8" Self-propelled Howitzer M55, early production1-7

M55: General
Date of first acceptance August 1952
Manufacturer Pacific Car and Foundry Co. Crew
6 men:
  • Chief of section in turret right
  • Gunner in turret right front
  • Driver in turret left front
  • Three cannoneers in turret rear
M55: Dimensions
Combat weight ~98,000lbs
~44.000kg		 Height over AAMG mount 136.6"
347.0cm
Length without howitzer 311.4"
791.0cm		 Howitzer overhang forward in travel position 0"
Width over fenders 141.0"
358.1cm		 Tread 110.0"
279.4cm
Ground clearance 18.5"
47.0cm		 Fire height ~95"
~240cm
Turret ring diameter 59.5"
151cm		 Ground pressure, zero penetration 11.6psi
.817kg/cm²
M55: Armament
Type Mount Ammunition Traverse Max traverse rate Elevation Max elevation rate
8" Howitzer M47 M86 in turret 10 rounds 60°
(30° left or right;
manual and hydraulic)		 10°/sec +65° to -5°
(manual and hydraulic)		 7.5°/sec
.50cal M2HB MG Flexible in cupola AA mount 900 rounds 360°
(manual)		 -- Manual --
Aiming equipment
Panoramic telescope M100 and telescope M99 for gunner
M55: Armor
Assembly
Welding
Hull
Rolled homogeneous steel
Location Thickness Angle from vertical
Upper front 1.0"
2.5cm		 10°
Lower front 1.0"
2.5cm		 59°
Sides 0.5"
1.3cm		 0°
Rear 0.5"
1.3cm		 22°
Top 0.5"
1.3cm		 90°
Floor 0.5"
1.3cm		 90°
Turret
Rolled homogeneous steel
Location Thickness Angle from vertical
Front 0.5"
1.3cm		 20°
Sides 0.5"
1.3cm		 0°
Rear 0.5"
1.3cm		 0°
Top 0.5"
1.3cm		 90°
M55: Automotive
Engine Continental AV-1790-5B or -7B; 12 cylinder, 4 cycle, 90° vee gasoline
Horsepower Net: 704@2,800rpm
Gross: 810@2,800rpm		 Torque Net: 1,440 ft-lb@2,000rpm
Gross: 1,610@2,200rpm		 Fuel capacity 380gal
1,440L
Transmission General Motors CD-850-4 or -4B, 2 ranges forward, 1 reverse
Steering Mechanical, wobble stick
Brakes Multiple disc
M55: Suspension
Type Road wheels Track return rollers
Torsion bar 7 independently sprung dual/track 3 dual/track
Drive sprockets Idlers Shock absorbers
13-tooth front drive Dual trailing adjustable at rear of each track On first 2 road wheels/track
M55: Track
T80E6
Center guide, double pin, rubber backed steel
Width 23"
58cm		 Pitch 6"
15cm		 Shoes/track Left side: 89
Right side: 90		 Ground contact length 184"
467cm
T84E1
Center guide, double pin, rubber chevron
Width 23"
58cm		 Pitch 6"
15cm		 Shoes/track Left side: 89
Right side: 90		 Ground contact length 184"
467cm
M55: Performance
Max level road speed 35mph sustained
56kph sustained		 Max trench 96"
240cm
Max grade 60% Max vertical obstacle 42"
110cm
Min turning diameter Pivot Max fording depth 60"
150cm
Cruising range ~150mi
~240km

The M55 was based on components of the M46 and M47 Patton tanks. The engine and transmission were at the front, and the large turret was at the rear. The entire crew was housed in the turret, with the driver stationed at the front left of the turret. Improvements in the medium tank series were grafted onto the M55 as they appeared; the AV-1790-7B engine and CD-850-4B transmission were introduced, and a steering wheel replaced the wobble stick control. The 155mm self-propelled gun M53 utilized the same chassis, and the M86 mount could accept either ordnance. Ammunition stowage racks were interchangeable between the two vehicles as well. The Army converted all of its M53s to M55s starting in 1956, but the Marine Corps continued to use the M53.

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References

  1. Hunnicutt, R.P. Patton: A History of the American Main Battle Tank, volume 1. Navato, CA: Presidio Press, 1984.
  2. TM 9-2350-210-12 Operation and Organizational Maintenance 155-mm Self-propelled Gun Cannon M52 (T97) and 8-inch Self-propelled Howitzer Cannon M55 (T108). Washington, DC: Headquarters, Department of the Army, 30 July 1959.
  3. FM 6-93 155-mm Gun M53, Self-propelled and 8-inch Howitzer M55, Self-propelled. Washington, DC: Dept. of the Army, Jul 1957.
  4. ORD 9 SNL G-259 List of All Service Parts of Gun, Self-propelled, Full Tracked: 155-mm, T97 and Howitzer, Self-propelled, Full Tracked: 8-in, T108. Washington, DC: Department of the Army, 6 January 1956.
  5. TM 9-500 C3 Data Sheets for Ordnance Type Materiel. Washington, DC: Headquarters, Department of the Army, 12 October 1966.
  6. Crismon, Fred W. U.S. Military Tracked Vehicles. Osceola, WI: Motorbooks International, 1992.
  7. Hogg, Ian V. The Greenhill Armoured Fighting Vehicles Data Book. London: Greenhill Books, 2000.
Last updated 5 Sep 2024.
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