Science Fair Experiments Using Water to Power a Fan

Waterwheel Principles

• A waterwheel is a wheel with a series of paddles or buckets attached to the outer rim. An undershot waterwheel's paddles create drag when they are placed in a flowing current, causing the wheel to turn. An overshot waterwheel has water piped into buckets near the top of the wheel. The heavy buckets on one side of the wheel cause it to turn. As the buckets reach the bottom of the wheel, the water pours out of them and they make the return journey to the top of the wheel light and empty. An undershot wheel is simpler to construct, but an overshot wheel will provide more power from the same flow of water.

Building a Waterwheel

• A science fair waterwheel can be constructed from an old bicycle or lawnmower wheel with the tire removed. For an undershot wheel, glue a series of balsa wood squares to the outside of the wheel, sticking straight out from the edge. You can experiment with different lengths and spacings to determine the most efficient layout, recording the results as part of your project display. For an overshot wheel, Easter egg halves make excellent buckets. For the most efficient wheel, these should be glued into place at such an angle that they will be straight up and down when they are just to one side of the wheel's center. This will allow them to hold the maximum amount of water through the greatest distance around the wheel.

Providing the Water

• Water can be poured manually through your model for a one-off display or pumped from the end of the model to the beginning using a tabletop fountain pump. The pump should be kept completely underwater at all times while it is running; if a pump is allowed to run without pumping water, it can be damaged. For an undershot wheel, a river can be simulated by a short length of half-pipe running at a shallow angle to a deep-well painting tray. For an overshot wheel, a smaller length of half-pipe can be used to direct the water into the buckets, with the painting tray being used to catch the runoff.

Powering the Fan

• For a demonstration of old-fashioned water power, you can power a fan blade by linking it directly to your waterwheel. Attach a large sprocket or pulley on a shaft turned by your waterwheel and attach it by a chain or belt to a small sprocket or pulley which will turn a second shaft attached to the prop from an old fan. By using a large sprocket on the waterwheel and a small sprocket on the fan, you can make the fan spin faster than the waterwheel.

Hydroelectric Power

• Your waterwheel can also be used to power a small, battery-powered fan. By attaching your waterwheel to a small electric turbine, you can generate a small amount of electricity. You can wire this turbine to a handheld fan and pump enough power into it to get it spinning pretty quickly. This sort of demonstration works best if you are using a fountain pump to provide a steady stream of water and if you are using an overshot wheel to get the greatest efficiency out of your setup. Remember, that electricity and water never mix, so keep your turbine and fan well-separated from your waterwheel and your water supply under control.