38-ton High-speed Tractor M61-9

M6: General
Date of first acceptance February 1944 Total acceptances 1,235
Manufacturer Allis-Chalmers Manufacturing Co. Crew
11 men:
  • Driver in hull left front
  • 10 passengers
M6: Dimensions
Combat weight 76,000lbs
34,500kg		 Height 104.0625"
264.3188cm
Length 257.8125"
654.8438cm		 Width 120.5"
306.1cm
Tread 98.5"
250cm		 Ground clearance 21.5"
54.6cm
Ground pressure, zero penetration 9.99psi
.702kg/cm²
M6: Armament
Type Mount Ammunition Traverse Elevation
.50cal M2HB MG Flexible on ring mount M49C, M49A1C, or M66 600 rounds 360°
(manual)		 +85° to -20°
(manual)
M6: Armor
None
M6: Automotive
Engine Two Waukesha 145GZ; 6 cylinder, 4 cycle, in-line gasoline
Horsepower Net: 382@2,100rpm
(191/engine)		 Torque Net: 1,078 ft-lb@1,500rpm
(539/engine)		 Fuel capacity 300gal
1,135L
Transmission Selective constant mesh, 2 ranges forward, 1 reverse
Steering Controlled differential, steering levers
Brakes Mechanical on controlled differential
M6: Suspension
Type Road wheels Track return rollers
Horizontal volute spring 3 bogies/track;
2 dual wheels/bogie		 3/dual track
Drive sprockets Idlers Shock absorbers
13-tooth front drive Dual trailing adjustable with volute spring at rear of each track None
M6: Track
T73
Center guide, double pin, rubber bushed, steel, chevron
Width 22"
56cm		 Pitch 6"
15cm		 Shoes/track 84 Ground contact length 176.375"
447.993cm
M6: Performance
Max level road speed 21mph
34kph		 Max trench 102"
259cm
Max grade 57.73% Max sideslope 57.73%
Max vertical obstacle 30"
76cm		 Min turning diameter 53'
16m
Max fording depth 54"
140cm		 Cruising range ~110mi, roads
~180km, roads

The high-speed tractor M6 was intended as a prime mover for artillery loads of 30,000-60,000lb (13,600-27,200kg), specifically the 120mm gun M1, 8" gun M1, and 240mm howitzer M1. The crew cab featured two compartments, with the front able to hold the driver and four passengers and the rear compartment housing five or more men. An ammunition and cargo box mounted at the rear was divided into five compartments: the outer two contained shell racks and hold-down bars; the center was for powder charges and dunnage; the lower left compartment held the snatch block, towing chains, hoist, and extra oil; and the lower right compartment held water cans. A Gar Wood 6M823 60,000lb (27,200kg) capacity winch with 300' (90m) of 1" (2.5cm) cable was provided, as well as controls for air and electric brakes for towed loads. The engine compartment was between the cargo box and crew compartment. The engines and torque converters were the same as found in the 18-ton high speed tractor M4, but this lighter vehicle only used a single engine and torque converter compared to the M6's pair of each. The engines in the M6 could be used independently of each other if the clutch for the disabled engine was locked out by first turning its stop screw out of the clutch housing and against the depressed clutch throw-out lever to hold the clutch in the disengaged position, then removing the short link rod that connected to the throw-out lever. Rubber-backed steel T80E2 or rubber T84E2 tracks were able to be used if the drive sprockets were first spaced out.

The amount of ammunition able to be carried seems a contentious topic. TM 9-788/TO 19-75AJ-66 claims that 32 rounds and 32 propelling charges could be stowed when towing the 120mm gun M1; or 14 rounds, 14 propelling charges, 50 primers, and 25 fuzes when towing either the 8" gun M1 or 240mm howitzer M1. The Catalogue of Standard Ordnance Items lists 24 rounds of 4.7" antiaircraft ammunition, 20 rounds for the 240mm howitzer M1, or 24 rounds for the 8" gun M1. TM 9-2800-1/TO 19-75A-89 asserts 14 rounds of 240mm or 8" ammunition or 32 rounds of 120mm ammunition could be carried.

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References

  1. Hunnicutt, R.P. Bradley: A History of American Fighting and Support Vehicles. Navato, CA: Presidio Press, 1999. Reprinted with permission from Bradley, R.P. Hunnicutt ©1999, available from Presidio Press, 505B San Martin Drive, Suite 160, Navato, CA 94945.
  2. Crismon, Fred W. U.S. Military Tracked Vehicles. Osceola, WI: Motorbooks International, 1992.
  3. TM 9-788/TO 19-75AJ-66 38-ton High-speed Tractor M6. Washington, DC: Departments of the Army and the Air Force, 12 May 1952.
  4. TM 9-1785A Ordnance Maintenance--Engine, Engine Accessories, and Torque Converter for 18-ton M4 and 38-ton M6 High Speed Tractors. Washington, DC: War Department, 27 March 1944.
  5. TM 9-1788 Ordnance Maintenance--Tractor, High-speed, 38-ton, M6--Power Train, Suspension, Body, and Equipment. Washington, DC: War Department, 22 September 1944.
  6. ORD 9 SNL G-184 List of All Service Parts for Tractor, High Speed, 38-ton, M6 (Allis-Chalmers). Washington, DC: Headquarters, Army Service Forces, 1 June 1945.
  7. Catalogue of Standard Ordnance Items, second edition 1944, volume I: Tank and Automotive. Washington, D.C.: Office of the Chief of Ordnance, Technical Division, 1 June 1945.
  8. TM 9-2800-1/TO 19-75A-89 Military Vehicles (Ordnance Corps Responsibility). Washington, DC: Departments of the Army and Air Force, 13 February 1953.
  9. Sola, Samuel, Vincent Bobkowski, and Kara Crocker. Weapon Mounts for Secondary Armament. Santa Monica, CA: G. O. Noville & Associates, Inc., April 1957.
Last updated 25 Oct 2023.
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