Pressure builds as bridges are put to test in annual engineering competition

`It can only go so far'

June 06, 2007|By Sharahn D. Boykin | Sharahn D. Boykin,Sun reporter

With a loud pop and crack, it took only seconds to destroy what had taken three Naval Academy seniors a year to build.

Yesterday, newly commissioned Ensign Kevin Meier loaded the trio's 2-foot-long bridge into a guillotine-like contraption as part of a nationwide competition for collegiate mechanical engineering students.

The bridge rested between two brackets that held it steady while a mechanical foot pushed down and applied weight to the bridge.

Meier estimated the bridge, made of carbon fiber, could hold 7,000 pounds.

Pop ... crack ... the foot stops at 4,670 pounds.

There went the Naval Academy's entry in the decade-old contest by the Society for the Advancement of Material and Process Engineering Symposium and Exhibition at the Baltimore Convention Center. A sort of demolition derby for the intellectual set, it drew 50 entries worldwide. The winner will be announced this morning.

Building a lightweight bridge that can withstand several thousand pounds makes a good engineering project because it allows students to apply and test theory, said Richard E. Link, a professor at the Naval Academy.

"But it can only go so far," he added.

In previous years, bridges submitted by the academy have come in second place, said Howard Kliger, a consultant who organizes the contest. The Naval Academy contestants usually do well until their bridges are defeated by entries from the University of Washington and the University of California, Santa Barbara, he added.

Contestants used a variety of materials to build the bridges but were limited to the components in a kit. Materials include carbon fiber, fiberglass, foam core, wood and aluminum.

Most of the lightweight materials used in the contest were developed for use in the airplane industry, said Peter J. Joyce, a professor at the Naval Academy and an adviser on the project.

The academy team built the bridges to meet their senior design project requirement. Meier, Kevin Burnett and John Modrak built 20 small bridges last year before settling on the final two. Initially the team spent a few hours a week working on the bridges, but as the competition date grew closer, they spent about eight hours a week working on them.

"You do trial and error and find an idea you like and test it," Meier said.

Amid a small crowd of mostly men in casual wear, Meier stood out in his white naval uniform. He stepped up to load the second bridge, a red one made of glass and Teflon, between the two arms and braced himself as the mechanical foot slowly descended.

Pop ... crunch ...

"You want to stop it before it destroys it?" Meier yelled.

But before the machine could be stopped, the mechanical foot flew off the contraption, sparing the bridge any more damage.

Meier had also predicted that the red bridge, weighing in at just under 2 pounds, would hold 7,000 pounds. He was closer this time: It withstood 6,020 pounds.

Neither Meier nor his advisers were sure what happened with the red bridge, but they speculate that the joints failed.

"It was strong, but not strong enough," Joyce said.

"This guy ... he's the beast," said Link as he held the red bridge.

The crowd gathered around again as another contestant loaded a bridge.

"You might want to stand back," he warned the crowd.

Crack ... crack ...

"Oh!" the crowd cheered in unison at the demise of yet another little bridge.

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