Automotive Design and Production

OCT 2013

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AD&P; > October 2013 > FEATURE > The Chassis Challenge for the Humvee Replacement > Zachary Peterson > zpeterson@autofeldguide.com ride in a JLTV and I don't want to say it's like riding in a Cadillac, but it isn't far of." Hyperbole aside, Oshkosh's JLTV design, the Light Combat Tactical All-Terrain Vehicle (L-ATV), leverages an enhanced version of the TAK-4 independent suspension system, which is already deployed in the company's mediumduty MRAP All-Terrain Vehicle (M-ATV). The improved "TAK-4i" system provides 20 in. of wheel travel to navigate uneven terrain (a 4-in. improvement over the existing system), a single reduction axle, adjustable suspension height for transportability (to ft aboard transport ships), and high-performance disc brakes to stop in extreme conditions as well as to reduce wear. "The M-ATV is the current benchmark for of-road mobility and protection, performing a mission profle closest to what JLTV would perform," explains John Bryant, Oshkosh senior vice president of defense programs. "With JLTV, the customer needs the protected mobility of an M-ATV in a much smaller, lighter-weight, more transportable package that's also capable of even greater of-road mobility." The M-ATV vehicle weighs (27,500 lb.) about twice as much as the L-ATV (14,000 lb.). Lockheed Martin also leveraged the suspension of its JTLV ofering from an MRAP vehicle. The truck has Meritor's (meritor.com) ProTec high-mobility independent suspension, used in the Caiman MRAP (built by BAE Systems, a member of Lockheed's JLTV team). This technology ofers a turning radius up to 35°, 21 in. of total independent wheel travel and limited-slip diferential, no-spin diferential and drivercontrolled diferential lock. "This is a proven system, providing us a tremendous level of ride quality, while also facilitating key mobility requirements," says Kathryn Hasse, director of the Lockheed JLTV efort. 42 The tricky part was integrating the chassis and its components with other competing requirements such as armor and transportability, Hasse says. To overcome the challenge, she explains her team borrowed a concurrent engineering approach from the commercial automotive world. Design, manufacturing and maintenance all worked in parallel toward developing the JLTV, meeting along the way to chart progress and fx potential problems upfront. "We did a lot of model development and did weekly model reviews with our entire supply base," she explains. "From a manufacturing perspective, we did a series of virtual builds working with our component suppliers and our manufacturing supplier, BAE Systems." Hasse adds, "We proceeded to build prototype vehicles and put them on essentially a four-post [road simulator] to do an accelerated lifecycle test— assimilating the type of terrain in the durability testing that the vehicles will undergo. And then we built an actual running chassis and put it through reliability and performance testing at our test track facilities." So far, the Lockheed JLTV has gone through 180,000 test miles, both virtually and on test tracks. "We did a tremendous amount of work virtually because frankly it's expensive to build hardware," she says. "We took advantage of technology and virtual tools to do the design and assembly before we shelled out the cash to buy the hardware and integrate it." This approach helped Lockheed anticipate and fx possible issues before the prototypes were tested by the government, and long before, if the military u The Oshkosh L-ATV climbs a rocky incline in a demonstration earlier this year at Marine Corps Base Quantico, VA.

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