The Light Tank Mark IV was the last two-man light tank to be produced for the British Army, and the first in which the armoured hull was used as the chassis. It was developed from two Vickers Experimental India Pattern tanks of 1933, the No 1 (L2E1) and No 2 (L2E2), which had been designed to be lighter and faster than the existing British light tanks.
The No.1 was two feet shorter and eight inches wider than the Light Tank Mk III, and its hull was redesigned to reduce the number and weight of armoured plates. Suspension was the same four spring Horstmann system as on the Mark III, although the rear idler was removed and the rear road wheel was used to adjust track tension. A commercial roughly hexagonal Vickers turret was installed. The No.2 used the standard War Department light tank turret – a rectangular model with sloped side armour, and the 9mm armour was coated with steel plates to bring the weight up to the right level.
The two India Pattern light tanks were used as the basis of the Light Tank Mark IV, but with one major change. All earlier British light tanks had been built around a chassis, with the armour and automotive components mounted onto the frame of the chassis. On the Mark IV the armour plate itself was used to form the chassis, with all other components mounted on the armour. This saved weight and increased the strength of the vehicle. The Mark IV also had a higher superstructure and a water filled header tank at the top of the turret to increase the water pressure in the water filled jacket around the machine gun. As on the two India Pattern prototypes there was no rear idler, and as a result the ride wasn't as good as on the Mark III. The Mark IV was powered by the 88hp Meadows EST engine, a more powerful model than on the earlier light tanks. The turret was similar to the version used on the Mark III and the No.2 prototype, but with a new rotation system. The turret rung sat on nine ball bearing rollers mounted in brackets on the traversing ring on the hull. One revolution of the traverse wheel turned the turret through five degrees.
The Mk IV suffered from a series of problems. Its centre of gravity was too high for its length, making it somewhat unstable. It had a poor cross country performance, partly due to the lack of a rear idler. By the time the Mk IV appeared the Army had realised that a single .303in machine gun was inadequate, and it was also becoming clear that a two man tank was of no real use, as the commander was overwhelmed with duties (tank commander, radio operator, gun loader, aimer and firer), and the Mk V would be a three man tank.
Light Tank Mk IV
Production: 34 (1934)
Hull Length: 11ft 6in
Hull Width: 6ft 10in
Height: 7ft 1in
Weight: 4.3 tons
Engine: Meadows six cylinder, 88bhp
Max Speed: 36mph
Max Range: 125 miles operation radius
Armament: One .303in Vickers machine gun