A Brand New Design The Mark IV was an efficient model, but many issues shown by war experience had still to be solved by mid-1917. A new design, studied by William Tritton, was ready within days, incorporating a set of brand new features, including a new hull, improved transmission, engine and steering system. But while a wooden mock-up was built, industrial priorities dictated a radical turn. When it appeared that the new transmission and steering system originally planned for the Mark IV were ready for production, the War Cabinet decided to urgently built this improvement of the Mark IV, renamed Mark V. Some features of the original new design will be implemented in the post-war variants of the Mark V.
The Mark V kept all the external features of the Mark IV including the hull, rollers and tracks in order not to disrupt production. However a new, more powerful drive-train and transmission were ready at the beginning of 1917 and tests ordered by William Stern were conducted on modified Mark IVs. These systems included petrol-electric schemes, hydraulic systems, a multiple clutch system (a single driver was needed), and Wilson's own epicylcic gearbox design (4 forward gears , one reverse). A new, more powerful 19 liter six cylinder in-line Ricardo engine (150 bhp) was chosen (giving a power/weight ratio of 5.2 bhp/ton). Autonomy was 70 km (45 mi) with 450 liters fuel capacity (93 gallons), or enough for approximately 10 hours on a rugged terrain. The hull was fitted with a second rear cabin with observation slits and hinged sides allowing the fitting of an unditching wooden beam. The rear part of the hull also received an additional machine-gun mount. Only available in small quantities by mid-1918, the impact of the Mark V was not significant, but three months later, they were numerous enough to make a difference. The first major engagement was the battle of Hamel, on 7 July 1918, when 60 tanks led the victorious offensive of the Australian troops against the German lines. Later, in August, 288 Mark V and V*s were involved, together with numerous Mark A Whippet, in the battle of Amiens, a complete success. The Mark V took part in eight major offensives until the armistice. At the same time, Canadian and US Army troops trained on Mark V's. The 301st American Heavy Tank Battalion was entirely equipped with these, and were thrown in action from September to November 1918 against the Hindenburg line with heavy losses (18 of 21 were lost or disabled). After the armistice, 70 Mark V's were given by the British government to the White Russian faction fighting against the Bolsheviks. But as the situation worsened, a growing number of captured Mark V's took action under the red flag. There is no record of duels between red and white Mark V's, but they ended as a substantial part of the Red Army and were thoroughly studied. They took part in several actions in 1921, including the battle of Tbilissi. Lithuanian and Latvian Mark V's were still active in 1939. Four variants were built during and after the war. The first was the famous "hermaphrodite", a bunch of modified "females" to include a "male" artillery sponson. These mix type tanks were conceived in response to the growing number of captured German Mark I and IV tanks. The giant A7V was very rare at that time. The Mark V* or "star" was a lengthened (six feet) version designed by Tritton during the fall of 1917, to deal with the Hindenburg line, and its very wide trenches (3.47 m/11.39 ft). Major Philip Johnson of the Central Tank Corps Workshops took leadership of this project. The pre-serie tanks were conversions of regular, stretched Mark Vs with reinforced heavy girders. 400 male and 200 female were ordered, of which 579 were built by March 1919. Some arrived in time for the last offensives of November 1918. They were fitted with guidance rails for the unditching beam, two extra machine-guns in their rear cupola, two side doors with extra machine-gun mounts and a total weight of 33 tons. The extra space was thought to be best used for troop transport, but the internal conditions were still unbearable.
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