Mark III Tank - Three Basic Designs, WWII Tactical and Technical Trends, No. 10, October 22, 1942 (Lone Sentry)

Close examination of a considerable number of photographs of Mark III tanks, together with those available for examination in the Western Desert, indicates that the Mark III fighting-type tank is found in three basic designs.

Of these, the first has an armor basis of 30 mm (1.18 in) all around. The front sprocket has eight spokes, and the rear idler, though having eight spokes, is almost solid. This type is known originally to have been produced mounting a 37-mm gun and either one or two machine guns coaxially in the turret, with one machine gun firing forward in the hull. Later, however, the 50-mm was substituted for the original principal armament, and this mounting has only one machine gun mounted coaxially in the turret, the hull machine gun being retained. Of the actual specimens examined, all mounted the 50-mm gun (many are now mounting the long-barrelled type), and in these there has invariably been a Variorex gearbox, the steering being hydraulically operated. This basic type, irrespective of armament, has not been found to carry any additional armor, improvised or otherwise.

The second type has an armor basis of 30 mm all around with additional 30-mm plates bolted on. This type has a six-spoke front sprocket, and the rear idler, although having eight spokes, is more open than the first type. An ordinary six-speed gear box and hydraulically operated steering gear are fitted. Neither photographs nor specimens of this type have shown any principal armament other than the 50-mm gun with one coaxial machine gun. Moreover, every individual tank of this type has had similar additional 30-mm plates on the front and rear, this additional armor not having been found on any other type of Mark III fighting tank. The inference is, therefore, that this additional armor is actually part of the design of the tank and probably incorporated during manufacture. There have been no indications that this type originally mounted a 37-mm gun, although this remains a possibility.

The third type has 50-mm armor on the front and rear, with 30-mm armor on the sides. No additional armor has been found on any tanks of this type, and the armament has always been found to be the 50-mm gun with a coaxial machine gun and one machine gun in the hull. The front sprocket and rear idler are similar to those in the second type, and an ordinary six-speed gear box is fitted, the steering being operated by mechanical linkage. The driver's and hull gunner's entrance doors have been changed from the former double doors to single doors hinged at the forward edge. In place of the normal mantlet protecting the hull machine gun, a more hemispherical mantlet is fitted.

The following minor differences of design between these three basic types have also been noted. Originally on the first type the armor protecting the driver's visor consisted of two plates, one being raised, and the other lowered, to give protection. The third type, and probably the second type as well, have had a single hinged piece of armor which can be lowered to give protection. The third type has also had a slightly different design of the two shields protecting the exhausts from the steering tracks. In the first and second types the air filters were located between the rear bulkhead of the fighting compartment and the engine, air being drawn from the fighting compartment. These filters were believed to be an oil-soaked gauze type. On the third type this arrangement superseded by four oil bath filters, installed over the top of the engine blocks.

The suspension on all these types has been the same, the familiar six small bogie wheels with three return rollers, a front sprocket, and a rear idler. Two early types, however, are known to have had respectively five large bogie wheels and eight small bogie wheels. Both these types mounted a 37-mm gun. Nothing has been heard of either type over a considerable period, and it is probable that they were prototypes only and not produced in significant numbers.

It is known that Mark III fighting tanks have been produced in at least five models designated 'E', 'F', 'G , 'H', and 'J.' These models have consecutive chassis number blocks, and it is logical to assume that they are successive developments. There should therefore be a link with the development shown above, but so far it is not possible definitely to say what each model designation represents. It is, however, known that the first type described above has included Model 'G' tanks, and the third type has included Model 'J' tanks. All three types are known to have been in existence early in 1941, the third type probably being at that time a very new production.

It should be specially noted that, in describing German armor thickness, round numbers are almost invariably given. Careful measurement, has shown that these figures are frequently incorrect. 30-mm, for example, should almost invariably be up to 32-mm.