The materials you will need

• 8 wood sticks of even length.
• 4 old tennis balls.
• A bike dynamo
• A ring the size of the dynamo’s head.
• A tightening ring the size of the dynamo.
• Electric wire
• An ammeter (if you want to use the device as an anemometer) or a bike lamp.
• A pole to set the device.

Building the device

1. At the end bit of each stick put a half tennis ball, then fix all of the sticks on the ring that’s the size of the dynamo’s head.
2. Fix the ring with the wood sticks on the head of the dynamo.
3. Fix the dynamo at the top of the pole with the tightening ring.
4. Set the pole in the ground and hold it with guys.
5. Plug the wire in the dynamo and the bike lamp or the ammeter according to the use you want to make of the device.

To use it as an anemometer you will need to calibrate the ammeter first. Put marks in mph on the ammeter.

You can use this device without a dynamo. Let the sticks loose around the axis and that way you’ll get an idea of the wind speed just by looking at the rotating speed.