page_title: Mark V tank
section_title: Modifications
hierarchical_section_title: Mark V tank / Modifications
caption_attribution_description: English: Inside view of a Mark IV Lodestar III tank of First World War. Photo taken through peephole. Royal Military Museum, Brussels, Belgium.Español: Vista del interior de un tanque Mark IV Lodestar III de la Primera Guerra Mundial. Fotografía tomada a través de una mirilla. Museo Real del Ejército y la Historia Militar de Bruselas.
context_page_description: The British Mark V tank was an upgraded version of the Mark IV tank.
  The tank was improved in several aspects over the Mark IV, chiefly the new steering system, transmission and 150 bhp engine, but it fell short in other areas, particularly its insufficient ventilation leading to carbon monoxide poisoning for the crew. Various versions were fitted with a variety of armament including 6-pounder guns and machine guns.
  It was first deployed in July 1918 on the Western Front at the Battle of Hamel; then at the Battle of Amiens, and on the Hindenburg Line during the closing months of World War I.
  During the Allied intervention in the Russian Civil War on the White Russian side, four Mark Vs were delivered to Archangelsk, four to Reval, Estonia, and around 70 were delivered to Novorossisk in southern Russia. The survivors were captured and used by the Red Army.
  There were two main further variants, the lengthened Mark V* and a few Mark V**s with a more powerful engine and wider tracks. A planned Mark V*** was never built. There are eleven surviving Mark V tanks.
context_section_description: In early 1917, some British tanks were tested with various experimental powerplant and transmissions ordered by Albert Stern. These included petrol-electric schemes, hydraulic systems, a multiple clutch system, and an epicyclic gearbox designed by Major W. G. Wilson. Though the petrol-electrics had advantages, Wilson's design was capable of production and was selected for use in future tanks.
  The use of Wilson's epicyclic steering gear in the Mark V meant that the driver could control all aspects of the transmission: three extra crew members had been required in previous versions of the tank, two gearsmen to change low and high gears on either side of the tank, and the commander who operated the brakes and skid steering. There was much more space at the rear after the removal of the massive differential gear (originally designed for the Daimler-Foster agricultural tractor) fitted to all the earlier tanks. On the roof towards the rear of the tank, behind the engine, was a second raised cabin, with hinged sides that allowed the crew to attach the unditching beam without exiting the vehicle. An additional machine-gun mount was fitted at the rear of the hull.
  The Mark V had a new, more powerful six cylinder engine (also ordered by Stern) designed by Harry Ricardo, displacing 19 litres and developing 150 bhp (110 kW). According to J. F. C. Fuller, the Ricardo engine was of a "somewhat unorthodox design", but it was highly efficient and, with proper care and attention, gave very little trouble. This 'unorthodox' description related to Ricardo's use of crosshead pistons which separated the lubricating oil from the heat of combustion, with the crosshead and gudgeon pin running in its own separate guide. The engine used conventional poppet valves, unlike the Daimler sleeve valve engines used in the previous tanks; because very few men or officers had any experience of adjusting valve mechanisms, extra instruction was needed for tank personnel. The Ricardo engine could have been considerably more powerful, but its design was restricted by two considerations. Firstly, it needed to fit in the exact same footprint as the original Daimler 105 hp engine in the older tanks Marks I–IV, resulting in a taller engine; secondly, Wilson had advised Ricardo that the proposed 200 bhp (150 kW) would place too much strain on the transmission, and it was limited to 150 bhp.
caption: The huge differential gear at the rear of a Mark IV tank
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