Frictionless Bearings in a Model of Inductive Magnetic Levitation
Ryan Thompson, Doug Goncz, Brad Bynum, Austin Nehmer
Society of Physics Students, Northern Virginia Community College, Annandale, Virginia 2012
Introduction
We are conducting a series of experiments involving the
repulsion between a circular Halbach array and a circular
arrangement of inductive copper coils. The Halbach array was
built with particularly magnetizes Nd magnets (Fig 1). Their
specific arrangement concentrates a sinusoidally variable
dodecamagnet on the strong side while leaving the other side
much weaker. The coils are then suspended from a force
sensor, which measures the force of gravity pulling down. The
Halbach is then spun, with the strong side as close to the coils
as possible (Fig. 4), which generates eddy currents in the
inductive coils according to Faraday’s Law. These currents
generate a magnetic field which provides for repulsion and,
eventually, levitation. It is expected that the force of repulsion
upward will be strong enough to overcome gravity if the two
pieces relative velocities are high enough.
Results
Conclusions
After organizing the Nd magnets into the circular Halbach array, it
was noticed that the magnetic field on the strong side was stronger
than the magnets were individually.
In conclusion, we have merely witnessed inductive magnetic
repulsion; however, with the proper improvements magnetic
levitation is possible. One of the major necessary
improvements includes dynamically balancing the magnetic
array. Once this has been achieved the magnetic array
(Helvetica, 44 pt.)
blah blah blah.....This section was all be altered should any
tests be conducted using a modified magnetic array. That
would then push the above acknowledgements over to the
results section and possibly even the materials/methods. Also
levitation may have then been achieved.
Figure 1.
The 12 magnets alternate
magnetizations so that the
face shown goes from North
to counter clockwise to
South to clockwise and then
starts over.
The weak side has a magnetic field of only 0.3 Tesla, varying
slightly around the base.
During experimentation it was noticed that the force acting on the
force sensor oscillated back and forth between a value which
was greater and lesser in magnitude compared to the average
force.
The above graph epitomizes the results of our hard work and
experimenting. While this chart shows Force vs. Time, one can
also infer this to be Force vs. Rotational Velocity. As time
passed, the velocity was consistently increased by pressing the
“Up” button about every second. After about sixteen seconds this
run was aborted as well due to stress on the rotating machine.
Had this process continued, achieving 4,000 rpm at about the
forty second mark levitation should have been recorded.
In the future we plan to obtain a more powerful rotator, balance
the Halbach array, and more stable guidance system for the
coils. With these improvements our final results will be improved,
and levitation should be achieved.
Materials and Methods
Literature cited
Tosney, Kathryn 2006. How to create a poster that graphically
communicates your message. Professor of Biology-The University of
Michigan.
http://www.biology.lsa.umich.edu/research/labs/ktosney/file/PostersH
ome.html
Ritchison, Gary 2006. Guidelines for poster presentations. Scientific
Literature and writing.
http://www.biology.eku.edu/RITCHISO/posterpres.html
Figure 2.
Final
magnet
forced
into
position
using 1/2
ton
press.
The circular Halbach was constructed using twelve
0.6 Tesla Nd magnets. Ten of these magnets were
inserted by hand into a circular ring of aluminum and
secured into place using screws around the outer ring.
The final two were positioned using a half ton press
(Fig. 2).
After restricting the coils from spinning and/or swaying back and
forth, a more desirable result was found. This result is
highlighted by the pink lines shown above in which the average
force acting upon the force sensor is eventually reduced by a
factor of almost four newtons.
The ring of coils (Fig. 3) consists of five eighteen gage
copper wire coils. Each ring consists of approximately
two hundred turns and have an outer diameter of 1.25”
an inner diameter of 0.75” and a height of 1.00”. These
five coils were then secured to a non magnetic board
every 72 degrees.
Figure 3.
Inductive Coils, each coil
completes a separate loop within
itself.
This particular run was aborted after about eighty seconds because
the rotator and coil system became unstable due to the high
rotational velocities. This lack of stability may have been increased
due to an imbalance of the magnets spun with the rotator. Without the
magnets attached, the rotator is capable of spinning at 4,000 rpm but
when the complete system is set up 1,500 rpm seems to be the
maximum speed we can achieve.
Figure 6.
Force sensor is
suspending coils
above circular
Halbach array.
Clips shown
apply only a
horizontal force
in order to
prevent sway.
Acknowledgments
We thank Walerian Majewski for laboratory assistance, Robert Woodke for
machine shop assistance, and Data Studio for statistical observations.
Funding for this project was provided by grants received by the Society of
Physics Students as well as the Northern Virginia Community College
Educational Foundation.
For further information
More information on this and related projects can be obtained by
contacting wmajewski@nvcc.edu or thomps55@illinois.edu
or visiting www.spsnational.org
A rotator used to spin the magnets (Fig 4).
Figure 4.
Our rotator, which plugs
into the wall and spins in
either direction at speeds
up to 4,000 rpm.