Friday, October 5, 2012

Personal Fan

• 8'' 1x2'' pine
• Plastic cup or bottle
• Masking tape
• Aluminum foil
• Hobby motor
• 1 AA battery
• Solid core wire (we like telephone wire)
• Thumb tacks
• A broccoli rubber band, or inner tube cut off

• Small wood saw
• Scissors
• Wire strippers
• A hammer
• Hot glue gun

First take a piece of foil and fold it to make a 2" x .75'' strip and tack it loosely in place on one side of the handle.

Add a second tack under the end of the foil (not through it). Then twist two lengths of telephone wire (with ends stripped) onto each tack so the exposed copper touches the tack.

Hammer the tacks in to lock the wires in place; this completes the fan's switch.

To complete the circuit cut and add a third piece of wire and create a path that goes from the switch to the motor to the battery and back to the switch.  Stretch a broccoli rubber band or a cut off piece of inner tube around the battery, and simply stick the ends of the wires under the band to hold them in place.    

Hot glue the motor to the top of the handle and bend the foil up so the motor will remain off until pressed into the tack. Once you've made sure you circuit works and there are no loose connections, tape the battery to the handle to secure it.

To make the propeller cut an elongated oval at a diagonal out of the side of a plastic cup or bottle at an angle.

Use a tack to poke a hole in the propeller that is a little smaller than the motor shaft so it will stay on once pressed in place.  You can always add a little glue for more security.

The final fan should look something like this.

Things to do and notice: 
Despite being a simple circuit project, most of the experimentation with the project can be done with the propeller.   This type of propeller tends to work better spinning in one direction than the other, which is worth looking at and trying to explain. The diameter, width, and curvature will all effect how much air the propeller will move. Going with particularly large propellers from large bottles or very small propellers tend not to be very effective. The trade off between curvature and area can be further understood by simply making many different sizes of propellers from different containers and experimentally comparing their effectiveness.

Here's a decorated fan in action:

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