Saturday, 3 August 2019

When Late is not Better than Never

The saying "fast enough is well enough" applies to a whole slew of armoured vehicles that arrived too late to take part in the war. One of them was the Heavy Tank T29, the next tank after the M6 to be built in any kind of series. This tank was supposed to be America's answer to the Tiger Ausf.B. The Americans got their King Tiger, but only two years after WWII ended. At that point the Heavy Tank T29 looked rather obsolete.

Plus sized Pershing

The American heavy tank program was in torpor in 1944. The active development of the Heavy Tank M6 quickly petered out. The tank turned out to be unsuitable for the Army's needs. Rather, the requirements changed, and the old tank did not meet new ones. A tank was needed with better mobility than the 57 ton M6 could achieve. As a result, the Heavy Tank M6 turned out to be unnecessary by 1943. The GMC M10 tank destroyer could defeat enemy heavy tanks, and the M4 series tanks could handle anything else. Combat in Italy showed that there was little need in a new heavy tank.

The appearance of the King Tiger tank in Normandy was a wakeup call. The first such tank was knocked out on July 18th, and on July 31st General Electric proposed a conversion for the M6 to install a more powerful gun. That was the start of the M6A2E1 project.

105 mm T5E1 gun initially used on the Heavy Tank T29.

It seemed that the conversion of the M6A2 would be a quick fix. At the same time, Major General Gladeon Barnes, who by the middle of August was the Chief of Research and Engineering in the Ordnance Department, started to doubt this solution. The M6 had poor mobility as is, and the mass of the M6A2E1 grew to 77 tons. This meant that mobility decreased further. Another method existed to obtain a new tank, albeit a longer one. On August 14th Barnes proposed the idea of creating two heavy tanks: the T29 and T30. They would differ from one another only in armament.

On August 22nd the M6A2E1 program was shut down. The decision was later changed: two M6A2E1s were converted to test turrets in order to accelerate the T29 tank program. This gave birth of a myth of the M6A2E1 with the T29 turret. In reality, the M6A2E1 turret was initially designed for the T29. Trials showed that the turret could be improved, and turrets installed on actual T29s were different.

Initial T29 turret.

The Medium Tank T26 was the best American tank when the T29 program was launched. In the summer of 1944 preparations were underway for mass production of this tank. It was better than any American tank of the era due to its low hull, torsion bar suspension, and improved running gear. Almost nothing was left from the American medium tanks that could trace their lineage back to the Light Tank T2. With such a promising platform, the Tank-automotive Center took this platform as the foundation. This didn't mean that the T29 would be a clone of the T26, but the overall concept was based on this tank. In the summer of 1944 the T26 was also reclassified as a heavy tank.

A heavy tank's difficult road

Work on the T29 began in the fall of 1944. On September 14th the Ordnance Committee authorized production of two experimental tanks. Two more prototypes would receive 155 mm T7 guns and would receive the index Heavy Tank T30 (the first mention of such a tank was made on August 14th, 1944). This tank, as well as later variants, deserve their own articles.

Heavy Tank T29 pilot, produced by Pressed Steel Car Co. Inc, 1947.

Development at the Tank-automotive Center went quickly, and the Ordnance Committee was optimistic. The tank was eagerly awaited due to the situation of the Western front. The biggest gun available to American tankers was the 90 mm M3 used on the Heavy Tank T26E3 and GMC M36 tank destroyer. These vehicles were effective against Panthers, but something bigger was needed to deal with the King Tiger. The Heavy Tank T26E4 was introduced as a temporary measure. One such tank made it to the battlefield, but did not see much action.

The Ordnance Committee authorized production of 1200 Heavy Tanks T29 on March 1st, 1945. At this point the tank existed only on paper. The contract was given to the Pressed Steel Car Co. Inc from New Jersey, one of the largest tank manufacturers. If the war continued there would be no issue with producing these tanks. Most likely they would have had the same turret as the M6A2E1. However, the story of this tank went in a different direction.

This is how the tank looked originally. Later alterations affected its looks.

The first sign that the course was changing happened on April 12th, 1945. The order was reduced to 1152. Four additional experimental tanks were ordered. One of them was armed with the T53 120 mm gun, which started the history of another brother of the T29, the Heavy Tank T34. This reduction in production was only the first step. When the war in Europe ended on May 8th, the need to fight King Tiger tanks disappeared. Japan's surrender meant that a mass produced heavy tank was no longer needed.

On August 23rd, 1945, the Ordnance Committee radically changed the production plan for the T29. Only two would be built instead of 1152. One tank would be built in its entirety, the other only partially. Further work on the tank and any materials or documentation were transferred from Pressed Steel to the Detroit Arsenal.

The same tank after improvements. Most changes affected the rear hull and internal components.

In practice, this meant not only the near total cancellation of the project, but a radical reduction in the pace of development. Conclusions made as a result of the trials of the M6A2E1 meant that a large number of changes had to be made to the turret, and the end of the war slowed the program down even further. The Americans were not alone: the development of the Soviet IS-4 slowed down also, as well as other tank programs in other nations. As a result, development of the T29 took years. On July 10th, 1947, the Ordnance Committee ordered the reduction of tanks built at the Detroit arsenal from 10 to 8. That didn't matter, as not a single tank had been built yet. Pressed Steel produced their prototype first.

The improved tank as viewed from the rear.

The selection of the Heavy Tank T26 as an example to follow allowed the Heavy Tank T29 to retain a reasonable mass. It was slightly heavier than 64 tons, or only 7 tons more than the Heavy Tank M6. The lower hull meant that the T29 was slightly lower than its predecessor. This was still a giant with an enormous turret, developed from the one used on the Heavy Tank M6A2E1.

Two years did not go to waste. The turret was radically improved. The gun mantlet increased in thickness to 203-279 mm and became much larger. The protection of the turret was also impressive: 178 in the front, 127 mm along the sides, 102 mm in the rear. The commander's station and cupola moved back to the turret bustle. The number of hatches in the turret increased to 3. This was partially caused by the number of tanks on the T29 platform that would have even heavier weapons. The number of ventilation fans increased to 2. Unlike the M6A2E1, the gun had no muzzle brake. The machineguns also changed: instead of one M1919A4 Browning .30 cal the tank had two coaxial M2HB .50 cal machineguns.

Ford GAF engine and CD-850-1 cross-drive transmission.

The protection of the hull compared poorly to the protection of the turret. The Heavy Tank T26 (by this point Medium Tank T26) inspired not only the shape of the hull, but its protection. 102 mm of front armour was enough for a medium tank, but not for a nearly 65 ton heavy. The angle of the front armour was changed from 46 to 54 degrees, but that did not help much. The running gear was also taken from the M26. Initially, the 580 mm wide T80E1 track was used, the same as on the M26. The number of road wheels was increased to 8 since the hull was longer.

Cutaway diagram of the Heavy Tank T29.

The biggest difference was in the rear of the hull. The heavier tank needed a more powerful engine. This was the Ford GAC, a relative of the Ford GAF, the engine used on the M26. The number of cylinders increased to 12, and the volume to 277 L. The maximum power output was 770 hp. The power to weight ratio was higher than on the King Tiger. Initially, the tank had the EX-120 General Motors electromechanical transmission, but after initial trials it was replaced with the Alisson CD-850-1 cross-drive transmission.

A tank for experiments

The purpose of the pilot tank produced by Pressed Steel was to test components of the tank before the Detroit arsenal began production of the pilot batch. This tank rarely appeared in correspondence. The eight tanks being built in Detroit had a higher priority, although there was a caveat. The T29 was never going to enter mass production. These tanks were being built as mobile laboratories to test components of prospective tanks. The 8 tanks that were built had registration numbers between 30162834 and 30162841.

Heavy Tank T29 #7 during trials in Fort Knox.

The first T29 tanks were ready by the fall of 1947. They had no major differences from the prototype, but many small ones. The tank still used the T123 gun mount, but the mantlet was different. Bulges to protect from splash were added, which made the removal of the gun mount more difficult. Some changes were made to other elements of the turret, especially the stowage. Changes were made to the running gear as well. Since the ground pressure increased, the tracks were replaced with the T80E3 with track extenders, which increased their width to 711 mm.

The same tank from the front. The T5E1 guns did not last long on the T29 tanks.

One of the tanks, #7, was transferred to the Armor Board in Fort Knox in June of 1948. The army held trials here, which the M26 and T30 later joined. The trials lasted until 1949, but were largely academic, as mass production was never on the table. Experimental tanks appeared much more often at the Aberdeen Proving Grounds, where reliability trials were held. The first T29 prototype was sent there in October of 1947, but it did not stay long.

Allison V-1710-E32 engine used on the Heavy Tank T29E1.

Even though the Ford GAC was powerful enough for a large tank like this, a search was on for an alternative. The engine had to be more powerful to raise the tank's mobility. The Allison V-1710, widely used on American fighters during WWII, was a perfect solution. The Allison V-1710-E32 was created based on the airplane engine. The power was lowered to 870 hp. The engine worked in conjunction with the CD-850-1 transmission.

The first T29 prototype was sent to General Motors, where it had to be converted. The Allison V-1710-E32 was longer than the Ford GAC, and the engine compartement had to be lengthened. This tank was indexed Heavy Tank T29E1. The tank went through trials, but the Allison V-1710-E32 was not widely used. Practice showed that a purpose made tank engine was needed.

105 mm T5E2 gun. It was first used on the Heavy Tank T29E2, later on four more tanks.

The armament of the Heavy Tank T29 evolved in a similar way. The converted vehicle was indexed Heavy Tank T29E2. The biggest difference was the T5E2 gun, developed in the summer-fall of 1946. The gun had a double maffle muzzle brake, which allowed the reduction of recoil cylinders from three to two. The tank received a new turret, indexed T5. It had hydraulic traverse and elevation mechanisms. This invention from the Massachusetts Institute of Technology was tested here, but not used on other tanks.

The gun was a different story. A decision was made to convert tanks ##3, 4, 5, 6, and 7 to use the T5E2. The gun mount was also changed to the T123E1. The conversion to the new standard did not happen all at once. For instance, tank #7 was tested with the old system, and the T5E2 was installed later. 

Typical T29 with the T5E2 gun.

Three T29 tanks were active tested at the Aberdeen Proving Grounds: ## 3, 4, and 6. The tanks were tested at a different time. #3 arrived on May 28th, 1948, tank #4 arrived on April 1st, tank #6 arrived on October 22nd, 1947. Tank #3 travelled 2686 km during trials, tank #4 travelled 1400, and tank #6 3314 km. During trials tank #4 received the improved CD-850-2 transmission. The long runtimes were due to the fact that the tanks were going through reliability trials, testing components that would later be used in other tanks.

The same tank from behind. Experimental tanks could look different from one another depending on what equipment was being tested at the time.

Tank #3 became the subject of experiments almost as soon as it arrive. On July 16th the tank was tested on cross-country terrain. The transmission had to be repaired after 235 km. Serious issues came later. On August 13th, after 750 km of driving, a whole slew of engine and transmission issues surfaced. The tank had to be removed from trials for 1.5 months. On September 29th the tank returned to trials, but not for long. On October 8th, after driving for 309 km, the engine broke down, taking a number of transmission elements with it. The engine and transmission had to be replaced. The tank returned to the repairs workshop for a long stay. The remaining trial runtime was only completed in 1949, after several changes of the engine and transmission bloc.

The engine compartment is larger than on the M26 due to a bigger engine.

T29 #4 had an even more dramatic career. The tank remained immobile for its first 1.5 months at Aberdeen. The design of the engine and transmission was being worked on. The tank was broken in between June 9th and 25th, 1948. Multiple issues with the engine and suspension were noted. However, the tank ended its first 328 km in much better shape than tank #3. The tank only drove for 184 km in July, as it was plagued by various technical defects.

The runtime between late July and early October was even less: 80 km. In late October, after only 592 km of trials, the engine had to be replaced. The new engine did not last for long. The cooling system broke after 230 km. The engine was first extracted, and then replaced entirely. The tank drove for another 275 km before the new engine broke as well. In late January of 1949, after 1170 km of travel, a decision was made to install a new CD-850-2 transmission. The tank completed the rest of its trials with a new transmission.

A typical episode of trials. The engine and transmission had to be removed for repairs very frequently.

The lengthy trials of tank #6 began first, on November 10th, 1947. It drove for 752 km by late February, when its transmission fell apart. Issues with engine components were also recorded. The tank returned to trials on March 17th and travelled for 182 km by the end of April, when issues with the steering and engine cropped up.

Defects plagued the tank for the whole summer of 1948. Similar issues continued in the fall. The engine was replaced in late December after another major breakdown. This happened after 1707 km of driving, a significant distance, but one that could only be covered at the cost of multiple engine repairs. However, the replacement engine was also problematic. After this performance the fate of the Ford GAC was sealed. The Heavy Tank T30 was being tested nearby with the Continental AV-1790-1 engine. This engine was hardly flawless either, but it was more powerful and at least as reliable as the Ford GAC.

Heavy Tank T29E3 at the Aberdeen Proving Grounds.

In addition to the pilot tank and the first production tank, the last tank also kept its initial armament. This tank was used as a test bed for new tank optics. The Heavy Tank T29E3 had the biggest difference from its cousins. The T31E1 stereoscopic rangefinder introduced characteristic "ears" to the tank. The sights were also changed. The T93E2 telescopic sight was installed, and T141, T144, and T145 panoramic sights were also tested.

Unlike other tanks, the T29E3 was chiefly used to test optical devices.

Unlike tanks ##3, 4, and 6, tank #8 did not take part in extended mobility trials. The experiments chiefly had to do with sights, and gave poor results (especially the rangefinder). The Heavy Tank T29E3 was moved to Fort Knox at the end of its trials, where the tests continued. This "banishment" saved the tank. The vehicles at Fort Knox that were undergoing trials were saved, the rest were scrapped. The preserved T29 and T29E3 became a part of the Patton museum, and are now on display at the National Armor and Cavalry Museum at Fort Benning.

The T31E1 stereoscopic rangefinder gave the tank its "ears".

The T29 family of tanks proved to be a mixed bag. They were obsolete as soon as they were built and already had an unsatisfactory hull, which was vulnerable to medium and large caliber guns. The tank turned out to be insufficiently agile, and trials showed that the engine and transmission were unreliable. The 105 mm T5E1 and T5E2 gun was ineffective against new tanks, most notably the IS-3. The appearance of this tank at the Victory Parade in Berlin on September 7th, 1945, made further production of this tank pointless.

The decision to limit the production of the tank turned out to be correct. The T29 proved itself useful as a test stand. The CD-850 transmission was installed on M46 Patton tanks, and later migrated to the M103, the only American heavy tank produced on a truly large scale.


9 comments:

  1. The 12 cylinder Ford GAC would of made a fine improvement if placed in modified M-26's.The engine was originally built as a 12 cylinder and only lost 4 cylinders so it could be put in Sherman tanks.

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    1. I wonder if the full sized one could have fit into an M4A4.

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    2. Hard to say. But someone did manage to put a Ford GAA V-8 in the engine bay of a 69 Mustang Fastback. I say in because the 1100 ci. engine stuck out of the engine bay about two feet, as well as back into the drivers compartment. Fun aside the new Continental AV-1790 V-12 and cross drive transmission eventually turned into a great combination. But not in the M-46 or 47.Many would of welcomed something simpler.

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  2. Maybe the M-26 project should have been pushed out earlier? More for infantry support than the usual complaint about tank fighting; I always thought the US Army lacked a proper breakthrough tank (when the Japanese are knocking out your Shermans on Iwo with their not-exactly-fearsome AT weapons--well, you get the idea).

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    1. To be fair previous experience indicated Japan had little in the way of tanks. Plus those Sherman's were being hit at short range and often from the sides. We might of been better off with a heavily armored Sherman hull with 4 sponson mounted .50 cal. machine guns.

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    2. ...so basically just the old M2 Medium but with more armour?

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    3. William Sager: I'm ok with something like the Sherman Jumbo, but with something more potent than the 76 mm. As they eventually mounted the NATO 105 mm on Sherman, maybe they could have put in the same 90 mm as on the Pershing? Again, think not so much for the anti-armor, but the HE round.

      As for the need for thicker armor, I was just thinking of this after seeing a documentary of the fighting on Iwo Jima, where essentially you have an attack against a strongly fortified infantry defense, and the Shermans supporting the attack were quickly taken out in short order, putting the burden on the poor bloody infantry. Sure, as you say, some of those were side shots and mines and stuff, but I am thinking "Hmm, some IS-2s and ISUs would have sure been helpful there" (not only thicker armor, but their main gun with their huge, highly destructive, HE rounds can provide overwatching fire from a longer range where they are harder to take out).

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    4. Some IS-2s and ISUs would also have been a mite tricky to ship across the Pacific and bring over the beaches. The US military hardcapped the mass of its wartime AFVs for a reason.

      Anyway, the GMC M36 Jackson was basically a modified Sherman hull with 90 mm in the turret and IIRC the basic M4 hull could take the Pershing turret without too many problems too so it's not like that was an issue, but I'm pretty sure for Pacific Theater conditions where hardcore armour penetration ability generally wasn't in demand the standard-issue 105 mm howitzer version oughta done fine?

      P sure the later IDF "Super Shermans" kind of creaked under their new high-velocity 105 mm guns even with all the technological improvements inbetween though, and would almost certainly have been considered to have unacceptable mobility by the wartime US military - all the more so for Pacific conditions where you generally had to assume zero infra or as close as made no difference.

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  3. The first pilot T29 was built sometime before October 1945.

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