[Steven Dufresne] of Rimstar.org is at it again with another very functional science experiment. This week he’s showing us how he made a large electrostatic motor, also known as a Corona Motor.

A Corona motor makes use of a cool
phenomenon called the Corona discharge, which is the ionization of a fluid
(in this case, air) surrounding a conductor that is energized. He’s done other high voltage experiments that take advantage of this, like his Ion Wind propelled Star Trek Enterprise!

The motor works by using an even number of electrodes on the motor, each electrically charged; positive, negative, positive, negative, etc.

Because each electrode is the opposite charge, they want to repel each other — but since the cylinder is electrically insulated, the charges have no where to go — instead the cylinder begins to rotate as the charges attract back and forth — when a positive charge on the insulation meets a negatively charged electrode, the charge is removed by ionization (creating the corona effect), and the cycle continues. The direction of rotation is determined by the angle of the electrodes. The motor can get going pretty fast but doesn’t have that much torque or power.

For a full explanation of the project, check out [Steve’s] explanation in the following video:

And how to make it!

This is actually [Steve’s] second Corona motor, as he already designed a simpler one that is easier to build previously.

1. zach says:

Interesting…. what is the advantage of such a motor though? At the end of the day, I imagine the number of hp you can get is proportional to the amount of electricity the motor is going to consume. Wouldn’t you end up burning the same amount of electricity at the end? Is this particular design more efficient in any way?

I still think it is an interesting concept but I am curious as to whether it would be practical to use in any given application.

1. I haven’t done efficiency tests yet. But the reason I’m doing it is to work up to trying out atmospheric electricity – for the fun of it. You lift a wire up into the air a few hundred feet by a kite, balloon or drone, with sharp points at the top. It’s long been know that there’s a voltage gradient of 100v/meter of height (from The Feynman Lectures on Physics, the values varies a lot depending on location and atmospheric conditions.) The available charge however is small. Oleg Jefimenko managed to make a more advanced one of this design that got 0.1 horsepower this way in the 1960s or 70s.

1. Solenoid says:

That’s a very interesting idea, I didn’t know about the 100V/m gradient up there… well thunder most come from somewhere after all. Instead of floating a huge generator up high you just send a wire up there and bring the potential down to the generator.

2. Steve Schear says:

One of the pioneers in electrostatic motors/generators was Oleg D. Jefimenko and . I was researching in this area long ago too and he was kind enough to send me a copy of his “Electrostatic motors; their history, types, and principles of operation. Star City [W. Va.], Electret Scientific Co. [1973]. LCCN 73180890” A new revised version is available His experimental handbook, “Electrostatic Experiments: An Encyclopedia of Early Electrostatic Experiments, Demonstrations, Devices, and Apparatus”, is also back in print

I have recently renewed my research in this and related areas and hope to have something to show here in 2016. Look forward to seeing others follow in his footsteps.

2. Look up Franklin’s bells.

Years ago I made a proof of concept motor using a styrofoam cup with two pieces of tin foil glued to opposite sides. Invert and balance on the end of a thin rod. A stiff (grounded) wire near one side and another wire near the other side with attached to a large piece of tinfoil taped to the front of out 26″CRT. Turn on (or off) the TV and watch the cup spin!

In theory have a bell (or motor) attached to a lightning rod would
a) warn of an approaching thunderstorm
b) if enough people did it, reduce the storm’s intensity by bleeding of some of the mounting charge in the clouds (*)

(*) my retired friend & I have a theory that all cell / radio towers everywhere are why thunderstorms are not as impressive as we recall from our childhood.

1. pcf11 says:

I don’t know about you and your friend’s theory. NASA has had to learn a bit about lightning due to where they have their facilities. Turns out the Cape is the lightning capitol of the world. Due to that no one is more interested in lightning research than they are. If your theory had any merit I’d think they’d be pursuing it. They are rocket surgeons after all.

http://www-pao.ksc.nasa.gov/kscpao/nasafact/pdf/Lightning-06.pdf

3. pcf11 says:

If those wires going to it are carrying the electricity then the electricity is not static electricity. Because by definition static electricity is ah, static.

1. I think the “static” comes from the fact that the charges that are static while they’re on the surface of the plastic cylinder being mechanically carried along between two adjacent electrodes. Even a Wimshurst machine is considered an electrostatic machine, yet the charges are static only while on the disks, and even then only for parts of the rotation. Reading books from the 1800s it’s clear that the term electrostatic comes from a time when less was known about the origins of electricity. Nowadays I consider it a misnomer, but it’s a part of the language.

1. pcf11 says:

You can have a static electric charge, but once current flows what you have is no longer static electricity.

1. Yes, but while the charged area of the cylinder is being rotated from one electrode to the next, the charge is stationary where it is on the plastic cylinder. During that brief period it is static. There are a whole bunch of machines classified as electrostatic machines that consist of both static and dynamic electricity. But they’re still called electrostatic machines. I’m not crazy about it either since I’ve seen it confuse so many people new to electricity.

2. Blue Footed Booby says:

Do you have a point–ie something interesting that springs from this distinction–or is it just semantics?

4. HaD, do dissimilar charges really repel each other?

“Because each electrode is the opposite charge, they want to repel each other”

1. h3ll0_w0rld says:

*feels a whole childhood of Bill Nye revolt within my being

5. Aidan says:

Nice hack!!

6. With a little work, he could massage that into a neat kickscammer project.

1. Solenoid says:

You could hook up the output to a high-voltage generator and throw in a good measure of magnets too: free energy for everybody!

1. mattthegamer463 says:

Haha my first thought exactly

7. I first thought, it would work by ion wind, but it seems to be electrostatic attraction of charged areas of the cylinder. The blade angle directs the ions to one side to change the cylinder asymmetric which creates a force. Very well built!

1. Almost. The blade sprays ions onto the cylinder and then repels the now charged section of cylinder while the next blade along attracts that section. I have diagrams on the webpage in case that’s not clear.
And thanks! I’m pretty happy with the way it turned out too. I have my fingers crossed to do some more experimenting with it outdoors this summer, weather permitting. I’m going to try to lift a grounded wire a few hundred feet up in the air, with sharp points at the top, and take advantage of the potential difference between that height and the ground and also the few free ions in the air up there. Hopefully I can get enough current through the wire and the motor to turn it. I have a quadcopter lined up to do the lifting but it’s uncertain I’ll be able to get the height.

1. A CD would also work and it is already conductive plated.
Your experiment will take a large scale. I think it needs a near lightning and elms fire on your ‘antenna’ which is a high risk. But it seem you can deal with high voltage ;-)

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