Charles Pringle (Mechanical Engineering Technology)
A model for a strong bridge that could span a set distance and rise up to allow for passage underneath was requested, and specifications for the design were given. The catch was the bridge portion needed to be made of exclusively balsa wood and glue. The model bridge was designed out of balsa wood to meet all the requirements. Using structural and material analysis and simple mechanical designs, a bridge was designed and constructed out of balsa wood, wood glue, and metal components used for articulation that met all of the criteria set by the assigner. The bridge was tested to ensure all specifications were met. The resulting bridge can hold 20kg of weight suspended from the center and rise 1400mm above rest, while remaining locked in the raised position. It spans the 400mm distance between the two abutments it was designed to rest on and allows for a car to pass over the bridge without raising over 25mm at any point. The overall weight of the bridge did not exceed 85 grams, and the road deck rested within 12mm of the abutment, allowing for the model cars to access the bridge deck with ease. Aside from an 8mm hole in the road deck for testing, no other obstructions were present. The resulting product was a functional and effective model of a bridge that, when tested, successfully held the required weight and could also easily be raised, locked, and lowered for passage beneath the bridge.
Keywords: MODEL BRIDGE, BALSA WOOD, TRUSS