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PDF plans for a 36cm or 44cm, Page 2
and a 41cm or 50cm Rainbow Bridge.
Coffee stir stick model
Plan for a 30cm bridge
Hey Frank, we took first place in the technology category!!! Kim
Properly assembled, the bridges in the above plans can carry 1,000 times their own weight but they are not the ultimate design. Use them as a starting point. The parts are few and easy to duplicate, so you can use your time more efficiently evaluating different configurations. Make several bridges and test your ideas.
When you test the load limit of your bridge, catastrophic failure is unlikely. As soon as the first glue joint pops, repair it and think how you can reinforce that weak point.
You can scale the measurements of the parts for longer building material.
What can you lighten? What needs reinforcing? Does doubling the thickness of the sticks increase the efficiency? Does the truss railing increase efficiency? Do 3 or more arches in a bridge increase the overall efficiency?
Some things you might consider:
- An arch needs fixed feet to carry a serious load. If you just place it on a flat surface, you'll have to tie the feet together with non-stretching string or wire, else you'll just have a weak beam bridge carrying less than 50 lbs.
- Sand the surfaces to be glued. Boards might be rough, warped or have splinters around the holes or a glaze on them.
- Don't clamp pieces together too quickly. Let the glue soak in for a few seconds or prime the surfaces with a thin glue solution first.
- Leave your glue lots of time to set. Read the glue instructions.
Have fun :-)