Bridge Contest from Junk Yard Wars

Here is a short, fun video showing creative bridge designs from very limited supplies. These bridges were required to be under 5oz in weight, but only had to span 8 inches.

I like this video because it is pretty clear why each bridge failed. Can you see a major design issue that could be improved in most of these bridges? Notice that they do incorporate triangles, but they are missing a key member.

The students were only given

• Cardstock
• Rubber bands
• Popsicle sticks
• Tape

to build their bridges.

Do you think you could improve on their designs? If so, how?

Analysis

These bridges are relatively short, only spanning 8 inches. Two popsicle sticks would cover that distance, meaning the builders had fewer joints to deal with. While I don’t know much about this organization or their students, it looks like they have not had much experience building bridges before. For first timers, their efforts are alright. However, if they had only connected their trusses at the top with a top chord, their bridges would have been so much stronger. If they had focused on their joints, making sure the joints were stiff and rigid, their bridges would have performed better.

Note the last bridge. Sometimes a simple beam bridge is the easiest and most effective design to choose. Perhaps with the extremely limited supplies it was not possible to make a good truss bridge, and that may be why the last bridge out performed the rest of the bridges by so much. Learning to take what is given you, whether in materials or rules/guidelines, and make the best structure for that particular situation is a valuable tool to have.