To describe the United States Army's M9 Armored Combat Earthmover (ACE) to someone who has never seen one, I'd have to say it is the combination of a tank, a dump truck, a bulldozer, and a low rider. This might sound like a strange combination, but it makes for a great combat engineering vehicle.

The M9 ACE is a highly mobile, air-transportable, amphibious, fully tracked combat vehicle used primarily to prepare firing positions for tanks, artillery, and other weapons systems including other combat engineering vehicles such as the M728 CEV. It can also be used to create or eliminate other obstacles such as tank ditches, berms, roadblocks, and minefields; or maintain and repair roads, supply routes, and temporary air fields. It is used extensively for both offensive and defensive operations including dozing, scraping, grading, excavating, hauling, towing, and winching.

The ACE features a front-mounted dozer blade behind which is a 26.1 cubic foot (6.7 cubic meter) scraper bowl. When a particular job requires a machine heavier than 37000 lbs (17000kg), the blade can be hydraulically lifted, and the scraper bowl can be filled with up to 9 tons of ballast bringing the vehicle weight up to 55000 lbs (25000kg). The rear has a two-speed winch capable of 25,000-pound line pull.

What makes the M9 most unique is its hydropneumatic suspension system. The vehicle has eight high-pressure hydraulic rotary actuators that connect to the roadwheels. It can tilt forward to dig steep trenches; backward to dig upward from a lower position or to help climb obstacles; or to either side for slanted digging. It's amazing to see this huge vehicle contort so smoothly - it puts any lowrider to shame.

A single driver operates this tracked vehicle, so his only method of contact with other members of his unit is by radio communication. The driver's cupola is located at the rear of the vehicle, and can be completely sealed for combat operations and chemical or biological attacks. When the hatch is closed, the driver operates and navigates with the help of numerous vision blocks much like small periscopes. For additional protection and concealment in combat situations, the vehicle is equipped with two smoke grenade launchers.

Technical Specifications


Date of First Acceptance: 1986
Manufacturer: BMY Combat Systems and United Defense LP
Unit Cost: $710,194

Dimensions and Measurements

Travel Weight: 37000 lbs (17000kg)
Combat Weight: 55000 lbs (25000kg)
Length: 20ft 5in (6.2m)
Width: 9ft 2in (2.79m)
Height: 9ft 11in (3m)
Ground Clearance: 13in (33cm)
Bowl Capacity: 8.7 cubic yards (6.7 cubic meters)
Fuel Tank: 134gal (507L)


Maximum Ground Speed: 30mph (50kph)
Maximum Swim Speed: 3mph (5kph)
Cruising Range: ~200mi (~320km)
Maximum Dig Grade: 60 degrees
Maximum Trench Crossing: 62in (1.6m)
Maximum Vertical Wall Crossing: 18in (46cm)
Turning Radius (Geared Steering): 45ft (13.7m)
Turning Radius (Clutch Brake): Pivot


Engine: Cummins V903C; eight cylinder, vee diesel
Horsepower: 295 at 2600rpm
Transmission: Clark 13.5 HR 3610-2, 6 speeds forward, 2 reverse


Assembly: Welding and Bolting
Type: Aluminum Armor, Steel and Aramid Laminate Plates


Type: Hydropneumatic
Road Wheels: 4 individually sprung per track
Drive Sprockets: Rear Drive


Width: 18in (46cm)
Ground Contact Length: 105in (2.67m)

Other Combat Engineering Vehicles


  • I have driven and performed maintenance on (though not dug with) an ACE

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