It happened on the ninth run of the endgame sequence, the last thirty seconds of a match when the robot had to lift all the way up and tip its final cell into the high tube. The lift went up, the arm swung, and there was a sound like a knuckle cracking, and the arm sagged and hung there, dangling a cell over the field like a sad toy.
Hector had it off in four minutes. The problem was the pinion gear that drove the arm's pivot, a small steel part the team had bought from a parts supplier in a pack of two. One of its teeth had sheared clean off. The second gear from the pack was already in use on the lift.
"We order a new one," Hector said.
Ms. Sato already had the supplier's site up. "Backordered. Ships in three to five weeks."
"Somebody else's?"
"I already posted on the forum. Two teams in Ohio have them and can't spare them before their own events." She took her glasses off and rubbed her eyes. "We can redesign around a different ratio. We'd lose the endgame lift, or most of it."
"That's forty points," Dez said. "Out of maybe a hundred and ten. We'd drop out of the top eight."
"Maybe."
"Definitely."
Nobody said anything. The beaver in goggles smiled down at them.
"What if we made one," Dez said.
"With what? The 3D printer?" Hector shook his head. "Plastic gear on a steel shaft at that torque? It'll strip in one match."
"Not plastic." Dez was looking at the broken gear in his palm. "Metal. On a lathe. Turn the blank, cut the teeth. My grandpa—"
He stopped. Ms. Sato was watching him.
"Your grandpa what?"
"He used to have a machine shop. He knows a man who still has one. Has his lathe, actually. The man bought it from him."
"Student-built rule," Ms. Sato said slowly. "Students have to build the robot. Adults can teach, adults can supervise, adults can't make the part."