Solar Racing Car Team Optimizes Unique Aerodynamic Design

Driver, Clayton Dailey, is ready for a ride in Aurum. Note the bulge in the chassis to accommodate his elbow. Image courtesy of Evan Dougherty, Michigan Engineering.

The eight-time winners of the American Solar Challenge, the University of Michigan (U-M), have unveiled the car they hope will propel them to a global win at the World Solar Challenge across Australia in October.

Dubbed “Aurum,” this golden vehicle is unique because of the placement of the cockpit behind the front right wheel. In fact, the chassis needed to be extended to accommodate the elbow of the seated driver.

In the last race, a rule change forced the cars to use four wheels instead of an option of three or four wheels. This change in the rules had U-M pondering and simulating a new set up for their vehicle.

In a three-wheel vehicle, a driver can sit behind the front center wheel with limited effects on the aerodynamics. However, when moving to four wheels, a center-seated driver no longer has this advantage.

"Last time, we realized the car is faster with the driver to one side," said Edina Lee, an electrical engineering sophomore. "This year, we said: What's the best version of a car with the driver to one side?"

Smokey Yunick capsule car. Photo courtesy of Carbon Press.

Therefore, much of the optimization for this car focused on the aerodynamics. U-M teamed up with engineering firm Exa. This sponsor helped the team to simulate more than 100 geometries using computational fluid dynamics. This optimization led the team to the quirky location of the driver seat reminiscent of the Smokey Yunick Indianapolis 500 capsule car.

The team isn’t shy to use high-end engineering software. For their latest win in the American Solar Challenge, the team used Siemens PLM software to design that race’s vehicle, named Quantum.

"It's a funky shape by the driver," said Pavan Naik, a junior at U-M studying industrial and operations engineering. "Drivers will actually be able to see the outer edge of the car when they look out the front windshield."

Another unconventional change saw the team move the steering wheel to the right side to better hug the road.

Jiahong Min of the U-M solar car team gives the car, Aurum, some love. Image courtesy of Marcin Szczepanski, Michigan Engineering.

"For the last race in 2013, the team built a good, safe, reliable car. This year, our emphasis is on the competition," said Lee. "We pushed really hard for a car that we think will be the fastest. For every element, we worked on not just improving what we had before, but making it better than anything out there."

For this race, the students focused on optimizing other systems as well. For the electrical system, U-M sourced a top-of-the-line, six-meter solar array and added a coating to improve the array’s efficiency. They also improved the mechanical system’s brakes, steering and suspensions.

After all was said and done, Aurum weighs in at 550 pounds with the driver. For reference, this is about a third of the weight of a Smart Car. This light weight can be attributed to the carbon fiber body and roll cage. The team reports that the car is safer and lighter than their previous versions.

The World Solar Challenge will see the U-M team race Aurum through an 1,800-mile course through the Outback. The race, for which it takes two years to prepare, will last eight days. Though U-M has won the American race eight times, they have yet to take gold on the world stage, settling instead for three bronze finishes.

As a result, the team will now focus on getting each driver ready to race. "There are two facets to a race — the car and the team," said Naik. "For the car, once you're done designing and building it, you can make small improvements, but for the most part, that's it. Now it's time to get the team ready."

For more on U-M’s solar racing team, follow this link.