Bridge Building

It was one of those opportunities that's too good to pass up.  On a lazy Saturday afternoon, Alex and I had just watched a documentary on bridges by David Macaulay.  At the end was a brief clip about how to teach the concepts to kids.  They suggested using drinking straws and pins to build a simple bridge, then figure out how to make it strong.  I realized, "hey, we have straws... we have pins!"  "Alex, do you want to try doing that?".  "Yeah!"

So we spent about an hour messing around with building bridges.

First we started with a trivial bridge "deck" 4 straws wide.  We decided to use match box cars to figure out how strong the bridge was.  With our initial design, the bridge could only hold 2 or 3 cars before buckling under the weight.

The program described trusses.  The simplified version was, "Build triangles".  So we started off with just a single triangle

That helped a little, but we soon figured out that we needed to underpin the entire length of the deck with a truss.  Using the straws, it was really easy to see and feel how the structure was stronger -- and why.

We just kept adding car after car to the load test, until finally the cars started to fall off because there wasn't room for them all!  (Not because the structure was failing!)

By the time it was all built up, the bridge was absurdly strong!  We crammed at least 25 cars onto it, and afterwards used the kitchen scale to weigh them - nearly 2 pounds!

We had a lot of fun