Hundreds of college engineering students recently experienced the thrill of Formula SAE (FSAE), SAE International's series of competitive challenges for open-wheel racecars that were designed and built by school teams from around the world.
The 97 FSAE racecars doting the infield of the Michigan International Speedway (MIS) on May 13-16 featured naturally aspirated or turbocharged one-, two-, or four-cylinder engines riding on carbon-fiber or steel chassis/frames. In creating the different racecars, each team made engineering decisions based on cost, time, and other factors.
The University of Akron began preparing for the 2009 Michigan event just two days after the 2008 competition. Frequent meetings and daily discussions defined team members' lives outside the classroom.
"The only day we weren't down in the shop was Sundays. We really tried to set ourselves up this year to not have to make any sacrifices," said University of Akron Team Captain Tim Gullatta as team members encircled their prized racecar during the first day of design judging inside an MIS garage. Akron's racecar was deemed ready for track testing and suspension setup in mid-March.
"We were going to run a blade-style antisway bar, but we went with a U-tube style," said Gullatta. "We had to do that as a last resort because we needed roll control on the car during track testing."
This year's 63.3-lb (28.7-kg) welded chassis gained about 4 lb (1.8 kg) from the 2008 entry. "Weight was not a chassis design goal for the 2009 car. Our goals for the 2009 chassis were to remove the rear box (giving the car a stronger mount for the differential), increasing the rigidity (949 lb·ft per degree in 2008 versus 1510.3 lb·ft per degree in 2009) and increasing driver legroom," said the team's Chassis Leader Jeff Wilson.
Even though carbon-fiber upper A-arms for the front suspension of the University of Colorado at Boulder's FSAE car underwent FEA reviews, "hard driving is the ultimate test," said Loren Heiman, fabricator of the components. The 2009 car did not debut carbon-fiber arms because "we didn't feel the carbon-fiber/aluminum lug front upper suspension A-arms were sufficiently tested on the car, so we went with 4130 steel upper front suspension A-arms," said Heiman. "We initially considered using carbon-fiber lugs, but that would have required a female mold as well as a male foam insert, which would have meant almost twice as much machining."
Rutgers University opted to forgo using an aluminum rear subframe produced by a water-jet process. "In previous years, we had a removable rear subframe that mounted directly to the engine and that made for a semistressed engine," said Christopher Keane, the team's Drivetrain Leader. The 2009 car sported rear-chassis-mounted differential carriers. Said Keane, "We now have a completely symmetrical drivetrain and that helps prevent torque steer. It's also easier to service because the parts are interchangeable side-to-side."
A nagging issue during a Sports Car Club of America (SCCA) autocross event three weeks before the FSAE Michigan competition prompted the team from the U.S. Naval Academy to re-evaluate using pneumatic gearshifts. "The transmission wasn't consistently getting in and out of gear every time. We decided to use a bolt-on, stick-style manual transmission at Formula SAE because the push-button pneumatic system wasn't reliable," said Midshipman First Class Ryan Golom. "We can't design for everything, so our number one goal was to design for reliability."
Like the U.S. Naval Academy, students at the University of Kansas design and build an FSAE racecar from scratch every year. The 2009 entry was the first in the University of Kansas' FSAE program history to incorporate an aerodynamic package focused on composite front and rear wings. "The three-piece rear wing is adjustable to four different positions—same with the front wing," said Robert Schelling, an exchange student from the University of Stuttgart in Germany.
Aerospace engineering student Schelling used Dassault Systemes' SolidWorks FloWorks analysis software to optimize the wings for minimum drag and maximum downforce. Knowing the 2009 car's ground effects might connect with the orange cones outlining the autocross course, the front wing was "designed to withstand cone impacts because the endplates and mounting plates are reinforced with additional plies of carbon fiber," said Schelling. According to Robert Sorem, University of Kansas FSAE Team Adviser and mechanical engineering professor, "It's not possible for them to do every imaginable design target because of time and money. Goals have to be set."
Michigan State University missed its primary goal of competing at FSAE Michigan. The debut of the team's first racecar—designed in tandem with computational fluid dynamics (CFD) software—was foiled by various manufacturing setbacks. Virtual assists on the racecar included using CD-adapco's STAR-CCM+ "to revise both the body design and develop an underbody which increases down-force while reducing drag on the car," noted James Guitar, Aerospace/CFD Team Leader. CD-adapco's engineering simulation software also was used to refine the sidepod and the radiator inlet designs.
Computer renderings played a significant role in the design of the University of New Hampshire racecar. "This is the first year we used a complete CAD vehicle model of the car right down to the nuts and bolts," said Jeremy Seiferth, the team's Technical Captain. With the exception of brake rotors, the 2009 car was an all-new package. Using math data as a design-for-build template, team members were spared hours of assembly aggravation. "We know from observation and past experience how much of a pain it is to take something apart when it doesn't fit," said Seiferth.
Teams that used digital design and analysis tools impressed design judge Ken Sperry, a former General Motors engineering group manager for airflow and power development. "I ask questions to see if team members are thinking logically. Are they supporting their decisions based on logic and data? Is the data coming from computer simulations, CFD, airflow testing, dynamometer testing? Have they grabbed a stopwatch and checked acceleration times? I want teams to back up their decision-making with data. It's also very important to see balance as it relates to cost, complexity, weight, power, and other considerations," said Sperry, a 19-year FSAE judge.
In addition to FSAE static evaluations addressing cost, presentation, and design, teams competed in acceleration, skidpad, autocross, and endurance dynamic events. Pennsylvania State University at University Park had the highest score in the static events. The winner of the combined dynamics event was Austria's Graz University of Technology. Lakehead University won the William C. Mitchell Rookie Award for best finish by a first-year team. FSAE teams on the grounds of MIS in Brooklyn, MI, included schools from Austria, Brazil, Canada, Japan, Singapore, South Korea, Venezuela, as well as the U.S.