Vickers A1E1 Independent from the front |
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The Vickers A1E1 Independent Tank was a large multi-turret tank designed to operate independently of the infantry, but only one prototype was produced.
The design of the Independent Tank was developed by Vickers in response to a General Staff specification of December 1922 that called for a very different vehicle to the eventual Independent. The General Staff wanted a long low tank with low ground pressure, good trench crossing abilities, and with the main gun carried in the nose, with machine gun sponsons on the sides. Vickers produced a design to this specification, but also produced their own design, for a multi-turreted tank. The two designs were submitted in March 1923, and the Vickers design was eventually judged to be superior. Some work on the prototype began in 1925, although the contract wasn’t signed until 15 September 1926.
The Independent Tank was 25ft long but only 8ft 9in wide (so it could travel by rail). This should have made it quite hard to steer, as were most other long but narrow tracked vehicles, but this appears not to have been a significant issue. One feature that was adopted on later tanks was the basic layout, with the hull contained between the suspension assemblies (on older tanks the hull tended to come all the way to the side of the tank, with the tracks running around the outside of the hull). The top of the hull was flat, and was only just above the height of the top of the tracks (as seen later on the Churchill tank). It was powered by a 360hp V12 Armstrong-Siddeley air-cooled engine. Wider turns were controlled by compound epicylics in the drive sprockets, controlled by a steering wheel. Tighter turns used the more conventional clutch and brake system, where the track on the inside was disengaged and stopped. It had a four gear synchromesh gear box.
Suspension was provided by four Vickers box-bogie units on each side, which provided a rather harsh ride. The tracks wore out quickly, and had to be replaced once, despite the tank only travelling 630 miles in total in eleven years!
The most obvious feature of the Independent was its five turrets. The main, central turret was raised above the others, and had 360 degrees of traverse. It was originally armed with a gun that had part of the recoil mechanism above it, but now carries a 3-pounder gun. The main turret was surrounded by four machine turrets, two in front and two behind. There may have been a mechanism in each turret that allowed the commander to indicate which direction to fire, or possible one in the main turret to indicate which way the other turrets were pointing, but this is uncertain. The driver sat in a central cab carried between the two forward turrets.
The rear of the tank was rebuilt in 1928 following advice from W.G. Wilson, giving it new drive sprockets but removing the compound epicyclics. New two-speed epicyclics replaced them.
Tests on the Independent Tank continued until 1935, when it was finally abandoned and sent to the Tank Museum at Bovington (where it remains to this day).
Although the Independent didn’t enter production in Britain, it does appear to have inspired some very similar designs overseas. In Germany the Neubaufahrzeug was quite similar, although only five prototypes were built. In the Soviet Union it appears to have inspired the most successful of the five turreted tanks, the T-35, of which 62 were built. This tank saw some combat early in the German invasion of the Soviet Union, but was a generally unsuccessful design.
Stats
Production: 1
Hull Length: 24ft 11in
Hull Width: 8ft 9in
Height: 8ft 11in
Crew: 8
Weight: 31.5 tons
Engine: 360hp V12 Armstrong-Siddeley air-cooled engine
Max Speed: 20mph
Max Range: 95 miles
Armament: One 3-pounder gun, four Vickers machine guns
Armour: 13-28mm
British Battle Tanks - World War I to 1939, David Fletcher.
An excellent history of British tanks from the earliest developments, through the battles of the First World War and on into the post-war period. Strongest on the First World War tanks, which fill the first three quarters of the book, helping to explain the problems faced by the developers, how they coped with the problems of the battlefield and how the design was improved in the light of experience, making it clear that the tanks of 1918 were actually very different from the tanks of 1916, despite looking very similar [read full review]
Vickers A1E1 Independent from the left 
Vickers A1E1 Independent from the back-left