Fernbank Bridge Numero Dos

If you have visited my Projects page, you probably have seen the Fernbank Bridge. It is coming up on a year since I built that bridge. Original Fernbank Bridge Which means, it is about time to build a sequel. Unfortunately, the date for the Atlanta Toothpick Bridge Competition (where I test the Fernbank Bridge) and our Science Olympiad regional competition are the same. It also just so happens that I am busy every single time slot.

The good news is that I have a brother who is willing to take the bridge to be tested without me. I just wish I could be there to see it, and get a chance to talk with the engineering students who volunteer there.

The question is, how should I build this Fernbank Bridge #2? Should I try and improve on the design used before or start completely by scratch? I had originally planning on building two bridges this year, but since I won’t actually be able to go I will only build one. The other design I was thinking about was the simple trapezoid seen a lot last year for the Science Olympiad bridges. Without the wood size constrictions, I should be able to build a super bridge.

Take a look at how the first Fernbank Bridge broke. Most of the bridge is perfectly intact. I talked with an engineer at the event and his thoughts were that the bridge must have started twisting at the breaking point. That could be an easy fix, since last year I didn’t have much in the way of lateral bracing.

Also, I had made the bridge 18 inches long, while the span was only 16 inches. That left some of the bottom chord resting on the testing platform, which could have induced twisting prematurely. That was a dumb error on my part.

Also, the top of the bridge is 8 inches long. The metal plate that pushes down on top of the bridge is an 8 inch square. I don’t know if the top of bridge needs to be exactly 8 inches like I had it. If I did a SciOly like bridge I would make the top chord only 4 inches long or so. Or, I could try the unusual arch bridge. With the bridge being as long as it is, I could probably rig up a little platform on top of the bridge so the loading plate could push evenly down. However, you don’t often find top-loaded arch bridges. There is a reason for that, and perhaps I shouldn’t try to break the norm.

It would be fun to make an arch bridge again. I haven’t made one in quite some time. I am not counting Popsicle Bridge #2 and #3, since those aren’t proper arches; they are more Camel Back trusses. I would have an excuse to take pictures of my wood bending setup.

On a side note:
Being so close to SciOly competition time, and Fernbank, I am once again inspired with lots of cool ideas for the website. None will be implanted now, but I am working a complete redesign that might look halfway decent. I plan to work with a real graphic artist this time. The new design will contain more of the content I didn’t add when 5.0.0 was released. Hopefully the site will be much more usable. I am looking for a good site search, may have to revert to using Google’s.

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