Heavy Tank Mark VIII1-10

Mk. VIII: General
Date of first acceptance January 1920 Total acceptances 100
Manufacturer Rock Island Arsenal Crew
11 men:
  • Commander in turret cupola
  • Six-pounder gunner in each sponson
  • Six-pounder loader in each sponson
  • Four machine gunners
  • Driver in hull front center
  • Mechanic in hull rear
Mk. VIII: Dimensions
Combat weight 86,900lbs
39,400kg
Height 123.0"
312.4cm
Length 410.5"
1043cm
Width over sponsons 144.0"
365.8cm
Tread 69.5"
177cm
Ground clearance 20.8"
52.8cm
Ground pressure, zero penetration 16.1psi
1.13kg/cm²
Mk. VIII: Armament
Type Mount Ammunition Traverse Elevation
Hotchkiss 6 pounder Mk. II Gun Side sponson 208 rounds Manual Manual
.30cal M1919 Browning tank MG Ball mount in each side door 15,100 rounds Manual Manual
Two .30cal M1919 Browning tank MGs Ball mounts in turret front Manual Manual
.30cal M1919 Browning tank MG Ball mount in turret rear Manual Manual
Mk. VIII: Armor
Assembly
Riveting
Hull
Rolled face-hardened steel plate
Location Thickness
Side plates 0.47"
1.2cm
Back plates, rear of gasoline tank 0.63"
1.6cm
Front wing plates 0.39"
1.0cm
Outside skirting plates 0.39"
1.0cm
Front sloping plate 0.47"
1.2cm
Front diaphragm plate 0.47"
1.2cm
Main turret side plates 0.63"
1.6cm
Main turret top plates 0.2"
0.6cm
Driver's turret plates 0.2"
0.6cm
Hemispherical turrets in doors and main turret 0.55"
1.4cm
Top plating of lookout turret 0.2"
0.6cm
Side lookout plating 0.63"
1.6cm
Sponson floor plates 0.3"
0.8cm
Sponson roof plates 0.2"
0.6cm
Sponson top shield 0.3"
0.8cm
Sponson bottom shield 0.3"
0.8cm
Sponson side plates 0.47"
1.2cm
Forward sponson floor plates 0.47"
1.2cm
Aft sponson floor plates 0.2"
0.6cm
Roof plate abaft turret 0.2"
0.6cm
Roof plate over engine 0.2"
0.6cm
Roof plate over gasoline tank 0.39"
1.0cm
Roof plate over driver 0.2"
0.6cm
Doors 0.47"
1.2cm
Mk. VIII: Automotive
Engine Liberty 12; 12 cylinder, 4 cycle, 45° vee gasoline
Horsepower Gross: 338@1400rpm Fuel capacity 240gal
908L
Transmission Epicyclic, 2 speeds forward, 2 reverse
Steering Epicyclic, levers
Brakes Mechanical, external contracting
Mk. VIII: Suspension
Type Road wheels Track return rollers
Rigid 14 lower track rollers with spacers and spring plates/track;
15 lower track rollers without spacers or spring plates/track
1 top track return roller/track
Drive sprockets Idlers Shock absorbers
35-tooth rear drive Adjustable at front of track None
Mk. VIII: Track
Continuous linked dished armor plate
Width 26.5"
67.3cm
Pitch 11.154"
28.331cm
Shoes/track 78 Ground contact length, zero penetration 102"
259cm
Mk. VIII: Performance
Max level road speed 5.5mph
8.9kph
Max trench 192"
488cm
Max grade 84% Max vertical obstacle 54"
140cm
Min turning diameter 40.5'
12.3m
Max fording depth 34"
86cm
Cruising range ~40mi
~64km

The Mark VIII, also known as the Liberty, International, or Anglo-American tank, was a continuance of the British rhomboid landship line of tanks. The plans were for the Mark VIII to be assembled in France using American automotive components and British armament and armor. The end of the World War I spelled the end of the manufacturing consortium, but the US pressed on to construct 100 vehicles with its own engine and armament. The tank had a nonrotating main turret on the hull with mounts for three machine guns, and atop this turret was the commander's lookout turret. The 6 pounder weapons had a caliber of 57mm, and the sponsons in which they were mounted were hinged so that the rear could be pivoted into the hull to reduce shipping width. The 6 pounders were then drawn in so that the 81" (270cm) loading gauge could be obtained. Likewise, the lookout turret was lowered flush with the main turret roof when shipping the tank. The tracks were chain-driven in that a bicycle-like chain from the transmission spun a roller sprocket, and this roller sprocket drove the track drive sprocket, which was at the time referred to as a road track driving wheel. The tank's tracks were made of armor plate which was 8mm (0.3") thick. The vehicle's ground pressure dropped to 13.85psi (.9723kg/cm²) at 1" (2.5cm) of penetration and continued down to 4.26psi (.299kg/cm²) at 15" (38cm) penetration. The two types of road track rollers were mounted alternately; the spring plates were spacers to hold the rollers in the proper position on their axle shafts. The US had removed the Mark VIII from service by 1932, but some of the tanks were offered to Canada for use as training vehicles after the start of World War II.

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References

  1. Preliminary Handbook of the Mark VIII Tank. Washington, DC: Office of the Chief of Ordnance, 6 Mar 1925.
  2. Hunnicutt, R.P. Firepower: A History of the American Heavy Tank. Navato, CA: Presidio Press, 1988.
  3. Broman, Glen. "The Mark VIII 'Liberty' Tank." The Armor Journal 3 (summer 2015): 36-46.
  4. Tank Data, vol. 1. Aberdeen Proving Ground, MD: US Army Ordnance School, Jul 1958.
  5. Handbook for the Q. F. Hotchkiss 2.244-inch, 6-pdr., 6-cwt, Mark II Gun with Tank Mounting. Washington, DC: Office of the Chief of Ordnance, Aug 1919.
  6. Miller, David. The Illustrated Directory of Tanks of the World. Osceola, WI: MBI Publishing Co., 2000.
  7. Crismon, Fred W. U.S. Military Tracked Vehicles. Osceola, WI: Motorbooks International, 1992.
  8. AGF Board No. 2. Development of Armored Vehicles, volume 1: Tanks. 1947.
  9. Wilson, Dale E. "World War I: The Birth of American Armor." Camp Colt to Desert Storm: The History of U.S. Armored Forces. Eds. George F. Hofmann, Donn A. Starry. USA: University Press of Kentucky, 1999.
  10. Kirk, William. "Heavy Tanks." TANKS! 18 Nov 2000. 5 Dec 2000 <http://mailer.fsu.edu/~akirk/tanks/UnitedStates/heavytanks/​HeavyTanks.html>. TANKS!

Last updated 28 Jan 2020.
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