The American army began thinking of motorizing their artillery back in WWI. For a long time, attempts were made to build an SPG on the chassis of the light tracked Holt tractor. In parallel, John Walter Christie was working on a similar vehicle. Neither project satisfied the US Army for various reasons. A second attempt at an SPG was made in 1930, but the Howitzer Motor Carriage T1 remained an experiment. The next opportunity to obtain self propelled artillery came a decade later in the form of the Howitzer Motor Carriage T18.
This blog is dedicated to bringing World War II era documents to the general public, with an overall focus on armoured warfare. Questions? Requests? Comments? Email me at tankarchives@gmail.com or find me on Twitter @Tank_Archives.
Showing posts with label M2 Light Tank. Show all posts
Showing posts with label M2 Light Tank. Show all posts
Saturday, 15 April 2017
Friday, 14 April 2017
Combat Car M1: Armour for American Cavalry
Traditionally, cavalry occupied a very strong position in the American army. As soon as there was an opportunity to obtain its own tanks, the cavalry took it. Since, officially, the cavalry was not allowed to have tanks, the name "combat car" was used, even though these vehicles were actually tanks. The Combat Car M1 and several similar vehicles on its chassis are typical representatives of the small family of interbellum cavalry tanks.
Wednesday, 12 April 2017
Nomenclature Confusion
Periodically, one can find information online that the M2 Light Tank, namely the M2A4, was shipped to the USSR as a part of Lend-Lease aid. Indeed, 31 "American light M2A4" tanks show up in the "Report on tanks arriving from England for use by the Red Army as of January 15th, 1942".
31 American light tanks just arrived at Arkhangelsk by convoy. The British ordered M2A4 tanks, so maybe they pawned a few off to the Soviets. Seems fairly bulletproof, but things aren't always what they seem.
Sunday, 18 December 2016
Light Tank M2: Two-Headed Light
In January of 1935, the Light Tank T2E1 arrived at Fort Benning for military trials. This vehicle was the result of nine years of trial and error, which began with the design of the Light Tank T1. Over time, the concept of the light tank changed radically. It transformed from a two man tank with an engine in the front and a 37 mm gun as the main armament to a 4 man tank with a rear engine, front transmission, and machineguns in a two man turret. As a result of the trials, the Light Tank T2E1 was accepted into service as the Light Tank M2A1.
Saturday, 27 February 2016
World of Tanks History Section: American Pre-War Tank Building
At the end of the 19th century, the United States of America began a sharp rise in the development of industry, science, education, and culture. The army and navy guaranteed protection from any opponent in the New World, and the oceans around North America acted as the most effective border guard against any transoceanic enemy.
Externally, the US practiced isolationist policies and kept far away from the wars that engulfed Europe. However, when WWI started, the situation changed. After a series of incidents that resulted in losses of American merchant vessels, President Wilson asked Congress to enter the war. On April 4th, 1917, the Senate allowed the United States to join the First World War.
On June 13th, 1917, General John Joseph Pershing and the first American expeditionary force arrived in Europe. This commander previously fought in local conflicts with the Apache and Sioux, in the Hispano-American War of 1898, and Pancho Villa's rebels. The positional war in Europe was somewhat different from what the American military imagined it to be, and Pershing understood the importance of an army that could deliver a powerful strike while remaining mobile. It is not surprising that he initiated the creation of armoured forces in the United States.
On January 26th, 1918, the American Tank Corps formed from two parts: the tank corps of the American Expeditionary Force in Europe and the Tank Force of the National Army, later renamed the Tank Corps of the National Army.
Proposals for armoured vehicles were sent to the American army before. In 1915, a businessman named Lowe proposed a 30 ton tank project based on the Willoc tractor. In 1917, the Holt tractor company proposed a vehicle that looked very similar to the British "Little Willie" tank, created by William Tritton.
Another interesting project was proposed by the Pioneer tractor company in Minnesota. The vehicle was nicknamed "Skeleton", due to its suspension. The tracks of the Skeleton were not attached to the hull, but to a metal frame with pipe connectors. A small rectangular hull, designed for two crew members, was located between these frames.
The military's lack of enthusiasm towards American tanks led to the necessity of purchasing foreign vehicle when General Pershing ordered the creation of a tank force. On September 12th, 1918, the American tankers fought their first battle at Saint-Michelle, a village south of Verdun. Lieutenant-Colonel Patton commanded the 344th and 345th tank battalions in this battle.
American armoured doctrine used small, light, medium, and heavy tanks. The battle-proven French Renault FT-17 was chosen as the light tank. This 6-ton vehicle was one of the most advanced in the world. The layout of the FT-17 was later accepted as classical: the armament was located in a rotating turret, engine in the rear, crew compartment up front. Initially, the Americans planned to order 3500 vehicles of this type. Some of these were to be built by the French, and some by the Americans. The Ford company purchased a license to manufacture these tanks.
American engineers altered the design of the tank. The driver's visibility was improved. Armour was increased. The Renault engine was replaced with an American one. The American version of the FT-17 was indexed M1917. The tank was armed with either a 37 mm gun or a machine gun.
Heavy tank units were to be armed with the jointly developed British-American Mark VIII Liberty tanks. This tank was a typical "rhombus" type, with fairly wide tracks, enclosing the entire hull. The vehicle weighed 39 tons, and was armed with two 57 mm Hotchkiss guns, with 5-7 rifle caliber machine guns for support. The 10-meter long tank was crewed by 8-11 people
The Liberty was the peak of British rhombus tanks. Perhaps, this direction could be developed further, but, as soon as the FT-17 was deemed superior, the time of the rhombus came to an end.
The Mk VIII did not fight in WWI. The Americans built about 100 of these vehicles in 1919-1920. Until 1930, it remained America's only heavy tank.
After WWI ended, large tank units proved too expensive for the USA, and, in 1920, the tank corps was disbanded. Over the next 20 years, the US did not have large tank units, but funding was periodically issued for new vehicles.
For examples, in the 1920s, the army staff considered the M1917 obsolete, and initiated the construction of a new light tank. Specialists from the Rock Island Arsenal, along with engineers from the Cunningham tractor company, presented the T1 project in 1924. This small 7-ton tank had a non-standard layout, with a rear turret, and front engine. The tank was armed with a 37 mm cannon and 7.62 mm machine gun. Numerous modifications of the T1 project were developed over its lifetime, but they all had their flaws, and were rejected.
The last of the Cunninghams, the T1E4 and T1E6, were meant to solve the flaws of their predecessors. Elements of the British Vickers 6-ton were used in their construction. The engineers achieved superior mobility with the same armament, but there were serious problems with the gearbox and the tanks were not mass produced.
The Americans designed new light tanks for seven years after the termination of the Cunningham program. One of these tanks was the T2 Light on a Vickers suspension. It was designed with machine guns and small caliber autocannons for armament. The T2 was not mass produced, but its creation led to valuable experience, leading to a mass produced M2 Light tank with a new suspension and machine gun armament. On December 29th, 1938, the Americans accepted and began production of a new M2A4 light tank. This tank was armed with a cannon. The new vehicle was maneuverable, and had armour comparable with American medium tanks of the time. Mass production of the M2A4, in which the Americans experimented with cast hulls and turrets, never got off the ground. Welding and riveting of armour continued until the spring of 1941.
In parallel with the T1 tanks, the Americans were developing a medium tank, superior to the Liberty in mobility, and to light tanks in protection. The new tank would have been indexed M1921. It weighed 23 tons, and was armed with a 75 mm howitzer in a rotating turret. This howitzer was capable of not only immobilizing, but completely destroying, a light tank with a direct hit. This was demonstrated practically, using poor M1917 tanks as targets. After 7 years of development, the vehicle was not mass produced due to high cost.
In parallel with the T1 Medium, another lighter medium tank was developed, the T2 Medium. It was built by the Cunningham company using the same layout as the light T1. The tank could accelerate up to 25 mph, and was armed with a 37 mm or 47 mm gun, and machine guns. The T2 Medium was the best tank developed by the Bureau of Ordnance. And yet, it was too expensive for an America that was struggling with the Great Depression.
The Great Depression led to a reconsideration of many principles of armoured warfare. Tank units were to be armed with light, mobile, and cheap vehicles. Engineer Christie proposed some projects, but the military's response to his convertible designs was rather unenthusiastic.
By 1934, Christie annoyed the military so much, that they were ready to accept anything, as long as they didn't have to deal with the persistent and rude engineer. In April of 1934, Captail Reiry proposed a tank project using the Christie chassis and 4 machine gun sponsons, along with a 37 mm gun in a rotating turret. The Bureau took the opportunity to reject the Christie suspension, and instead take a recently developed suspension unified with the T2 Light tank. The resulting vehicle was indexed T5.
After many modifications, the tank was built in December of 1937, with a wooden turret. In about a year, the tank received a real turret, and was sent to Aberdeen.
The T5 was protected by 25 mm thick armour, and propelled by a Continental air cooled engine, which allowed it to reach a speed of 31 mph on a highway. The armament included a 37 mm gun an several machine guns. The tank's turret and sides had openings for the crew's pistols.
In the summer of 1939, the tank was accepted under the index M2. The vehicle was produced in Rock Island.
The beginning of WWII in Europe forced the American government to reconsider their priorities for armoured forces. It was no longer a guarantee that they could sit this one out, and development of a better tank began. This resulted in the M3 tank being developed in the summer of 1940, but that is another story.
Original article available here.
Externally, the US practiced isolationist policies and kept far away from the wars that engulfed Europe. However, when WWI started, the situation changed. After a series of incidents that resulted in losses of American merchant vessels, President Wilson asked Congress to enter the war. On April 4th, 1917, the Senate allowed the United States to join the First World War.
On June 13th, 1917, General John Joseph Pershing and the first American expeditionary force arrived in Europe. This commander previously fought in local conflicts with the Apache and Sioux, in the Hispano-American War of 1898, and Pancho Villa's rebels. The positional war in Europe was somewhat different from what the American military imagined it to be, and Pershing understood the importance of an army that could deliver a powerful strike while remaining mobile. It is not surprising that he initiated the creation of armoured forces in the United States.
On January 26th, 1918, the American Tank Corps formed from two parts: the tank corps of the American Expeditionary Force in Europe and the Tank Force of the National Army, later renamed the Tank Corps of the National Army.
Proposals for armoured vehicles were sent to the American army before. In 1915, a businessman named Lowe proposed a 30 ton tank project based on the Willoc tractor. In 1917, the Holt tractor company proposed a vehicle that looked very similar to the British "Little Willie" tank, created by William Tritton.
Another interesting project was proposed by the Pioneer tractor company in Minnesota. The vehicle was nicknamed "Skeleton", due to its suspension. The tracks of the Skeleton were not attached to the hull, but to a metal frame with pipe connectors. A small rectangular hull, designed for two crew members, was located between these frames.
The military's lack of enthusiasm towards American tanks led to the necessity of purchasing foreign vehicle when General Pershing ordered the creation of a tank force. On September 12th, 1918, the American tankers fought their first battle at Saint-Michelle, a village south of Verdun. Lieutenant-Colonel Patton commanded the 344th and 345th tank battalions in this battle.
American armoured doctrine used small, light, medium, and heavy tanks. The battle-proven French Renault FT-17 was chosen as the light tank. This 6-ton vehicle was one of the most advanced in the world. The layout of the FT-17 was later accepted as classical: the armament was located in a rotating turret, engine in the rear, crew compartment up front. Initially, the Americans planned to order 3500 vehicles of this type. Some of these were to be built by the French, and some by the Americans. The Ford company purchased a license to manufacture these tanks.
American engineers altered the design of the tank. The driver's visibility was improved. Armour was increased. The Renault engine was replaced with an American one. The American version of the FT-17 was indexed M1917. The tank was armed with either a 37 mm gun or a machine gun.
Heavy tank units were to be armed with the jointly developed British-American Mark VIII Liberty tanks. This tank was a typical "rhombus" type, with fairly wide tracks, enclosing the entire hull. The vehicle weighed 39 tons, and was armed with two 57 mm Hotchkiss guns, with 5-7 rifle caliber machine guns for support. The 10-meter long tank was crewed by 8-11 people
The Liberty was the peak of British rhombus tanks. Perhaps, this direction could be developed further, but, as soon as the FT-17 was deemed superior, the time of the rhombus came to an end.
The Mk VIII did not fight in WWI. The Americans built about 100 of these vehicles in 1919-1920. Until 1930, it remained America's only heavy tank.
After WWI ended, large tank units proved too expensive for the USA, and, in 1920, the tank corps was disbanded. Over the next 20 years, the US did not have large tank units, but funding was periodically issued for new vehicles.
For examples, in the 1920s, the army staff considered the M1917 obsolete, and initiated the construction of a new light tank. Specialists from the Rock Island Arsenal, along with engineers from the Cunningham tractor company, presented the T1 project in 1924. This small 7-ton tank had a non-standard layout, with a rear turret, and front engine. The tank was armed with a 37 mm cannon and 7.62 mm machine gun. Numerous modifications of the T1 project were developed over its lifetime, but they all had their flaws, and were rejected.
The last of the Cunninghams, the T1E4 and T1E6, were meant to solve the flaws of their predecessors. Elements of the British Vickers 6-ton were used in their construction. The engineers achieved superior mobility with the same armament, but there were serious problems with the gearbox and the tanks were not mass produced.
The Americans designed new light tanks for seven years after the termination of the Cunningham program. One of these tanks was the T2 Light on a Vickers suspension. It was designed with machine guns and small caliber autocannons for armament. The T2 was not mass produced, but its creation led to valuable experience, leading to a mass produced M2 Light tank with a new suspension and machine gun armament. On December 29th, 1938, the Americans accepted and began production of a new M2A4 light tank. This tank was armed with a cannon. The new vehicle was maneuverable, and had armour comparable with American medium tanks of the time. Mass production of the M2A4, in which the Americans experimented with cast hulls and turrets, never got off the ground. Welding and riveting of armour continued until the spring of 1941.
In parallel with the T1 tanks, the Americans were developing a medium tank, superior to the Liberty in mobility, and to light tanks in protection. The new tank would have been indexed M1921. It weighed 23 tons, and was armed with a 75 mm howitzer in a rotating turret. This howitzer was capable of not only immobilizing, but completely destroying, a light tank with a direct hit. This was demonstrated practically, using poor M1917 tanks as targets. After 7 years of development, the vehicle was not mass produced due to high cost.
In parallel with the T1 Medium, another lighter medium tank was developed, the T2 Medium. It was built by the Cunningham company using the same layout as the light T1. The tank could accelerate up to 25 mph, and was armed with a 37 mm or 47 mm gun, and machine guns. The T2 Medium was the best tank developed by the Bureau of Ordnance. And yet, it was too expensive for an America that was struggling with the Great Depression.
The Great Depression led to a reconsideration of many principles of armoured warfare. Tank units were to be armed with light, mobile, and cheap vehicles. Engineer Christie proposed some projects, but the military's response to his convertible designs was rather unenthusiastic.
By 1934, Christie annoyed the military so much, that they were ready to accept anything, as long as they didn't have to deal with the persistent and rude engineer. In April of 1934, Captail Reiry proposed a tank project using the Christie chassis and 4 machine gun sponsons, along with a 37 mm gun in a rotating turret. The Bureau took the opportunity to reject the Christie suspension, and instead take a recently developed suspension unified with the T2 Light tank. The resulting vehicle was indexed T5.
After many modifications, the tank was built in December of 1937, with a wooden turret. In about a year, the tank received a real turret, and was sent to Aberdeen.
The T5 was protected by 25 mm thick armour, and propelled by a Continental air cooled engine, which allowed it to reach a speed of 31 mph on a highway. The armament included a 37 mm gun an several machine guns. The tank's turret and sides had openings for the crew's pistols.
In the summer of 1939, the tank was accepted under the index M2. The vehicle was produced in Rock Island.
The beginning of WWII in Europe forced the American government to reconsider their priorities for armoured forces. It was no longer a guarantee that they could sit this one out, and development of a better tank began. This resulted in the M3 tank being developed in the summer of 1940, but that is another story.
Original article available here.
Wednesday, 27 January 2016
Tank Destroyer Dead Ends
The United States built almost 19,000 tank destroyers during WWII. There was a great variety of them: tracked, half-tracked, and wheeled vehicles. The only class of vehicle that the Americans never turned into tank destroyers were heavy tanks. The American concept of a tank destroyer, a tank with lighter armour but a more powerful gun in an open turret, bred many other solutions that were later rejected. Let us recall some of these dead ends.
First Try
It is often thought that the Americans began work on tank destroyers after WWII began, but engineers started thinking about destroying enemy tanks in the mid 1930s. At the time, typical armament for American tanks was a pair of machineguns, one rifle caliber, and one large caliber (12.7 mm).
It was proposed to either use the short barrelled 37 mm infantry gun or an experimental 37 mm tank gun converted from the Browning semiautomatic AA gun equipped with a 5 round magazine. This gun was trialled on the T1 family of light tanks, but nothing came of it. As for the 37 mm infantry gun M1916, its armour piercing effect was even lower than that of the Browning M2HB that was installed in the light M2 and M1 Combat Car series tanks. Not surprisingly, the machinegun was preferred.
The American military realized that the AT capabilities of the heavy machinegun were limited. As soon as production of light tanks began, design of tank destroyers on their chassis started. The M2A1, America's first mass production light tank of the 1930s, served as a lab rat. Unlike the double turreted M2A2 and M2A3, their predecessor had one two-man turret with enough space to install a cannon.
Work on a tank destroyer on the M2A1 chassis was initiated by the Infantry Department on October 9th, 1936. The tank destroyer, classified as a tank support vehicle, received a 47 mm semi-automatic Browning cannon. This was effectively the same 37 mm semi-automatic cannon, but with a larger caliber. It was first trialled on the T2 Medium Tank. Like its smaller version, it was loaded with 5-round magazines.
The tank destroyer was built in July of 1937 in Fort Benning, Georgia. "Built" is a strong word, as it was more of a conversion. The stock turret was altered significantly, receiving a number of new components made from mild steel. The turret lost its roof and the two machineguns were replaced with the cannon, covered by a massive mantlet. Otherwise, the tank was identical to the M2A1 Light Tank.
Trials began to evaluate the worth of the vehicle as a tank destroyer. Sadly, the results were unsatisfactory. The penetration of the 47 mm gun was barely above 30 mm at 728 meters. This was enough for now, but the military understood very well that it wouldn't be for long.
At the same time, work was underway on the 37 mm M3 gun, which surpassed the 47 mm gun in penetration. The idea of a tank support vehicle was abandoned, but the idea of using an open turret on a tank chassis was still attractive to the military.
Overgunned
The American military returned to the idea of a tank destroyer in late 1941. Work started in several directions, both on the chassis and on guns. The 37 mm M3 gun turned out sufficiently powerful and worked well against enemy tanks. It was decided to mount this gun on light wheeled and tracked tank destroyers.
Additionally, the US had many 75 mm M1897 field guns, a version of the French Canon de 75 mle 1897. Even though this gun was old, it was capable of fighting tanks.
Finally, the M3 76 mm AA gun was explored as an anti-tank method. The M5 AT gun was built based on this gun's excellent ballistics. It eventually migrated to tanks and to light and medium tank destroyers, but none of this happened immediately.
Initially, the 7 ton Cletrac tractor, indexed M2 High Speed Tractor in February of 1941, was selected as the base for the 76 mm tank destroyer. Work on the tank destroyer began in December of 1940, and in November of 1941, the T1 Gun Motor Carriage was ready for trials. The result was a very agile vehicle that could reach a speed of 60 kph.
The military was satisfied, and it was standardized as the M5 Gun Motor Carriage in January of 1942. Mass production was planned, but never happened for several reasons. The process of improving the M5 GMC to match requirements dragged on. While this happened, the T35 GMC entered trials, created on the chassis of the M4 medium tank. The M5 GMC had only one advantage over this vehicle: speed. At the same time, the M5's armour was only a gun shield, the horizontal traverse was very limited, and the ammunition capacity low. As a result, work on the M5 GMC was not continued past a prototype.
Even before the T1 GMC made it to trials, work began on a 76 mm tank destroyer on the Light Tank M3 chassis. Initiated in September of 1941, the M20 Gun Motor Carriage project envisioned a light tank destroyer with a low silhouette. The use of an already established light tank as a base meant shortening the road to production.
As the Light Tank M3 was equipped with a large radial Continental W-670 engine, it was replaced with a car engine. A pair of V8 Cadillac 42-series engines was used. Due to this solution, the M20 was lower than its donor chassis. The project as short lived, however, as discussion at a conference dedicated to self propelled artillery in October of 1941 decided that the M3 chassis was ill suited for the 76 mm gun. The project was closed, but the M3 chassis would soon be in demand again.
In December of 1941, the Bureau of Ordnance proposed a sketch of a converted M4 turret on the M3 light tank chassis. According to the results of the conference, the 75 mm M1897 gun was the maximum that the M3 chassis could handle. The project, indexed T29 Gun Motor Carriage, was closed in April 1942 due to low interest, but already in May, work on a new tank destroyer with a 76 mm gun on the M3 chassis began.
The first variant, indexed T50 Motor Gun Carriage, was an evolution of the T29 GMC. A turret very similar to that of the M4 was installed on a modified M3 chassis. Aside from thinner armour, the new turret had no roof or rear. Theoretically, after installation of the 76 mm gun, there would be enough room for a gunner/commander and loader. The second variant, dated late June 1942, used the same gun, but with traverse limited to 15 degrees in each direction horizontally. The result was very similar to the T1 GMC. Even though this design lacked a gun shield, it would certainly have been installed if such a vehicle was built.
These projects were rejected. Both T50 GMCs had a very high center of gravity. The military also remarked that the 76 mm gun is too big and powerful for the small chassis. The second variant also offered poor mobility of fire, which was already one of the reasons for closing the T1/M5 GCM project.
In July of 1942, Buick produced a prototype of the 57 mm T49 GMC tank destroyer. This vehicle had nothing in common with the M3 Light Tank, and further development led to the creation of the T70 GMC, better known as the M18 GMC, or "Hellcat". Compared to the T49, which the military liked very much, the T50 seemed miserly and without a future.
Third Time's the Charm
Bad luck with the T29 and T50 didn't spell the end for attempts to make a tank destroyer out of the M3. Work continued, but the chassis changed. In September of 1942, the American Car & Foundry Co. began building a new tank indexed Light Tank M3A3. The chassis remained the same, but the turret and hull were altered. The M3A3 was the basis of the next design. The Bureau of Ordnance first started talking about this new design on August 13th, 1942, when a draft of a 76 mm tank destroyer with a rear mounted gun was sent in. This layout was used based on results of T1 GMC trials. The proposal was approved, and, on September 16th, 1942, the Bureau of Ordnance began a project of a new tank destroyer. On the third try, attempts to make a tank destroyer on the M3 light tank platform finally reached the practical stage.
Two parallel projects were launched to test two different power plant method. The T56 and T57 GMC only differed in engines: the T56 received a 288 hp Continental W-670 12-series, a turbocharged version of the stock M3A3 engine, and the T57 received a 400 hp Continental R-975-C1 engine, used on the M4 medium tank. Due to the more powerful engine, air filters were moved outside of the hull.
The vehicles designed by the American Car & Foundry Co. were significantly different from most American SPGs on a tank chassis. Only the M12 was similar, and that was designed for indirect fire, whereas the target for T56/T57 was enemy tanks.
The chassis and front of the M3A3 were unchanged. The engine compartment was moved from the rear of the hull to the middle, forming space in the rear for the gun mount, ammunition, and crew. At first, no gun shield was installed. A special ramp was deployed behind the vehicle for the crew to work on. In other words, it was less a highly mobile tank destroyer and more of a motorized anti-tank gun.
The T56 was ready first, and shipped to the Aberdeen proving grounds in November of 1942. The trials began with some confusion. The problem was that the 40 round ammunition rack completely covered access to the engine from the rear. Access from the top was no easier, as the whole gun had to be removed. Service of the vehicle using the crew's own resources was problematic.
The placement of the engine compartment in the center of the vehicle made the driver's compartment very crowded. The driver and his assistant had to sit in a very cramped space, and they still had it better than the rest of the crew, as the T56 and T57 had no seats for them at all.
Mobility trials over 190 km showed a maximum speed of 62.5 kph. On the other hand, the vehicle was overloaded in the rear. Firing trials showed that the Bureau of Ordnance was right to insist that the M3 was too small for such a gun. Every shot threw the T56 back 35 cm.
A gun shield was installed on the T56 during trials, as well as optics, since the T56 came from the factory with no sights installed. Due to the design of the gun, it had to be aimed by two crewmen.
The T57 GMC arrived at Aberdeen on December 8th, 1942. The gun mount was altered according to experience from T56 trials. The T57 GMC drove 1419 km between December 17th, 1942 and April 13th, 1943. Thanks to a more powerful engine, it achieved the speed of 80 kph on a highway and 48 kph off-road. That was the only advantage of this tank destroyer, as most problems with the T56 didn't go anywhere.
On January 7th, 1943, the Bureau of Ordnance gave an order for 6 prototypes of the 76 mm T70 GCM, an evolution of the T49 design. The first T70 was finished right as the T57's trials concluded, and there wasn't much to show off against this new competitor. With the same top speed and armament, the T70 had a proper turret. It is not surprising that the program to develop a tank destroyer on the M3 chassis was closed.
Original article by Yuri Pasholok.
First Try
It is often thought that the Americans began work on tank destroyers after WWII began, but engineers started thinking about destroying enemy tanks in the mid 1930s. At the time, typical armament for American tanks was a pair of machineguns, one rifle caliber, and one large caliber (12.7 mm).
It was proposed to either use the short barrelled 37 mm infantry gun or an experimental 37 mm tank gun converted from the Browning semiautomatic AA gun equipped with a 5 round magazine. This gun was trialled on the T1 family of light tanks, but nothing came of it. As for the 37 mm infantry gun M1916, its armour piercing effect was even lower than that of the Browning M2HB that was installed in the light M2 and M1 Combat Car series tanks. Not surprisingly, the machinegun was preferred.
The American military realized that the AT capabilities of the heavy machinegun were limited. As soon as production of light tanks began, design of tank destroyers on their chassis started. The M2A1, America's first mass production light tank of the 1930s, served as a lab rat. Unlike the double turreted M2A2 and M2A3, their predecessor had one two-man turret with enough space to install a cannon.
Work on a tank destroyer on the M2A1 chassis was initiated by the Infantry Department on October 9th, 1936. The tank destroyer, classified as a tank support vehicle, received a 47 mm semi-automatic Browning cannon. This was effectively the same 37 mm semi-automatic cannon, but with a larger caliber. It was first trialled on the T2 Medium Tank. Like its smaller version, it was loaded with 5-round magazines.
The tank destroyer was built in July of 1937 in Fort Benning, Georgia. "Built" is a strong word, as it was more of a conversion. The stock turret was altered significantly, receiving a number of new components made from mild steel. The turret lost its roof and the two machineguns were replaced with the cannon, covered by a massive mantlet. Otherwise, the tank was identical to the M2A1 Light Tank.
Trials began to evaluate the worth of the vehicle as a tank destroyer. Sadly, the results were unsatisfactory. The penetration of the 47 mm gun was barely above 30 mm at 728 meters. This was enough for now, but the military understood very well that it wouldn't be for long.
At the same time, work was underway on the 37 mm M3 gun, which surpassed the 47 mm gun in penetration. The idea of a tank support vehicle was abandoned, but the idea of using an open turret on a tank chassis was still attractive to the military.
Overgunned
The American military returned to the idea of a tank destroyer in late 1941. Work started in several directions, both on the chassis and on guns. The 37 mm M3 gun turned out sufficiently powerful and worked well against enemy tanks. It was decided to mount this gun on light wheeled and tracked tank destroyers.
Additionally, the US had many 75 mm M1897 field guns, a version of the French Canon de 75 mle 1897. Even though this gun was old, it was capable of fighting tanks.
Finally, the M3 76 mm AA gun was explored as an anti-tank method. The M5 AT gun was built based on this gun's excellent ballistics. It eventually migrated to tanks and to light and medium tank destroyers, but none of this happened immediately.
Initially, the 7 ton Cletrac tractor, indexed M2 High Speed Tractor in February of 1941, was selected as the base for the 76 mm tank destroyer. Work on the tank destroyer began in December of 1940, and in November of 1941, the T1 Gun Motor Carriage was ready for trials. The result was a very agile vehicle that could reach a speed of 60 kph.
The military was satisfied, and it was standardized as the M5 Gun Motor Carriage in January of 1942. Mass production was planned, but never happened for several reasons. The process of improving the M5 GMC to match requirements dragged on. While this happened, the T35 GMC entered trials, created on the chassis of the M4 medium tank. The M5 GMC had only one advantage over this vehicle: speed. At the same time, the M5's armour was only a gun shield, the horizontal traverse was very limited, and the ammunition capacity low. As a result, work on the M5 GMC was not continued past a prototype.
Even before the T1 GMC made it to trials, work began on a 76 mm tank destroyer on the Light Tank M3 chassis. Initiated in September of 1941, the M20 Gun Motor Carriage project envisioned a light tank destroyer with a low silhouette. The use of an already established light tank as a base meant shortening the road to production.
As the Light Tank M3 was equipped with a large radial Continental W-670 engine, it was replaced with a car engine. A pair of V8 Cadillac 42-series engines was used. Due to this solution, the M20 was lower than its donor chassis. The project as short lived, however, as discussion at a conference dedicated to self propelled artillery in October of 1941 decided that the M3 chassis was ill suited for the 76 mm gun. The project was closed, but the M3 chassis would soon be in demand again.
In December of 1941, the Bureau of Ordnance proposed a sketch of a converted M4 turret on the M3 light tank chassis. According to the results of the conference, the 75 mm M1897 gun was the maximum that the M3 chassis could handle. The project, indexed T29 Gun Motor Carriage, was closed in April 1942 due to low interest, but already in May, work on a new tank destroyer with a 76 mm gun on the M3 chassis began.
The first variant, indexed T50 Motor Gun Carriage, was an evolution of the T29 GMC. A turret very similar to that of the M4 was installed on a modified M3 chassis. Aside from thinner armour, the new turret had no roof or rear. Theoretically, after installation of the 76 mm gun, there would be enough room for a gunner/commander and loader. The second variant, dated late June 1942, used the same gun, but with traverse limited to 15 degrees in each direction horizontally. The result was very similar to the T1 GMC. Even though this design lacked a gun shield, it would certainly have been installed if such a vehicle was built.
These projects were rejected. Both T50 GMCs had a very high center of gravity. The military also remarked that the 76 mm gun is too big and powerful for the small chassis. The second variant also offered poor mobility of fire, which was already one of the reasons for closing the T1/M5 GCM project.
In July of 1942, Buick produced a prototype of the 57 mm T49 GMC tank destroyer. This vehicle had nothing in common with the M3 Light Tank, and further development led to the creation of the T70 GMC, better known as the M18 GMC, or "Hellcat". Compared to the T49, which the military liked very much, the T50 seemed miserly and without a future.
Third Time's the Charm
Bad luck with the T29 and T50 didn't spell the end for attempts to make a tank destroyer out of the M3. Work continued, but the chassis changed. In September of 1942, the American Car & Foundry Co. began building a new tank indexed Light Tank M3A3. The chassis remained the same, but the turret and hull were altered. The M3A3 was the basis of the next design. The Bureau of Ordnance first started talking about this new design on August 13th, 1942, when a draft of a 76 mm tank destroyer with a rear mounted gun was sent in. This layout was used based on results of T1 GMC trials. The proposal was approved, and, on September 16th, 1942, the Bureau of Ordnance began a project of a new tank destroyer. On the third try, attempts to make a tank destroyer on the M3 light tank platform finally reached the practical stage.
Two parallel projects were launched to test two different power plant method. The T56 and T57 GMC only differed in engines: the T56 received a 288 hp Continental W-670 12-series, a turbocharged version of the stock M3A3 engine, and the T57 received a 400 hp Continental R-975-C1 engine, used on the M4 medium tank. Due to the more powerful engine, air filters were moved outside of the hull.
The vehicles designed by the American Car & Foundry Co. were significantly different from most American SPGs on a tank chassis. Only the M12 was similar, and that was designed for indirect fire, whereas the target for T56/T57 was enemy tanks.
The chassis and front of the M3A3 were unchanged. The engine compartment was moved from the rear of the hull to the middle, forming space in the rear for the gun mount, ammunition, and crew. At first, no gun shield was installed. A special ramp was deployed behind the vehicle for the crew to work on. In other words, it was less a highly mobile tank destroyer and more of a motorized anti-tank gun.
The T56 was ready first, and shipped to the Aberdeen proving grounds in November of 1942. The trials began with some confusion. The problem was that the 40 round ammunition rack completely covered access to the engine from the rear. Access from the top was no easier, as the whole gun had to be removed. Service of the vehicle using the crew's own resources was problematic.
The placement of the engine compartment in the center of the vehicle made the driver's compartment very crowded. The driver and his assistant had to sit in a very cramped space, and they still had it better than the rest of the crew, as the T56 and T57 had no seats for them at all.
Mobility trials over 190 km showed a maximum speed of 62.5 kph. On the other hand, the vehicle was overloaded in the rear. Firing trials showed that the Bureau of Ordnance was right to insist that the M3 was too small for such a gun. Every shot threw the T56 back 35 cm.
A gun shield was installed on the T56 during trials, as well as optics, since the T56 came from the factory with no sights installed. Due to the design of the gun, it had to be aimed by two crewmen.
The T57 GMC arrived at Aberdeen on December 8th, 1942. The gun mount was altered according to experience from T56 trials. The T57 GMC drove 1419 km between December 17th, 1942 and April 13th, 1943. Thanks to a more powerful engine, it achieved the speed of 80 kph on a highway and 48 kph off-road. That was the only advantage of this tank destroyer, as most problems with the T56 didn't go anywhere.
On January 7th, 1943, the Bureau of Ordnance gave an order for 6 prototypes of the 76 mm T70 GCM, an evolution of the T49 design. The first T70 was finished right as the T57's trials concluded, and there wasn't much to show off against this new competitor. With the same top speed and armament, the T70 had a proper turret. It is not surprising that the program to develop a tank destroyer on the M3 chassis was closed.
Original article by Yuri Pasholok.
Saturday, 26 December 2015
Light Tank M2A4: Catching Up
The American M2A4 light tank surpassed the stereotype that American interbellum tank building lagged behind European levels. It was mobile, well armed, and well protected. Work on this vehicle began more than a year before WWII and resulted in one of the best light tanks of its time.
Return of the cannon
There is an opinion that the Americans missed out on tank development in the interbellum years and were not ready for war. In reality, American tank designers kept track of what was happening in the world while they went their own way. Their specific theater of war needed specific vehicles. They had to be fast, and instead of a cannon, use two coaxial machineguns, one of which was high caliber. This was enough in order to fight light tanks and armoured cars of the era. The Americans embraced this concept in the mid 1930s. Price was another important factor. One of the reasons why Christie's proposal was rejected was because a light tank with the same armament, speed, and armour cost half as much.
Serious changes in American tank building were triggered by the same events as changes in Soviet tank building: the Spanish Civil War. This was the first war that saw the full spectrum of anti-tank measures, including high caliber machineguns. The 16 mm of front armour on American tanks reliably protected them from rifles, but was useless against high caliber machineguns. The M2A3 that appeared in 1938 had 22 mm of front armour, but the military knew that it was a band-aid solution.
The first person to raise the question of changing the definition of a modern tank was Lieutenant Colonel Gladeon M. Barnes, a key figure in American tank building. Barnes had many inventions to his name. He started in artillery, but began working on tanks in the 1930s. Barns worked on perfecting the Christie suspension: the idea of positioning the springs at an angle belonged to him. In 1936, Barnes patented the torsion bar suspension, which would appear on American tanks 7 years later.
After John Walter Christie lost the army's favour, Barnes became the main competitor of Harry Knox and Major John Christmas, who held a monopoly on suspensions for American tanks. Barnes was a serious adversary for Knox and Christmas since he, unlike Christie, was a high-ranking military man (Major General by 1943). In 1938, he also headed the design bureau at the Bureau of Ordnance.
Barnes thought that a new generation light tank should be armed with a 37 mm gun and have 38 mm (1.5 inches) of front armour. If such a tank used automotive components and was produced in large amounts, it could cost $20,000. The potential tank was designed with no turret, but the overall direction was correct. This happened in April of 1938, almost a year and a half before the start of WWII, so accusing the Americans of doing nothing until the start of the war is rather improper.
Christmas and Knox
The ball was in Christmas and Knox's court. In July of 1938, Christmas proposed two draft projects. The first was more of a conceptual vision of what a tank that used automotive components could look like. Two 8-cylinder Buick engines were proposed, with a combined power of 280 hp. The engines would be placed in parallel, connected with individual drivetrains with the frontal transmission. This layout forced the removal of the hull gunner, and the driver was positioned in the center.
Despite the fact that this design had obvious drawbacks, Christmas managed to get it produced in metal. The tank, indexed Light Tank T6, was produced in June of 1939. It is notable that this was the first American tank to use large-scale casting. The transmission cover and final drive covers were both cast, this later became a signature solution of American medium tanks. As for the layout with two engines, it was later used on the M5 and M24 light tanks, as well as the M3A3, M3A5, and M4A2 medium tanks.
The second draft was far more interesting. As the first variant, it had a suspension with three road wheels per side, but the rear idler was lowered to the ground, effectively increasing that number to 4. As with the Light Tank T6, this design was equipped with horizontal springs. The engine of the 10.5 ton tank was the same as that of the M2 light tank, a radial Continental W-670 engine with aircraft ancestry. The main feature was a one-man turret with a 37 mm gun and a coaxial Browning M1919 machinegun. This layout seemed a lot more promising.
A lecture hall for American tankers
The reality was a lot more practical than any drafts. According to the decree of the OCM #14844 issued on December 29th, 1938, the new tank was not built from scratch. Instead, the last built M2A3 was used, with serial number 321. The conversion was made at Rock Island Arsenal, where American tanks were made before the war. No changes were made to the suspension. The hull of the tank was minimally changed, with only a change to the engine compartment and the addition of a machinegun by the driver.
The turret was made from scratch. The idea of a one-man turret was discarded, and it was enlarged to fit two people. There were no seats in the turret, the commander and loader had to stand. A driveshaft connected the rear engine and front transmission, which the tank crew had to step over. The armour of the turret was 25 mm thick, same as the hull. This reliably protected the tank from high caliber automatic weapons.
The first prototype of the M2A4 light tank was sent to Aberdeen on May 11th, 1939. After a series of trials, a series of corrections was composed by the Bureau of Ordnance. A commander's cupola was added with observation devices along its perimeter. The idea of an additional hull machinegun was approved, and another one was added on the right.
The gun, a tank version of the 37 mm AT gun designed by Gladeon Barnes, also demanded changes. The barrel was shortened by 13 cm to reduce the risk of damaging it while driving in a forest. Another significant change was the addition of an armoured cover for the recoil mechanism. Brackets were welded onto the front of the tank to cause bullets and small fragments to ricochet. A vehicle with all these changes returned to the proving grounds in October of 1939. As a result of these trials, the M2A4 was approved for service.
The first mass production M2A4 was produced in May of 1940. It's worth noting that before the M2A4, American tanks were built at the Rock Island Arsenal. The main producer of this new vehicle was American Car & Foundry Company. The majority of M2A4 tanks were assembled here, 365 in total. Another 10 were built in April of 1941 at Baldwin Locomotive Works. Late production vehicles received an improved gun mantlet, and a portion of the tanks were equipped with Guiberson T-1020 diesel engines.
The age of the Light Tank M2A4 was not long. In March of 1941, production of the superior Light Tank M3 began, better known by the name "Stuart", given to it by British tankers. Nevertheless, despite falling in the shadow of its younger brother, the M2A4 was an important step for American tank building. The characteristics of the tank were among the best in its class. They were close to those of the Czechoslovakian LT vz. 38, while superior in mass and speed. Due to its powerful gun, the M2A4 could fight almost any tank of the era. All tanks of this type were equipped with radios, a very important feature. Additionally, like other members of the M2 family, the M2A4 was very fast, reaching a speed of 58 kph. Few tanks of the era could manage such a feat.
Like other M2 series tanks, the M2A4 was somewhat of a learning instrument for American tankers. It was the main participant in large exercises held to work on combat action. In summer of 1941, these tanks began being replaced with the superior Light Tank M3, but the M2A4 remained in training until until the end of 1942.
These tanks were the first that the United States sent out as a part of the Lend-Lease program. In early 1941, 36 tanks were sent to Great Britain. Since code names were given in the spring of 1941, the M2A4, unlike the Medium Tank M3, did not receive a proper name. This tank was used, in part, by the 9th Queen's Royal Lancers while the regiment was located in England in the summer-fall of 1941. These tanks did not see combat, as the first Stuart I tanks started arriving in the spring of 1941. There is information that the 7th Tank Brigade received these tanks in 1942 and used them in Burma, but it has not been confirmed.
Unlike the British, the Americans used the M2A4 in battle. The Marine Corps, traditionally equipped with hand-me-downs, received 36 M2A4s. The 1st Tank Battalion attached to the 1st Marine Division fought at Guadalcanal. The battalion had a rather heterogeneous composition: A company had M2A4 and M3 tanks, while C company managed to receive new M3A1 tanks.
The battalion landed in Guadalcanal in August of 1942. During battle, the light tanks showed themselves equally well. The M3 and M3A1 were superior designs and had improved armour, but in practice, the M2A4 proved equivalent. The battle of Guadalcanal was very unusual in the sense that American and Japanese tankers did not fight each other, but enemy AT guns and infantry. The 1st Battalion fought here until January of 1943.
One M2A4 light tank survived to this day, from the A company of the 1st Tank Battalion. This tank was bogged down in a swamp during the battle for Henderson Field in October of 1942. The M2A4 spent nearly 70 years there, until a private collector recovered it in 2009. According to available information, the tank is partially restored, and might one day be functional again. Since the M2A4 has a significant number of parts in common with the much more common M3 and M3A1, this is a very possible outcome.
The Light Tank M2A4 ended up in the shadow of its more numerous brother, the Light Tank M3. Nevertheless, it became the first truly modern American tank, matching or even surpassing foreign competitors. Only luck pulled it off the stage so quickly.
Original article by Yuri Pasholok.
Return of the cannon
There is an opinion that the Americans missed out on tank development in the interbellum years and were not ready for war. In reality, American tank designers kept track of what was happening in the world while they went their own way. Their specific theater of war needed specific vehicles. They had to be fast, and instead of a cannon, use two coaxial machineguns, one of which was high caliber. This was enough in order to fight light tanks and armoured cars of the era. The Americans embraced this concept in the mid 1930s. Price was another important factor. One of the reasons why Christie's proposal was rejected was because a light tank with the same armament, speed, and armour cost half as much.
Serious changes in American tank building were triggered by the same events as changes in Soviet tank building: the Spanish Civil War. This was the first war that saw the full spectrum of anti-tank measures, including high caliber machineguns. The 16 mm of front armour on American tanks reliably protected them from rifles, but was useless against high caliber machineguns. The M2A3 that appeared in 1938 had 22 mm of front armour, but the military knew that it was a band-aid solution.
The first person to raise the question of changing the definition of a modern tank was Lieutenant Colonel Gladeon M. Barnes, a key figure in American tank building. Barnes had many inventions to his name. He started in artillery, but began working on tanks in the 1930s. Barns worked on perfecting the Christie suspension: the idea of positioning the springs at an angle belonged to him. In 1936, Barnes patented the torsion bar suspension, which would appear on American tanks 7 years later.
After John Walter Christie lost the army's favour, Barnes became the main competitor of Harry Knox and Major John Christmas, who held a monopoly on suspensions for American tanks. Barnes was a serious adversary for Knox and Christmas since he, unlike Christie, was a high-ranking military man (Major General by 1943). In 1938, he also headed the design bureau at the Bureau of Ordnance.
Barnes thought that a new generation light tank should be armed with a 37 mm gun and have 38 mm (1.5 inches) of front armour. If such a tank used automotive components and was produced in large amounts, it could cost $20,000. The potential tank was designed with no turret, but the overall direction was correct. This happened in April of 1938, almost a year and a half before the start of WWII, so accusing the Americans of doing nothing until the start of the war is rather improper.
Christmas and Knox
The ball was in Christmas and Knox's court. In July of 1938, Christmas proposed two draft projects. The first was more of a conceptual vision of what a tank that used automotive components could look like. Two 8-cylinder Buick engines were proposed, with a combined power of 280 hp. The engines would be placed in parallel, connected with individual drivetrains with the frontal transmission. This layout forced the removal of the hull gunner, and the driver was positioned in the center.
Despite the fact that this design had obvious drawbacks, Christmas managed to get it produced in metal. The tank, indexed Light Tank T6, was produced in June of 1939. It is notable that this was the first American tank to use large-scale casting. The transmission cover and final drive covers were both cast, this later became a signature solution of American medium tanks. As for the layout with two engines, it was later used on the M5 and M24 light tanks, as well as the M3A3, M3A5, and M4A2 medium tanks.
The second draft was far more interesting. As the first variant, it had a suspension with three road wheels per side, but the rear idler was lowered to the ground, effectively increasing that number to 4. As with the Light Tank T6, this design was equipped with horizontal springs. The engine of the 10.5 ton tank was the same as that of the M2 light tank, a radial Continental W-670 engine with aircraft ancestry. The main feature was a one-man turret with a 37 mm gun and a coaxial Browning M1919 machinegun. This layout seemed a lot more promising.
A lecture hall for American tankers
The reality was a lot more practical than any drafts. According to the decree of the OCM #14844 issued on December 29th, 1938, the new tank was not built from scratch. Instead, the last built M2A3 was used, with serial number 321. The conversion was made at Rock Island Arsenal, where American tanks were made before the war. No changes were made to the suspension. The hull of the tank was minimally changed, with only a change to the engine compartment and the addition of a machinegun by the driver.
The turret was made from scratch. The idea of a one-man turret was discarded, and it was enlarged to fit two people. There were no seats in the turret, the commander and loader had to stand. A driveshaft connected the rear engine and front transmission, which the tank crew had to step over. The armour of the turret was 25 mm thick, same as the hull. This reliably protected the tank from high caliber automatic weapons.
The first prototype of the M2A4 light tank was sent to Aberdeen on May 11th, 1939. After a series of trials, a series of corrections was composed by the Bureau of Ordnance. A commander's cupola was added with observation devices along its perimeter. The idea of an additional hull machinegun was approved, and another one was added on the right.
The gun, a tank version of the 37 mm AT gun designed by Gladeon Barnes, also demanded changes. The barrel was shortened by 13 cm to reduce the risk of damaging it while driving in a forest. Another significant change was the addition of an armoured cover for the recoil mechanism. Brackets were welded onto the front of the tank to cause bullets and small fragments to ricochet. A vehicle with all these changes returned to the proving grounds in October of 1939. As a result of these trials, the M2A4 was approved for service.
The first mass production M2A4 was produced in May of 1940. It's worth noting that before the M2A4, American tanks were built at the Rock Island Arsenal. The main producer of this new vehicle was American Car & Foundry Company. The majority of M2A4 tanks were assembled here, 365 in total. Another 10 were built in April of 1941 at Baldwin Locomotive Works. Late production vehicles received an improved gun mantlet, and a portion of the tanks were equipped with Guiberson T-1020 diesel engines.
The age of the Light Tank M2A4 was not long. In March of 1941, production of the superior Light Tank M3 began, better known by the name "Stuart", given to it by British tankers. Nevertheless, despite falling in the shadow of its younger brother, the M2A4 was an important step for American tank building. The characteristics of the tank were among the best in its class. They were close to those of the Czechoslovakian LT vz. 38, while superior in mass and speed. Due to its powerful gun, the M2A4 could fight almost any tank of the era. All tanks of this type were equipped with radios, a very important feature. Additionally, like other members of the M2 family, the M2A4 was very fast, reaching a speed of 58 kph. Few tanks of the era could manage such a feat.
Like other M2 series tanks, the M2A4 was somewhat of a learning instrument for American tankers. It was the main participant in large exercises held to work on combat action. In summer of 1941, these tanks began being replaced with the superior Light Tank M3, but the M2A4 remained in training until until the end of 1942.
These tanks were the first that the United States sent out as a part of the Lend-Lease program. In early 1941, 36 tanks were sent to Great Britain. Since code names were given in the spring of 1941, the M2A4, unlike the Medium Tank M3, did not receive a proper name. This tank was used, in part, by the 9th Queen's Royal Lancers while the regiment was located in England in the summer-fall of 1941. These tanks did not see combat, as the first Stuart I tanks started arriving in the spring of 1941. There is information that the 7th Tank Brigade received these tanks in 1942 and used them in Burma, but it has not been confirmed.
Unlike the British, the Americans used the M2A4 in battle. The Marine Corps, traditionally equipped with hand-me-downs, received 36 M2A4s. The 1st Tank Battalion attached to the 1st Marine Division fought at Guadalcanal. The battalion had a rather heterogeneous composition: A company had M2A4 and M3 tanks, while C company managed to receive new M3A1 tanks.
The battalion landed in Guadalcanal in August of 1942. During battle, the light tanks showed themselves equally well. The M3 and M3A1 were superior designs and had improved armour, but in practice, the M2A4 proved equivalent. The battle of Guadalcanal was very unusual in the sense that American and Japanese tankers did not fight each other, but enemy AT guns and infantry. The 1st Battalion fought here until January of 1943.
One M2A4 light tank survived to this day, from the A company of the 1st Tank Battalion. This tank was bogged down in a swamp during the battle for Henderson Field in October of 1942. The M2A4 spent nearly 70 years there, until a private collector recovered it in 2009. According to available information, the tank is partially restored, and might one day be functional again. Since the M2A4 has a significant number of parts in common with the much more common M3 and M3A1, this is a very possible outcome.
The Light Tank M2A4 ended up in the shadow of its more numerous brother, the Light Tank M3. Nevertheless, it became the first truly modern American tank, matching or even surpassing foreign competitors. Only luck pulled it off the stage so quickly.
Original article by Yuri Pasholok.
Monday, 23 March 2015
M2A2 Tanks in the Antarctic
"Excerpts from the assistant USSR military attache in the USA, Major Barayev.
Performance of American M2A2 light tanks in the southern polar territories (Antarctica) according to the American Antarctic expedition.
1. Reduction of tank weight.
Before tanks were sent to the polar expedition, it was decided that they should be lightened. All armament and a part of the armour was removed. When tanks arrived to the polar stations, it was determined that they were still too heavy to work in the icy conditions of the Antarctic. Turrets were removed in order to increase power per ton and improve stability.
The tank ground pressure was reduced to 5 or 6 psi. This was still not ideal, as previous experience in soft snow showed that the ideal value is 4 psi.
2. Power.
In order to increase the tank's power when moving on soft snow and reduce instances of falling through, additional plates made from 1/4 inch thick armour taken from the turret were welded to the tracks. The width of the plates was 8 inches, and they increased the width of the track by 7 inches, to a total width of 11 inches. These plates were welded on the inside of the tracks. This improvement increased the tank's power and protected it from falling through the snow.
3. Controlling the tank.
When the tank moved across loose snow, the snow was thrown up and blocked the driver's viewport. This was resolved by installing a protective plate, a regular automotive fender. It is necessary to install a special de-icing attachment to the glass window on the driver's viewport. The Antarctic service could investigate this issue, but it is preferable if the Army took it upon itself to solve it.
4. Carburettor.
The carburettors didn't have any problems in the cold. They worked normally, but it was assumed that all gasoline had to be filtered through suede to prevent water from getting into the carburettor.
The fuel line to the carburettor runs next to the engine, so the gasoline that goes through it is heated up by the engine's heat.
It is recommended that the fuel tank should be insulated, preventing excessive freezing.
5. Air filter.
Difficulties were encountered with the air filter when it was frozen. Freezing stopped the air from being sucked in and destroyed the pipe to the carburettor. In order to prevent this rubber pipe from rupturing, it is recommended to use a metal pipe. In the end, the air filter was thrown out entirely, as there is no need for it in the polar atmosphere with no mud or dust.
The pipe was replaced with one leading to the engine compartment near the batteries, where air was gathered without any filter.
6. Batteries.
The batteries worked well in cold conditions and no difficulties were encountered. Nevertheless, it is recommended to add a special insulation layer around the battery crates, considering that drafts are formed in this compartment once the air intake pipe is routed here.
7. Oil filter.
Like the air filter, the oil filter is completely unnecessary in polar conditions. In practice, the oil froze in it and caused it to rupture. The expedition removed all oil filters after a series of such cases.
8. Heating the engine.
The last two American expeditions to the Antarctic used Van Pregg heaters to heat up engines. They worked well for heating aircraft engines, but the best heater for tank engines turned out to be the Primus heater. This heater is made in Sweden in two sizes: 3 gallons and 5 gallons. It can keep the temperature of the engine compartment, and thus the motor, to 50 degrees Fahrenheit. Heated air is channeled into the engine compartment through a hose into an area with no electric wiring or fuel lines.
Oil is heated to a temperature of 120 degrees in special tanks with the same heaters. After being heated, the oil is poured into the crankcase and the engine starts. The engine can start at a temperature of 50 degrees, but before moving the tank, the engine temperature is increased to 100 degrees.
During Antarctic expeditions, it was determined that it takes about one hour to heat up the engine to 50 degrees using Primus heaters.
Primus heaters also work well to heat groups of people working outdoors. They do have a drawback, the corrugated pipes, despite being coated in fibers, crack in the cold and break. This can be fixed by adding an elastic metal insert inside the pipe.
9. Lubrication of the tank.
SAE 40 oil was used to lubricate the tank, but experience showed that SAE 50 oil was the superior lubricant for tanks working in winter conditions. Even with an outside temperature of -60 Fahrenheit, the engine worked well and maintained a temperature of 100 Fahrenheit.
Lubricating the wheels, crankshafts, etc. was not problematic and caused no faults. There was also no need to add additional lubrication to these components.
10. Generator.
The generator insulation ended up covered in lubrication oil, but the cause was not discovered at the time.
11. Rubber tracks.
Tracks work well, even in very low temperatures. They do not crack, bulge, or wear prematurely.
12. Speedometer.
The temperature of the fighting compartment dropped so much that the oil in the speedometer became viscous and the speedometer stopped working. In order for this mechanism to work properly, it is necessary to develop and apply some kind of heating device.
13. Clutch.
When the fighting compartment was exposed to an outside temperature of less than -60 degrees, the cold air entered the tank and froze the clutch to the point that it ceased to work normally, as the disks slipped. Experience showed that when the tank stops with an exterior temperature of -50 to -60 degrees, the clutch has to be heated, otherwise the aforementioned problems are unavoidable.
At 0 Fahrenheit, the clutch worked normally,
14. Marches.
At the Western base (Little America), one tank made a 30 mile march at a temperature of -60 Fahrenheit. The tank moved in second gear, dragging a sled with a 2 ton weight. The tank could not move at a higher gear, as it was impossible to control the sled at higher speeds. The tank worked flawlessly at higher speeds without a sled, except for the driver's window being covered with snow.
The following lubricants and fuel were used for aircraft, which the expedition also had:
Performance of American M2A2 light tanks in the southern polar territories (Antarctica) according to the American Antarctic expedition.
1. Reduction of tank weight.
Before tanks were sent to the polar expedition, it was decided that they should be lightened. All armament and a part of the armour was removed. When tanks arrived to the polar stations, it was determined that they were still too heavy to work in the icy conditions of the Antarctic. Turrets were removed in order to increase power per ton and improve stability.
The tank ground pressure was reduced to 5 or 6 psi. This was still not ideal, as previous experience in soft snow showed that the ideal value is 4 psi.
2. Power.
In order to increase the tank's power when moving on soft snow and reduce instances of falling through, additional plates made from 1/4 inch thick armour taken from the turret were welded to the tracks. The width of the plates was 8 inches, and they increased the width of the track by 7 inches, to a total width of 11 inches. These plates were welded on the inside of the tracks. This improvement increased the tank's power and protected it from falling through the snow.
3. Controlling the tank.
When the tank moved across loose snow, the snow was thrown up and blocked the driver's viewport. This was resolved by installing a protective plate, a regular automotive fender. It is necessary to install a special de-icing attachment to the glass window on the driver's viewport. The Antarctic service could investigate this issue, but it is preferable if the Army took it upon itself to solve it.
4. Carburettor.
The carburettors didn't have any problems in the cold. They worked normally, but it was assumed that all gasoline had to be filtered through suede to prevent water from getting into the carburettor.
The fuel line to the carburettor runs next to the engine, so the gasoline that goes through it is heated up by the engine's heat.
It is recommended that the fuel tank should be insulated, preventing excessive freezing.
5. Air filter.
Difficulties were encountered with the air filter when it was frozen. Freezing stopped the air from being sucked in and destroyed the pipe to the carburettor. In order to prevent this rubber pipe from rupturing, it is recommended to use a metal pipe. In the end, the air filter was thrown out entirely, as there is no need for it in the polar atmosphere with no mud or dust.
The pipe was replaced with one leading to the engine compartment near the batteries, where air was gathered without any filter.
6. Batteries.
The batteries worked well in cold conditions and no difficulties were encountered. Nevertheless, it is recommended to add a special insulation layer around the battery crates, considering that drafts are formed in this compartment once the air intake pipe is routed here.
7. Oil filter.
Like the air filter, the oil filter is completely unnecessary in polar conditions. In practice, the oil froze in it and caused it to rupture. The expedition removed all oil filters after a series of such cases.
8. Heating the engine.
The last two American expeditions to the Antarctic used Van Pregg heaters to heat up engines. They worked well for heating aircraft engines, but the best heater for tank engines turned out to be the Primus heater. This heater is made in Sweden in two sizes: 3 gallons and 5 gallons. It can keep the temperature of the engine compartment, and thus the motor, to 50 degrees Fahrenheit. Heated air is channeled into the engine compartment through a hose into an area with no electric wiring or fuel lines.
Oil is heated to a temperature of 120 degrees in special tanks with the same heaters. After being heated, the oil is poured into the crankcase and the engine starts. The engine can start at a temperature of 50 degrees, but before moving the tank, the engine temperature is increased to 100 degrees.
During Antarctic expeditions, it was determined that it takes about one hour to heat up the engine to 50 degrees using Primus heaters.
Primus heaters also work well to heat groups of people working outdoors. They do have a drawback, the corrugated pipes, despite being coated in fibers, crack in the cold and break. This can be fixed by adding an elastic metal insert inside the pipe.
9. Lubrication of the tank.
SAE 40 oil was used to lubricate the tank, but experience showed that SAE 50 oil was the superior lubricant for tanks working in winter conditions. Even with an outside temperature of -60 Fahrenheit, the engine worked well and maintained a temperature of 100 Fahrenheit.
Lubricating the wheels, crankshafts, etc. was not problematic and caused no faults. There was also no need to add additional lubrication to these components.
10. Generator.
The generator insulation ended up covered in lubrication oil, but the cause was not discovered at the time.
11. Rubber tracks.
Tracks work well, even in very low temperatures. They do not crack, bulge, or wear prematurely.
12. Speedometer.
The temperature of the fighting compartment dropped so much that the oil in the speedometer became viscous and the speedometer stopped working. In order for this mechanism to work properly, it is necessary to develop and apply some kind of heating device.
13. Clutch.
When the fighting compartment was exposed to an outside temperature of less than -60 degrees, the cold air entered the tank and froze the clutch to the point that it ceased to work normally, as the disks slipped. Experience showed that when the tank stops with an exterior temperature of -50 to -60 degrees, the clutch has to be heated, otherwise the aforementioned problems are unavoidable.
At 0 Fahrenheit, the clutch worked normally,
14. Marches.
At the Western base (Little America), one tank made a 30 mile march at a temperature of -60 Fahrenheit. The tank moved in second gear, dragging a sled with a 2 ton weight. The tank could not move at a higher gear, as it was impossible to control the sled at higher speeds. The tank worked flawlessly at higher speeds without a sled, except for the driver's window being covered with snow.
The following lubricants and fuel were used for aircraft, which the expedition also had:
- Gasoline: 87 SGR (Army, about 92)
- Lubricating oil: Navy 1080, winter. Same as Veedal Aero-Special Heavy. "77" under Army specifications.
- Kerosene: regular commercial.
- Grease: Royal Special AAA for temperatures of -50 F.
Experience gathered by the Americans in their Antarctic expeditions is of some interest to us, and can be used when using American or Canadian tanks (Canadian MIIIA, American M3) in our harsh winter conditions.
It is especially important to consider the practice of carefully pouring gasoline into M3 tanks to avoid problems with the carburettor.
It is possible that we will see the same problems with oil and air filters when using these tanks. In order to avoid breakdowns, disconnect them from the engine during the winter campaign."
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