The Mark I was a rhomboid vehicle with a low centre of gravity and long track length, able to grip muddy ground and cross trenches. Sponsons (also called "barbettes") on the hull sides carried two naval 6-pounder guns. There were two Hotchkiss machine guns in the sponsons and two removable guns for the front and back.
| Mark I Tank | |
|---|---|
| Type | Tank |
| Place of origin |  United Kingdom |
| Service history | |
| In service | 1916–1931, and 1945 (briefly) |
| Used by | United Kingdom Germany Soviet Union United States France Canada Australia Estonia Latvia |
| Wars | First World War, Russian Civil War, Second World War |
| Production history | |
| Designer | William Tritton, Major Walter Gordon Wilson |
| Designed | 1915 |
| Manufacturer | William Foster & Co. of Lincoln Metropolitan Carriage, Birmingham |
| Produced | 1915–1919 |
| Number built | 150 |
| Variants | Mark II, Mark III, Mark IV, Mark V series, Mark VI, Mark VII, Mark VIII, Mark IX, Mark X, Gun Carrier Mark I |
| Specifications | |
| Weight | Male: 28 tons (28.4 tonnes) Female: 27.4 tonnes |
| Length | 32 ft 6 in (9.94 m) with tail |
| Width | 13 ft 9 in (4.33 m) [male] |
| Height | 8 ft 0.5 in (2.44 m) |
| Crew | 8 (commander, driver, two gearsmen and four gunners) |
| | |
| Armour | 0.23–0.47 in (6–12 mm) |
| Main armament | Male: Two 6 pdr QF or 6 pdr 6 cwt QF Female: Four .303 Vickers machine guns |
| Secondary armament | Male: Four .303 in Hotchkiss Machine Guns Female: Two .303 in Hotchkiss machine guns |
| Engine | Daimler-Knight 6 cylinder sleeve valve petrol engine 105 hp |
| Power/weight | Male: 3.7 hp/tonne Female: 3.8 hp/tonne |
| Transmission | primary gearbox:2 forward and 1 reverse secondary:2 speeds |
| Operational range | 6.2 hours endurance |
| Speed | 4 miles per hour maximum |
The hull was undivided internally; the crew shared the same space as the engine. The environment inside was extremely unpleasant; the atmosphere was contaminated with poisonous carbon monoxide, fuel and oil vapours from the engine and cordite fumes from the weapons as ventilation was inadequate. Temperatures inside could reach 50 °C (122 °F). Entire crews lost consciousness inside the tank or became violently sick when again exposed to fresh air.
To counter the fumes inside and the danger of bullet splash or fragments and rivets knocked off the inside of the hull, the crew wore helmets with goggles and chainmail masks. Gas masks were standard issue as well, as they were to all soldiers at this point in the war. The side armour of 8 mm initially made them largely immune to small arms fire, but could be penetrated by the recently developed armour-piercing K bullets. There was also the danger of being overrun by infantry and attacked with grenades. The next generation had thicker armour, making them nearly immune to the K bullets. In response, the Germans developed the 13.2 mm Mauser anti-tank rifle, and also a Geballte Ladung ("Bunched Charge")—several regular stick grenades bundled together for a much bigger explosion.
A direct hit on the roof by an artillery or mortar shell could cause the fuel tanks (which were placed high in the front horns of the track frames either side of the drivers' area, to allow gravity feed) to burst open. Incinerated crews were removed by special Salvage Companies, who also salvaged damaged tanks. They were forbidden to speak about this aspect of their work with still living tank crews.
Steering was difficult; controlled by varying the speed of the two tracks. Four of the crew, two drivers (one of whom also acted as commander; he operated the brakes, the other the primary gearbox) and two "gearsmen" (one for the secondary gears of each track) were needed to control direction and speed, the latter never more than a walking pace. As the noise inside was deafening, the driver, after setting the primary gear box, communicated with the gearsmen with hand signals, first getting their attention by hitting the engine block with a heavy spanner. For slight turns, the driver could use the steering tail: an enormous contraption dragged behind the tank consisting of two large wheels, each of which could be blocked by pulling a steel cable causing the whole vehicle to slide in the same direction. If the engine stalled, the gearsmen would use the starting handle—a large crank between the engine and the gearbox. Many of these vehicles broke down in the heat of battle making them an easy target for German gunners. There was no wireless (radio); communication with command posts was by means of two pigeons, which had their own small exit hatch in the sponsons, or by runners. Because of the noise and vibration, early experiments had shown that radios were impractical, so lamps, flags, semaphore, coloured discs, and the carrier pigeons were part of the standard equipment of the various marks.
During the First World War, British propaganda made frequent use of tanks, portraying them as a wonder weapon that would quickly win the war. They were featured in films and popular songs.
