Bridge Building

I was introduced to the world of balsa wood bridges in my sophomore year, when I had to make one for a physics project. The requirements were fairly straightforward: the bridge had to be made of 1/8" x 1/8" balsa wood, and had to pass a minimum width (the bridge itself was to be suspended between two tables, with a hanging weight). I decided to experiment with the design - most of my classmates were using truss designs, but those were inefficient, especially for this scenario (the bridge was fairly long, and only touched a surface on two sides). I opted for an upside-down arch design, which ended up working too well. I overbuilt the bridge, exceeding the maximum allowed weight, and holding the maximum 15kg mass without any trouble at all (four arches, on retrospect, was overkill).

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My next major bridge was in my first Science Olympiad competition (same year) - I was in charge of the Elevated Bridge event. This event was a lot more difficult than my physics project: the bridge was much longer, and had to be elevated so a mass could pass underneath it. I used a different arch design, right-side up and incorporating arches on top of arches. The design worked out nicely (it broke just before the maximum weight, achieving maximum efficiency), but it wasn't as strong and I felt that I could do better.

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The next year, I felt a lot more prepared for the Elevated Bridge event, which I was in charge of yet again. The rules required a bridge that was even longer and higher this time - it was very challenging! I decided to go back to my upside down arch design, adding legs and increased stabilizers (for fear that the bridge would tip over). This bridge ended up being the best yet - very solid, yet not too heavy. It just barely held the maximum 15kg; you could hear wood straining at that mark. Fortunately, it didn't break, so I took it home as a keepsake.

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Building balsa wood bridges has been very fun these past three years! It's definitely a worthwhile experience, buying, sanding, steaming, gluing, and cutting the wood. I've learned a lot more about bridges as a result, and got a hands-on experience that was lots of fun at the same time.