Here is an electrostatic motor that' s easily built for a science project. The rotor was constructed by laminating a strip of aluminum foil between layers of plastic packaging tape and rolling it into a tube. The tube was mounted on an axle using cardboard end caps w/flat washers at the centers as bearings. Stationary electrodes or stators were made from a ring of nails suspended co-axially w/respect to the rotor and energized w/negative, high voltage DC. A framework made from drinking straws, tape and plastic covers of tin cans maintained the stators in proper alignment around the rotor.
The project provides an opportunity to learn about Coulomb's Law which describes electrostatic attraction/repulsion between charged points. Specifically, the rotor spins because negatively charged surface areas of the rotor are repelled after they contact the electrically hot stators. Each charged area then deposits excess electrons to the adjacent, grounded stator on the ring as the rotor turns. The charge-discharge cycle repeats as each neutralized area of the rotor approaches the next energized stator. I used re-purposed recyclables and some basic hardware for this project to reduce construction costs to a minimum.
This project requires high voltage direct current (HVDC), so choose a power source that is appropriate for your level of experience.
Step 1: Parts & Tools
- Rotor must be light in weight.
- Rotor must be balanced.
- Stators must be well insulated from each other to prevent internal arcing.
Axle (1) -- 15 cm x 0.3 cm dia coat hanger.
Axle Bearings (2) -- Stainless steel flat washers w/0.3 cm ID hole (http://www.smallparts.com).
Axle Sleeves (2) -- 3 cm x 0.4 cm dia drinking straws (included w/small packages of soft drinks).
End Caps (2) -- approx 4.0 cm dia discs (use cardboard end cover from 3-ring binder).
Lining Strip (1) -- 2.5 cm x 15 cm strip of AL foil.
Stators (6) -- 5 cm length nails.
Stator Housing Assembly
Rims (2) -- Plastic flip lids from mixed nut containers.
Rim Supports (12) -- Std size drinking straws (1/4 inch dia).
Suspension Bands (2) -- Rubber bands.
Plastic Horseshoe (1) -- Scrounged from discard box at local schoolyard after community fair; or make one from cardboard.
Scrap Acrylic or Cardboard Sheet (1) -- Cut to appropriate size.
Spacer -- plastic bottle cap.
Power Source (1) -- Typical sources of HVDC in the low microamp range such as room air ionizers, Van de Graaffs and Whimshursts may be too weak to power this motor. Consider a high potential transformer. Simco's CH-30 Chargemaster (http://www.simco.biz) is one of the "amp-kicking" bad boys of electrostatic generators. Sometimes these units are available through electronic auctions at large discounts by liquidation vendors who don't know what they can do!
Color-coded Wire Binding Posts (2)
Color-coded HV Wire (red & black)
Packaging/Shipping Tape (5.0 cm wide)
Typical Connecting Hardware (small bolts, lock & flat washers, nuts)
Handheld Hole Punch