Technology Model - Australian AC1 Sentinel Tank 1942

When design work began in November 1940, the AC1 was originally intended to be a 2 pounder gun-equipped vehicle, a true Cruiser tank,[3] with a weight of between 16 and 20 tonnes.[4] Due to a lack of home grown experience in tank design, a mission was sent to the US to examine the M3 Like the Canadian Ram, the Australian Cruiser was to be based on the engine, drive train, and lower hull of the American M3 Medium tank, mated to an upper hull and turret built closely along the lines of a British Crusader. By 1942, attempting to keep pace with German tank developments, the design specification had become more like an American medium tank, resulting in a heavier design and a higher silhouette profile.
The Australian Cruiser tank Mark 1 (AC1) was designated "Sentinel" in February 1942. Manufactured by the New South Wales Railway Company, fabrication took place at Sydney's Chullora Tank Assembly Shops with serial production vehicles emerging in August 1942,. The hull was cast as a single piece, as was the turret; a technique not used on the hull of any other tanks of the era.
The Sentinel was designed to mount either a QF 2 pounder or a QF 6 pdr However, as the production order for 6 pounder tank guns had not been acted on, none of these were available and the first 65 tanks were built with the 2 pounder. Two Vickers machine guns were carried as secondary armament, one in the hull and a second mounted coaxially beside the main gun. The preferred engines suitable to power a 28 tonne tank, a Pratt & Whitney Wasp single row petrol radial, or a Guiberson diesel radial, were not available within Australia, so the Sentinel was powered by the combined output of three Cadillac V8 engines – petrol car engines with a displacement of 346 cu in (5.7 L) each. The three engines were installed in a clover-leaf configuration (two engines side-by-side to the front and a single to the rear) with all feeding power to a common gearbox.
Sixty-five production vehicles had been completed by June 1943. The completed Sentinel tanks were used for evaluation purposes only and were not issued to operational armoured units. The Australian Cruiser tank programme was terminated in July 1943 as it was thought better for Australia to put the effort spent on the AC tanks towards building her own railway locomotives and supporting the large number of US tanks due to arrive.