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Crushing Cars - The Story of America's WWII Heavy Tanks

 
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Crushing Cars - The Story of America's WWII Heavy Tanks - 1/20/2010 4:21:54 AM   
RyanCrierie


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Crushing Cars - The Story of America's WWII Heavy Tanks
By
Ryan Crierie (aka MKSheppard)
Copyright 2010

A very special thanks to: Richard P. Hunnicutt, without whose marvelous book Firepower, on US Heavy Tank Development, I could not have written this article.

NOTE: As mentioned above, this article is based heavily on Firepower -- but since I now have located the Record Group at NARA responsible for US WWII tank design, I can do my own research into US tank design, instead of relying on Hunnicutt. This article was written several years ago, I just cleaned it up to post on the internet.

The M6 Heavy Tank Program

US heavy tank design in World War II began with the German invasion of France on May 10, 1940. The success of the German Panzer arm beyond anyone's wildest expectations led to the Chief of Infantry of the US Army recommending that a requirement be established for a new heavy tank in the weight range of either 50 tons or 80 tons.

Two days later, moving with remarkable rapidity, the Ordnance Committee responded to that recommendation, by supplying it's own recommendation for a 50 ton tank development project.

By July 11, 1940, a preliminary design was approved and designated the Heavy Tank, T1.

This design was a multi-turreted vehicle very similar to the Soviet T-28 and T-35 tanks.

Armament consisted of the following:


  • Two primary turrets armed with the low velocity T6 75mm gun (Combined total coverage of 250 degrees)
  • One secondary turret armed with 37mm Gun and .30 Caliber Coaxial MG
  • One secondary turret armed with a 20mm Cannon and a .30 Caliber Coaxial MG

    NOTE: Both secondary turrets had a combined total coverage of 360 degrees.


  • Two .30 Caliber MGs in ball mounts on frontal armor plate
  • Two .30 Caliber MGs in ball mounts on diagonal armor plates in the rear hull area.

    Sanity however, soon returned; and this layout was revised into one with a single large electrically traversed turret, which was approved on November 22, 1940.

    The revised T1 was now equipped with a version of the 3-inch T9 Anti-aircraft gun, with a 37mm M5E1 gun as the coaxial weapon. Both weapons had power elevation and a gyrostabilizer early on, but the power elevation feature was deleted as the design progressed.

    Contrary to later US Tank design practices, the tank commander sat on the left side of the main gun.

    Secondary armament consisted of a .30 Caliber MG in the tank commander's cupola, which was of the same type as used on the M3 Medium Tank.

    The loader operated a .50 Caliber machine gun from his position. The driver had control of two .30 caliber machine guns mounted on the front armor, which he fired electrically. The assistant driver controlled twin .50 Caliber machine guns in a flexible mount.

    Early on in the development cycle, a crew of six to seven men was proposed. When the tank was standardized, it was specified at six. They were:

    1.) Commander
    2.) Gunner
    3.) Loader
    4.) Ammunition Passer
    5.) Driver
    6.) Assistant Driver

    Mobility was provided by a Wright G-200 aircraft radial, which developed 960 hp at 2,300 rpm. To successfully transmit the power from this very high-powered engine to the tracks required an entirely new transmission as no existing tank transmission could do the job.

    After some deliberation, a new Hydramatic transmission proposed by Oldsmobile was chosen. As a fallback, torque converter proposals by Schneider Hydraulic, Twin Disc Clutch, and Borg-Warner were to be studied as alternatives to the Hydramatic transmission.

    A General Electric Gas-Electric transmission was also approved for a single vehicle designated T1E2, due to recent studies by GE indicating that it would only add three tons to the tank's weight (as opposed to earlier studies during the transmission selection process which estimated added weight at 5 tons).

    By August 1940, contracts had been placed with Baldwin Locomotive Works for the pilot construction and 50 production models. Due to unforseen problems with the Hydramatic transmission resulting in it missing it's delivery date of May 1941, the pilot tank was completed using Twin Disc's torque converter as the T1E2.

    Baldwin began testing the T1E2 during August 1941 as it prepared it's plans for mass production of the design. The usual problems with such a new and heavy vehicle were found during this test, such as transmission problems and steering brake overheating.

    Finally, on December 8, 1941, the T1E2 was officially presented to the US Army at the Baldwin Locomotive Works during a demonstration which showed it alongside a M3 medium tank, which had been designed in parallel with the T1. Many features such as fixed machine guns used by the driver, and a commander's cupola with a .30 caliber machine gun were shared across both designs.

    The production version of the T1 benefited from experience gained in tank operation and design by eliminating the left fixed machine gun, as well as reducing the size of the driver's door in the frontal glacis (eliminating it completely and going to a roof hatch would have required too much in terms of delaying production). The commander's cupola was removed, and replaced with a hatch similar to that on the production M4 Medium, with a rotating ring allowing fitting of anti-aircraft machine gun.

    With America now at war, it was decided to get the new tank into production as quickly as possible, and not wait for the test program to finish. Any changes that needed to be made due to experience could be introduced into later production marks; as the US was already doing with the M3 Medium.

    In order to meet the expected numbers of tanks that would be needed by the Army, on February 14, 1942, several different versions of the T1 were officially named. They were:


  • T1 - Cast hull, Wright G-200 engine, Hydramatic transmission
  • T1E1 - Cast hull, Wright G-200 engine, GE electric drive transmission
  • T1E2 - Cast hull, Wright G-200 engine, Twin Disc torque converter transmission
  • T1E3 - Welded hull, Wright G-200 engine, Twin Disc torque converter transmission
  • T1E4 - Welded Hull, Four GM 6-71 Diesels, two Hydramatic transmissions

    Production orders had already been placed for the T1E2 and T1E3, and on April 13, 1942, standardization of these two vehicles as the Heavy Tanks M6 and M6A1 was recommended. By May 26, 1942, the recommendation was approved.

    Despite funding having been allocated for 1,084 heavy tanks, the changing requirements of the Armored Force reduced the number authorized to just 115. With these reduced requirements, and the standardization of the M6 and M6A1, the T1 and T1E4 were cancelled on June 11, 1942.

    The T1E1 program was allowed to continue informally, due to the pilot tank showing exceptional performance; and it's standardization as the M6A2 was proposed, but not approved. On August 10, 1942, the Army recommended that the T1E1 be classified as a limited procurement type to allow 115 to be manufactured for extended service test.

    Due to the procurement of heavy tanks having been increased from 115 vehicles to 230 in June; the result was that all the T1E1s would be sent to the U.S. Army, with the M6 and M6A1s sent overseas via lend-lease.

    By September 1942, heavy tank production was expected to consist of 50 M6s and 65 M6A1s for Britain, and 115 T1E1s for the US. Production was expected to start in either October or November of that year.

    However, the opinion of the Army was shifting against the heavy tank. On December 7, 1942; the Commanding General of the Armored Force, General Jacob Devers, wrote to the Commanding General of the Army Ground Forces; stating that:

    "Due to its tremendous weight and limited tactical use, there is no requirement in the Armored Force for the heavy tank. The increase in the power of the armament of the heavy tank does not compensate for the heavier armor".

    This was also accompanied by general opinion in the Armored Force that it was better to use the available shipping to carry two 30-ton medium tanks instead of one 60-ton heavy tank.

    In light of the Armored Force's opinion, the Services of Supply approved the termination of the heavy tank production program after 40 units had been produced.

    The first M6 production model was delivered in December 1942; while Fisher/General Motors produced just a single M6A1 pilot. Due to the cancellation of the Fisher contract, all production tanks ended up being built by Baldwin Locomotive Works. The last production tank, a T1E1, was delivered in February of 1944.


    M6 and M5 at Fort Knox, showing disparity in size

    Breakdown of M6 series production


  • 1 - T1E1 Pilot
  • 20 - T1E1
  • 1 - T1E2 Pilot
  • 8 - M6
  • 1 - Fisher M6A1 Pilot
  • 12 - M6A1
  • Total: 43

    Despite the termination of the heavy tank program, the various models were shipped to Aberdeen Proving Ground anyway, to see what they performed like. The reports from Aberdeen were highly critical of the M6 and M6A1; with the conclusion that the tanks were unsatisfactory unless a complete redesign was performed.

    Among the problems encountered were:


  • Crew positions were awkward, making it difficult to operate the main gun and secondary machine guns.
  • The Direct sight telescope was located so close to the 3" gun, that the gunner could only use it with his left eye.
  • The tank commander had no way to deliver machine gun fire to the sides and rear without exposing himself due to the removal of the .50 caliber machine gun cupola from production turrets.

    Aberdeen also considered the 37mm co-axial cannon to be rather superflous and recommended that it be replaced with a more conventional .30 caliber machine gun.

    Experiments and Modifications to the M6 Series.

    Despite the program being effectively dead in the water, this did not stop the Army from further developing the M6 series experimentally.

    The 90mm Gun Armed T1E1



    Due to the Armored Force now considering the 3 inch gun as inadequate for a heavy tank, the Ordnance Department began a test program in which the pilot T1E1 at Aberdeen had the 90mm gun T7 installed experimentally. This gun was eventually standardized as the 90mm gun M3 and installed in the Pershing.

    Firing tests showed that the T1E1 provided a stable gun platform for the 90mm gun, but the turret was in need of a redesign to accomodate the efficient operation of the new gun.

    However, by the time the firing tests had been done and the reports written up, the Army Ground Forces had cancelled the heavy tank program, and the 90mm program did not proceed any further.

    The 105mm Gun Armed M6A2E1



    Shortly after D-Day, there was some thought in the Ordnance Department that there would be a need for a small number of tanks with thick armor and a powerful gun to break through fortified areas.

    To this end, they put forth a proposal to modify several existing T1E1s by doing the following tasks:


  • Removal of the Bow Machine Gun Mounts
  • Removal of the Driver's Vision Door
  • Welding additional steel plate onto the front to bring frontal protection up to the equivalent of 7.5 inches of vertical armor.
  • A new turret mounting the 105mm gun T5E1.
  • Modifying the turret ring from 69" to 80" to accept the new turret.

    It was hoped that fifteen T1E1s could be so modified in 90 days if the project was assigned a high enough priority. The remaining other five T1E1s left over after the conversions would be used as spare parts.

    An OCM of August 14, 1944 recommended the modification of the 15 tanks and gave them a tentative designation of Heavy Tank, M6A2E1. The hoped-for goal was delivery by November 15th.

    However, the Army Ground Forces had been indifferent to the project, and the Army Service Forces referred the matter of the program to Eisenhower in a cablegram of August 2, 1944. His reply of August 18th stated that the 15 modified tanks weren't wanted as they were considered impractical for the ETO. Upon this, the project was effectively killed off for the better. Early tests at Aberdeen with a T1E1 loaded to the 77-ton weight of the M6A2E1 showed it couldn't even climb a 40 percent slope, and since the final drive reduction gearing would not have been changed in the very short time available for conversion, the modified tanks would have been limited to operating on very favorable terrain.

    The T29/M6A2E1 Hybrids



    After the M6A2E1 project died, it was requested that two T1E1s be converted anyway to quasi-M6A2E1 standards to test the new heavy tank T29's armament and turret. Following approval of the request, the modifications were carried through, albeit without the hull armor from the original M6A2E1 program, as it was not needed for a demonstrator vehicle.

    The End of the M6 Program

    On December 14th, 1944 the M6, M6A1, and T1E1 were classified as obsolete.

    All were scrapped except a single T1E1 which has remained at Aberdeen Proving Ground, MD for the last sixty-five years, and recently was restored at least externally. It is likely that it will be moved down south to the new U.S. Army Ordnance Museum complex in Virginia as part of BRAC, which will see most of Aberdeen's existing exhibits (about 60%) move down south.

    The following photos were taken in September of 2008.






    Technical Data of M6 Series

    T1E1
    63.5 ton combat weight
    6 man crew
    3" M7 Main Gun with 75 Rounds
    37mm M6 Coaxial with 202 Rounds
    2 x .50 Caliber M2HB MGs in Fixed Front Hull Mount with 6,900 rounds
    .30 Caliber M1919A4 MG in fixed Bow Mount with 5,500 rounds (total .30 cal)
    .30 Caliber M1919A4 MG in flexible Anti-Aircraft Mount

    Front Upper Hull: 83mm at 30 degrees
    Front Lower Hull: 102-70mm at 0 to 60 degrees
    Side Upper Hull: 44mm at 20 degrees
    Side Lower Hull: 70mm at 0 degrees (includes track armor)
    Rear Hull: 41mm at 17 degrees
    Top Hull: 25mm at 90 degrees
    Hull Floor: 25mm at 90 degrees

    Gun Mantlet: 102mm at 0 degrees
    Front Turret: 83mm at 7 degrees
    Side Turret: 83mm at 0 degrees
    Rear Turret: 83mm at 0 degrees
    Top Turret: 25mm at 90 degrees

    Engine
    Wright G-200 Radial 960 hp @ 2,300 RPM
    464 gallons of 80 octane gasoline providing a cruising range of 100 miles on roads
    Top speed 20~ MPH on roads.

    T1E2
    63 tons combat weight
    6 or 7 man crew
    3" T12 Main Gun with 75 Rounds
    37mm M5E1 Coaxial with 200 Rounds
    2 x .50 Caliber M2HBs in Flexible Twin Hull Mount with 8,000 rounds (total .50 cal)
    2 x .30 Caliber M1919A4 MG in fixed Bow Mount with 10,000 rounds (total .30 cal)
    .30 Caliber M1919A4 in commander's cupola
    .50 Caliber M2HB in flexible Anti-Aircraft Mount

    Front Hull: 76mm at 0 degrees
    Front Side Hull: 64mm at 0 degrees
    Rear Side Hull: 51mm at 0 degrees
    Rear Hull: 51mm at 0 degrees
    Top Hull: 25mm at 90 degrees
    Hull Floor: 25mm at 90 degrees

    Gun Mantlet: 76mm at 0 degrees
    Front Turret: 76mm at 0 degrees
    Side Turret: 76mm at 0 degrees
    Rear Turret: 76mm at 0 degrees
    Top Turret: 25mm at 90 degrees

    Engine
    Wright G-200 Radial 960 hp @ 2,300 RPM
    477 gallons of 80 octane gasoline providing a cruising range of 100 miles on roads
    Top speed 22~ MPH on roads.

    M6
    63.25 ton combat weight
    6 man crew
    3" M7 Main Gun with 75 Rounds
    37mm M6 Coaxial with 202 Rounds
    2 x .50 Caliber M2HBs in Flexible Twin Hull Mount with 6,900 rounds
    .30 Caliber M1919A4 MG in fixed Bow Mount with 5,500 rounds (total .30 cal)
    .30 Caliber M1919A4 in flexible Anti-Aircraft Mount (or .50 M2HB)

    Front Upper Hull: 83mm at 30 degrees
    Front Lower Hull: 102-70mm at 0 to 60 degrees
    Upper Side Hull: 44mm at 20 degrees
    Lower Side Hull: 70mm at 0 degrees (including track armor)
    Rear Hull: 41mm at 17 degrees
    Top Hull: 25mm at 90 degrees
    Hull Floor: 25mm at 90 degrees

    Gun Mantlet: 102mm at 0 degrees
    Front Turret: 83mm at 7 degrees
    Side Turret: 83mm at 0 degrees
    Rear Turret: 83mm at 0 degrees
    Top Turret: 25mm at 90 degrees

    Engine
    Wright G-200 Radial 960 hp @ 2,300 RPM
    477 gallons of 80 octane gasoline providing a cruising range of 100 miles on roads
    Top speed 22~ MPH on roads.

    M6A1
    63.15 ton combat weight
    6 man crew
    3" M7 Main Gun with 75 Rounds
    37mm M6 Coaxial with 202 Rounds
    2 x .50 Caliber M2HBs in Flexible Twin Hull Mount with 6,900 rounds
    .30 Caliber M1919A4 MG in fixed Bow Mount with 5,500 rounds (total .30 cal)
    .30 Caliber M1919A4 in flexible Anti-Aircraft Mount (or .50 M2HB)

    Front Upper Hull: 83mm at 30 degrees
    Front Lower Hull: 102-70mm at 0 to 60 degrees
    Upper Side Hull: 44mm at 20 degrees
    Lower Side Hull: 70mm at 0 degrees (including track armor)
    Rear Hull: 41mm at 17 degrees
    Top Hull: 25mm at 90 degrees
    Hull Floor: 25mm at 90 degrees

    Gun Mantlet: 102mm at 0 degrees
    Front Turret: 83mm at 7 degrees
    Side Turret: 83mm at 0 degrees
    Rear Turret: 83mm at 0 degrees
    Top Turret: 25mm at 90 degrees

    Engine
    Wright G-200 Radial 960 hp @ 2,300 RPM
    477 gallons of 80 octane gasoline providing a cruising range of 100 miles on roads
    Top speed 22~ MPH on roads.

    M6A2E1
    77 ton combat weight
    5 man crew
    Armament Data
    105mm T5E1 Main Gun with 60 rounds
    .30 caliber M1919A4 Coaxial with 4,000 rounds
    .50 Caliber M2HB in flexible Anti-Aircraft Mount with 600 rounds

    Front Hull: 191mm at 0 degrees
    Upper Side Hull: 44mm at 20 degrees
    Lower Side Hull: 70mm at 0 degrees (including track armor)
    Rear Hull: 41mm at 17 degrees
    Top Hull: 25mm at 90 degrees
    Hull Floor: 25mm at 90 degrees

    Gun Mantlet: 191mm at 0 degrees
    Front Turret: 191mm at 0 degrees
    Side Turret: 89mm at 0 degrees
    Rear Turret: 208mm at 0 degrees
    Top Turret: 25mm at 90 degrees

    Engine
    Wright G-200 Radial 960 hp @ 2,300 RPM
    464 gallons of 80 octane gasoline providing a cruising range of 100 miles on roads
    Top speed 18~ MPH on roads.

    < Message edited by RyanCrierie -- 1/20/2010 4:25:53 AM >


    _____________________________

  • Post #: 1
    RE: Crushing Cars - The Story of America's WWII Heavy T... - 1/20/2010 6:37:45 AM   
    06 Maestro


    Posts: 3988
    Joined: 10/12/2005
    From: Nevada, USA
    Status: offline
    That is an impressive machine. I don't recall seeing that before.

    At Ft Knox there is a US assault gun that was rather huge. It was considered a requirement for a successful attack on Germany's border fortifications. At some point, well before it was needed, info came it that it would not be needed. I think only 2 were built. I don't recall the specs, but it did dwarf the nearby Panther.

    I think I found it.

    T28
    http://img521.imageshack.us/img521/7923/t28ji4.gif

    It had a weight of 95 tons with a 105 or 120mm gun. Very impressive, but apparently never sent into action.

    < Message edited by 06 Maestro -- 1/22/2010 7:25:08 AM >


    _____________________________

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    Thomas Jefferson


    (in reply to RyanCrierie)
    Post #: 2
    RE: Crushing Cars - The Story of America's WWII Heavy T... - 1/20/2010 7:47:30 PM   
    Jeffrey H.


    Posts: 3154
    Joined: 4/13/2007
    From: San Diego, Ca.
    Status: offline
    From those photos, the restored vehicles can almost pass for some new monster SUV.

    _____________________________

    History began July 4th, 1776. Anything before that was a mistake.

    Ron Swanson

    (in reply to 06 Maestro)
    Post #: 3
    RE: Crushing Cars - The Story of America's WWII Heavy T... - 1/22/2010 3:36:22 AM   
    SLAAKMAN


    Posts: 2810
    Joined: 7/24/2002
    Status: offline
    That is a beautiful tank!!


    _____________________________

    Germany's unforgivable crime before the Second World War was her attempt to extricate her economy from the world's trading system and to create her own exchange mechanism which would deny world finance its opportunity to profit.
    — Winston Churchill

    (in reply to Jeffrey H.)
    Post #: 4
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