Strong arms
A cantilever is an arm-like building structure that sticks out from a supporting structure and usually bears a load or weight of some kind. Cantilevers are used everywhere. The most common use is as a support to hang signs, but they are also used in bridge construction.
With this project, you will be the engineer. You will design and build a cantilever structure (a "strong arm") a minimum of 60 cm out from the side of a table using only newspaper, string and tape.
Materials
- newspaper
- broom handle or similar piece of wood – doweling (to roll newspaper)
- masking tape
- string
- plastic cup (or yoghurt container)
- marbles, pennies or other small, heavy items
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Procedure
- Design and build a strong arm. There’s no right or wrong way to build a strong arm, just do whatever you want with the materials. Remember, you will hang something off your arm 60 cm from the table edge, so make sure your arm is at least 60 cm long.
- Attach your strong arm to the edge of the table.
- Make the testing device by attaching a string to the plastic cup (or yoghurt container) so the cup won’t tip.
- To test your strong arm, hang the cup from your arm 60 cm out from the table. One-by-one, add marbles or pennies to the cup. Once your arm has broken, you can weigh the cup (or count the marbles or pennies) to see how much it held. (If you don’t want to break your arm, stop adding weight as soon as there’s any bending.)
Taking it a Step Further
Think you can improve on your first design? Record how much weight it held and try again. See if you can improve your results. Build several arms and try to find out what design works best.
Hints and Tips
Engineers use various techniques to strengthen structures. Bundling is a technique in which a collection of materials is fastened together. When bundled together and tied securely, the material is significantly stronger than individual items in the bundle.
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