In today's green-friendly world, people constantly look for ways to reuse items that will otherwise end up in already over-burdened landfills. Untold billions of plastic straws end up in landfills, but you can find a second life for at least some of them. Since straws flex, they make ideal building blocks for demonstrating certain engineering theories. Straws can help you discover or teach the ways a system might come together. A straw structure can be a project that studies construction, science, physics and creative design all in one. It's an excellent way to reuse a product that does not easily biodegrade in order to help the environment while having some fun.
Exploratoruim.edu states that all structural action consists of tension and/or compression. When you create a straw structure to teach this theory, therefore, you must provide tension or compression to each individual straw.
Create a pencil sketch of your bridge so you have a plan of action. You'll need two 4-by-4 pieces of solid wood, cut 12 inches long, and a large pack of straws. Each piece of wood represents one end of your bridge; the starting point and the end point. Position the two pieces facing each other with a space between them--this space is where you will place your bridge. Glue a few straws up the inside edge of both pieces of wood, parallel to the wood. Once you complete the bridge, you will attach it to the straws that are glued to the wood.
To build your bridge, attach straws to each other using straight pins and glue. Insert the straws end-to-end and secure them with the pins. Straws are flexible, so manipulate them into shape to create your structure. Use more pins and glue to attach the straw bridge to the stabilizing straws on the wood posts. Once completed the bridge will be a firm structure still capable of movement. As each straw moves, it will display either tension or compression.
Tensegrity, or tensional integrity, uses the theory of compression and tension just like a bridge design. You can build another straw structure to further highlight this theory using a tensegrity structure to create a polyhedral form out of straws. Just like with the bridge, you'll need to connect the straws with something that allows movement. For the polyhedral form, you'll use rubber bands to connect the straws. The resulting figure is a ball capable of expanding and contracting.
To create this structure, insert paper clips into the ends of straws and attach rubber bands to the paper clips. Layer the straws in a circular pattern to form a pentagon with five outward struts. When you pull the ball outward from both sides, it expands and creates tension; letting go causes the structure to compress.
Create small boxes of straws and stack them on top of one another on a flat, solid surface. Use straight pins and glue to hold the straws together. Make each successive box smaller than the one beneath it. The final result is one structure comprised of many smaller ones. To strengthen the tower, put a piece of cardboard between each layer. Adapt this basic technique to recreate miniatures of some of the world's most famous towers, such as the Eiffel Tower.
- Photo Credit the bridge image by timur1970 from Fotolia.com
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