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June 01, 2004  |   Comments (0)   |   Post a comment

Streamlined school buses at the end of this tunnel?

by Paul Hartley


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PORTLAND, Ore. — Freightliner LLC recently unveiled the world’s first “truck-specific” wind tunnel, but it’s likely that research done at the facility will influence the shape of mirrors, grills and body panels used across the company’s broad product spectrum.

“We’ll definitely benefit from having that tunnel,” said John Mellberg, creative vehicle stylist for Thomas Built Buses. “I think it will be quite interesting to work there with school buses.” Mellberg says his company’s aerodynamically styled Saf-T-Liner C2, introduced last November, was designed without the benefit of such a tool.

The 12,000-square-foot facility, located a few blocks from Freightliner’s headquarters in Portland, is probably the most rapidly built and lowest-priced full-scale tunnel on the planet: 11 months of construction and an estimated price tag of $3 million, roughly one-tenth of the cost of similarly sized tunnels.

Matt Markstaller, Freightliner’s wind tunnel project manager, credited these achievements to the thousands of hours of computational fluid dynamics testing done before any dirt was moved.

“You always take risks when building something new,” Markstaller said. “We minimized those risks as much as possible with a lot of computerized design work that simulated [the tunnel’s] actual operating conditions.” Freightliner’s engineering staff, Portland State University and Mercedes-Benz Trucks in Stuttgart, Germany, all contributed to this effort.

Markstaller said a big factor in keeping costs low was his background: He’s a vehicle engineer, not an aerodynamicist. “A true aero guy wouldn’t have done things like we did because he’s trained in a certain way. A lot of elements in this project came from the fact that I had no preconceived notions about what a wind tunnel had to be.”

This non-traditional thinking is apparent in key components. Ten commercially available HVAC fans “flow” the tunnel (the alternative being a massive and pricey custom-made unit). Two small ramps hold the test vehicle against a load cell, which delivers drag-force measurements. A partial trailer-like structure protrudes from the rear wall to help mimic the currents around tractor-trailers.

During development, Markstaller consulted Rabi Mehta, a research scientist for NASA, who gave advice on materials, interior shapes and equipment. Mehta says he’s impressed with the finished facility. “I understand that the [air] flow quality is pretty good,” he said. “That’s critical.”

Michael von Mayenburg, Freightliner’s senior VP of engineering and technology, said the tunnel will be key for improving vehicular aerodynamics. He hopes to cut drag resistance 15 percent and boost fuel economy 5 percent by 2007.

Von Mayenburg’s target coincides with the Environmental Protection Agency’s next rule change on diesel-engine emissions. Any gains made in the wind tunnel might be lost when the 2007 cleaner-diesel technology is adopted. But in such a scenario, Freightliner and Thomas Built could still have an edge on competitors that are unable to offer equally slippery vehicles.

 


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