Chapter Five
During the later years of the interwar period most tank experts felt that the day of the heavy tank was over. Since 1938, British tank strategy had called for a mix of well-armed and well-protected infantry tanks to assist in breaking through enemy lines, together with fast, lightly gunned and lightly armoured cruiser tanks which could exploit breaks in the line and rampage at will, causing havoc in the enemy’s rear areas.
However, when Britain declared war on Germany in 1939 there were those who foresaw a return to the trench warfare of the earlier conflict. If this were the case, then heavy tanks would be required once again, with the emphasis on their trench-crossing performance. The speed with which the German Wehrmacht conducted their Blitzkrieg campaigns across Belgium and France, with highly mobile tanks and infantry working together to keep the enemy off-balance, soon put paid to this notion–but not before Britain had designed a pair of heavy tanks.
The heavy tank did not become an issue again until the latter years of the conflict and by this time, it was the twin imperatives of firepower and protection that were driving the development.
Heavy Tank–TOG
During the early years of the Second World War, Sir Albert Stern, who had played a part in designing tanks during the previous conflict, gathered together some former associates and set about designing a tank capable of operating across the typical shelled and waterlogged ground that had formed the front line in 1914. Design work started in February 1940, and William Foster & Company of Lincoln was selected for production.
Dubbed TOG–for ‘the old gang’–the first prototype, TOG I, was ready for trials in October 1940. It was powered by a 600bhp Paxman-Ricardo twelve-cylinder diesel engine driving electric motors via a pair of generators, and was capable of a maximum speed of 8.5mph, although the length of track made steering something of a challenge. The original design had included sponson-mounted guns, but by the time the first prototype had been constructed these had been superseded and were replaced by the turret of a Matilda II mounting a 2-pounder (40mm), together with a bow-mounted 17-pounder (76.2mm).
TOG 1 was subsequently fitted with a Fluidrive hydraulic drive system, when it was redesignated TOG IA; a second prototype, TOG II, appeared in March 1941, using the diesel-electric drive system of TOG I, but with torsion-bar suspension and lower tracks. Initially, TOG II was fitted with a dummy 77mm gun and turret, but this was replaced by a Stothert & Pitt turret with Metadyne traversing gear, carrying a 6-pounder (57mm). In the subsequent TOG II* this was replaced by a 17-pounder (76.2mm). A planned TOG IIR variant, which would have been shorter, was never completed.
Needless to say, there was no series production.
Heavy Assault Tank (A33)
The A33 heavy assault tank was an attempt to produce a standard or ‘universal’ tank chassis designed for a crew of five, which could be adapted to both the infantry and cruiser roles. Two prototypes were constructed by English Electric in 1943, against competition from Rolls-Royce, before the project was abandoned.
The basis of the tank was an up-armoured A27 hull, with a maximum thickness of 114mm, giving a considerable combat weight of 45 tons. The engine was the 27-litre V12 Rolls-Royce Meteor, producing 600bhp, driving the rear sprockets through a five-speed Merritt-Brown transmission with steering through a controlled differential. Although both prototypes were armed with the ubiquitous 6-pounder (57mm) gun, with both coaxial and hull-mounted 7.92mm Besa machine guns, it was envisaged that, if the tank eventually went into production, the main gun would be replaced by the 75mm weapon.
The work was terminated in May 1944.
Heavy Assault Tank (A39)–Tortoise
In 1942, the War Office initiated the development of a heavy tank destroyer that would be able to penetrate easily the armour of all other tanks and tank destroyers of the period, without putting itself at risk. In order to avoid what was described as the ‘vicious circle of power and speed demanding heavier suspensions, leading to more weight, more track area, greater length, and more power’, the Department of Tank Design (DTD) decided that it would abandon all conventional tank design considerations and approach the basic layout with a completely open mind.
Design work was initiated by Nuffield Mechanizations and Aero in 1944, with a view to having the first vehicle ready by 1945. General arrangement drawings and a detailed specification were prepared in 1944, followed by a full-size wooden mock-up for approval, and, by 1947 Nuffield had built six running prototypes. By any standards, the Tortoise was a huge, lumbering beast. The one-piece cast hull provided accommodation for a crew of seven, and measured up at 285in in length, with an overall width, including the track guards, of 147in. The lack of a conventional turret saved a considerable amount of weight, but also allowed the designers to build more strength and integrity into the hull since there was no need for a turret ring–always a weak area. Nevertheless, it was 230mm thick at its maximum, and the vehicle weighed 78 tons.
Power came from a Rolls-Royce Meteor 600bhp 27-litre V12 petrol engine driving the front sprockets through a Merritt-Brown six-speed gearbox. The drive sprockets were protected by huge armoured castings, and the track guards were made of 25mm-thick armoured steel. There was torsion-bar suspension, with eight wheel stations per side.
The main gun, a 32-pounder (94mm) weapon derived from a naval anti-aircraft gun, was carried in a huge 24in-diameter ball mount and, with a muzzle velocity of 3,050ft/sec, this was the most powerful gun to be fitted to a British tank up to that time. Secondary armaments included a 7.92mm Besa machine gun carried in a ball mounting on the left-hand side of the glacis plate, with a pair of similar weapons in a roof cupola for anti-aircraft defence.
Whilst the Tortoise embraced the principles of firepower and protection wholeheartedly it was almost certainly at the expense of mobility–top speed on the road was quoted as 12mph, with 4mph achievable across country, and the range was just twenty-eight miles on the road. The sheer size and lack of manoeuvrability of the machine ensured that it would have been of very limited tactical value, and the project was abandoned soon after the delivery of the prototypes.
With tracks running around its perimeter, the 400in-long hull of what was dubbed ‘TOG’ had some similarities with the familiar rhomboid tanks of the First World War, and was constructed from twin cement-bonded steel plates with a maximum thickness of 76mm. The tank was initially fitted with the turret of a Matilda II mounting a 2-pounder (40mm) gun, together with a bow-mounted 17-pounder (76.2mm) which was later to be fitted to the Challenger. In TOG II* form, as seen here, the 17-pounder gun was fitted into a conventional turret. (Tank Museum)
Just two examples of TOG were constructed and, whilst it would be fair to wonder ‘what were they thinking?’, the series was apparently only abandoned because the 80-ton combat weight was considered to be excessive. The photograph shows the TOG II*, which has survived at the Tank Museum. (Warehouse Collection)
Described as a heavy assault tank, the A33 was intended to provide a ‘universal’ tank chassis that could be adapted to both the infantry and cruiser roles. It was constructed on an up-armoured A27 hull, and was powered by the 27-litre V12 Rolls-Royce Meteor engine. (Warehouse Collection)
The first of the A33 prototypes (seen here) used the track and horizontal volute spring suspension (HVSS) of the American M6 heavy tank, whilst the second (designated A33-R/L) used a widened version of the A27 Cromwell tracks, with suspension designed by the LMS workshops. The rear view shows the auxiliary fuel tanks and air intakes for the Rolls-Royce engine. (Warehouse Collection)
With its 32-pounder (94mm) main gun and 225mm-thick cast hull, the A39 Tortoise heavy assault tank was designed to take on the fearsome German tank hunters–the SdKfz.173 Jagdpanther, which was armed with the 88mm PaK L/71 gun; the SdKfz.181 Tiger tank with its 88mm KwK36 L/56 gun; and the 128mm PaK44-equipped SdKfz.186 Jagdtiger. (Warehouse Collection)
There were massive problems in transporting the A39 Tortoise on the road, with trials in Germany indicating that a minimum of two Diamond T tractors were required. (IWM, MVE 136162)
Here, Tortoise prototype number 1 has been loaded onto one of Pickfords’ 100-ton girder trailers, supplied by Cranes, supported on a pair of two-line solid-tyred bogies. The two Scammell drawbar tractors that are visible would have been sufficiently powerful to move the 78-ton Tortoise plus the dead weight of the trailer, but probably only on metalled surfaces. (IWM, MVE 9902-3)