Pikes Peak, Colo., 23 June—The bug of the day for the Ohio State students and their Buckeye Current electric motorcycle is a throttle that suddenly quits.
It surfaces in today’s first run to the summit in by Rob “The Bullet” Barber, the bike’s British pro driver. On the way down the motor cuts out, and though it takes Barber just a few seconds to reset the system, seconds matter.
Today’s runs are just time trials, and they cover just the top third of the the Pikes Peak International Hill Climb course, which starts halfway up, at the Devil’s Playground—named for its affinity for lightning—and rises 407 meters (1,335 feet) to the summit, which towers 3895 meters above sea level. That’s two and two-thirds miles.
Tomorrow come the qualifying rounds, and on Sunday, the race itself—the only time Barber will get to ride all the way from the bottom to the top. If the motor cuts out periodically, it’ll cost him time—and confidence. For instance, when his motor stops during coasting—say, through one of the scores of hairpin turns here—he’d have to wonder whether it’s dead or merely resting. Will it be be there to give the jolt of power he need to accelerate out of the turn?
The motor’s cutting out is “a little disconcerting,” says Aaron Bonnell-Kangas, the leader of the team and a graduate student in electrical engineering. “Though we’ve had problems with the throttle cutting out before, it was at high speeds; this one came after the run was over.”
“Holy crap, he hit 3,000 rpm’s,” says Polina Brodsky, a fourth-year mechanical engineering student, as she looks up from a laptop screen that’s analyzing the mass of data downloaded from the bike, now standing in the team’s pit.
“We put a lot of effort into designing these electronic systems” to analyze data, says Sean Harrington, a team leader who studies electrical engineering. “We design with debugging in mind.” That provides a search-and-destroy power that comes in handy during the frantic days before a big race.
I ask Bonnell-Kangas what’s so bad about 3,000 rpm’s, and what the old problem with the throttle was all about.
“It was caused by the inverter,” he says, referring to the device that turns a battery’s direct current into alternating current, which changes direction in regular cycles. “The motor is synchronous, which means the inverter has to keep up. The inverter is rated at 500 Hertz [cycles per second], which corresponds to 3,000 rpm in the motor. Above 3,000 rpm the inverter would try to put out more power than it could. So we designed a control system to keep the motor below that critical speed.”
The mystery is why the motor cut out going down the mountain. Was the motor revving to no purpose?
Barber offers a clue during his subsequent time trials. “The first time, it cut out on the way back,” he tells Bonnell-Kangas. “The second time, after a hard run, it cut out just at the finish; the third time, it cut out earlier. It’s cutting out further back every time. I reckon something’s about to fail.”
After three hours on the mountain the team heads home, and though the ride is all downhill, their workday—which began at 3:30 am—is only just beginning. They have found their bug, but they still haven’t tracked it to its lair and killed it.