Medium Tank M3A4

Medium Tank M3A4

Medium Tank M3A4

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.

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






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TM 3-360 Flame Thrower Mechanized, E12-7R1 (Installed In Medium Tanks M4A1 And M4A3) 1945 (1945)[Leather Bound]

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Medium Tank M3 Lee / M3 Grant: M3a1, M3a2, M3a4, M3a5 by Slawomir Zajaczkowski (Paperback, 2020)

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Chrysler A57 Multibank Tank Engine

When the United States entered World War II, there was a desperate need for a medium tank engine. Chrysler responded with a very unusual idea. Chrysler had its 251 cu in (4.1 L) straight six-cylinder, L-head engine available in large numbers. Under the direction of Executive Engineer Harry Woolson, the Engine Design department, headed by Mel Carpentier, designed a new powerplant that utilized the 251 cu in (4.1 L) engine. The basic idea was to combine five of these six-cylinder engines into a five-bank, 30-cylinder, single engine for medium tanks. This new engine, referred to as the Multibank, was given the designation A57.

Chrysler A57 engine as displayed at the Walter P. Chrysler Museum. Note the central water pump feeding the five engine banks, the individual distributors for each engine bank, and the row of carburetors at top: three on the left and two on the right.

The Multibank A57 engine had a large cast iron crankcase that formed the central structure of the powerplant. Five Chrysler 251 cu in (4.1 L) six-cylinder engines were bolted to this central crankcase. Two of the engines were bolted to the lower portion of the crankcase, one on each side, with their cylinders angled 7-1/2 degrees above horizontal. Two addition engines were bolted to the crankcase above the first two, with their cylinders 27 degrees above horizontal. The fifth engine was bolted vertically at the top of the crankcase. The five six-cylinder engines made up the banks of the A57.

The A57 engine was mounted in the rear of the tank, and the crankshaft output flanges faced the front of the tank. The A57 retained the five crankshafts of the five six-cylinder engines. A drive gear was coupled to the crankshaft of each engine bank. These five drive gears meshed with a single, central gear (all gears had herringbone teeth). The central gear drove the output shaft of the power plant. The output shaft went through the radiator and drove the cooling fan and clutch, which was attached to a drive shaft and then transmission.

A view of the gear case revealing the central drive gear that is driven by five outer gears, each coupled to their respective engine bank’s crankshaft. (Adrian Barrell image)

The A57 was originally equipped with five belt-driven water pumps. However, the belts would often break because of the alternating loads on the crankshaft pulleys. The design was changed to a single water pump with five outlets (one for each engine bank). This single water pump was driven by an accessory shaft from the central drive gear located on the opposite end of the central crankcase. Also at the rear of the tank, each engine bank had its own ignition coil and distributor that was gear-driven from the camshaft.

The first production engines had a single-barrel carburetor mounted directly on the intake manifold for each of the five engine sections. The different pipe lengths and contours leading from the air cleaner to the carburetors resulted in unequal fuel distribution. Metal vanes were added to direct airflow, and ultimately the five carburetors (each connected to its respective engine with a downpipe) were relocated in the same plane above the engine. This change simplified throttle linkages, the air cleaner arrangement, and maintenance.

The A57 Multibank had two oil pumps located in the central crankcase. One oil pump was a scavenge pump to transfer oil to a remote reservoir. The second pump was pressure pump that took oil from the reservoir and delivered high-pressure oil to all five engine sections.

The 5,244 lb (2,379 kg) Chrysler A57 engine package being installed in a M4A4 Sherman tank. Note the engine’s size in comparison to the installers.

The A57 engine had a 3.4375 in bore and 4.50 in stroke, giving a total displacement of 1,253 cu in (20.5 L) from its 30 cylinders. The engine produced 445 hp (332 kW) and 1,060 lb ft (1,437 N m) of torque at 2,400 rpm. Given the arrangement of the engine sections, the Multibank was a relatively short but heavy engine, weighing 5,244 lb (2,379 kg) including radiator, cooling fan and clutch. Construction of the A57 utilized existing tooling from the 251 cu in (4.1 L) Chrysler six-cylinder engine, and the engines shared cylinder blocks, cylinder heads, pistons, connecting rods, and crankshafts.

On 3 June 1942, nine months after the initial engine discussion, the first of 109 M3A4 tanks were built with the A57 engine. However, the M3A4 tank was quickly replaced by the M4A4 Sherman tank, the first being produced on 30 June 1942. From April 1942 to September 1943, 9,965 Chrysler Multibank engines were built 7,500 engines were installed in production tanks, and the remainder were built as spare engines. The A57 engine proved to be a very durable, reliable, and efficient power plant for medium tanks. Reportedly, the engine would still run with two of the five engine banks disabled from combat damage.

A number of Chrysler A57 Multibank engines survive, and some are still in working order in restored tanks.

Side view showing the relatively short length of the of the A57 engine at the Walter P. Chrysler Museum.

While similar engine concepts, no direct relation has been found between the Chrysler Multibank and the Perrier-Cadillac 41-75.

A Blunted Sickle - Thread II

I agree that the United States will have no big impetus for heavy tanks, so IMHO M3 Stuart will be the mainstay of their tank forces, especially for Marines, while US Army can maybe develop something stronger, maybe M4 Sherman. I still think that US will form at least one Armoured Division, after all, that was the trend then. So, Shermans in Armoured Division, while Stuarts in Infantry divisions and Marines. Later, in late 40s things like M41 Walker Bulldog and even later in late 50s T95 Medium tank.

Will the US bring forming of Organisation of American States forward? I know Pan American Union exists allready, maybe they will try to make that organisation more effective/stronger? As some sort of official US interests zone.


1st and 2nd Armored date from July 15, 1940, mostly created from existing Cavalry Regiments.

Heavy Tank request started in on May 20, 1940, that would have been a mult-turreted effort like the Independent or Char 2C, that was changed to a single turret tank by October 24, 1940 after combat reports from France were reviewed.
Original plans to use the V-12 Allison were sidelined to expected large aircraft orders, and used a Wright radial instead.

What was to be the T1 Heavy Tank of approximately 50 tons had a contract signing with Baldwin Locomotive in August 1940 for a pilot prototype followed by 50 production units. This unit started testing on September 19th, 1941 by Baldwin.
After updates, was presented to the Army for further testing on December 8, 1941

US Medium Tank development dates from the M1921 tank

that had Liberty engine and cast steel tracks. This was tested until 1932

The T2 Medium was 'inspired' by the Vickers Medium

with 47mm in turret, and 37mm in bow. Liberty powered in 1931

At this time, Walter Christie enter the medium tank search, moving up from the lights he had been designing

He did several more models, each one faster than the last, ignoring Army requests for more armor and guns

Much of the US Medium armored force in 1933

Troubles dealing with Christie lead to the T1E1 Light being supersized to the T5 Medium in 1938

In 1939, it was known that the 37mm was nearing its end as a useful AT gun, and a medium would need HE ability in addition to MGs to engage infantry, after reports from Poland were studied on the Mk IV tank.

The T5E2 was converted in 1939. Note Welding and Riveting construction with the T5 series.

Tests with the M2 and T5E2 occurred during the 1940 Maneuvers, when the Army had only 18 working Medium tanks

Army wanted 75mm armed tanks as fast as possible, so the M2 would have a new superstructure and MG armed turret with Stereo range finder replaced with a 360 degree turret with 37mm gun.

Baldwin current Tank production line was busy with what would become the M6 Heavy, so the Army's main Tank and Artillery production line at Rock Island Arsenal would used to make M2s for training

On August 28th, 1940, the order for 1000 Medium Tanks M2A1 was officially cancelled and replaced with a contract to produce Medium Tanks M3. However, the contract with the Rock Island Arsenal was not cancelled so that its production facilities were kept busy. An agreement was made for 126 tanks of that type, which were ready by December of 1940. The production rate gradually decreased, since the Medium Tank M3 was in higher demand. The last M2A1 were delivered in August of 1941, with Medium Tanks M3 built in parallel. In total, the US Army received 84 M2A1 medium tanks.

All this, while what the T6 was being worked out to be built,with design goals set in August 31, 1940 of the new tank will be using the M3 running gear and chassis, would become the Sherman. OTL pressure on M3 improvements and further variant developments delayed the T6 design committee until February 1st, 1941

Now in this TL, the British are not as desperate for tanks, so not all of the OTL builders of Baldwin, ALCO, Lima, Pressed Steel, DTA and Pullman will not be tasked with making interim M3 for C&C and later LL. Some would be made at Pullman and Rock Island for training, and to get some Medium Tanks in the US Army's two new Armored Divisions, the Army requested 360 M3s be built to build up numbers till the T6 could be built.

OTL, the first M3 tanks were running on March 13, 1941, around 5 months ahead of the M6 Heavy. The brand new Detroit Tank Arsenal, built by Chrysler, built its first M3 in April.

However, there will be no Grants, or M3A1,M3A2,M3A3,M3A4 and M3A5 subtypes, that effort goes into the T6, so the Sherman(won't be called this, as all the 'General' names were applied by the British) and the M4 Medium will be around ahead of OTL.


Even though iTTL, the Japanese won't be US Allies, I don't see that affecting the Soviet building tank traversable roads or rail toward Chukotka any more than OTL. On the other hand, it may be 10 or more years after OTL when such a land connection is made from the US through Canada (the push toward the Alaska Highway just isn't there).

This reminds me of the semi serious suggestion on this board that the US in World War II should have just let the Japanese conquer Alaska. The troops wouldn't have been able to go anywhere, would have had a good chance to freeze to death and the soldiers that would have been able to get to Seattle would have been the grandchildren of the original soldiers and would all speak English.




Love the post, but I have a counter statement to the bit in brackets (minute 5:06):

General Ripper


Do like that, though Stuart, Lee, Grant and Sherman do seem to come from the British for the purchases for the Western Desert.

Per the Video, that seems to have come from the South Africans, who knew what honey was good for


ACtually, I believe the French had one which could do the job.

The Canon antichar de 29/20 mm Larsen. From what I can find, it weighted 200kg and could penetrate 56 mm of armor at 400m.

OTL, there were only 50 of the ordered before the defeat. ITTL? I believe many more. Unless they go for Brandt Grenades type all the way.


ACtually, I believe the French had one which could do the job.

The Canon antichar de 29/20 mm Larsen. From what I can find, it weighted 200kg and could penetrate 56 mm of armor at 400m.

OTL, there were only 50 of the ordered before the defeat. ITTL? I believe many more. Unless they go for Brandt Grenades type all the way.

Rufus Shinra

ACtually, I believe the French had one which could do the job.

The Canon antichar de 29/20 mm Larsen. From what I can find, it weighted 200kg and could penetrate 56 mm of armor at 400m.

OTL, there were only 50 of the ordered before the defeat. ITTL? I believe many more. Unless they go for Brandt Grenades type all the way.

*googles the Brandt grenade*

Wow, talk about a good contribution to the war effort.


17th September 1941
Dr Merritt from the tank branch of Woolwich Arsenal meets with senior civil servants and RAC officers to discuss the progress of the Churchill and Black Prince projects. Overall his report is that both tanks are at almost the same state of readiness for production, somewhat to their surprise. The Black Prince tank is a little bigger, more expensive and more complicated than the Churchill design, but clearly outmatches the latest German tanks (the Churchill is considered to be broadly equivalent to them).
The engine issue is a thorny one. The Lion engine is easier to produce and lighter, while the Rootes-Coatalen engine is a little heavier but significantly more compact. Both engines in their current form require non-standard fuels and will be damaged if used with pool petrol, and when de-tuned to a level suitable for service produce about the same amount of power. The real joker in the pack is the fact that the Ford GAA engine is now becoming available in quantity, can use pool petrol and is both lighter and more compact than the other engines. This hadn't been predicted at the start of the development process, but all present agree that given its advantages over the alternative engines (and the fact that it is already being produced in quantity, while the others would need a new production line setting up) mean it is the obvious choice and could be adopted for both tanks.
In the end it is decided to standardise on the Black Prince design fitted with the Ford GAA engine, the final clincher being that the 6pdr is considered just a little bit too anaemic to face the rumoured new German tanks and the Churchill cannot easily be upgraded to take the bigger gun. The 6pdr Valentine is generally considered good enough until the new Black Prince becomes available, particularly given that the Archer self-propelled gun armed with the same 77mm HV gun as the Black Prince will very soon be entering service in quantity and will give armoured units sufficient firepower to stop any of the new German tanks.

This is very relevant to the discussions about American armor, because the new British tank is going to be using a Ford GAA engine, which means the Ford Motor Company is going to be doing a lot of liaison with the Entente about what State-of-the-Art is in tanks, and they'll take that back to Detroit and then Washington.

In short, Id be expecting Ford to push a proposal for an Americanised Black Prince.


In 1939, the U.S. Army possessed approximately 400 tanks, mostly M2 Light Tanks, with 18 of the to-be-discontinued M2 Medium Tanks as the only ones considered "modern". [5] The U.S. funded tank development poorly during the interwar years, and had no infrastructure for production, little experience in design, and poor doctrine to guide design efforts.

The M2 medium tank was typical of armored fighting vehicles (AFVs) many nations produced in 1939. When the U.S. entered the war, the M2 design was already obsolete with a 37 mm gun, 32 mm frontal armor, excessive machine gun secondary armament and a very high silhouette. The Panzer III and Panzer IV's success in the French campaign led the U.S. Army to order immediately a new medium tank armed with a 75 mm gun in a turret. This would be the M4 Sherman. Until the Sherman reached production, an interim design with a 75 mm gun was urgently needed.

The M3 was the solution. The design was unusual because the main weapon — a larger caliber, low-velocity 75 mm gun — was in an offset sponson mounted in the hull with limited traverse. (The sponson mount was necessary because at the time American tank plants were incapable of casting a turret big enough to hold the 75mm main gun). A small turret with a lighter, high-velocity 37 mm gun sat on the tall hull. A small cupola on top of the turret held a machine gun. The use of two main guns was seen on the French Char B, the Soviet T-35, and the Mark I version of the British Churchill tank. In each case, two weapons were mounted to give the tanks adequate capability in firing both anti-personnel high explosive ammunition and armor-piercing ammunition for anti-tank combat. The M3 differed slightly from this pattern having a main gun which could fire an armor-piercing projectile at a velocity high enough for efficiently piercing armor, as well as deliver a high-explosive shell that was large enough to be effective. Using a hull mounted gun, the M3 design could be produced faster than a tank featuring a turreted gun. It was understood that the M3 design was flawed, but Britain [6] urgently needed tanks.

The M3 was tall and roomy: the power transmission ran through the crew compartment under the turret cage to the gearbox driving the front sprockets. Steering was by differential braking, with a turning circle of 37 ft (11 m). The vertical volute-sprung suspension (VVSS) units possessed a return roller mounted directly atop the main housing of each of the six suspension units (three per side), designed as self-contained and readily replaced modular units bolted to the hull sides. The turret was power-traversed by an electro-hydraulic system in the form of an electric motor providing the pressure for the hydraulic motor. This fully rotated the turret in 15 seconds. Control was from a spade grip on the gun. The same motor provided pressure for the gun stabilizing system.

The 75-mm was operated by a gunner and a loader. Sighting the 75-mm gun used an M1 periscope — with an integral telescope — on the top of the sponson. The periscope rotated with the gun. The sight was marked from zero to 3,000 yd (2,700 m) [7] with vertical markings to aid deflection shooting at a moving target. The gunner laid the gun on target through geared handwheels for traverse and elevation.

The 37-mm was aimed through the M2 periscope, though this was mounted in the mantlet to the side of the gun. It also sighted the coaxial machine gun. Two range scales were provided: 0-1,500 yd (1,400 m) for the 37-mm and 0-1,000 yd (910 m) for the machine gun.

Though not at war, the U.S. was willing to produce, sell and ship armored vehicles to Britain. The British had requested that their Matilda and Crusader tank designs be made by American factories, but this request was refused. With much of their equipment left on the beaches near Dunkirk, the equipment needs of the British were acute. Though not entirely satisfied with the design, they ordered the M3 in large numbers. British experts had viewed the mock-up in 1940 and identified features which they considered flaws — the high profile, the hull mounted main gun, the lack of a radio in the turret (though the tank did have a radio down in the hull), the riveted armor plating (whose rivets tended to pop off inside the interior in a deadly ricochet when the tank was hit by a non-penetrating round), the smooth track design, insufficient armor plating and lack of splash-proofing of the joints. [8] The British desired modifications for the tank they were purchasing, including the turret being cast rather than riveted. A bustle was to be made at the back of the turret to house the Wireless Set No. 19. The tank was to be given thicker armor plate than the original U.S. design, and the machine gun cupola was to be replaced with a simple hatch. With these modifications accepted the British ordered 1,250 M3s. The order was subsequently increased with the expectation that when the M4 Sherman was available it could replace part of the order. Contracts were arranged with three U.S. companies. The total cost of the order was approximately 240 million US dollars, the sum of all British funds in the US it took the US Lend-Lease act to solve the financial shortfall.

The prototype was completed in March 1941 and production models followed, with the first British-specification tanks produced in July. Both U.S. and British tanks had thicker armor than first planned. [9] The British design required one fewer crew member than the US version due to the radio in the turret. The U.S. eventually eliminated the full-time radio operator, assigning the task to the driver. After extensive losses in Africa and Greece the British realized that to meet their needs for tanks both the Lee and the Grant types would need to be accepted.

The U.S. military used the "M" (Model) letter to designate nearly all of their equipment. When the British Army received their new M3 medium tanks from the US, confusion immediately set in [10] between the different M3 medium tank and M3 light tank. The British Army began naming their American tanks after American military figures, although the U.S. Army never used those terms until after the war. [11] M3 tanks with the cast turret and radio setup received the name "General Grant", while the original M3s were called "General Lee", or more usually just "Grant" and "Lee". The M3 brought much-needed firepower to British forces in the North African desert campaign.

The chassis and running gear of the M3 design was adapted by the Canadians for their Ram tank. The hull of the M3 was also used for self-propelled artillery as with the original design of the M7 Priest, of which nearly 3,500 were built, and recovery vehicles.

M3 Lee

In early 1941 an entry of the United States of America in the war became more and more possible. Well aware that their existing M2 medium tank wouldn't be a match for current Axis armor development, the US Army decided to develop a completely new medium tank design - the M4 Sherman. But this took time, and as a quick stop gap solution the M3 medium tank was created - in fact it was the fastest tank development ever: It took only six months from first drawings to the start of the production. This was possible because the M3 was in fact a redesigned M2, featuring the same chassis and turret. The main change was the superstructure: It was adopted to carry a 75mm gun in the right side sponson, giving the M3 a respectable firepower. This design on the other hand created a very high silhouette, and more worse, it doesn't allow the tank to fight in hull down position. This made the M3 an easy target.

However, its good armor protection, reliability and firepower was very welcomed by the British tankers who were the first to use the M3 in combat in North Africa. The M3 could easily defeat any axis contemporary tank and its multi-purpose gun gave the British crews the possibility to use high explosive shells against soft targets and strongpoints for the first time. The 40mm gun of the genuine British tanks only fired solid armor piercing rounds.

The British gave the M3 its popular name, the "Lee", and requested a different turret design with room for the radio equipment and without the small machine gun cupola to reduce height. These tanks were called "Grant" (see nomenclature below). M3 Lee tanks were also in service with the US Army in Tunisia and with the Soviet Army on the eastern front. In 1943, the M4 Sherman reached the frontlines in great numbers and replaced the now obsolete M3 almost completely. Many M3 were converted for special purposes later, such as prime movers, recovery vehicles and the like. Others were sent to East Asia to fight against the Japanese, where they still performed well.

The M3 medium tank in Battlegroup42 was one of the oldest models still in the mod. It will be replaced by a much better one in the final release.

M3 Lee

The M3 Lee, officially Medium Tank, M3, was an American medium tank used during World War II. In Britain, the tank was called by two names based on the turret configuration and crew size. Tanks employing US pattern turrets were called the "Lee", named after Confederate general Robert E. Lee. Variants using British pattern turrets were known as "Grant", named after Union general Ulysses S. Grant.

Design commenced in July 1940, and the first M3s were operational in late 1941. [2] The U.S. Army needed a medium tank armed with a 75mm gun and, coupled with the United Kingdom's immediate demand for 3,650 medium tanks, [3] the Lee began production by late 1940. The design was a compromise meant to produce a tank as soon as possible. The M3 had considerable firepower and good armor, but had serious drawbacks in its general design and shape, including a high silhouette, an archaic sponson mounting of the main gun preventing the tank from taking a hull-down position, riveted construction, and poor off-road performance.

Its overall performance was not satisfactory and the tank was withdrawn from combat in most theaters as soon as the M4 Sherman tank became available in larger numbers. In spite of this, it was considered by Hans von Luck (an Oberst (Colonel) in the Wehrmacht Heer and the author of Panzer Commander) to be superior to the best German tank at the time of its introduction, the Panzer IV (at least until the F2 variant). [4]

Despite being replaced elsewhere, the British continued to use M3s in combat against the Japanese in southeast Asia until 1945. [5] Nearly a thousand M3s were supplied to the Soviet military under Lend-Lease between 1941–1943.