Whether you are building model bridges for a school project, a contest, or just for fun, it's important how to know how to build a bridge that will last. If you follow a few simple principles, you should easily be able to build model bridges that stand up to pressure.
- Skill level:
- Moderately Challenging
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Things you need
- Graph paper
- Miniature saw or utility knife
- Clamps or clothespins
Design your bridge on paper. When drawing, pay special attention to the area where most of the weight will be concentrated. This area should be about two inches long and toward the centre of the bridge. Make one drawing for each side of the bridge.
Design the truss, or the bridge supports. Decide whether to have even supports throughout the bridge or a tapered design.
Label which areas of the bridge will require more strength. Use a total force of 100 to calculate how much force each piece of the bridge will need to bear.
Go to the hobby store to buy wood and glue. Make sure to get wood that is dense enough to withstand the weight you will be putting on the bridge.
Tape one design down to a flat surface. Cut each piece of wood to size using a miniature saw or utility knife. Tape the top and bottom of the bridge to the design. Place the side supports and glue them down. Place something heavy over the wood until the glue dries and repeat the process for the other side of the bridge.
Once the glue on both sides is completely dry, take two piles of books and put them at a distance equal to the width of your bridge. Tape each side of the bridge to one of the piles of books. Take two pieces of wood and glue them across the top of the bridge. Repeat on the bottom of the bridge. Follow your design to continue making horizontal connections across the bridge.
When the glue has dried, take the bridge off the pile of books. Glue connections on the bottom of the bridge.
If the bridge appears to be leaning, pull it back into shape with clamps.
Let the glue dry for 24 hours.
Tips and warnings
- When buying wood, keep in mind that darker woods are usually stronger than lighter coloured woods.
- Balsa wood tends to be weaker than basswood.
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