Popular Science ( April 1971 )
The
Amazing Motor That Draws Power from the Air
by
C.P. Gilmore & William J. Hawkins
Would you believe an electric motor made almost entirely of plastic?
That can run on power transmitted through open air? And sneak free
electricity right out of the earth's electrical field?
At the University of West Virgina we saw a laboratory full of such
exotic devices spinning, humming, and buzzing away like a swarm of
bees. They are electrostatic motors, run by charges similar to those
that make your hair stand on end when you comb it on a cold winter's
day.
Today, we use electromagnetic motors almost exclusively. but
electrostatics have a lot of overlooked advantages. They're far lighter
per horsepower than electromagnetics, can run at extremely high speeds,
and are incredibly simple and foolproof in construction.
"And, in principle," maintains Dr Oleg Jefimenko, "they can do anything
electromagnetic motors can do, and some things they can do better."
Jewel-like Plastic Motors.
Jefimenko puts on an impressive demonstration. He showed us motors that
run on the voltage developed when you hold them in your hands and scuff
across a carpet, and other heavier, more powerful ones that could do
real work. Up on the roof of the University's physics building in a
blowing snowstorm, he connected an electrostatic motor to a specially
designed earth-field antenna. It twirled merrily from electric power
drawn out of thin air.
These remarkable machines are almost unknown today. Yet the world's
electric motor was an electrostatic. It was invented in 1748 by
Benjamin Franklin.
Franklin's motor took advantage of the fact that like charges repel,
unlike ones attract. He rigged a wagon-wheel-sized, horizontally
mounted device with 30 glass spokes. On the end of each spike was a
brass thimble. Two oppositely charged leyden jars -- high voltage
capacitors -- were so placed that the thimbles on the rotating spokes
barely missed the knobs on the jars ( see photo ).
As a thimble passed close to a jar, a spark leaped from knob to
thimble. That deposited a like charge on the thimble, so they repelled
each other. then, as the thimble approached the oppositely charged jar,
it was attracted. As it passed this second jar, a spark jumped again,
depositing a new charge, and the whole repulsion-attraction cycle began
again.
In 1870, the German physicist J.C. Poggendorff built a motor so simple
it's hard to see what makes it work. The entire motor, as pictured
here, is a plastic disk ( Poggendorff used glass ) and two electrodes.
The electrodes set up what physicists call a corona discharge; their
sharp edges ionize air molecules that come in contact with them. These
charged particles floating through the air charge the surface of the
palstic disk nearby. Then the attraction-repulsion routine that
Franklin used takes place.
A few papers on electrostatic motors have trickled out of the
laboratories in recent years. But nobody really showed much interest
until Dr Jefimenko came on the scene.
The Russian-born physicist was attending a class at the University of
Gottingen one day shortly after World War II when the lecturer, a Prof.
R.W. Pohl, displayed two yard-square metal plates mounted on the end of
a pole. He stuck the device outside and flipped it 180 degrees. A
galvanometer hooked to the plates jumped sharply.
"I could never forget that demonstration," said Jefimenko. "And I
wondered why, if there is electricity in the air, you couldn't use it
light a bulb or something."
Electricity Everywhere
The earth's electrical field has been known for centruries. Lightning
and St Elmo's fire are the most dramatic manifestations of atmospheric
electricity. But the
field doesn't exist just in the vicinity of these events; it's
everywhere.
The earth is an electrical conductor. So is the ionosphere, the layer
of ionized gas about 70 kilometers over our heads. The air between is a
rather poor insulator. Some mechanisms not yet explained constantly
pumps large quantitites of charged particles into the air. The charged
particles cause the electrical field that Jefimenko saw demonstrated.
Although it varies widely, strength of the field averages 120 volts per
meter.
You can measure this voltage with an earth-field antenna -- a wire with
a sharp point at the top to start a corona, or with a bit of
radioactive materials that ionizes the air in its immediate vicinity.
near the earth, voltage is proportional to altitude; on an average day
you might measure 1200 volts with a 10-meter antennas.
Over that past few years, aided by graduate-student Henry
Fischbach-Nazario, Jefimenko designed advanced corona motors. With
David K. Walker, he experimented with electret motors. An electret is
an insulator with a permanent electrostatic charge. It produces a
permanent electrostatic charge in the
surrounding space, just as a magnet produces a permanent magnetic
field. And like a magnet, it can be used to build a motor.
Jefimenko chose the electrostatic motor for his project because the
earth-field antennas develop extremely high-voltage low-current power
-- and unlike the electromagnetic motor -- that's exactly what it needs.
The Climactic Experiment
On the night of Sept. 29, 1970, Jefimenko and Walker strolled into an
empty parking lot, and hiked a 24-foot pole painted day-glow orange
into the sky. On the pole's end was a bit of radioactive material in a
capsule connected to a wire. The experimenters hooked an electret motor
to the antenna, and, as Jefimenko describes it, "the energy of the
earth's electrical field was converted into continuous mechanical
motion."
Two months later, they successfully operated operated a corona motor
from electricity in the air.
Any Future In It?
Whether the earth's electrical field will ever be an important source
of power is open to question. There are millions -- perhaps billions --
of kilowatts of electrical energy flowing into the earth constantly.
Jefimenko thinks that earth-field antennas could be built to extract
viable amounts of it.
But whether or not we tap this energy source, the electrostatic motor
could become important on its own.
* In space or aviation, it's extreme light weight could be crucial.
Jefimenko estimates that corona motors could deliver one horsepower for
each 3 pounds of weight.
* They'd be valuable in laboratories where even the weakest magnetic
field could upset an experiment.
* Suspended on air bearings, they'd make good gyroscopes.
In a particularly spectacular experiment, Jefimenko turned on a Van de
Graaff generator -- a device that creates a very-high-voltage field.
About a yard away he placed a sharp-pointed corona antenna and
connected it to an electrostatic motor. The
rotor began to spin. The current was flowing from the generator through
the air to where it was being picked up by the antenna.
The stunt had a serious purpose: The earth's field is greatest on
mountaintops. Jefimenko would like to set up a large antenna in such a
spot, then aim an ultraviolet laser beam at a receiving site miles away
at ground level. The laser beam would ionize the air, creating an
invisible conductor through apparently empty space.
To be sure, many difficulties exist; and no one knows for sure whether
we'll ever get useful amounts of power out of the air. But with
thinking like that, Jefimenko's a hard man to ignore.
Popular
Science ( May 1971 )
Electrostatic
Motors You Can Build
by
C.P. Gilmore & William J. Hawkins
When we crank up the electrostatic motor at the top of this page,
people always want to know what makes it run. It is mysterious --
there's nothing but a plastic disk and two strange electrodes. Yet
there it is, spinning merrily.
In "The Amazing Motor That Draws Power From the Air", last month, we
told about our visit to the laboratory of Dr Oleg Jefimenko at the
Universioty of West Virginia, who has designed and built a variety of
these ingenious machines. now, as promised, we bring you details on how
you can build your own electrostatic motor from simple materials.
The devices that you see here are corona-discharge motors. The
sharp-pointed or knife-edge electrodes create a corona, which ionizes
or charges the air particles floating by. These charged particles
transfer their charge to the closest part of the plastic rotor and
charge it up, just as you can charge your body by walking across a wool
rug on a dry winter's day.
Once a spot on the rotor assumes a charge, it is repelled from the
chargin electrode by electrostatic forces, and at the same time is
attracted to the other electrode, which has an opposite charge. When
the charged section of the rotor reaches the opposite electrode,
another corona discharge reverses the polarity and starts the whole
thing over again.
The Concept is Simple
And so are the motors. But that doesn't mean thery're easy to build.
These motors run on millionths of a watt; they've got no power to waste
turning stiff bearings or slightly misaligned rotors. So they must be
built with watch-making precision.
They're made of acrylic sheet, rod, and tube stock -- Plexiglas and
Lucite are two of the better-known brands. Acrylic cuts and works
beautifully. Cut edges can be sanded so they have a white, frosted
appearance that, in contrast with clear surfaces, gives your finished
motor a sparkling, jewel-like appearance. If you like clear edges, you
can buff them on a wheel and the whole thing becomes transparent.
Drill and tap the acrylic and assemble parts with machine screws. This
allows for fine adjustment and alignment. Later, you can make the whole
thing permanent by putting a little solvent along the joints. The
solvent flows into the joint and fuses it permanently.
Details of framework, support and so on aren't important; change them
if you like. but work with care if you want to avoid headaches. The
Poggendorff motor looked simple; we slapped it together in a couple of
hours, hooked up the power source -- and nothing happened. We gave it a
few helpful spins by hand, but it wouldn't keep running.
The cure took about 3 hours. First, we noticed that the outer edge of
the disk wobbled from side to side about 1/16 of an inch as the wheel
revolved. So the rotor-electrode distance was constantly changing.
There was a little play in the 1/4" hole we had drilled for the
electrodes -- so they weren't lined up absolutely square with the disk.
Then we noticed that the disk always stopped with one side down. The
imbalance was only a fraction of an ounce -- but it was too much.
We drilled out the old hub and cemented in a new one -- this time,
carefully. We lined up the electrodes -- precisely. Then, once more
spinning the disk by hand, we added bit of masking tape until it was
perfectly balanced. We connected the power -- and slowly... slowly...
the disk began to turn. After about a minute, we clocked some turns
with a watch and found it was spinning at 200 rpm. A moment later, we
lost count. It was a great feeling.
Where Tolerances Are Brutal
We had even more trouble with the octagonal-window machine. When it
wouldn't run and we turned the shaft by hand, we could feel the rotor
dragging. We took it apart, felt all the surfaces on the rotor and the
framework's insides and found a few bits of hardened cement, which we
removed. We filed down all edges on the rotor adn the windows to make
sure there were no beads or chips dragging.
The rotor and corner separators are made from the same sheet of 1/2"
plastic, so rotor clearance is achieved by putting shims at the corners
to hold the side plates slightly more than 1/2" apart. With the 1/16"
shims we were using, we could see that the sides were slightly
misaligned so the shaft was not being held at a true 90 degrees. We
drilled slightly oversized holes in the corners of one side piece and
carefully adjusted until the rotor was turning true in the slot. To
give the motor more torque, we put a bead of cement along the outer
edge of each aluminum-foil electrode to stop corona leakage. The motor
ran.
Take A Giant Step
Once you've built these machines, why not design your own? Start with
the Jefimenko 1/10 hp model (pictured) as a challenge. Then plan one
from scratch. You can power your motors with a laboratory high-voltage
supply, a Van de Graff generator, or a Wimhurst machine or any other
high-voltage source. We've been running ours on the home-built Wimhurst
machine shown in the photos. (If you don't want to build one, Wimhurst
machiens are available from scientific supply houses such as Edmund
Scientific ).
The discharge globes are traditional for high-voltage machines. They
aren't necessary, but they give a quick check on machine operation and
a satifying arc when you move them within 1/2" of each other.
Incidentally, that funny smell is ozone. But its concentration is too
low to be harmful. The generator is safe, too. You can hold both
electrodes in your hands and all you'll feel is a tingle. This
particular generator, we estimate, puts out about 30,000 volts.
To make wiring simple, we used standard connectors on the Wimhurst
collectors, and meter leads with regular banana plugs and alligator
clips to hook up the motors.
Last month, we mentioned seeing Dr Jefimenko run his electrostatic
motors on electricity tapped from the earth's field. We haven't had a
chance to try this yet with ours, but it should work. If you want to
try, you'll need a needle-pointed piece of music wire a few inches long
to start a corona, plus several hundred feet of fine copper wire.
Connect the pointed wire to the fine conductor, get the sharp point up
into the air at least 200-300 feet with a kite or balloon, and hook the
wire to one side of the motor. Hook the other side of the motor to
ground. The earth field antenna should at times be able to develop up
to 20,000 volts from the earth's electrical field. If nothing happens,
check your equipment, or try another day. The field changes constantly.
http://en.wikipedia.org/wiki/Oleg_D._Jefimenko
Oleg
D. Jefimenko
(October 14, 1922, Kharkiv, Ukraine - May 14, 2009, Morgantown, West
Virginia, USA) - physicist and Professor Emeritus at West Virginia
University.
Biography
Jefimenko received his B.A. at Lewis and Clark College (1952). He
received his M. A. at the University of Oregon (1954). He received his
Ph.D. at the University of Oregon (1956). Jefimenko has worked for the
development of the theory of electromagnetic retardation and
relativity. In 1956, he was awarded the Sigma Xi Prize. In 1971 and
1973, he won awards in the AAPT Apparatus Competition. Jefimenko has
constructed and operated electrostatic generators run by atmospheric
electricity.
Jefimenko has worked on the generalization of Newton's gravitational
theory to time-dependent systems. In his opinion, there is no objective
reason for abandoning Newton's force-field gravitational theory (in
favor of a metric gravitational theory). He is actively trying to
develop and expand Newton's theory, making it compatible with the
principle of causality and making it applicable to time-dependent
gravitational interactions.
Jefimenko's expansion, or generalization, is based on the existence of
the second gravitational force field, the "cogravitational, or
Heaviside's, field". This is might also be called a gravimagnetic
field. It represents a physical approach profoundly different from the
time-space geometry approach of the Einstein general theory of
relativity. Oliver Heaviside first predicted this field in the article
"A Gravitational and Electromagnetic Analogy" (1893).
Selected publications
Books
* "Electrostatic motors; their history, types, and principles of
operation". Star City [W. Va.], Electret Scientific Co. [1973]. LCCN
73180890
* "Electromagnetic Retardation and Theory of Relativity: New Chapters
in the Classical Theory of Fields", 2nd ed., Electret Scientific, Star
City, 2004.
* "Causality, Electromagnetic Induction, and Gravitation: A Different
Approach to the Theory of Electromagnetic and Gravitational Fields",
2nd ed., Electret Scientific, Star City, 2000.
* "Electricity and Magnetism: An Introduction to the Theory of Electric
and Magnetic Fields", 2nd ed., Electret Scientific, Star City, 1989.
* "Scientific Graphics with Lotus 1-2-3: Curve Plotting, 3D Graphics,
and Pictorial Compositions". Electret Scientific, Star City, 1987.
Book chapters
* "What is the Physical Nature of Electric and Magnetic Forces?" in Has
the Last Word Been Said on Classical Electrodynamics? -- New Horizons,
A. E. Chubykalo, Ed., (Rinton Press, Paramus, 2004 ).
* "Does special relativity prohibit superluminal velocities?" in
Instantaneous Action at a Distance in Modern Physics: "Pro" and
"Contra", A. E. Chubykalo, Ed., (Nova Science, New York, 1999).
Papers
* "A neglected topic in relativistic electrodynamics: transformation of
electromagnetic integrals". arxiv.org, 2005.
* "Presenting electromagnetic theory in accordance with the principle
of causality", Eur. J. Phys. 25 287-296, 2004.
doi:10.1088/0143-0807/25/2/015
* "Causality, the Coulomb field, and Newton's law of gravitation"
(Comment), American Journal of Physics, Volume 70, Issue 9, p. 964,
September 2002.
* "The Trouton-Noble paradox," J. Phys. A. 32, 3755–3762, 1999.
* "On Maxwell's displacement current," Eur. J. Phys. 19, 469-470, 1998.
* "Correct use of Lorentz-Einstein transformation equations for
electromagnetic fields", European Journal of Physics 18, 444-447, 1997.
* "Retardation and relativity: Derivation of Lorentz-Einstein
transformations from retarded integrals for electric and magnetic
fields", American Journal of Physics 63 (3), 267-72.
* "Retardation and relativity: The ease of a moving line charge",
American Journal of Physics, 63 (5), 454-9.
* "Direct calculation of the electric and magnetic fields of an
electric point charge movingwith constant velocity," Am.J.Phys. 62,
79-84, 1994.
* "Solutions of Maxwell's equations for electric and magnetic fields in
arbitrary media," Am. J. Phys. 60, 899-902 1992.
* "Electrets," (with D. K. Walker) Phys. Teach. 18, 651-659, 1980.
* "How can An Electroscope be Charged This Way?", TPT 56, 1979.
* "Water Stream 'Loop-the-Loop'", AJP 42, 103-105, 1974.
* "Franklin electric motor," Am. J. Phys. 39, 1139-1141, 1971.
* "Operation of electric motors from atmospheric electric field," Am.
J. Phys. 39, 776-779, 1971.
* "Demonstration of the electric fields of current-carrying
conductors," Am. J. Phys. 30, 19-21, 1962.
* "Effect of the earth's magnetic field on the motion of an artificial
satellite," Am. J. Phys. 27, 344-348, 1959.
Encyclopedia Article
* "'Maxwell's Equations'", Macmillan Encyclopedia of Physics,
Macmillan, New York, 1996.
http://www.integrityresearchinstitute.org/FutureEnergy/FutureEnergyTech.html
The next energy breakthrough is Dr. Oleg Jefimenko's electrostatic
motors. Discovered by Ben Franklin in the 18th century, electrostatic
motors are an all-American invention. They are based on the physics of
the fair-weather atmosphere that has an abundance of positive electric
charges up to an altitude of 20 km. However, the greatest concentration
is near the ground and diminishes with altitude rapidly. Dr. Jefimenko
discovered that when sharp-pointed antennas are designed for a
sufficient length to obtain at least 6000 volts of threshold energy,
the fair-weather current density available is about a picoampere per
square meter. Such antennas produce about a microampere of current.
However, small radioactive source antennas may be used instead that
have no threshold voltage and therefore no height requirements. Similar
to a nuclear battery design of Dr. Brown, these antennas have larger
current potentials depending upon the radioactive source used (alpha or
beta source) and ionize the air in the vicinity of the antenna.
Electrostatic motors are lighter than electromagnetic motors for the
same output power since the motor occupies the entire volume. For
example, it is expected that a motor one meter on a side will provide a
power of one megawatt and weigh 500 kg or less. Electrostatic motors
also require very little metal in their construction and can use mostly
plastic for example. They can also operate from a variety of sources
and range of voltages. As Dr. Jefimenko points out, "It is clear that
electrostatic motor research still constitutes an essentially
unexplored area of physics and engineering, and that electrostatic
motor research must be considered a potentially highly rewarding area
among the many energy-related research endeavors."[5] The atmospheric
potential of the planet is not less than 200,000 megawatts. He has
succeeded in constructing demonstration motors that run continuously
off atmospheric electricity. Jefimenko's largest output motor was an
electret design that had a 0.1 Hp rating.[6] Certainly the potential
for improvement and power upgrade exists with this free energy machine.
http://forum.allaboutcircuits.com/newsgroups/viewtopic.php?t=67792
Book
Report
So I go out on my step and what to my wondering eyes doth appear but
the box from Amazon.com containing the Jefimenko books that Bill Miller
shamed me into finally buying. So I take a quick look inside and decide
to give an initial report here. (Too much vector math in there for a
thorough review.)
These books have some amazing advanced thinking in the understanding of
Maxwell and EM. One first thought is the consideration of causality.
This is typically totally ignored in the EM community. Evidence of that
is the fact that EM waves are widely held to be propagated by the E
field creating the H field and the H field creating the E field as it
goes along. Too bad it's just not true! Jefimenko points out that
causality demands that that an event must be PRECEDED by it's cause!
Simultaneous events CANNOT be "causal" of each other. Hence E and H
fields of waves are created by the WAVE SOURCE not each other! Same
things goes for the E field created by Faraday induction. It simply
cannot be "caused" by the time-varying Magnetic Field. "Magnetic
induction" is therefore a misnomer. Such induction is caused by the
source CURRENT and NOT the magnetic field!
This leads Jefimenko on to note that contrary to the "one E field"
theory that has been believed for so many years, the inductive E field
is clearly NOT the same field as an electrostatic E field. Jefimenko
terms this inductive E field the "Electrokinetic Field" to show that it
is a different field from the electrostatic E field. Very good.
However, old habits die hard and even Jefimenko persists in writing an
expression for a "total E field" following Maxwell as consisting of a
sum of the electrostatic and electrokinetic parts as if they were both
the "same" kind of E field.
Jefimenko then proceeds to illustrate the electrokinetic fields with a
series of calculations and examples using his formulas as an approach.
He presents it as basically a "new" way of doing this and in one sense
it is compared to the commonly used and non-causal bogus "flux linkage"
methods. However, he fails to note that the causal Neumann formula is
in essence identical to his formulation and has been a standard
formulation for years for the calculation of the "electrokinetic field"
or what is usually termed "mutual induction". Nevertheless his example
calculations are important basic references to the topic of Faraday
induction. And the consideration of causality clearly shows that the
Neumann approach has the edge over the "flux linkage" ideas with at
times fail to give correct results.
But the subject doesn't end with induction, he pulls gravity into the
mix. Of particular interest is that he shows that once you introduce
causality into Newton's theory of gravitation, interesting things start
to happen! Relativity suddenly begins to show up and even more
interesting "action-reaction" is soon discovered to actually be a law
that does NOT hold in all cases! The electromagnetic nature of gravity
quickly becomes strongly hinted at and without action-reaction laws,
those dreamed of devices such as anti-gravity ships and the
"force-glove" that you wear to push over a building become theoretical
possibilities! These are truly books full of thought-provoking new ways
of looking at tired old physics!
I'm not going to be going through the large quantity of field theory
math in these books in a hurry, but that's OK because clearly taking
the time to go through in detail WILL be worth the effort! What can I
say? Listen to Bill Miller and get that order off to Amazon.com now. At
roughly $25 each these two books are a huge bargain to the usual EM
text books costing hundreds of dollars and then being full of bogus
ideas and misunderstandings of the established theories. Just do it! I
did and I'm not sorry I did!
Benj
http://stupac2.blogspot.com/2007/04/bizarre-and-intriguing-story-of-oleg.html
The
Bizarre and Intriguing Story of Oleg Jefimenko and the Solutions to
Maxwell's Equations
I recently heard the story of Oleg Jefimenko during a lecture on
Electrodynamics, specifically the general solution to Maxwell’s
Equations.
Jefimenko’s tiny bit of fame comes from Jefimenko’s Equations, which
are the general solution to Maxwell’s equations expressed solely in
terms of sources, that is charge and current distributions. The
equations are messy and difficult to work with, and aren’t used much in
practice. But they do reveal certain bits of physics (such as the
applicability of the quasistatic approximation (the link goes to a
thermodynamics page, but the idea is the same) and that fields must be
created by sources), and it’s always nice to have the general solution
to a problem available.
These equations weren’t written down until 1966, about a century after
Maxwell’s Equations were known. Some people will claim (as the
Wikipedia article cited does) that Jefimenko’s Equations were written
down earlier, but those earlier versions are always slightly different
and not quite complete. What’s really funny is that Jefimenko wrote
them down in an attempt to formulate an alternative to Maxwell’s
equations.
When my current Professor, David Griffiths, was in the process of
writing a paper on the subject, he independently derived Jefimenko’s
equations, and tried to figure out if anyone had done it before. Other
than some slightly tricky and annoying math, they’re not hard to
derive, so someone must have done it. He found that Jefimenko had
written them in a book that was published by a company that had only
published one other work, also by Jefimenko (apparently regular
publishers wouldn’t take his books, so he went to a prestige press). He
contacted Jefimenko, and Jefimenko didn’t believe that he had solved
Maxwell’s equations, but that he had created an electromagnetic theory
separate from (and doubtless better than) Maxwell’s. Of course he had
done no such thing, his formulation is exactly equivalent to Maxwell’s,
but he wasn’t buying it.
According to Griffiths, Jefimenko currently submits one or two papers a
week to American journals, gets denied, then publishes them in Europe
(where review is apparently not as stringent). I don’t know what
they’re about, the Wikipedia article says he focuses on overthrowing
Einstein’s General Relativity and Maxwell.
I found this story behind some esoteric equations to be pretty amusing,
and thought others might agree. I hope you’ve enjoyed the convoluted
and intriguing story behind Jefimenko’s equations.
[Most of my information comes from a lecture with Griffiths, and as
such could not be found online. Anything that is available online has
been referenced.]
http://electretscientific.com/
Electret Scientific Co
P.O. Box 4132
Star City, WV
26504 USA
Books
by Professor Oleg Jefimenko
(also available from www.Amazon.com)
Gravitation and Cogravitation --
Developing Newton's Theory of Gravitation to its Physical and
Mathematical Conclusion,
Paperback - List Price US$ 22.00
Hardback - List Price US$ 32.00
Electrostatic Experiments -- An
Encyclopedia of Early Electrostatic Experiments,
Demonstrations, Devices, and Apparatus,
by G.W. Francis (author), Oleg Jefimenko (editor)
Paperback - List Price US$ 24.00
Hardback - List Price US$ 48.00
Electromagnetic Retardation and
Theory of Relativity -- New Chapters in the Classical Theory of Fields,
2nd edition,
Paperback - List Price US$ 24.00
Hardback - List Price US$ 44.00
Causality, Electromagnetic Induction,
and Gravitation -- A Different approach to the Theory of
Electromagnetic and Gravitational Fields, 2nd
edition,
Paperback - List Price US$ 22.75
Hardback - List Price US$ 32.50
An Introduction to the Theory of
Electric and Magnetic Fields, 2nd edition,
Hardback - List Price US$ 72.00
Electrostatic Motors -- Their
History, Types, and Principles of Operation,
Out of Print -- free e-book download available soon
http://www.amazon.com/Electrostatic-Experiments-Encyclopedia-Demonstrations-Apparatus/dp/0917406133
Electrostatic Experiments: An
Encyclopedia of Early Electrostatic
Experiments, Demonstrations, Devices, and Apparatus (Paperback)
http://www.amazon.com/Electrostatic-Motors-Oleg-D-Jefimenko/dp/0917406028
Electrostatic Motors
(Paperback)
by Oleg D. Jefimenko
Scientific American ( October, 1974
)
Electrostatic Motors Are Powered by
Electric Field of the Earth
by
C. L. Stong
Although
no one can make a perpetual motion machine, anyone can tap the earth's
electric field to run a homemade motor perpetually. The field exists in
the atmosphere between the earth's surface and the ionosphere as an
electric potential of about 360,000 volts. Estimates of the stored
energy range from a million kilowatts to a billion kilowatts.
Energy in this form cannot be drawn on directly for
driving ordinary
electric motors. Such motors develop mechanical force through the
interaction of magnetic fields that are generated with high electric
current at low voltage, as Michael Faraday demonstrated in 1821. The
earth's field provides relatively low direct current at high voltage,
which is ideal for operating electrostatic motors similar in principle
to the machine invented by Benjamin Franklin in 1748.
Motors of this type are based on the force of mutual
attraction between
unlike electric charges and the mutual repulsion of like charges. The
energy of the field can be tapped with a simple antenna in the form of
a vertical wire that carries one sharp point or more at its upper end.
During fair weather the antenna will pick up potential at the rate of
about 100 volts for each meter of height between the points and the
earth's surface up to a few hundred feet. At higher altitudes the rate
decreases. During local thunderstorms the pickup can amount to
thousands of volts per foot. A meteorological hypothesis is that the
field is maintained largely by thunderstorms, which pump electrons out
of the air and inject them into the earth through bolts of lightning
that continuously strike the surface at an average rate of 200 strokes
per second.
Why not tap the field to supplement conventional energy
resources?
Several limitations must first be overcome. For example, a single sharp
point can draw electric current from the surrounding air at a rate of
only about a millionth of an ampere. An antenna consisting of a single
point at the top of a 60-foot wire could be expected to deliver about a
microampere at 2,000 volts; the rate is equivalent to .002 watt. A
point-studded balloon tethered by a wire at an altitude of 75 meters
might be expected to deliver .075 watt. A serious limitation appears as
the altitude of the antenna exceeds about 200 meters. The
correspondingly higher voltages become difficult to confine.
At an altitude of 200 meters the antenna should pick up
some 20,000
volts. Air conducts reasonably well at that potential. Although nature
provides effective magnetic materials in substances such as iron,
nickel and cobalt, which explains why the electric-power industry
developed around Faraday's magnetic dynamo, no comparably effective
insulating substances exist for isolating the high voltages that would
be required for electrostatic machines of comparable power. Even so,
electrostatic motors, which are far simpler to build than
electromagnetic ones, may find applications in special environments
such as those from which magnetism must be excluded or in providing low
power to apparatus at remote, unmanned stations by tapping the earth's
field.
Apart from possible applications electrostatic motors
make fascinating
playthings. They have been studied extensively in recent years by Oleg
D. Jefimenko and his graduate students at West Virginia University. The
group has reconstructed models of Franklin's motors and developed
advanced electrostatic machines of other types.
Although
Franklin left no drawing of his motor, his description of it in a
letter to Peter Collinson, a Fellow of the Royal Society, enabled
Jefimenko to reconstruct a working model [see illustration at right].
Essentially the machine consists of a rimless wheel that turns in the
horizontal plane on low-friction bearings. Each spoke of the "electric
wheel," as Franklin called the machine, consists of a glass rod with a
brass thimble at its tip. An electrostatic charge for driving the motor
was stored in Leyden jars. A Leyden jar is a primitive form of the
modern high-voltage capacitor. Franklin charged his jars with an
electrostatic generator.
The high-voltage terminals of two or more Leyden jars
that carried
charges of opposite polarity were positioned to graze the thimbles on
opposite sides of the rotating wheel. The motor was started by hand.
Thereafter a spark would jump from the high-voltage terminal to each
passing thimble and impart to it a charge of the same polarity as that
of the terminal. The force of repulsion between the like charges
imparted momentum to the wheel.
Conversely, the thimbles were attracted by the
oppositely charged
electrode of the Leyden jar Franklin placed on the opposite side of the
wheel. As the thimbles grazed that jar, a spark would again transfer
charge, which was of opposite polarity. Thus the thimbles were
simultaneously pushed and pulled by the high-voltage terminals exactly
as was needed to accelerate the wheel.
Franklin was not altogether happy with his motor. The
reason was that
running it required, in his words, "a foreign force, to wit, that of
the bottles." He made a second version of the machine without Leyden
jars.
In this design the rotor consisted principally of a
17-inch disk of
glass mounted to rotate in the horizontal plane on low-friction
bearings. Both surfaces of the disk were coated with a film of gold,
except for a boundary around the edge. The rotor was thus constructed
much like a modern flat-plate capacitor.
Twelve evenly spaced metal spheres, cemented to the edge
of the disk,
were connected alternately to the top and bottom gold films. Twelve
stationary thimbles supported by insulating columns were spaced around
the disk to graze the rotating metal spheres. When Franklin placed
opposite charges on the top and bottom films and gave the rotor a push,
the machine ran just as well as his first design, and for the same
reason. According to Franklin, this machine would make up to 50 turns a
minute and would run for 30 minutes on a single charge.
Jefimenko gives both motors an initial charge from a
20,000-volt
generator. They consume current at the rate of about a millionth of an
ampere when they are running at full speed. The rate is equivalent to
.02 watt, which is the power required to lift a 20-gram weight 10
centimeters (or an ounce 2.9 inches) in one second.
Jefimenko wondered if Franklin's motor could be made
more powerful. As
Jefimenko explains, the force can be increased by adding both moving
and fixed electrodes. This stratagem is limited by the available space.
If the electrodes are spaced too close, sparks tend to jump from
electrode to electrode around the rotor, thereby in effect
short-circuiting the machine. Alternatively the rotor could be made
cylindrical to carry electrodes in the form of long strips or plates.
This scheme could perhaps increase the output power by a factor of
1,000.
Reviewing the history of electrostatic machines,
Jefimenko came across
a paper published in 1870 by Johann Christoff Poggendorff, a German
physicist. It described an electrostatic motor fitted with a rotor that
carried no electrodes. The machine consisted of an uncoated disk of
glass that rotated in the vertical plane on low-friction bearings
between opposing crosses of ebonite. Each insulating arm of the crosses
supported a comblike row of sharp needle points that grazed the glass.
When opposing combs on opposite sides of the glass were
charged in
opposite polarity to potentials in excess of 2,000 volts, air in the
vicinity of the points on both sides of the glass was ionized. A bluish
glow surrounded the points, which emitted a faint hissing sound. The
effect, which is variously known as St. Elmo's fire and corona
discharge, deposited static charges on both sides of the rotor.
Almost the entire surface of the glass acquired a
coating of either
positive or negative fixed charges, depending on the polarity of the
combs. The forces of repulsion and attraction between glass so charged
and the combs were substantially larger than they were in Franklin's
charged thimbles. The forces were also steadier, because in effect the
distances between the combs and the charged areas remained constant. It
should be noted that adjacent combs on the same side of the glass
carried charges of opposite polarity, so that the resulting forces of
attraction and repulsion acted in unison to impart momentum to the
disk, as they did in Franklin's motor.
By continued experimentation Poggendorff learned that he
should slant
the teeth of the combs to spray charge on the glass at an angle. The
resulting asymmetrical force made the motor self-starting and
unidirectional. When the teeth were perpendicular to the glass surface,
the forces were symmetrical, as they were in Franklin's motor. When the
machine was started by hand, it ran equally well in either direction.
Poggendorff was immensely pleased by the rate at which
his machine
converted charge into mechanical motion. He concluded his paper with a
faintly odious reference to Franklin's device. "That such a quantity of
electricity must produce a far greater force than that in the
[Franklin] electric roasting spit," he wrote, "is perfectly obvious and
nowadays would not be denied by Franklin himself. With one grain of
gunpowder one cannot achieve so much as with one hundred pounds."
Electrostatic motors are now classified in general by
the method by
which charge is either stored in the machine or transferred to the
rotor. Poggendorff's machine belongs to the corona type, which has
attracted the most attention in recent years. Although its measured
efficiency is better than 50 percent, Poggendorff regarded it merely as
an apparatus for investigating electrical phenomena. He wrote that "it
would be a sanguine hope if one wanted to believe that any useful
mechanical effect could be achieved with it."
Poggendorff's
negative attitude toward the usefulness of his design may well have
retarded its subsequent development. A modern version of the machine
constructed in Jefimenko's laboratory has an output of approximately .1
horsepower. It operates at speeds of up to 12,000 revolutions per
minute at an efficiency of substantially more than 50 percent. In one
form the modern corona motor consists of a plastic cylinder that turns
on an axial shaft inside a concentric set of knife-edge electrodes that
spray charge on the surface of the cylinder [see illustration at left].
Forces that act between the sprayed charges and the knife-edge
electrodes impart momentum to the cylinder.
Machines of this kind can be made of almost any
inexpensive dielectric
materials, including plastics, wood and even cardboard. The only
essential metal parts are the electrodes and their interconnecting
leads. Even they can be contrived of metallic foil backed by any stiff
dielectric. The shaft can be made of plastic that turns in air
bearings. By resorting to such stratagems experimenters can devise
motors that are extremely light in proportion to their power output.
Corona motors require no brushes or commutators. A potential of at
least 2,000 volts, however, is essential for initiating corona
discharge at the knife-edges.
A smaller and simpler version of the machine was demonstrated in 1961
by J. D. N. Van Wyck and G. J. Kühn in South Africa. This motor
consisted of a plastic disk about three millimeters thick and 40
millimeters in diameter supported in the horizontal plane by a slender
shaft that turned in jeweled bearings. Six radially directed needle
points grazed the rim of the disk at equal intervals. When the machine
operated from a source of from 8,000 to 13,000 volts, rotational speeds
of up to 12,000 revolutions per minute were measured.
I made a corona motor with Plexiglas tubing two inches
in diameter and
one and a half inches long. It employed stiffbacked single-edge razor
blades as electrodes. The bore of the tube was lined with a strip of
aluminum foil, a stratagem devised in Jefimenko's laboratory to
increase the voltage gradient in the vicinity of the electrodes and
thus to increase the amount of charge that can be deposited on the
surface of the cylinder. I coated all surfaces of the razor blades
except the cutting edges and all interconnecting wiring with
"anticorona dope," a cementlike liquid that dries to form a dielectric
substance that reduces the loss of energy through corona discharges in
nonproductive portions of the circuit.
The axial shaft that supports the cylinder on pivot
bearings was cut
out of a steel knitting needle. The ends of the shaft were ground and
polished to 30degree points. To form the points I chucked the shaft in
an electric hand drill, ground the metal against an oilstone and
polished the resulting pivots against a wood lap coated with tripoli.
The bearings that supported the pivots were salvaged
from the
escapement mechanism of a discarded alarm clock. A pair of indented
setscrews could be substituted for the clock bearings. The supporting
frame was made of quarter-inch Lucite. The motor can be made
self-starting and unidirectional by slanting the knife-edges. Those who
build the machine may discover, as I did, that the most difficult part
of the project, balancing the rotor, is encountered after assembly. The
rotor must be balanced both statically and dynamically.
Static balance was achieved by experimentally adding
small bits of
adhesive tape to the inner surface of the aluminum foil that lines the
cylinder until the rotor remained stationary at all positions to which
it was set by hand. When the rotor was balanced and power was applied,
the motor immediately came up to speed, but it shook violently. I had
corrected the imbalance caused by a lump of cement at one end of the
rotor by adding a counterweight on the opposite side at the opposite
end of the cylinder. Centrifugal forces at the ends were 180 degrees
out of phase, thus constituting a couple.
The dynamic balancing, which is achieved largely by
cut-and-try
methods, took about as much time as the remainder of the construction.
To check for dynamic balance suspend the motor freely with a string,
run it at low speed and judge by the wiggle where a counterweight must
be added. Adhesive tape makes a convenient counterweight material
because it can be both applied and shifted easily.
I made the motor as light and frictionless as possible
with the
objective of operating it with energy from the earth's field. The field
was tapped with an antenna consisting of 300 feet of No. 28 gauge
stranded wire insulated with plastic. It is the kind of wire normally
employed for interconnecting electronic components and is available
from dealers in radio supplies.
The upper end of the wire was connected to a 20-foot
length of metallic
tinsel of the kind that serves for decorating a Christmas tree. The
tinsel functioned as multiple needle points. Strips cut from window
screening would doubtless work equally well.
The upper end of the tinsel was hoisted aloft by a
cluster of three
weather balloons. Such balloons, each three feet in diameter, and the
helium to inflate them are available from the Edmund Scientific Co.
(300 Edscorp Building, Barrington, N.J. 08007). The weight in pounds
that a helium-filled balloon of spherical shape can lift is roughly
equal to a quarter of the cube of its radius in feet. To my delight the
motor began to run slowly when the tinsel reached an altitude of about
100 feet. At 300 feet the rotor made between 500 and 700 revolutions
per minute.
A note of warning is appropriate at this point. Although
a 300-foot
vertical antenna can be handled safely in fair weather, it can pick up
a lethal charge during thunderstorms. Franklin was incredibly lucky to
have survived his celebrated kite experiment. A European investigator
who tried to duplicate Franklin's observations was killed by a bolt of
lightning. The 300-foot antenna wire can hold enough charge to give a
substantial jolt, even during fair weather. Always ground the lower end
of the wire when it is not supplying a load, such as the motor.
To run the motor connect the antenna to one set of
electrodes and
ground the other set. Do not connect the antenna to an insulated object
of substantial size, such as an automobile. A hazardous charge can
accumulate. Never fly the balloon in a city or in any other location
where the antenna can drift into contact with a high-voltage power
line. Never fly it below clouds or leave it aloft unattended.
A
variety of corona motors have been constructed in Jefimenko's
laboratory. He has learned that their performance can be vastly
improved by properly shaping the corona-producing electrodes [see
illustration at right]. The working surface of the rotors should be
made of a fairly thin plastic, such as Plexiglas or Mylar. Moreover, as
I have mentioned, the inner surface of the cylinder should be backed by
conducting foil to enhance the corona. Effective cylinders can be
formed inexpensively out of plastic sewer pipe. Corona rotors can of
course also be made in the form of disks.
One model consists of a series of disks mounted on a
common shaft.
Double-edged electrodes placed radially between adjacent disks function
much like Poggendorff's combs. This design needs no foil lining or
backing because a potential gradient exists between electrodes on
opposite sides of the disks. It is even possible to build a linear
corona motor, a design that serves to achieve translational motion. A
strip of plastic is placed between sets of knife-edge electrodes
slanted to initiate motion in the desired direction.
Notwithstanding the problem of handling potentials on
the order of a
million volts without effective insulation materials, Jefimenko
foresees the possibility of at least limited application of corona
power machines. In The Physics Teacher (March, 1971) he and David K.
Walker wrote: "These motors could be very useful for direct operation
from high-voltage d.c. transmission lines as, for example, the 800 kV
Pacific Northwest-Southwest Intertie, which is now being constructed
between the Columbia River basin and California. It is conceivable that
such motors could replace the complex installations now needed for
converting the high-voltage d.c. to low-voltage a.c. All that would be
required if corona motors were used for this purpose would be to
operate local low-voltage a.c. generators from corona motors powered
directly from the high-voltage d.c. line."
As Jefimenko points out, a limiting factor of the corona
motor is its
required minimum potential of 2,000 volts. This limitation is
circumvented by a novel electrostatic motor invented in 1961 by a
Russian physicist, A. N. Gubkin. The motor is based on an electret made
in 1922 by Mototaro Eguchi, professor of physics at the Higher Naval
College in Tokyo.
An electret is a sheet or slab of waxy dielectric
material that
supports an electric field, much as a permanent magnet carries a
magnetic field. Strongly charged carnauba-wax electrets are available
commercially, along with other electrostatic devices, from the Electret
Scientific Company (P.O. Box4132, Star City, W.Va. 26505). A recipe for
an effective electret material is 45 percent carnauba wax, 45 percent
water-white rosin and 10 percent white beeswax. Some experimenters
substitute Halowax for the rosin.
The ingredients are melted and left to cool to the solid
phase in a
direct-current electric field of several thousand volts. The wax
continues to support the field even though the external source of
potential is turned off [see "The Amateur Scientist, SCIENTIFIC
AMERICAN, November, 1960, and July, 1968]. The electret reacts to
neighboring charges exactly as though it were a charged electrode, that
is, it is physically attracted or repelled depending on the polarity of
the neighboring electrode.
Gubkin harnessed this effect to make a motor. The rotor
consisted of a
pair of electrets in the shape of sectors supported at opposite ends of
a shaft. The center of the shaft was supported transversely by an axle.
When the rotor turned, the electrets were swept between adjacent pairs
of charged metallic plates, which were also in the form of sectors.
The plates were electrified by an external source of
power through the
polarity-reversing switch known as a commutator. The commutator applied
to the electrodes a charge of polarity opposite to the charge of the
attracted electret. As the electret moved between the attracting
plates, however, the commutator switched the plates to matching
polarity. The alternate push and pull imparted momentum to the rotor in
exact analogy to Franklin's motor.
Gubkin's motor was deficient in two major respects. The
distances
between the electrodes and the electrets were needlessly large, so that
the forces of attraction and repulsion were needlessly weak. Moreover,
during the electret's transit between electrodes its surfaces were
unshielded. Unshielded electrets attract neutralizing ions from the air
and lose their charge within hours or days.
Motors
based on the slot effect can be designed in a number of forms. One
design consists of an electret in the shape of a wafer-thin sheet of
Mylar supported by a flat disk of balsa wood 100 millimeters in
diameter and three millimeters thick. (A long-lasting charge is
imparted to the Mylar by immersing it in a field of a few thousand
volts from an electrostatic generator after the motor is assembled.)
This rotor is sandwiched between four semicircular sectors that are
cross-connected [ see illustration ].
The electret is mounted on a four-millimeter shaft of plastic that
turns in jeweled bearings. The conducting surfaces of the commutator
consist of dried India ink. The brushes are one-millimeter strips of
kitchen aluminum foil. The motor operates on a few microwatts of power.
Jefimenko has demonstrated a similar motor that was designed to turn at
a rate of about 60 revolutions per minute and develop a millionth of a
horsepower on a 24-foot antenna having a small polonium probe at its
upper end. (By emitting positive charges probes of this type tap the
earth's field somewhat more efficiently than needle points do.) The
performance of the motor easily met the design specifications. The
charm of these motors lies in the fact that, although they do not
accomplish very much, they can run forever.
Bibliography
ATMOSPHERIC ELECTRICITY. J. Alan Chalmers. Pergamon Press, 1968.
ELECTROSTATIC MOTORS: THEIR HISTORY, TYPES AND PRINCIPLES OF OPERATION.
Oleg D. Jefimenko. Electret Scientific Company, 1973.
ELECTROSTATICS AND ITS APPLICATIONS. Edited by A. D. Moore. John Wiley
& Sons, 1973.
Annales
de la Fondation Louie de Broglie 32 (1 ) : 117 ( 2007 )
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