Like it’s two earlier predecessors the A7E3 continued the development towards what British tanks of the 1930’s would look like and help contribute to the later more successful Cruiser series tanks and even play a role in the development of the Matilda II and Churchill tanks.
Although the A7E1 and A7E2 proved to not be reliable the design proved that it could be improved upon and this leads to the introduction of the A7E3. Although the two earlier tanks started to look like the later Cruiser tanks the A7E3 resembles those tanks the most with the turret looking more like that of the later tanks and the introduction of the 2-pdr (40mm) gun which had a much more effective anti tank capabilities to the 3-pdr found on the late 1920’s medium tanks.
Like it’s predecessors it was built from mild steel riveted together with a maximum of 14mm of armour protection on the hull, the tank would be built in May 1934 however it wouldn’t enter trials until 1936 at Farnborough. The A7E3 received the WD number T.1340, registration number BMM 117 and proving grounds number MEE961. The tank surpassed it’s two predecessors despite being heavier at 18.2 tons with the engine and transmission being improved upon after the lessons of it’s predecessors. It’s top speed of 39km/h on roads whilst 26km/h when driven off-road, this was helped by a new solution in regards to engines with the idea of combining two engines together in this case two 6 cylinder 7.74L 126hp engines which were to be used in AEC Regent double decker busses was chosen and combined to create a 252hp engine which was much more powerful than what had been used to power the earlier two tanks.
The suspension was the same as the A7E2’s which didn’t help the tank out alongside it’s breaks causing the tank to breakdown on multiple occasions with the brakes first breaking down after 124km of trials whilst it would breakdown 6 more times throughout the testing, the suspension broke down after 274km of trials, the gun however although it was said to be slightly better than when fitted and tested on the A7E2 due to the wider turret.
The tank was also tested with a 3-inch howitzer a gun for the idea of giving the tank more roles to specialise into which would remain an idea for British tanks right into the beginning of the cold war with the AVRE tanks.
Although during the trials the tank would receive modifications those modifications would hinder the tanks speed and also with ideas floating around of trying other suspension types of the Christie and Vickers-Horstmann types to improve the speed alongside the idea of fitting the Liberty L-12 engine alongside the Christie suspension both which would be realised upon the construction of the A13 Mk II Cruiser Mk IV tanks. But at the time these ideas where put down due to how similar tests with the American T2 tank was proving to be.
After the many breakdowns and the introduction of the A9 Cruiser Mk I the A7 program had ended although the lessons learnt from the vehicles would be implemented in some form on almost all of the tanks leading up to the 2nd world war. The cruiser tanks would share the ideas of the hull and turret design and shape with them all being armed with a 40mm as well as close support variants although armed with a 3.7inch howitzer instead of a 3inch. Meanwhile the infantry tanks would take engine and suspension ideas from the A7 tank with the A12 Matilda II tanks using combined engines and the A22 Churchill tanks using the suspension of the A7 which worked much better on a slower vehicle tank the ideas of the more mobile cruiser tank the A7 was going towards. Unlike the A6 Medium tanks the A7’s traces could be felt in some way across many of the upcoming tanks used by the British of the latter half of the 1930’s and their heavier infantry tanks.
Dimensions (L-W-H): 6.83m x 2.73m x 2.94m (22’4’’ x 8’10’’ x 9’6’’ ft)
Total Weight: 18.2 tons
Crew: 5 (driver, commander, gunner, loader, hull machine gunner)
Propulsion: 2x 6 cylinder 7.74L 126HP AEC bus engines, 252hp engine. (240hp engine according to Armoured Archives video on the A7 series)
Transmission: 4 speed
Power to Weight Ratio: 13.85hp/ton (13.19hp/ton according to the 240hp engine of Armoured Archives video)
Suspension: Vertical Coil Spring
Top Speed: 39km/h (24 mph) 26km/h off-road (16mph)
Main Armament: 40mm 2-pounder gun or 76mm 3-inch howitzer
Vertical Guidance: unknown
Secondary Armament: 2x (7.7mm) 0.303 Vickers Machineguns (one in turret, one inside the hull)
Armour: 9-14mm thick hull
Maximum 12mm thick turret
A7E3 Fast Medium Tank - Tank Design & Development - YouTube (Armoured Archives video on the A7 tank series)