Electrostatic Motor Debug/Repair
(Actually, homemade devices rarely work correctly the very first time.)
Detailed debugging is down below, but first read these:
1. DON'T MAKE MAJOR CHANGESFirst, did you build your motor to be somewhat like the one I described in the instructions? It can seem boring to simply copy someone else's idea exactly. It's easy to insert many improvements as you go. This makes the motor YOURS and no longer mine. But if your device doesn't work, what then? Maybe one of your improvements actually made the motor not work. If your motor isn't made from three 2-liter plastic pop bottles with aluminum foil glued to them, then I probably cannot help you debug it unless you hire me to come out to your house and take a look. The solution? First build a motor like mine, since we KNOW that this one works. Then, after you have a working motor, go and add all your alterations and improvements one at a time and see what happens. (In the electronics kit business, when the customers make additions to a device BEFORE making it work first, it's called "Ego Improvements.")
2. USE A RELIABLE POWER SUPPLY AT FIRSTNext, what are you using as a power supply? Before trying feeble power supplies like balloons/wool, electrophoruses (electrophori?), or Kelvin waterdroppers, try something fairly powerful such as a VandeGraaff machine, neg-ion gen, or the foil-on-TV-screen trick. Get the motor working with a known-good power supply before going off to try your own power supply ideas. This way you'll know to not blame the motor when the fault might be high humidity or a weak power supply. These motors need more than 5,000 volts DC to operate. This can be easily provided by a hefty "static electric" source.
3. BATTERIES WON'T WORKThis motor needs a "static electric" power supply (in other words, a power supply that puts out high voltage at low current.) Use a TV screen, or a VandeGraaff Generator, or a Negative Ion Generator. I found that my motor would not turn unless the voltage was at least 5,000 volts (and 7,000 volts was much better.) Batteries cannot run this motor unless you have about 4,000 of them hooked in series! (4000 times 1.5 volts is 6,000 volts)
4. TESLA COILS WON'T WORK (or will they?)Tesla coils are no good because they are high-voltage AC and this motor requires high-voltage DC.
Maybe this is not true! firstname.lastname@example.org reports that his pop-bottle
motor starts turning when the motor is placed near his large,
floor-standing Tesla coil, while one bottle of the motor is connected to
ground. Weird! Do Tesla Coils actually emit some microamperes of direct
current into the air? Possibly. If so, then in theory a Tesla Coil could
run this motor, but only if some corona-rectification is allowed to occur,
and not if wires are used to connect the motor directly to the Tesla Coil
terminals. But even that might be OK! Somebody with a TC should try it.
(I tried it with a tiny solid-state tesla coil from a Plasma Sphere, but
it would not run the motor.)
5. BOTTLE ROTATES EASILY, FRICTION MUST BE VERY LOWOther possible problems: does the center bottle turn very freely? VERY VERY freely? It must. Here's a way to judge whether its friction is low enough. Get the bottle spinning slowly by hand, turning about once per second, then let go. It should keep turning for one or two revolutions or more. If not, friction is far too high. Check out the metal point bearing and make sure it hasn't drilled itself into the metal bottle cap. Don't use a plastic bottle cap, the plastic is too soft to provide a good bearing. The bottle must turn VERY easily, otherwise the feeble electrostatic forces won't be able to move it. Some people get good results by attaching a tiny pencil to the top of the center rod, so the graphite pencil point serves as the "sharp point" which the bottlecap rides upon. I highly recommend using a tiny glass test-tube as a bearing. Glue it upside-down in the bottle cap. Don't let the bottle slam down onto the metal rod, or the sharp point will break the test tube! Some sort of tiny, metal, cup-shaped object might also work OK. A metal thumbtack with point removed? Also put a little oil near the bottom of the metal rod where it rides against the hole in the rotor bottle's bottom.
ORGANIZED DEBUGGINGIf it still won't work, then you need to look for the problem. Use this "debugging sequence" below.
Note: if you hate making sparks with your knuckles, then hold a metal
object in your hands (use a quarter, or a pop can), and jump the spark to
the metal. Painless!
OTHER POSSIBLE PROBLEMSThe metal of the commutator wires must be directly connected to the foil of their respective STATOR bottles. Commutator wires are electrically a part of the stator foils, so when the power supply is operating, both the wires and the stator foils acquire the same polarity of charge imbalance. If the commutator wires don't make good contact with the foil on their corresponding stators, either the stator foils won't get charged, or no charge will flow down the wire to leap across to the rotor bottle. So, make sure there is no plastic on either end of the commutator wires, and that bare metal touches bare foil. If you have taped your commutator wires securely to the foil of the stator bottles, make sure that there is no tape, hot glue, etc., between the foil and the metal wire.
The commutator wire's tips need to be very close to the surface of the
rotor bottle, but should not scrape along it as it turns. The gap between
the wire's tip and the rotating bottle's surface must be as small as
possible. If it is too large, then the motor will operate successfully
only if the power supply voltage is raised high enough to force sparks to
jump across the large gap. If the gap is tiny, then even a weak supply
will run your motor. If you ARE seeing tiny sparks jumping between
the wire tips and the rotor bottle foils, then the spacing between
commutator tip and rotor surface is probably OK, and the power supply
voltage is probably high enough. Apply power and give the center bottle a
slow spin by hand, and you should hear a slight clicking noise as the tiny
sparks jump. Lack of clicking noise indicates either too low a supply
voltage, or that something on the motor is providing an unwanted leakage
path which shorts out the power supply and reduces its voltage too much.
If you use a strong power supply such as a VandeGraaff or Wimshurst
machine, you can even try increasing the gap to one or two inches and the
motor will still run! In this case the electric current takes the form of
silent streams of charged air rather than sparks. Your motor then runs
via sliding contacts made of invisible ion-beams! Very hard even for
scientifically-trained passersby to figure out. <grin> However,
get the motor running before trying this.
Make sure there is a complete circuit path between your power supply and
the motor. If you use a VandeGraaff, you must connect TWO wires between
it and the motor. One wire goes between the large sphere and the foil of
one of the stator bottles. The other wire goes from the generator's metal
base and to the other stator bottle's foil. If you use the TV set,
connect one stator bottles' foil to ground, connect the other stator
bottle to the TV screen's foil. Wires can be connected to metal surfaces
by simply taping them there. (Make sure to strip any plastic coating off
the wire ends, you need metal-to-metal contact!) If you attempt to use
the wool/balloon method, connect the unused stator bottle's foil to
ground. (Hint: if ground is entirely unavailable, try spreading a few feet
of aluminum foil on the floor and connecting your motor to that.)
Are sparks jumping between the central rotor bottle and the FOIL SURFACE
of the stator bottles? This is bad. Or are your stator bottles too close
or too far from the rotor bottle? About 1/2 in. spacing seems to work OK.
If this space is too large, the electrostatic drive force will be greatly
reduced. If this space is too small, sparks will jump from the rotor
bottle and act as a leakage path, greatly reducing the driving voltage on
the stator foils, and slowing or stopping the motor.
If the humidity is high (above 40% to 50%), it's possible that your power
supply is being shorted out by leakage along the plastic surface of wires
to ground. Try using plastic cups to support your high-voltage connecting
wires up off the table surface. (Wires connected to ground need not be
lifted.) Leakage can also happen across the plastic surface of the
bottles. This can be cured by warming the exposed plastic parts with an
electric blow dryer. (Don't heat them up too much, or they will soften
and distort!) Or, store the whole setup in a cold, air-conditioned room
for a couple of hours, then operate it in that room. Or, wait to try
again on a day which isn't as humid. Hint: if you rub a balloon on your
arm hairs and the charged balloon can make the arm-hairs rise, the
humidity is low enough. If no amount of rubbing with a balloon can lift
your arm-hair, then humidity is probably too high.
If you use a VandeGraaff generator or Wimshurst generator, try taping some
strips of tissue to the metal generator sphere so you can monitor the
voltage. Cut or tear out a 2" x 1/4" kleenex strip and tape one end to
the metal, so the strip hangs down. When the generator is operated, this
strip should be repelled from the metal and lift outwards. If it does
not, it means that no high voltage is being created. If high voltage is
missing, first try totally disconnecting the motor from the generator,
then run the generator all alone. If the kleenex still does not rise,
then there is something wrong with the generator! Could be high humidity.
If so, you can warm the moving parts of the generator with an electric
blow dryer (open the vandegraaf sphere or base if necessary, and blow-dry
the belt while it's running.)
Finally, check for possible shorts throughout your entire motor. There
must be no surface connections between the three foils of the rotor
bottle, and there must be about 1/2" space between them. There must be no
connections between the foil on the stator bottle and the wooden base.
Many sorts of tape count as a "connection" because of their conductivity,
so don't let any tape touch both the wooden base and the foil of the
bottles. The first motor I ever built would not run no matter what I did.
I discovered that the duct tape I used to connect stator bottles to base
was conductive. It was touching the wood base and the stator foils. The
wood base was conductive also, and the whole motor was shorted out by the