Vickers Main Battle Tank Mark 4

The gunner was provided with a Vickers Instruments L30 telescopic laser sight as a main sight. The sight was monocular, with a magnification of ×10, and was fitted with a Neodimium-YAG laser rangefinder and a cathode-ray tube for injection of fire-control data. In addition to his main sight, the gunner was also provided with a Vickers Instruments GS10 periscopic sight. This was mounted in the turret roof and provided a ×1 wide angle field of view and was used for surveillance and target acquisition.

The commander had a ring of six fixed ×1 periscopes around his hatch to give all-around vision. The commander's main sight was a French SFIM VS580-10 gyrostabilized panoramic sight. Two degrees of magnification ×3 and ×10 were provided, it also incorporated a Nd-YAG laser rangefinder. In addition, a gyrostabilised panoramic thermal sight, the Dutch Philips-USFA UA 9090, was also mounted on the turret roof, in front of the loader's hatch.

The loader has at his disposal one rotating periscope.

The driver was originally provided with only one vision block which was later supplemented by two side-looking vision blocks.

The basic hull structure of the Valiant was fabricated from aluminium armour, allowing optimum use of Chobham armour within an overall weight of 47 tonnes. Emphasis was placed upon frontal protection covering a 60° arc. In addition, however, Chobham armour was also applied along the full length of the hull sides (heavy ballistic skirts). The turret structure was made of welded steel plates, with a layer of Chobham armour added to the front and sides.[3]

The first prototype was armed with a Royal Ordnance L7 105 mm rifled gun, 56[3] to 60[2] rounds are carried, 30 of which are stowed in the hull, to the left of the driver.

In 1982 it was rearmed with the Royal Ordnance L11 120 mm rifled gun, 42[2] to 52[3] rounds are carried, 21 rounds are stowed in the hull, to the left of the driver. Alternatively, the Valiant can be armed with the Rheinmetall Rh-120 120 mm smoothbore gun, 44 rounds are carried[3], 28 rounds are stowed in the hull, to the left of the driver.

The secondary armament of the Mk. 4 includes a 7.62 mm FN MAG coaxial machinegun which was later replaced on the Valiant's Universal Turret by a 7.62 mm Hughes EX-34 Chain Gun. This externally-powered weapon has been adopted because of the advantages it offers to the crew, including its ability to eject faulty rounds without a stoppage of the gun and the elimination of gun fumes in the turret.

The Mk. 4 was first fitted with a General Motors Detroit Diesel 12V-71T engine[5] developing 915 bhp and subsequently fitted a Rolls-Royce V-12 diesel engine, the CV12 TCA Condor, virtually the same engine as that fitted in the British Army FV4030/4 Challenger 1 main battle tank, but is rated at 1000 bhp instead of 1200 bhp. The lower power rating increase its durability and, because it is less highly turbocharged, its response is more rapid, which increases the tank acceleration. The engine has a minimum specific fuel consumption of 207 g/(kW⋅h).

The transmission of the Valiant does not follow the trend to use torque converters and hydrostatic steering. Instead, it is a modified version of the six-speed TN-12 transmission produced for the FV4201 Chieftain, but made fully automatic by means of an electronic control system.[6] The all-mechanical transmission has the inherent advantage of being more efficient, which means that more of the engine power is available to drive the tank, instead of being dissipated by oil coolers. At the same time, the skill and effort generally required of drivers by mechanical transmissions are eliminated by the electrical controls.

The suspension of the Valiant is almost the only feature carried over with little change from the Vickers Mark 1 and Mark 3 MBTs. In principle, it is of a conventional, torsion bar type, but it is unique in having secondary torsion bar springs in the trailing arms of the first two and the last road wheels on each side. The secondary torsion bars provide more effective springing at the most critical wheel stations and signifi cantly improve the ride over rough ground. The total vertical wheel travel is 303 mm (bump : 202 mm / rebound : 101 mm)[2]