Armored Combat Earthmover M91-6

M9: General
Date of first acceptance 1986 Total acceptances 620
M9: Manufacturer BMY Combat Systems Crew 1 man
M9: Dimensions
Travel weight 37,000lbs
Height above cupola 118.00"
Length 245.50"
Width 110.00"
Tread 88.00"
Ground clearance 13.00"
Ground pressure, zero penetration 9.5psi
M9: Armament
M9: Armor
Welding and bolting
Operator's station
Aluminum armor, steel and aramid laminate plates
M9: Automotive
Engine Cummins V903C; eight cylinder, 4 cycle, vee diesel
Horsepower 295@2600rpm Fuel capacity 134gal
Transmission Clark 13.5 HR 3610-2, 6 speeds forward, 2 reverse
Steering Geared steer and clutch-brake
M9: Suspension
Type Road wheels Track return rollers
Hydropneumatic 4 individually sprung dual/track Flat track
Drive sprockets Idlers Shock absorbers
Rear drive Front road wheels act as idlers None
M9: Track
Single pin, rubber padded steel
Width 18"
Ground contact length 105"
M9: Performance
Max level road speed 30mph
Max water speed 3mph
Max trench 62"
Max sideslope with 18,000lbs (8200kg) in bowl 40%
Max grade with 18,000lbs (8200kg) in bowl 60% Max vertical obstacle 18"
Min turning diameter Pivot Max fording depth 36"
Cruising range ~230mi, roads
~370km, roads

The US Army's search for an armored combat earthmover, or universal engineering tractor, spanned thirty years. The resulting M9 ACE features a front-mounted dozer blade behind which is an 8.7 cubic yard (6.7m3) scraper bowl. For jobs requiring a heavier machine, the blade could be raised and the bowl could be filled with dirt, bringing the vehicle's weight up to 57,000lbs (26,000kg). Originally, a 25,000lb (11,000kg) winch was mounted in the lower rear hull, beneath the engine and transmission. This was replaced by a 35,000lb (16,000kg) model with 165' +/- 2' (50.3m +/- .6m) of 3/4" (1.9cm) wire rope. The dozer blade was positioned by adjusting the hydropneumatic suspension. The operator is stationed at the rear of the vehicle and is provided with a cupola containing eight vision blocks. After the vehicle had entered service, modifications were performed that increased the vehicle's weight to the point that swimming was no longer feasible. The amphibious requirement was therefore dropped.

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  1. TM 5-2350-262-10 Operator's Manual Armored Combat Earthmover (ACE) M9 (NSN 2350-00-808-7100). Washington, DC: Dept. of the Army, Jun 2007.
  2. Hunnicutt, R.P. Sheridan: A History of American Light Tank, volume 2. Navato, CA: Presidio Press, 1995. Reprinted with permission from Sheridan, R.P. Hunnicutt ©1995, available from Presidio Press, 505B San Martin Drive, Suite 160, Navato, CA 94945.
  3. Crismon, Fred W. U.S. Military Tracked Vehicles. Osceola, WI: Motorbooks International, 1992.
  4. Federation of American Scientists. "Armored Combat Earthmover - (M9 ACE)." DOD 101. 19 Feb 2000. 7 Nov 2001 <>. DOD 101
  5. US Army TACOM. "M9 ACE - Description and Mission." 7 Nov 2001 <>.
  6. Reyes, Larry. "ACE." Email to the author. 16 May 2006.

Last updated 11 Apr 2017.
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