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The Heavy Assault Tank A33 (Excelsior) was a design for a heavier version of the Cromwell A27M and was produced when the Churchill infantry tank appeared to be a failure.
When the Churchill first entered service it was unacceptably unreliable, and for quite some time production was expected to end quite early. By the end of 1942 the British were focusing their efforts on the production of a 'universal' tank that could fill both the Infantry and Cruiser tank roles, but it was clear that it would take some time for this to appear, and a replacement for the Churchill would be needed.
Three designs were suggested. Rolls Royce put forward two - the A31, which was a Cromwell with extra armour and the A32, which had the same level of armour as the Churchill and new suspension to cope with the extra weight. English Electric, which had also been involved in the original design of the A27 series, put forward the third suggestion. This used the basic A27 Cromwell hull and turret (a loosely hexagonal design, with vertical sides), with extra armour (114mm on all vertical frontal faces) and the T1 suspension and tracks from the American M6 heavy tank. The M6 had eight pairs of road wheels on each side, carried in four dual bogies on each side, connected to a horizontal volute spring suspension system. The English Electric design used three of the dual bogies, for a total of six pairs of road wheels on each side.
The English Electric design was selected, and designated as the A33. It was to weigh 40 tons, carry a 75mm gun and have 6in of frontal armour. Three pilots were produced by late 1943 in two versions. The first used the American tracks and suspension and a 6-pounder gun, while the second used a wider version of the Cromwell tracks, and a new suspension system that used helical springs, and carried a British 75mm gun. This system was designed by the LMS with the designation "R/L Heavy" (R/L presumably standing for Rolls Royce/ LMS). A third pilot, with a lighter version of the R/L suspension, wasn’t built. The second prototype was completed, but the suspension system was found to be too complex.
The first prototype did two 1,000 mile cross country test runs. On the first one, which began in November 1943, it was described as reliable, but picked up two tons of mud! The second almost destroyed the prototype, but a running range of 2,000 miles was still rather impressive for a new design. However by the time these trials were carried out the Churchill had proved itself in combat in Tunisia and Italy and remained in production. There was thus no need for the A33, and the project came to an end.
On 2 December 1943 the A33 was also tested against a Churchill that had been loaded to 50 tons to test out a possible design for the Infantry Tank 'Black Prince' (A43). The overloaded Churchill was described as 'hardly worse' than the A33, not exactly a ringing endorsement of either design.
Stats
Production: 3
Hull Length: 22ft 8in
Hull Width: 11ft 1.5in
Height: 7ft 11in
Crew: 5 (commander, driver, gunner, loader, co-driver)
Weight: 100,000lb combat weight
Engine: 600hp Rolls-Royce Meteor V12
Max Speed: 24mph road, 12mph cross country
Max Range: 130 miles road radius
Armament: One 75mm OOF and two 7.92mm Besa machine guns
Armour:20-114mm