Last week, we finally tested our bridge and it loaded 34-pounds of sand. At first, the bridge wasn't long enough to fit in a two foot long span. Therefore, we decided to add an extra 2.125" long chord on the base. By doing this, the bridge became symmetrical.
The bridge started to twist when we added weights because of the structure of our bridge design. We added an extra 5' long chord on the top truss to make the bridge more stable. However, the 5" long chord was beyond the width of the bridge, so it didn't fit too well with the gussets. When we added the load, the bridge started to twist lightly. There were two groove gusset plates in the middle which pulled apart, at first. Then two members from the support points could not hold the load any more, so the bridge collapsed. We planned to fix these problems on our next three-foot bridge design.
For K'NEX numbers, I would like to know the accurate tension of every piece truss members during the bridge loading. That would help me to design a more serviceable bridge by calculating some trigonometry functions with those databases.
Next week, we will start designing the three-foot long bridge on the basis of previous designs.
- Yilei Jiang
No comments:
Post a Comment