All-mechanical magnetic levitation
Youtube maglev video
More billb videos
NOTE: this is an adult-level project. It requires a machine shop in
order to build it, and the finished project is extremely dangerous.
For simple and safe, try simple maglev train.
While working on science museum exhibits in 1990 I came up with the above
idea: it is known that a spinning metal disk will lift and fling a strong
magnet. Therefore, metal rods with opposite spin will lift a magnet but
it sideways. It works! I used "sched-80" heavy wall copper tubes about
long, with 1/4" wall thickness. I hammered aluminum plugs into the
carved shaft-tips with a lathe, built endblocks and bearings, spun them
with an AC/DC motor, and managed to levitate a stack of two 3/4" diameter
neodymium magnets. The spinning tubes must move at about 5000 RPM before
the magnet starts floating.
The tubes I ordered from ALASKAN COPPER AND BRASS, Seattle WA,
1-800-552-7661. The exact size isn't too important, but the tube should
have a VERY thick wall, 3/16" to 1/4" thick if possible. My copper tubes
were about 1-1/4 OD and 12" long, about $25 each back then [ P. Ledlie has
found a second source for tubes: "Copper and Brass Sales" at 503-254-2600,
more expensive though. ] Alaskan Copper has a stock size tube of 1" ID,
1-5/16" OD which should work.
I used an old motor I already had, a Dayton AC/DC 115V 1/15HP 5000RPM
unit. I believe that these are sold in Grainger catalog under universal
AC/DC type, 1/15 horsepower. The drive belt was a large O-ring, I put a
1/2" pulley on the
motor shaft, and moved the copper tube bearing endblocks so the tubes
O-ring/belt slightly (so when the motor spun one tube, the other tube also
touched the belt and spun.) Note that the arrows in the above drawing are
wrong, the magnet floats MUCH higher if the tubes spin the other way
instead. Spin them so they "blow" the magnet upward rather than "sucking"
If you wish to reproduce the above device, be aware that you'll probably
need access to a machine shop. To connect bearings to the tubes, I made
tapered aluminum plugs on a lathe, chilled them and hammered them into the
ends of the tubes, carved them into small shaft stubs which fit my ball
bearing races, then carved some plastic end blocks using drillpress and
WARNING WARNING WARNING
Note that when many pounds of copper tube is spinning at 5000RPM, it is EXTREMELY DANGEROUS. If you bump your fingers against it, it could EAT YOUR ENTIRE ARM INSTANTLY. Or if the sharp edges of a magnet get caught, the magnet could explode and the pieces fly out like bullets. It's FAR more dangerous than any power tool. For safety I made a close-fitting plexiglas box to cover the tubes: I heated a sheet of plexi on a greased aluminum foil sheet in an oven, molded it over the top of the tubes while wearing heavy gloves, then carved it square and used it as the top plate in a plexiglas box. The magnets only hover about 1/4" above the spinning tubes, so if you build a cover, it must be close-fitting without touching. The cover isn't required for initial testing, just for operation around curious fingers.
Try to avoid using steel for anything except the ball bearings, otherwise
the hovering magnet will be sucked to the end of the tubes. If you decide
to make the tubes lots shorter than 12", be aware that the magnet might
become unstable and drift towards the steel ball bearings. This
might be fixable: put a small piece of iron below the tubes, close
enough to attract the magnet to remain centered, but not so close
that it pulls the magnet down into the tubes.
Other notes: neodymium-iron-boron (NIB) cylinder magnets are required.
Ceramic or alnico magnets are too weak, although they might hover if the
RPMs of the tubes could be doubled or tripled. Samarium-Cobalt magnets
work, but are too expensive. One source for rare-earth NIB magnets is
Force Field, www.wondermagnet.com.
I know that their 3/4" dia, 3/8" thick NIB
disk works well. I haven't tried the small cylinders, but they PROBABLY
work OK. See my NEODEMO file
for more fun things to do with
NIB supermagnets. Heed the safety warning!
Another way to make a magnet hover: use a superconductor. When a magnet
approaches a superconductor plate, it induces a circle of moving charge.
Since the superconductor has no resistance, the current will never be
slowed, the repelling fields will not die away, and the magnet will hover.
But superconductors require super-cold liquid nitrogen for their
operation. They are also fairly expensive: $10 to $20 for a 1" disk.
If we could just MOVE our magnet suddenly sideways across the copper,
a new pattern of current would be induced, and the magnet would be
repelled again. If we could move the magnet rapidly across the metal
plate, it would lift up and fly. One form of "Maglev Train" uses this
effect, it contains powerful magnets in its lower surface, and "flys" over
a thick aluminum trough.
The magnet-roller device turn the train idea upside-down. The "train"
stays still and the track moves fast.