Bridge Building Tip Sheet

• Use a small balsa wood saw (about $3) instead of an exacto knife to make cuts
• Cut small notches to connect bridge components
• Use a basic carpenter's glue
• Yellow glues contain aliphatic resin, used in the majority of winning bridges
• Fewer pieces mean fewer problems
• Keep pedestals (feet) simple
• Clamp glued pieces for about half an hour (use protective strips to avoid damaging the balsa). If you don't have any clamps you can use clothes pegs. C-type clamps are available quite inexpensively at Canadian Tire
• Design for strength at the load application point
• Construct roadway of thin, narrow strips of balsa
• Don't glue down ends of road ways…they usually bend upwards under load
• Use minimal support under roadway, except at load application points
• Roadway must support a small Hot Wheels-type car
• Most bridges bend inwards (as viewed from one end); consequently they require horizontal bracing
• Write your team number prominently on a main horizontal beam of your bridge and on both sides of the bridge
• Double check that a 40 cm-long board will fit between the pedestals (feet) of your bridge
• Double check that a 5 cm cube will fit underneath your bridge and along your roadway. You can make a nearly perfect 5 cm cube from Lego bricks
• Do not cover your bridge with any material. Glue should be used only to join components
• Use light sandpaper (number 150 or higher) to gently clean your bridge and remove excess glue
  
• Some common mistakes:
• Using a single sheet of balsa for roadway (solution: cut into strips)
• Making outside width 5.0 cm instead of inside dimension
• Making overall length 40 cm instead of span (between pedestals)
• Forgetting 2.0 cm height requirement at 40 cm width
• Not allowing room for bolt(s) on test frame

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Copyright 1980-
Peter L. Vogel