Heavy Tank T34

The Heavy Tank T34 was based on the Heavy Tank T29 and Heavy Tank T30, and was armed with a modified 120mm anti-aircraft gun. It didn’t enter production, but the post-war Heavy Tank M103 was largely based on it.

Work on the Heavy Tank T29 and Heavy Tank T30 began in 1944. They were originally almost identical, apart from the use of different guns - a 105mm gun in the T29 and a 155mm gun in the T30. Early in 1945 the Ordnance Department began work on turning the 120mm anti-aircraft gun into a tank gun. It soon became clear that this gun would have better armour piercing abilities than the high velocity 105mm gun or the lower velocity 155mm gun, and in May 1945 the Ordnance Department recommended that two of the T30 pilots be armed with the 120mm gun instead, as the Heavy Tank T34. This was approved on 31 May.

Originally the T34 was to have used the same Ford GAC engine as the T29 and T30. After the end of the war with Japan this was changed. The T30 was to use a Continental AV-1790 engine, while the T34 was to use an Allison V-1710 aircraft engine. In November 1946 the T34 specifications were modified. It was now to use the Continental engine, and at the same time the Ordnance Department recommended the use of two chassis from the T30 programme.

It isn’t entirely clear which vehicles the two T34 pilots were actually based on, but it is likely that one was produced using a T29 chassis and the other using a T30 chassis. Most sources only mention the original order for two T30 chassis, but this must have been expanded at some point, as three tanks survive.

The Heavy Tank T34 used the same chassis, superstructure and turret as the T29 and T30. This had eight road wheels, and a simple hull with a sloped front and a largely horizontal top, almost level with the top of the tracks. All three used guns with separate ammunition, so carried a gunner, two loaders and the commander in the massive turret. The 120mm gun of the T34 used lighter shells than the 155mm gun in the T30, so the elaborate loading system tested out in the T30E1 wasn't required. A heavy weight had to be welded to the back of the turret to balance the heavier gun.

The pilot models of the T34 weren't delivered until 1947. The two T34s went for tests at Fort Knox and the Aberdeen Proving Ground. The main problems were with the 120mm gun. At least two men were hospitalized by flarebacks caused by unburned powder gasses being sucked into the turret with the ejected cartridge case and then igniting. Even when this didn’t happen a dangerous level of noxious gases soon formed in the turret.

It took two attempts to fix the flareback problem. The first used a bore scavenging system, in which compressed air was pumped into the gun tube before the breech was opened, to force any unburned gasses out of the muzzle. This solution worked, but took up too much space, needing a air compressor and storage for the compressed air.

The second system was an aspirator type bore evacuator, designed for the earlier 90mm guns T15E4 and M3E4. In this system a cylindrical chamber was installed just behind the muzzle. A series of holes were drilling into the gun barrel, pointing diagonally towards the muzzle, heading from the chamber into the barrel. When the gun was fired, the barrel and the chamber were both pressurised by the expanding powder gasses. The pressure in the barrel dropped quickly, as the gasses flowed out of the muzzle. The high pressure gases in the chambers then emptied down the diagonal holes, and emerged from the muzzle at high speed. This sucked all of the unburned gasses out of the rest of the barrel, and the breech could then be opened safely. This proved to be a simple and effective system, and became a standard feature of post-war tank guns.
No production orders were placed for the T34, which was felt to be too heavy. However in 1948 a work began on lightened version of the design, the Heavy Tank T43, which later entered production as the 120mm gun combat tank M103.

Hull Length: 25ft without gun; 38ft 7.5in with gun
Hull Width: 12.5ft
Height: 10ft 7in
Crew: 6
Weight: 143,600lb combat loaded
Engine: 810hp Continental AV-1790-3
Max Speed: 22mph roads
Max Range: 100 miles road cruising speed
Armament: One 120mm gun






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How to cite this article: Rickard, J (24 March 2017), Heavy Tank T34 , http://www.historyofwar.org/articles/weapons_heavy_tank_T34.html

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