8" Self-propelled Howitzer M55, early production1-3
M55: General
Date of first acceptance August 1952
Manufacturer Pacific Car and Foundry Co. Crew 6 men
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 --
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
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
Rear 0.5"
1.3cm
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@2800rpm
Gross: 810@2800rpm
Torque Net: 1440 ft-lb@2000rpm
Gross: 1610@2200rpm
Fuel capacity 380gal
1440L
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
M57: 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. Crismon, Fred W. U.S. Military Tracked Vehicles. Osceola, WI: Motorbooks International, 1992.

  3. Hogg, Ian V. The Greenhill Armoured Fighting Vehicles Data Book. London: Greenhill Books, 2000.



Last updated 28 Aug 2008.

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