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Summer 2010

32

U.S. Army CSM Gregory Frias, 4th Brigade Combat Team, 2nd Infantry Division, points in the direction he wants a Stryker vehicle to stage as the driver navigates a muddy road at a combat outpost in Muquadiah. Through research into composite armor development at TARDEC, Army vehicles can be better protected, lighter and more mobile. (U.S. Army photo by SPC LaRayne Hurd.)

group initiative is to partner with industry to implement new technologies for critical parts manufacturing and technology advancement.

One method the AMTG has investigated involves reducing the weight of an axle or wheel- end component, which has a multiplying effect because there is more than one per vehicle. The Stryker, and similarly the U.S. Marine Corps’ Light Armored Vehicle (LAV), has four axles and eight wheels, making it an ideal candidate for weight savings using this method. For wheel- end components, there is further benefit due to the correlation of unsprung mass to sprung mass. For each pound of unsprung mass saved, such as in the wheel, there is equivalent savings of three to five pounds in sprung mass for an average of four pounds of sprung mass.

Composite Materials

Reduce Weight One such wheel-end component is the brake drum, which has been made of cast iron for

decades. TARDEC’s AMTG developed a technology that enables a conversion from cast iron components to lightweight aluminum composite materials. This produces a military truck- sized brake drum that can reduce the weight of each Stryker brake drum by 45 percent compared to a standard cast iron drum. With a 45-percent weight reduction, a Stryker could remove approximately 250 pounds of unsprung mass from its wheel- ends. Taking into account the correlation to sprung mass, this averages to 1,000 pounds of sprung mass weight savings elsewhere in the vehicle.

The new aluminum composite brake drum designed for use on the Stryker, LAV, Family of Medium Tactical Vehicles and Armored Support Vehicle, has been tested to Federal Motor Vehicle Safety Specification (FMVSS) 121. In addition, the new brake drum has undergone extensive testing by the U.S. Army TACOM Life Cycle Management Command using the Automotive- Tank Purchase Description-2354

test. Successful testing was performed on a dynamometer at Link Engineering Company’s Link Testing Laboratories – Detroit. The lightweight drum met or exceeded its cast iron counterpart during testing.

Following testing, the lightweight brake drum was mounted on the front axle of a 26,000-pound GVW vehicle for the FMVSS stopping distance test as well as an additional 10-stop fade test. The stopping distance test was successful. More notably, in the 10-stop fade test, as the liner temperatures continued to rise, the brake pedal force remained consistent. This is in contrast to cast iron drums, which require greater pedal force to stop the vehicle with each successive brake application as the temperature rises.

Another benefit of aluminum- based brake drums may be increased survivability. Based on industry studies, ductile aluminum components are believed to absorb more energy from a mine blast, leading to the conclusion that a blast is further reduced with an aluminum-based brake drum rather than a brittle, cast iron drum mounted inside the wheel rim. Furthermore, the aluminum- based brake drum will dissipate heat three times faster than the cast iron brake drum, bringing the vehicle to a stable temperature more quickly, thereby reducing a vehicle’s heat signature faster. With the lightweight brake drums reducing the weight per vehicle, more drums can be shipped per pallet, facilitating transportation, logistics and sustainability requirements.

Metal Matrix Composites (MMC) Provide Next-

Generation Solutions The lightweight aluminum composite brake drum is made possible with the use of MMCs,

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