Mousetraps, rubber bands, and 67 future engineers

In Shriver Hall Auditorium, a large A-frame structure supports a 10-foot cable, at stage center. But today's show isn't a theatrical production. It's a race between 23 contraptions, costing no more than $15 apiece, to see which can traverse the cable fastest, dropping a payload most accurately on a bull's-eye below.

The scene is a command performance for 67 Johns Hopkins freshman engineering students, concluding the Freshman Experiences in Mechanical Engineering course with a mousetrap and rubber band challenge aptly named "Hang in There." The annual competition is a hallmark of the undergraduate experience at the Whiting School of Engineering, requiring students to think creatively, solve problems differently, and learn from often-made mistakes.

"Most students want to go straight to the lab," says Steven Marra, a senior lecturer, who is teaching the course this year. "With this challenge, we force them to think about how energy is transferred, what obstacles they will encounter, and how they will accomplish a goal, before they start building a prototype."

The assignment: Use two mousetraps, six rubber bands, and $15 of materials to build a vehicle that will start on a cable (five feet above the ground), traverse it (without falling), and release a payload (a 20-gram weight) in order to hit a bull's-eye drawn on paper below. There's no pushing or pulling. Vehicles must battle friction and convert stored energy to propel vehicles forward and release the weight.

As the race begins, students clutch a wide array of contraptions. Double-Trouble, designed by the only all-female team of Amy Sun, of Canton, Mich., and Samantha Lott, of Boynton Beach, Fla., uses a trap door for payload release. Team Accuracy, designed by Sydrake Abdi, of Martinsburg, W.Va.; Alexandros Bennink, of Paris; and Mary Theresa Nahill, of Winchester, Mass., makes a battering ram from rubber bands. "Basically it's like a slingshot," Abdi says. Release the Kraken uses the energy from the mousetrap to turn an axle, which both turns the wheel (moving the vehicle forward) and drops the weight.

A few vehicles perform flawlessly to "oohs" and "aahs" of the crowd. Others succumb to mishaps such as a snag on the cable line. In the end, it comes down to Release the Kraken against the R&B Butterflies.

"This is it. On your mark, get set, go," shouts Marra. The crowd goes crazy. Release the Kraken flies across the cable, drops the payload, hits the bull's-eye dead center. "Yes!" shouts Luke Brown, of York, Pa., who wins with partners Evan Adamo, of Syracuse, N.Y., and Josh Harris, of West Windsor, N.J. The prize: A $25 Barnes & Nobel gift certificate for each student on the team.

For others, the learning experience is just as sweet. After filling a notebook with more than 40 ideas and working on his team's prototype for weeks, Bennink, of Team Accuracy, concludes: "I learned that you have to pick the right design rather than the one that comes first to your mind. The design that sounds the best at first isn't always the best in the end. We found that it's best to get as simple as possible."