The US T29 - a 70 Ton Beast Built to Battle Tigers - Tank Historia

The US T29 – a 70 Ton Beast Built to Battle Tigers

The T29 is a little-known US heavy tank built during the Second World War as an answer to heavy German armor encountered in Europe. This was a 70 ton, late war design, and carried a powerful high-velocity 105 mm gun in an enormous turret.

The T29 was a unique vehicle and the first of its kind ever to grace the US Army inventory. Incorporating a plethora of innovative design features, the tank was destined to steamroll through the Nazi heartland with ease. But alas, the T29 would never get to fire a shot in anger since it came too late in the war to meet actual production numbers.

Instead, the Army decided to use the T29 as a testing model for various new technologies that today seem like a no-brainer, but in the immediate post-World War Two era were truly revolutionary concepts. These design concepts were so successful that many of them, in principle, are still in use today in modern heavy tanks like the M1 Abrams.

Contents

Background

In the immediate months following the Normandy landings, the US Army realized they were outgunned on the battlefield by larger German tanks like the Tiger.

Though tanks like the Sherman were excellent pieces of equipment, they still wanted a tank that could both take and dish out a ton of punishment with a great chance of crew survivability single-handedly.

The Army first dipped its toe in the water with the T26, eventually becoming the M26 Pershing heavy tank. Though its combat performance was positive, it was still not a proper heavy tank since it weighed in around 46 tons. However, for the sake of morale, the Army designated the Pershing as a heavy tank so that troops felt like they were not totally outgunned on the battlefield.

An M26 Pershing at Fort Benning.
The Pershing was a solid tank, about on par with the Tiger I. This was not good enough, considering the Tiger entered service over two years earlier. Image credit – Pierre-Olivier B CC BY-SA 2.0.

The quest for an actual heavy tank would have to continue.

But even before the Army deployed the M26 into combat in appreciable numbers just after the Battle of the Bulge, the T29 program came into existence on paper in the fall of 1944. After several months of positive feedback from frontline units using the Pershing, the Army decided to turn the drawings into reality.

In February 1945, the Army asked to procure 1200 of the new vehicles to smash what was left of the Third Reich’s armor.

An M6A2E1 at Aberdeen Proving Ground.
Before the T29, the US had tried to get a large gun into action with the M6A2E1.

Fortunately for the Germans, the production was prolonged due to the number of new technologies being tested, and just one T29 was completed by the war’s end. Not wanting to forget the numerous lessons learned in blood, the Army decided to cancel the order but produce ten units as test vehicles to see what worked and what did not.

Read More AMX-50 Surbaissé – A Mighty French Autoloader

Hence, the T29 program truly came into existence in the immediate aftermath of World War Two as a way to incorporate the feedback gleaned from soldiers and commanders alike into technologies that the military could apply to future Army vehicles.

Engineering and Design

The T29 was an absolute beast of a tank. Coming in at 70 tons with a full combat load of ammunition, fuel, and crew, the tank’s combat load rivaled that of the Tiger II it was meant to destroy. The vehicle itself was also large, with a height of just over 10 feet, a length of almost 38 feet with the gun facing forward, and a width of about 12 and a half feet.

With a full crew of six consisting of a driver, co-driver, two loaders, a gunner, and tank commander, the T29 was the most heavily manned tank the Army had ever created. It was also the most heavily armored since its frontal hull sported a minimum of four inches of armor, with areas on the turret reaching 250 mm thick.

The gun mantlet is an interesting point of discussion on the T29. The gun mantlet of the T29 is 280 mm thick – a fact well known by World of Tanks players.

An American heavy tank at Fort Benning.
One of the T29’s most distinguishing features was its enormous turret. Pierre-Olivier B CC BY-SA 2.0.

But when some measurements were taken on the mantlet, it was found to actually be just over 200 mm thick.

To power all of this mass, engineers at Aberdeen Proving Grounds requested the Ford Motor Company to produce an engine specially designed just for this program which would become the 12-cylinder gasoline-injected Ford GAC engine.

The GAC actually got its start during the beginning of World War Two as an aircraft engine. However, due to the Navy not wanting it for its planes and the Army contractually obligated to purchase other engines for its armored vehicles, Ford shelved the design until Army engineers came knocking, needing a super powerful engine to propel their largest tank ever designed.

Ford GAA V8.
The GAA (shown here) was a V8 version of the V12 GAC. The GAC, used in the T29, was a development of a Ford aero engine. Image by Alf van Beem.

Ford happily obliged, and the result was fantastic. Producing an impressive 770 hp and 1,560 foot-pounds of torque, the original T29 could travel eight mph at low speeds, 22 mph on open roads, and had a range of 100 miles with its 295-gallon fuel capacity.

While the base model T29 and later T29E3 kept this same engine, the T29E1 was the only model to receive a different engine. It got the General Motors V-1710-E32 which General Motors supercharged to give it an impressive 870 hp and an impressive 1,800 foot-pounds of torque.

Read More Conqueror – Britain’s Answer to Soviet Heavies

But standard to all models of the T29 was the CD-850-1 transmission. The CD-850-1 transmission was truly unique in that it was the first time the Army had decided to couple their transmission to the engine.

Before, all previous tanks had a drive train connecting the two, which meant troubleshooting problems and replacing parts was a real hassle. Having them coupled saved time in the field and made the engineering problem less complicated.

CD-850 transmission in an M47.
The T29’s CD-850 cross-drive transmission would become commonplace on future US tanks. Image by ain92 CC BY-SA 2.0.

The new transmission also made driving the tank much easier.

Both output shafts had equal energy distributed onto them when moving forward. But when the driver wanted to turn, he simply had to move the wobble stick left or right. Doing so would put all the power output onto the desired shaft and make the vehicle turn. Creating such an ingenious system actually made this behemoth even more maneuverable than its lighter-weight counterparts when getting it out of rough terrain or tight maneuvering situations.

The T29 was also one of the first tanks to have what is known today as an Auxiliary Power Unit. An APU is like a mini engine that runs when the power is out. However, while later APUs were designed to provide emergency power if having lost it during a casualty, the APU on the T29 was made for fuel economy.

A T29E3 at Fort Benning.
Despite its immense size (yes, that’s an Abrams on the left), the T29 was surprisingly easy to drive. Image by T29E3 Pierre-Olivier B CC BY-SA 2.0.

With its already limited range of 100 miles, having the APU on to keep the radios working, heat or air pumping, and ventilation flowing was vital since these functions required far less electricity than running the main engine, thereby increasing fuel economy.

The tank also had five-inch extenders that slipped onto the tracks to increase their total width. This was to help with ground pressure.

Read More IS-4 – The Forgotten Soviet Heavy Tank

The smaller a surface area is, the more immense the amount of pressure the same kind of weight will put on it if nothing else changes. By extending the surface area of the tracks, the folks at Aberdeen helped prevent heavier tanks from becoming stuck in mud or soft ground as quickly. These worked so well that the ground pressure for the track was about the same as human footstep!

Gun and Turret

The Army had mounted a 105mm gun on some models of the Pershing tank, but this was not standard, and they wanted to see if they could make it so. As a tank killer, the 105mm gun was seen as the minimum standard to punch through any enemy armor soldiers could encounter. To this end, the Army mounted either the T5E1 or T5E2 105 mm gun, depending on the variant.

The T29 only stocked 63 rounds on board of two types: High-Velocity Armor Piercing and High Explosive ammunition.

The HVAP rounds had already been used by US tanks in Europe and had seen great success. The HVAP fired by the T29 could penetrate a massive 360 mm of armor from 450 meters away.

T30 heavy tank.
This vehicle is a T30, a development of the T29 that was armed with a huge 155 mm gun. This gun actually had worse anti-armor capabilities than the 105 mm on the T29. Image by T30 Pierre-Olivier B CC BY-SA 2.0.

However, the Army also wanted to potentially make the T29 a multi-purpose vehicle, given its limited range. That is why there was HE on board since they also experimented with indirect fire support to make the tank a mobile artillery platform.

Though results from this testing are not known, what was common between the two types of ammunition was the need for both powder charges and rounds to be stored since this ammunition was not self-contained. Because of this, the tank needed two loaders, one for the rounds and one for the charges.

Read More Why do Tanks use Angled Armor?

In between the rounds sat the tank commander. This was a very precarious position since it sat directly behind the gun’s breech. The commander would most certainly be killed if there ever were a catastrophic gun casualty where the recoil system failed.

A T29E3 at Aberdeen Proving Ground.
A T29E3 from above. Note the centrally-located commander’s position. This layout would appear again on the M103.

However, that was incredibly unlikely due to all the excellent design work that went into the turret. One of the best ways the engineers wanted to ensure the turret did not wear down the turret ring or damage its mountings was to properly balance the gun.

They did this by purposefully enlarging the rear of the turret. While some might think they did this as a comfortability factor for the commander, that was not the case since the added weight of the back end of the turret acted as a counterbalance to the gun.

Another interesting part of the turret is what looks like ears sticking out of either side. These are actually its range finders and, at the time, were a great leap forward in fire control technology. While tanks before used a variety of ways to estimate range, from the Mark 1 Mod 1 eyeball to various tables and gun sights, the armored community had not incorporated fire control computers like their brothers in arms in the artillery or onboard naval vessels did.

The T29E3's range finder ears.
This is the T29E3. Note the “ears” sticking out the sides of the turret. These protrusions contained a range finder, another feature that would become common on later tanks. Image by Pierre-Olivier B CC BY-SA 2.0.

For the first time in American tank history, the Army put a rudimentary fire control computer on its tanks. These rangefinders were accessible to the commander and were controlled by a joystick near his chair. They worked by bringing two different images down together until they matched, and the computer performed some simple trigonometry to calculate the distance and angle needed to traverse the gun.

The commander could then relay this information to the gunner and start looking for the next engagement. While the gunner was supposed to get a superimposed image of what the commander was seeing, the engineers had a hard time getting this to work reliably. In practice, the gunner would have to rely on the commander for these crucial pieces of information.

The T29’s Fate

A number of closely related heavy tanks were developed around the same time as the T29, namely the T30 and T34. These tanks swapped the T29’s 105 mm gun for a 155 mm and 120 mm gun respectively.

Sadly the vehicles never entered production. As with so many late war designs, the end of the war meant they were no longer needed. For a short time it was thought that they could be used in the Pacific, but Japan surrendered before the vehicle was ready.

The prototypes continued to be used in the testing of new technologies, engines and guns for a few years after the war until the entire project was cancelled.

Read More The M53/55 – 203.2 mm of American Freedom

However the T29 project was not a waste – far from it in fact. The project would lead into the development of another heavy tank, the T43. This would eventually become the M103.