40th Annual ME 72 Competition: Bot Hockey, Caltech Style

Recent uncharacteristic rainy weather spoiled original plans to host the 40th annual ME 72 Engineering Design Competition on Beckman Lawn. But the students of ME 72, their TAs, and instructors made the most of the change, hosting the capstone competition instead in the Jim Hall Design and Prototyping Lab, the same subbasement space in the Eudora Hull Spalding Laboratory of Engineering where the students spent hundreds of hours building, testing, and tweaking the robots that battled for glory on Tuesday, March 11.

The location change and resulting space constraints came with the added benefit that the whole event was livestreamed and recorded by Academic Media Technologies.

Every year, third-year mechanical and civil engineering Techers take ME 72, a two-term, project-based course that culminates in the engineering design competition. The details of the challenge vary from year to year. Last year's students engineered blimps that played "airship quadball."

The name of the game this year? Bot Hockey—but with a Caltech twist.

Course advisor Michael Mello (PhD '12), teaching professor of mechanical and civil engineering, drew inspiration for this year's competition from the existing bot hockey community. But he asked co-instructors Paul Stovall and Trent Wilson to design and build a 20 x 12 foot street hockey rink with a ferromagnetic surface for the occasion.

Then, beginning in October, five teams consisting of five or six students each drew up plans for a trio of robots that could take on the role of goalie, shooter, and midfielder in a rousing game of street hockey. The students were advised to place magnets on the undersides of their robots, increasing their bots' surface traction on the metal rink.

"It completely changes the maneuverability and the kinetics and kinematics of what goes on on this (ferromagnetic) floor. So that's our spin," Mello said at the start of the event. "We're not trying to change things, but we're Caltech, and we have to do things a little bit differently."

The students then spent many afternoons and weekends working in the shop with the help of TAs, who themselves participated in the ME 72 competition last year, to bring their designs to life. This year's competition involved heavy machining, with students using water jet cutters, 3D printers, lathes, and automated devices such as computer numerical control machines to cut out, print out, and otherwise engineer and refine their hockey bots.

On Tuesday, the event looked like a cross between an episode of BattleBots and a game of street hockey. Robots of different configurations sped around the rink, bashed into competitors, and tried to protect their goal while pushing or shooting a puck into the opposite goal.

The five teams, with names like Five Guys Plus Fries and Wayne Botzky, faced off in a round-robin style tournament with one team competing against another for five minutes. The various teams brought different strategies and strengths to bear on the challenge. Some engineered their three robots with as many redundant parts as possible, while others made completely unique robots for each player role. Several goalie bots included netting or other types of shields to try to block pucks headed for the goal. Some shooter bots had built-in mechanisms that allowed them to take in the puck and then quickly shoot it back out toward the goal. Other bots had scrapers in front that helped them push pucks and anything else in their way, often with tremendous force.

As the tournament went on, more and more shrapnel—pieces of acrylic, screws, and bearings from the robots—came off in the rink. Some repairs were completed in the rink with duct tape. At one point, a student cut a dangling motor from one of the robots, so the game could continue. But each team was also given two five-minute time outs that they could use as needed. And as the event's longtime master of ceremonies Gunnar Ristroph (BS '06) pointed out, the relocation of the competition to the mechanical engineering shop meant that the teams all had "home court advantage" with the ability to repair bots on the fly at the work benches where they were built.

In the end, THE VROOMBAS won third place with their extremely reliable circular robots reminiscent of vacuum robots. The final round came down to the Puckboiz, who had gone undefeated all day, and the Penguinators. The teams tied 1-1 and went into a two-minute sudden death face-off. In the final 10 seconds of the match, a Puckboiz bot drove the puck into the opposing goal with no resistance to clench the victory.

"The championship, the trophy, the everything goes to Puckboiz!" shouted an enthusiastic Ristroph. The winning team included undergraduate students Kyrillos Bastawros, Kyle Chen, Alexis Herfurth, Randy Ngo, Kristina Sevier, and Audrey Wong.

Looking back on the whole experience, members of the Puckboiz team said ME 72 is more than just a class or an assignment; it is a tradition steeped in the importance of communication and grit. Heading into that final round, one of the Puckboiz's two shooter bots had a 3D-printed shooting mechanism that had cleanly broken off, and another bot eventually losing some steering control. "But we kept going. We were like, we can still win this," Sevier says. "All our hard work—the all-nighters, collaborating on so many things—the fact that it paid off, and the way it did, was a gift."