks hull.

This initial version of the M-3 attempted to retain the heavy machinegun armament of the M-2A1. With the placement of the 75mm, a new auxiliary turret was mounted on the left sponson (with two .30-caliber machine guns). Armor thickness was increased to 51mm on the hull front and 38mm on the hull sides and rear.

Observing the shortcomings of the design, it was initially planned to limit total production to only 360 vehicles and to push the development of a tank that mounted the 75mm gun in a turret. But the urgent need for large numbers of new tanks by the British for the Middle East would not permit the limited production run.

The decision was made to delete the sponson machine guns and install pistol ports to cover these areas. The radio set was moved into the space vacated by the auxiliary turret. Fuel capacity was increased and the turret floor was lowered to give more head room in the turret.

In the meantime, the British designed a new turret with more room for the crew and a radio set carried in the extended turret bustle. The cupola was replaced by a circular hatch fitted with a rotating split hatch cover. The British named their version the General Grant I and the U.S. model was referred to as the General Lee I, both would be used in the North Africa fighting. Total production of the M-3 came to 4,924 tanks.

Combat Weight was 30.7 tons. Powerplant was a Wright-Continental R975 EC2 9-cylinder radial engine. This allowed the M-3 a maximum road speed of 24mph and a cruising range of 120 miles.

Armor protection comprised: Hull Front: ranging from38mm to 51mm; Hull sides of 38mm; Hull rear of 38mm, Hull top of 13mm; Hull bottom ranging from 13mm to 25mm. Turret Front, sides and rear of 51mm; Turret top of 22mm.

Armament comprised a 75mm Gun M-2 or M-3 (with 50 rounds of ammo); a 37mm Gun M-5 or M-6 (with 178 rounds of ammo) and three .30-caliber machineguns (coaxial, cupola antiaircraft and fixed glacis plate mount, fired by the driver) (total of 9,200 rounds of .30-caliber).

The Cruiser Tank Grant I was very similar, with a combat weight of 31 tons. The turret front armor was increased to 76.2mm.

Armament comprised a 75mm Gun M-2 (with 65 rounds of ammo), a 37mm Gun M-5 or M-6 (with 128 rounds of ammo), three .30-caliber machineguns (coaxial and two fixed in the glacis plate and provided with 4,084 rounds of ammo).

The M-3A1
One of the dangers of the M-3 was its riveted construction. The M-3A1 was made with cast armor upper hull. Production began in February 1942 and ended that August after a total run of 300 vehicles. Vehicle stats are the same as for the M-3, with a combat weight of 31.5 tons.

The M-3A2
The primary feature of this version was that upper hull was welded. Production began in January 1942 but ended after only 12 vehicles were completed.

The M-3A3 and M-3A5
By the Summer of 1941 it was rapidly becoming apparent that the limiting factor in armored vehicle production was the lack of suitable engines. The air-cooled radials of the Light Tank M-3 and the early versions of the Medium Tank M-3 were required for use in training aircraft, thus restricting the production of future tanks. Starting in August of 1941 contracts were let for the development of new tank engines. One of the first was a General Motors unit that consisted of a pair of standard 6-71 diesel truck engines. A noted feature of this design was its symmetrical engine block, allowing accessories to be mounted on either side of the blocks, placing them on the outside of the power plant. Another advantage of this power plant was that if one engine failed, the other could still be used to operate the tank.

A disadvantage was that the new engine was larger than the radial engine it replaced, requiring modifications to the engine compartment. To protect the radiators installed at the rear, the side and rear armor plates were extended down to the level of the tracks and the rear plate was sloped about 10 degrees from the vertical. The engine compartment doors of the M-3 was replaced by a single lower plate and a dust deflector was installed.

Because of the larger engine compartment, fuel tankage was reduced from 175 gallons to 148 gallons, but the superior performance of the diesel engines actually increased the cruising range to 160 miles.

This new vehicle, with its welded hull was standardized as the M-3A3 and a total of 322 were produced between January thru December 1942.

The same power plant was installed in the riveted hull version and this was standardized as the M-3A5, total production run during the same period was 591 vehicles.

The M-3A4
The final production version of the Medium Tank M-3 was the M-3A4, like the A3/A5 it also used an alternative powerplant, in this case the Chrysler A57 30-cylinder multibank engine. This was five 6-cylinder automobile engines, mounted in a star configuration and geared to operate as a single unit.

The large power plant required modifications to the standard M-3 hull. The engine compartment was lengthened by 11 inches and the hull upper rear armor plates were moved back 15 inches. A 4.25-inch blister in the hull floor was provided to give clearance for the cooling fan. Another bulge on the top of the rear deck covered the single radiator assembly which cooled the entire power plant. It also forced the removal of the two vertical fuel tanks in the engine compartment, but this was compensated by the enlargement of the two sponson fuel tanks.

The longer hull also required modifications to the suspension system, The center and rear bogie assemblies were moved to the rear, increasing the space between each set of bogies by 6 inches.

Combat weight was increased to 32 tons. There was no change to the armament or armor protection. The production run lasted from June 1942 to August 1942 when it was changed over to the new Medium Tank M-4. Total run was 109 vehicles.

Medium Tanks Ram I and Ram II

No discussion of the Medium Tank M-3 would be complete with adding the Canadian versions. The Medium Tanks Ram I and Ram II. The Grant I was always considered to be a interim version until the new Medium Tank M-4 entered service. Concerned over the shortcomings of the M-3 design, the British Tank Mission in collaboration with the Canadian General Staff designed a modified M-3 for production in Canada. This tank would use the standard M-3 power train and running gear, but with a redesigned upper hull and turret.

The Ram I featured a low silhouette cast turret mounting a British 2-pounder gun with a coaxial M-1919A4 machine gun. An additional .30-caliber machine gun was mounted on the turret roof for antiaircraft protection. The upper hull was a single large casting with the driver located on the right front and a small auxiliary turret on the left, mounting a .30-caliber machine gun. Hull doors on each side provided access to the interior. The Ram I entered production in January 1942 and consisted of a run of 50 vehicles before supplies of the new British 6-pounder arrived.

Combat weight was 32 tons. Armor protection comprised: Hull front: from 44mm to 76.2mm. Hull sides: from 44mm to 64mm. Hull rear: 44mm. Hull top 25mm to 44mm. Hull bottom: 13mm to 25mm. Turret front was 76.2mm. Turret Sides ran from 64mm to 76.2mm. Turret top was 25mm.'

Armament comprised a 2-pounder Gun Mark IX or Mark X (with 171 rounds of amm) and three .30-caliber machine guns (coaxial, antiaircraft and bow turret with 4,715 rounds of ammo). Crew consisted of 5 men (tank commander, gunner, loader, driver and assistant driver).

Power planet was the Wright-Continental R974 EC2 9-cylinder radial engine. Maximum road speed was 24mph. cruising range was 120 miles.

A total of 1,899 Ram II tanks through September 1943. Major modifications included the replacement of the auxiliary turret with a ball mounting and the removal of the hull side doors mid-way through the production run.

Combat weight was increased to 33 tons. There was no change to vehicle performance or armor protection.

Armament comprised a 6-pounder Gun Mark III or mark IV (with 92 rounds of ammo) and three .30-caliber machine guns (coaxial, antiaircraft and bow with 4,440 rounds of .30-caliber ammo).
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