Step 6: How it Works.
When the rotor turns, it brings the next piece of foil to collect charge, and also moves the first piece towards the earth connection to discharge. The whole process repeats for as long as you supply charge to the motor. The only real limiters to the speed are balance - wobbly rotors will turn more slowly - and friction. The top speed of your motor will be controlled by friction on the balance point (so make it small and slippery, but don't use grease, try graphite) and by air friction on the cup (so try not to have too many wrinkles or loose edges).