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The Quest For the Best
Toothpick Bridge

Well, the saga continues. After starting to get a couple emails from physics students wanting help deciding what sort of bridge to try, I thought I would look around myself.

I stumbled across the Japan Aviation College's Annual competition. The very interesting thing about this was the history. They have been doing this for about 5 years. Each year, the winning bridge holds more weight. From something like 20kg to 120kg!

The Japanese are pretty sharp!

It seems like there is always a dichotemy in design. Especially in the fineness possible with mathematics. In a span the size of these bridges, given the crudeness of the construction method and the inherent weakness in the materials, what is more important, the exact shape of the curve, mathematically speaking, or the curve that maximizes the strengths of the building components?

The restrictions and rules of competitions vary greatly.

Two things come to mind when I consider these differences. How will the bridge be tested? Is there a maximum weight restriction and will there be an award given for the best ratio of weight held to bridge weight.

The winning design seems to maximize the bridge design for the contest rules and the strengths of the building components.

In the case of the animated loop in the corner of this page, notice the simple triangular truss. The triangle is one of the strongest shapes in math or nature.

I also wonder, from seeing the testing setup, whether the bridge is allowed to exert a lateral force on the testing table. I think this would be a distinct advantage. When I was a boy, I used to climb up the doorway of our kitchen by just putting one foot on either side and wedging my weight between them. If the toothpick bridge is allowed to press laterally on the table, then the tension aspect of the base of the triangle may not be doing its job.

While you're here, let me know what you think of this page in an email.

If you would be interested in more detailed instructions or other designs, let me know that as well. I would like to hear about the rules for various contests and how the grading and testing is done. My name is and just click on it for my email.

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