The concept of the cruiser tanks was that it would be more mobile, like cavalry, and to be more mobile would be lightly armed and lightly armored.
A new cruiser design was sought in January 1941 to replace the Crusader and to have armor of 65 mm, weight 24 tons, and carry a 6 pdr (57 mm) gun in a turret with a 60" ring. The A.24 Cruiser Mk VII Cavalier was a result and was found to be inadequate.
The General Staff drew up specifications in late 1941 for a heavy cruiser tank that's main armament was larger and would be propelled by a better engine.
Early models of the Cromwell were riveted with later models being welded. The Cromwell was the first British tank to have an all welded hull. It was not well liked by the crews as it didn't have good armament and lacked armor protection.
In January 1942 Birmingham Railway Carriage and Wagon Company took over the design. In January 1943 production models first appeared.
With experience in Africa, the General Staff change the specifications to include the 75 mm gun that would allow HE ammunition to be fired at infantry and anti-tank targets. The ammunition was American made and taken from the Lend Lease supplies. Initially the gun was a bored out 6 pdr. (57 mm) which had it's problems, which were corrected in May 1944.
23 rounds of 75 mm was stored in the turret and the rest around the walls of the fighting compartment. There was a No. 19 wireless set in the back of the turret. The turret was boxed shaped and had armor bolted onto an inner skin.
In 1941 two designs were submitted. One with a Liberty engine that was produced by Nuffield and the other with a Rolls-Royce Meteor engine that was produced by Leyland. The Meteor engine was proven to be very reliable and based on the Rolls-Royce Merlin aero engine. Approximately 80% of the components of the engine were similar to the aero engine. The M in the A27M stood for Meteor.
Initially Rolls-Royce produced the engines, but it was contracted out so that Rolls-royce could concentrate on aircraft engines.
The engine was placed between two air cleaners and two fuel tanks. The radiators were mounted upright in the back. There were curved flame guards on the deck. Some storage was lost, and local modifications often added additional storage.
There was a 7.92 mm Besa machine gun in the hull. Up until the Cromwell IV there was a hood over the machine gun's periscopic sight.
In the turret the 75 mm gun and Besa machine gun would be fired by pressing a pedal located in the floor.
In the turret was 23 rounds of 75 mm ammunition and 41 rounds around the hull.
The loader could fire a 2" bomb thrower that was located in the roof of the turret and had a range of 150-450 yards.
Comparison of Main Tank Armament Performance
The armor plate that made up the hull was single skin armor that was riveted or welded. The Cromwell Mk V's and Mk VII's were welded. There were side panels that added protection for the suspension.
The driver, on the right, and co-driver/hull machine gunner sat in the forward compartment. The rest of the crew was in the turret and the loader was also the radio operator. The turret could be rotated in 15 seconds.
The commander was behind the gunner on the left side of the turret. The earlier commander's cupola had 2 episcopes and later models having 8 episcopes. The gunner would use a telescopic site for aiming the gun.
The driver had a lever, to change gears, and steering levers located between his knees. There were two periscopes and an armored visor for the driver to see through. There were doors above the driver's seat to allow his entry, otherwise he could go through the turret. In later models side doors were added for the driver and hull gunner to be able to exit the tank easier.
There was a storage bin above the left track guard and two storage bins above the right track guard.