The Paper Bridge Game gave each team 20 sheets of standard copy paper and 14 feet of masking tape to create a bridge spanning 20 inches. No attachment of the bridge at the abutments was allowed. Both teams were allowed unlimited materials for advance testing of structures. The bridge able to sustain more load at the center span was the winner. Here, Alex and Chloe are consulting Lilly's 3D renderings of their team's proposed design, with several trial truss structures on the table.
The finished bridge, ready fro weight loading from the center of the span. (The black string is attached to a bucket, which is then loaded with plates until the bridge fails)
Alex loads in plate after plate until finally....
The two beams supporting the southwest side of the truss buckle and collapse due to compression loading, an impressive and unexpected failure. Before failure this bridge held over 8lbs, almost quadruple the weight of the losing bridge. Interestingly, the losing bridge was very educational also because it was a very strong design with one fatal flaw, namely that it did not incorporate any twist resistance in it's very robust and simple truss structure, and so failed through twisting and distortion without any buckling due to compression or ruptures due to tension. (sorry no camera was out during the testing of the losing bridge)
The tower challenge was to build a tower using tiny balsa sticks, each about a foot long, and 2.5 x 5 mm. in section. A budget of 168 sticks was allowed and the goal of the tower was to support a weighted tennis ball (about 3.5 ounces) within one foot of the ceiling in room 211. Andrew was the chief engineer for the base of the tower. With coaching from Scobie and help from Tamlyn, he built the larger structure that was intended to support approximately the first 4 feet of height. Reinforced tetrahedral buttresses were added at the bottom for stability.
Scobie proposes a method for checking the straightness of the top courses of the tower structure. Too much distortion will lead to collapse.
After producing most of the vertical truss pairs for the upper sections of the tower, Joy creates a triangular course station, required for 'hoop strength' at each course joint.
A larger course station is tested for a level fit at the top of the lower tower section.
Simon assembles a triangular station.
Tamlyn and Andrew finishing the lower structure
A tennis ball's view. The three close struts at the top of the tower will cradle the load. This view is through those struts looking into the upper tower structure which is now over 6 feet long.
A look through the center of the upper tower structure from its other end
The tennis ball (loaded with BB's for weight) is perched atop the upper structure within the '1 foot from the ceiling' goal and the upper structure is loaded onto the lower structure and taped in place.
An ominous leaning is immediately apparent, quickly earning the tower it's name: The Leaning Tower of PSCS!
The reinforced and buttressed tower base. Rules call for the base to be free standing (no attachment to the floor)
Despite the leaning, the tower holds! A proud tower team gazes up at the tennis ball. Luc madly calls Andy downstairs in the office, knowing he'll want to see this structural victory! The final tower weighed less than 12 ounces and stood freely over 14 feet tall while successfully supporting a 3.5 ounce weighted tennis ball within one foot of the ceiling!
After 2-3 minutes, the leaning superstructure is more than the joints can bear, and the top three feet hinge over, dumping the ball into Joy's hands.
A view of the entire tower taken from ground level from within the base of the structure.
Joy holds the “Icarus” ball after it's fall from grace. The tower remains stable.
