The design team made a test design bridge and we then videoed the testing process, fortunately the video was good enough to show the team where the weak points were and they then moved some balsa from areas that showed no stress to the weak areas, Balsa wood is twice as strong in tension as compression and they used this to their advantage, they made several versions until basically they ran out of time. Fortunately one team member was very skilled with his hands and did a superb job of making the bridge, my part was the use of my garage and tools and offer some advice in how to accurately make the bridge I supplied the testing rig and set up a sanding jig to get the angles right and they used my engineers square to make sure the bridge was square. One other team member analyzed the stresses and another wrote the report, the fourth team member didHi Tony, what does your daughter think was the determining factor for the increase of strength? or combination of things?
I bet it was fun putting the bridges under test and watching them crumble under the heavy hand of metal machine vs wood
Good way to test pot supports
I think that accuracy helped in the strength as all of the main bridge members took equal stresses. My daughter said the the stiffer bridge designs had the highest readings. The second place bridge of a similar design had a reading of 800-900N (she could not remember exact reading) but most where under 500N and some around 150N.
I am so impressed with strength of balsa wood 148.3 kg is more than twice my weight all on 12.5g, I have been doing some thinking about where it could be used in Backpacking and even in stoves, at the moment I think it could be used in a backpack support frame.
I do not have a picture of the winning design to post as I left my camera at home.
Tony
