The University of Michigan leaves Beatrice, Nebraska at a starting speed that is slower than normal; Michigan is winning, so it can afford to adopt a conservative strategy. After all, the drive ahead, moving west across Nebraska, is the most energy-consuming part of the race; the roughly 450-mile-long stretch between Beatrice and the End of Stage 3 location is almost entirely uphill.
Soon after leaving, the Strategy team sees more radiation in reality than their models show, so they have Aurum speed up a little, still playing it conservative.
But still, Aurum’s power numbers are higher than usual; the solar car is working harder than it should be. Typically, Strategy can tell if anything is wrong with the electrical systems of the solar car by looking at its telemetry data. In the Chase vehicle, however, the telemetry shows nothing suspicious. Engineering Director Clayton Dailey is driving, and similarly, he feels nothing out of the ordinary. Solar car drivers can sense something is wrong when the relays click, if the steering wheel displays any errors, if they hear any abnormal sounds or feel that the car isn’t handling acceleration well—Michigan puts its solar car through enough testing that drivers can tell when things are functioning normally and when something is off. But there seems to be no clear-cut reason why the power numbers are so high.
As the 6:00 PM End of Day charge approaches, Aurum’s front right tire pops and Clayton pulls off onto the side of the road as quickly as possible.
In about 12-15 minutes, team members complete a speedy tire change to replace the flat—and then, they hear hissing. This is very unexpected; it is a new tire, after all.
The team looks for the leak in the new tire. Crew Chief Perry Benson looks underneath the spats, the carbon fiber covering of the wheel, and gets close, listening carefully, trying to ascertain where the hissing noise is coming from. He spots it: a crack on the front right rim so thin that it looks like a piece of hair. Perry licks his finger and places it onto the hairline crack. “I could see bubbles,” he describes. “I knew it had cracked and was leaking.”
Everyone is surprised—and they should be. the probability of cracking a rim is extremely low. The team moves on to change the rear right tire as well, and to everyone’s shock and dismay, this one produces a hissing sound, too. The chances of cracking one rim is small enough, but two? Unheard of. The team ran them through all sorts of analysis and checks.
The team shifts its gaze forward and moves past its initial concern, concluding that general wear and tear—fatigue—is to blame for the incident. After all, these same rims have already gotten Aurum through thousands of miles—10,000 miles.
Michigan takes all of the rims and switches them out for spares, marking the old, damaged ones with red tape.
The team goes on to an End of Day location just outside of Alliance, Nebraska. Just as it does before every charging period—Start of Day, End of Day, checkpoint, and Stage stop—the team un-tapes the seams of the car, where 3M 471 vinyl tape holds the upper and lower portions of the car together. Aurum charges. Aurum charges, but it isn’t sunny enough for Aurum to gain back a lot of the power it expended during the day. Michigan is concerned about its charge and the implications that will have on performance tomorrow.
Despite the problem posed by the flat tire and the cracked rims, Michigan is able to get back onto the road fairly quickly; the race crew went through tire change drills before the race, and it has paid off. The University of Michigan’s foresight, preparation, and steady hand under pressure controlled and minimized the impact of the situation, ensuring that it would not end up negatively affecting the remainder of the race.