When Chris Patton was helping his Formula SAE team design a racecar for international competition, he made an unusual suggestion: angle the rear wheels outward in relation to the car. Common knowledge would warn against that move. Turning the rear tires outward makes the car less stable.
But Patton, a Ph.D. student in mechanical engineering at Oregon State University, had a powerful tool at his disposal: the ability to simulate the impact of that move.
The results were surprising — and positive.
“We would tell design judges at the competition that we were doing this, and they wouldn’t believe us. We would have to measure it in front of them,“ he says. “They’d tell us our car would be slow and undriveable. And then we’d go out and be the fastest car in competition.”
Being the fastest is one of the reasons why Oregon State’s Formula SAE team, in partnership with a student team at DHBW-Ravensburg in Germany, has been so successful. In May 2012, the team won for the third consecutive year in the U.S. championships in Michigan. In 2011 the team won Formula Student Germany, which is widely considered to be the premier competition in the world.
The trick for Oregon State’s team, at least in part, has been computer simulation. During his seven years with Formula SAE (sponsored by SAE International, formerly the Society of Automotive Engineers), Patton has set the team apart by expanding the range of parameters used in designing its car. The flexibility of Patton’s modeling structure is one of the key parts of his dissertation.
“We can basically program the car in a computer and make comparisons between different cars without having to build them,” Patton says. “I can say, ‘You want to add this parameter? And this parameter? Sure, just add it in.’”
By “program,” Patton means he writes scripts in the programming language MATLAB that represent all the characteristics the team needs to consider when designing a car — whether to turn the rear wheels outward or to make the body of the car narrower or wider.
He starts with processing tire data collected by the transportation research company Calspan and the Formula SAE Tire Testing Consortium. To the uninitiated, it might seem like the raw power of the engine is what drives the car’s motion. But tires, Patton says, are the foundation for the cars the team builds.
“Tires are where all of the motion of the car comes from,” he says. “All of the forces that dominate the movement of the car come from the tires.”
Tire data give him information about how the tires behave when they’re in motion. For example, he gets measurements for friction against pavement, tire pressure and temperature, and how tires behave when the driver applies the brakes.
Having a detailed sense of what the tires will do ultimately gives the team a much better idea of how to design other elements of the car, and it helps them understand how those elements will behave in competition.
“I’m pretty confident that no other teams are doing the modeling at the level we’re doing it. There might be some that are close, but I don’t think it’s very common. I would say that’s something unique to us,” Patton says.
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Note: See Relentless, a video about Oregon State’s SAE Formula racing team.
