Development of the A38 infantry/ assault tank began in August 1942, when Vickers-Armstrong were awarded a contract to produce three pilot models of a ‘heavy assault tank’ by the Ministry of Supply. The new type was intended to replace the Valentine infantry tank, and Vickers proposed an innovative design, incorporating angled frontal armour remarkably similar to that of the later Soviet IS-3 heavy tank.
The Vickers design was approved as the A38, intended as a relatively light (23-ton) infantry tank, supposedly optimised for use in the Far East. Responsibility for its development was initially passed to Birmingham Railway Carriage & Wagon Company, and then to Ruston & Hornsby, in order to free up Vickers facilities for higher priority work.
As the design evolved, weight crept up: the original two-man turret armed with a 6-pdr gun and coaxial Besa machine-gun was replaced by an enlarged three-man turret mounting the same armament. This new turret was a distinctly poor design, with a bulged front plate bolted to the rest of the structure. The bolts were a serious weakness, as they were liable to be sheared off by a direct hit, potentially splitting the turret.
The base of the turret front below the bulge formed a shot trap, while an armour-piercing round hitting the underside of the bulge could be deflected downwards through the thin armour above the driver’s position. Early Panthers had a similar problem – the type’s rounded mantlet had to be hastily redesigned after losses caused by rounds bouncing off and penetrating the roof of the driver’s compartment.
Attempts to improve the armour backfired, particularly when it was decided to weld several large plates below the transmission. This increased the load on the rear suspension and reduced the ground clearance from an acceptable 16.9 inches (43cm) to less than 10 inches (25cm). These changes resulted in the sole prototype weighing in at 27 tons when it was completed in 1944 – the increased weight brought its top road speed down from 16mph (26km/h) to 12mph (19km/h).
By this time, it was recognised that the design was obsolescent, and the prototype was only completed for automotive trials, primarily to assess the value of the suspension system. The trials report, issued by the Fighting Vehicle Proving Establishment at Chertsey in May 1945, was damning – the exposed suspension lubrication system was fragile and would be liable to damage when moving off-road, but the trials never got that far.
A road test on the first day was abandoned after 13 miles with the driver totally exhausted after wrestling with steering levers that needed a pull of up to 160lb (72kg) to operate. Changing gear was equally demanding – engaging ‘first’ pushed the gear lever behind the batteries and a crowbar was needed to release it. The officer in charge of the trials decided that they should be abandoned as it was impossible and unsafe to continue, reporting that in his view the entire project should be closed down.
The prototype was retained as an example of ‘how not to design a tank’ at the School of Tank Technology. Students would be asked to examine it and compile lists of all the design faults they could find.
Image: Wikimedia Commons/Tank Museum