Introduction: Build an Electrostatic Motor
This site gives information for building an electrostatic motor from 2 plastic soda (pop) bottles. To see a video of the motor in operation, click on the file "cap0001.mpg" below. Be patient - it's a big file (17 MB). For additional information on the procedure, click here.
Step 1: Base
Drill a hole in the wood just large enough for a bamboo skewer. The hole must be drilled as vertically as possible. Insert the skewer in the wooden base. The skewer serves as the axle for the rotor to spin on.
Step 2: Stator
Use the larger bottle as the stationary stator. Tape two pieces of foil (4 layers thick) on the bottle. These are the stator plates that will interact with the rotor plates. Cut tabs in the plastic and bend the tabs in slightly. Trim back the plastic to slightly less than the length of the foil. The foil tabs will allow charge to jump from the stator plate to the rotor plate, causing the rotor to spin. If possible, use some tape to insulate the foil tab so that only the tip is exposed.
Step 3: Rotor Bottle
Use the smaller bottle as the rotor. The rotor plates are made by taping 3 pieces of foil symmetrically on the bottle, keeping a separation of about 1 cm between the plates. The tape serves to insulate one plate from the next. Drill a small hole in the centre of the bottom of the rotor bottle for insertion on the bamboo skewer. Insert a screw inside the rotor cap in the exact centre to act as a "frictionless" pivot for the bamboo skewer.
Step 4: Assembly
Place the stator bottle on the axle. Next place the rotor bottle on the axle, ensuring that the bamboo axle is in the centre of the screw you put in the cap. You may have to adjust the length of the axle so the rotor and stator plates are properly aligned. Adjust the tabs on the stator bottle so that the foil tip comes very close to the rotor plate without rubbing. You may need to trim back the plastic tab a little but leave some foil extending past the end of the plastic. This way, if the foil tab touches the rotor, it won't slow it down.
Step 5: Operation
Using flexible copper wire, attach one of the stator plates to a Van de Graaff generator (or TV screen covered with foil), and the other plate to ground (e.g. a sink faucet). Turn on the generator or TV. It may take 10 or 15 seconds for enough charge to build up. You may have to give the rotor a gentle spin to get it going, but if it is made properly, it will start turning by itself. It should rotate up to 400 - 500 r.p.m.