Friday, May 04, 2012

bridge testing...

Today we tested the bridge models we'd made in wood shop. The lightest bridges were the winners, though one bridge made with an arched form reached a total over 600 lbs. before failure. The winners were chosen based on the the highest ratio of load to weight. We weighted each bridge, the lightest being 1 1/4 lb. and we used 80 lb. sand bags, buckets of gravel and rocks to gather enough weight to break the bridges. The strength of these simple forms was amazing. The photo below shows the winning bridge before being pushed to its limit at 301 lbs.
The photo at top shows an arched bridge just at the point of collapse.

Make, fix and create...

2 comments:

Anonymous said...

Doug,

So which design was the overall winner?

Mario

Doug Stowe said...

Mario, some of the designs that were just sticks of wood, laid horizontal with some side to side joining material supported an amazing amount of weight, but only by bending to extremes that would have been useless in bridges. The simple truss design shown in the bottom photo was winner on all counts. It supported 301 lbs without dramatic distortion and weighed 1 1/4 lb., less than half the weight of some others. All of the bridges surprised me except for one which tipped over from being poorly supported at the ends. I saw that coming.