British Armour Between the Wars - Design
|Mk. VIII||A25||Harry Hopkins||10||2pdr||100|
|Mk. E||Type B||Vickers 6 Ton||7||47mm||153|
|Mk I||Deacon AEC||12||6pdr||175|
One main shortcoming of early tanks were their slow speed and the short life of the tracks. One solution for these problems was some combination of tracks to maneuver on the battlefield, and wheels on the vehicle to drive to the battlefield. Famous American tank designer Walter Christie’s design had removable tracks so the tank could drive on its wheels. This solution is best known for its use on the Soviet BT tank series. Another wheel-track solution was more sophisticated. This solution consisted of a four-wheeled chassis merged with a tracked chassis. The wheels could be lowered or lifted and be fixed in the needed position, so the tank could either drive on its wheels or tracks. This system combined fast speed on roads with good terrain resistance, but it was very complex, resulting in difficulties in building and repairing, which led to high production costs. Due to the positive aspects of this system, it gained wide interest in multiple countries, including Britain and Sweden.
Another under-appreciated factor in inter-War tank design was the challenge of factory to fox-hole mobility. The tank had to be transported from the factory to the front lines, using some combination of roads, railways and ships, all of which had loading and dimension constraints. British railway loading gauge, the most restrictive in Europe, made it very difficult to provide large diameter turret ring needed by large caliber guns. This explains why British tanks were under-gunned, a problem only remedied by Centurion, which arrived too late for the war, (and which disregarded the railway loading gauge limitation).
The British Army's armored warfare doctrine called for two distinct types of combat tank. One type was to fight a battle of maneuver, fast and lightly armored, to break through or bypass enemy defenses. Attacks on vulnerable rear and flank areas would cause as much disruption as possible. The tanks were designated "cruiser tanks", just as the Royal Navy's cruisers were fast and lightly armored, and intended for independent operations. The rest of the force would be a complementary tank known as the "infantry tank" designed for combined arms operations, directly supporting infantry forces in the slow move against enemy positions. These vehicles would have heavier armor protection, and need a slow speed consistent with the pace of the accompnaying dismounted infantry advance. Doctrinally and operationally, both concepts were sound, and validated in the operational experience of World War II. The German Blitzkrieg across France in 1940 validated the Cruise Tank concept, just as the Allied advance across France in 1944 validated the Infantry Tank concept. The British problem was that it too often found itself with Infantry Tanks when Cruiser Tanks were needed.
As a consequence of these two doctrinal roles, firepower was neglected in tank design. As late as 1937, the very thin armor on most tank's of the world made armor-piercing machine guns, or at most a 20-mm cannon, seem entirely adequate for antitank defense. In fact, many soldiers believed that the tank was more vulnerable than ever because infantry had acquired some antitank training and equipment. Anticipating improvements in tank armor, the British standardized on a two-pounder (40-mm) antitank gun. This was also the standard weapon mounted in most British tanks well into World War II. Yet such a weapon could only penetrate German armor of 1939-42 design at 500 or fewer meters and was not designed to fire high explosive ammunition to suppress enemy infantry and towed antitank gun fire. Although Hobart called for a six-pounder (57-mm) tank gun in 1938, this was not stated as a formal requirement for tank design until after the fall of France in 1940.18 Even then, most turrets designed for the two-pounder were too small to be upgunned.
In the post-war decade, Britain, which then held an undisputed lead in the field, continued to develop special tank engines. The actual development was entrusted to the Armstrong Siddeley company which at the time was the dominant British air-cooled engine manufacturer. Naturally enough, the tank engines which it produced were aircooled, the first production model be: ing a V-8 of 90 b.h.p. used to power the well known Vickers Medium. A smaller 4-cylinder model was produced for the very successful VickersArmstrong 6-ton tank and two larger air-cooled engines were built for experimental British medium and heavy tanks: a 398 b.h.p V-12 for the A.1, or Independent, multi-turret heavy tank and a 180 b.h.p. V-8 for the A6, or sixteen-tonner, medium tank of the late twenties. The Armstrong Siddeley engines were rather expensive and bulky but their basic simplicity and the ability to dispense with the coolant, radiator and the vulnerable plumbing were sufficient to offset any drawbacks associated with the use of air-cooling.
By the early thirties the British were not alone in holding this view: the application of air-cooled engines was taken up in earnest in the United States; the Russians, who purchased 15 of the 6-ton tanks from Vickers Armstrong and copied it on a large scale as the T-26 copied also its aircooled engine. The Germans also adopted an air-cooled engine, a Krupp flat-four, for their first quantity produced tank—the PZ.Kpfw.I Model A. The Czechs too designed a flat-six air-cooled engine of 60 b.h.p. for one of the early Skoda tanks and the Japanese went into air-cooled engine development on some scale.
Britain, having pioneered the air-cooled tank engine, abandoned it completely in the 1930s. The reasons were almost entirely economic. In the wave of financial stringency which followed the depression, tank development funds were cut down drastically and the special air-cooled tank engines, such as the V-8 of the A.6 medium tank, had to be abandoned together with the rest of the project. Cost became a most important consideration and as a result the new British tanks of the mid-thirties came to be powered by commercial automotive engines.
Thus, the Cruiser Tanks Mark I and II were powered by six-cylinder in-line water-cooled A.E.C. engines, converted from the Associated Equipment Company's standard range of bus and truck engines, and the Infantry Tank Mark I was powered by a standard English Ford V-8. Something of this sort was foreshadowed in the late twenties in the development of the British machine gun carriers which were designed down to a price from the start. In consequence, they made use of the cheapest engine available at the time—that of the famous Ford, Model T. Subsequent developments of the Carden Loyd machine gun carriers—the Bren Gun carrier series—continued to be Ford-powered, though by this time the engine size went up to a V-8. The other offshoot of the Carden Loyd machine gun carriers, the Vickers-Carden-Loyd light tanks, were powered by Meadows industrial water-cooled engines or, in a few cases, by Rolls-Royce car engines.
Once more, the use of all these commercial engines was satisfactory as long as only moderate horsepowers were required. When the demand for performance and power went up aero engines had to be resorted to again, as in the case of the first British Christie-type fast tank, the A.13 or Cruiser Tank Mark III. By the time this tank was being designed the pressure of events was such that there could be no question of designing a special tank engine for it.
At the same time, the only up-to-date aero engine which was available — apart from the air-cooled radials which were not considered suitable for tanks in Britain — was the water-cooled V-12 Rolls-Royce. But the Rolls-Royce engines were all required for aircraft which had a much higher priority in the British defense planning than tanks. Consequently the choice fell back on the World War I Liberty. Cleaned-up a little, the 350 b.h.p. Liberty was put into production by the Nuffield organization and was used on British medium tanks right up to the Centaur of 1943. An exception was the Covenanter, which had a special, water-cooled flat12. However, this engine fell the victim of inadequate development and, in any case, it did not have a sufficient reserve of development potential for extended application.
A watercooled flat-12 was also designed by Vauxhall Motors, the British subsidiary of the General Motors Corporation, for the Churchill heavy tank but though robust it was far too heavy for its 325 b.h.p. and again it did not have sufficient development potential for use beyond this tank. French tank engines of the period were generally of the same type as those of the British light tanks, that is fairly robust, water-cooled, in-line automotive engines. Others too relied on this type of engine, for the light tanks at any rate.
By 1937 the British had embarked on a new line of tanks based on a chassis purchased from American tank inventor J. Walter Christie. The Christie suspension, patented by the outspoken and cantankerous inventor J. Walter Christie, used helically-wound coil springs acting independently on each of the suspension’s road wheels. While the Christie vehicles purchased for tests by the US Army in the 1930s had not proven particularly durable, there was the potential for higher speed and maneuvenbility inherent in this type of design, something that was not possible in the volute-bogie type of suspension used in the American medium and light tanks of the day.
There were problems with equipment. The Royal Tank Corps had to make do with the same basic tanks from 1922 until 1938, despite frequent changes in design and technology. Almost the only improvement came in the period 1930-32, when radio communications changed markedly. Until this time, each vehicle crew had to tune its radio by hand to a common frequency, and the motion of a moving tank could easily throw the radio off that frequency. Colonel Broad instigated a series of developments that eventually provided crystal-controlled, preset frequencies. The complexity and expense of such equipment, however, made distribution of radios down to individual tanks very slow. Only such radios could allow a commander to control his rapidly moving units while observing and leading from the front. During the 1930s, the confusion about tank roles combined with frequent changes in the defense bureaucratic structure to thwart good armored vehicle design.
British tank design seemed to share the same confusion and uncertainty pervading mechanized doctrine and organization. New tanks crept through the design and development process, ensuring their obsolescence before they could be delivered to combat units. Too many ideas — some contradictory — surrounded each new tank design, which in turn contributed to the general confusion.
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