Week 7

Last week in class we had the chance to test out our bridge. With the new gusset plates, the bridge was able to hold 21.4 pounds while retaining its $216,000 cost. It cost us $10,189 per pound and it spanned about 2 feet in length. Using a different set of gusset plates gave us joints that didn't come apart too easily and allowed us to use better angles for connections. We simply tried to have a low cost to weight ratio and use simple shapes to build our bridge. We placed focus on distributing any weight placed on the bridge and reinforce the joints. Our bridge performed pretty well and we were happy with the results.

Using K'nex made things a bit harder to understand than using WPBD. We can't see any of the stress or tension on individual parts nor can we use as many angles. I still hold on to the belief that spreading out the weight as equally as we can to all the different parts would give us the best cost to weight ratio so my goal is to find the shape that accomplishes that. The shape that I had the best success with in WPBD was an arc with triangles supporting it but this cannot be done with the K'nex since we were limited in angles and part lengths. The joints on the K'nex are also weaker than WPBD as they are more prone to coming apart under stress. Figuring out how the force is applied to each part through equations would possibly help us spread out the weight among each part and help us develop a better cost to weight ratio. This week we plan to modify our design to fit the 36" criteria for the next group bridge. We plan on mainly using the elements of our current bridge but we might make changes depending on whether they lower the cost to weight ratio or not.