Cal Poly’s Steel Bridge Team will decide this month if “home-made” will be the recipe for success at this year’s national collegiate competition.
The Steel Bridge Competition requires teams to build a 21-foot long bridge that can carry 2,500 pounds. The team is not purchasing pre-made parts for its bridge. Instead, the team is constructing all of the parts in its workshop.
“For the first time ever, the team is constructing a homemade bridge,” Lucas Hoffmann, a civil engineering senior and project manager, said.
The Steel Bridge Competition score is based on three factors. The judges score teams on how many people are in the bridge-building team, how long it takes to build the bridge and if the bridge can carry 2,500 pounds at any randomly chosen area.
In previous competitions, Cal Poly’s Steel Bridge Team did not finish as well as the team had hoped, said civil engineering senior and fabrication senior captain Riley Jones. In 2009, the team finished in 33rd place in the nation. Last year, the team finished in 12th place.
During last year’s national competition, the team saw another school use modified connectors in its bridge construction. Connectors are the pieces in the bridge that act as a bolt and nut, holding the different parts of the bridge together. The other school manually filed off two opposite sides of the threading on the connectors, for easy and instant connections, rather than using valuable time to screw together the connector.
“Connections are what will make or break your bridge in a competition,” Hoffman said.
Unlike the other team that manually filed the threads from the connector, the team uses machines that de-thread the connectors to exact measurements.
“Making our connectors, it’s never been done in such a precise way,” Jones said. “As Cal Poly students, we are fortunate to be able to access these machines to be able to do the work we have been doing.”
The team is using a CNC Lathe Machine. A lathe is an electric tool that rotates a piece on its axis along with making symmetrical cuts. The machine takes off the threaded tracks in each connection, one by one. The connectors are cut to bare metal on two opposite sides, one-fourth part of the cylinder, leaving the other two, opposite one-fourth parts with their threading.
The result of shaving threads off parts of the connectors makes snapping the pieces together quick. The normal connectors must be screwed together like a nut and bolt, which takes valuable time.
It takes each connection 13 minutes to be adjusted to the partially ribbed design. The machines need one of the captains to direct it by typing in dimensions, and setting up the pieces in the machine.
“This year the machines are going to make the biggest difference for us in the competition,” Hoffman said.
The team members began their designs three weeks before school started in the fall. They attended a program over the summer to begin analyzing the different structures of the bridge. The designing was finished by the first week of October.
Connections are a critical part of the bridge’s structure, but not the only ingredients.
“The welding takes up a good 20 hours a week,” Daniel Lister, a civil engineering senior and welding captain, said.
The team gets 3-foot steel tubes. Team members then weld seven steel tubes to create the skeleton of the bridge.
The American Institute of Steel Construction and the American Society of Civil Engineers made a few adjustments to the 2011 competition. The bridge must have each member, the individual vertebrae to the bridge, fit into a box 3-feet-long, 6-inches-wide and 4-inches-deep. The bridge also must include cantilevers, which are unsupported end pieces of the bridge.
“We spend 30 to 40 hours a week constructing our bridge,” Hoffman said. “The superiority of our connections make us way ahead of the competition. No steel bridge team in Cal Poly has ever put as much time and effort in as we have this year.”
During the competition, four teammates will split into pairs: the runners and the builders. The bridge parts are placed 30 feet away from the designated building area. The runners have to carry the pieces over to the builders. The builders manually construct their bridge. Both groups have boundaries, whereas the runners can’t be too close to the building area and the builders can’t be near where the dismantled bridge parts lie.
The regional competition is on March 23 through March 26 at California State University, Los Angeles. This year the team is looking to place nationally by doing its own welds, making its own connections and spending more than 30 hours a week on the project, Hoffman said.
“We want to begin building the program this year,” Hoffman said. “This year will begin the stepping stones to a tradition of finishing the competition well.”
This article was written by Ellery White