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Re: "Unconventional dynamo" = cylinder HPG



On Wed, 5 Jun 2002, Chuck Britton wrote:

Bill, do you have any performance figures on any of these designs????

On mine? No, I just slapped things together to see if they would move at
all when driven as motors. I only made a simple Faraday's disk and a
cylindrical homopolar motor based on rails and roller. Using neodymium
magnets gave distinct results, so I suspect that ceramic magnets might be
too weak for what I was doing.

I've always wanted to experiment with that "chevron slots" motor idea, but
I suspect that the torques only become significant at thousands of
amperes. Shorted car batteries are too scary! Or as a no-magnets
self-excited generator, the "chevron slots" rotor would probably need
liquid metal slip rings. (Think of it as the Amperian answer to the
Wimshurst machine. Magnetic fields from nowhere.)


My cylindrical roller was made from two neodymium cylinder magnets 0.75"
diameter, glued with alike poles facing. (I think those magnets are 0.5"
tall, so the assembly was 1" long.) I made a short HDPE pipe on a lathe,
where the pipe was a slip-fit on the magnets, and also was a slip fit on
the I.D. of some scrap copper pipe I had in my junk collection. So, the
whole cylindrical roller assembly had:

thick copper on the outer surface
layer of plastic to keep the magnet centered
N-S-N neodymium magnet assembly

It would roll nicely once all the oxide was sanded off the steel welding
rods I used as rails.

As a high-current power supply I used a weighty 5.0VAC 50-amp filament
transformer with a bridge made from 100-amp diodes, then drove it with a
variac. When I adjusted it for 50 amps short circuit current, then placed
the magnet-cylinder assembly on the two horizontal rails, it rolled
rapidly forwards with some sparking. (No dangerous velocities, and maybe
2m/sec^2 acceleration.) If I tilted the rails at about a 20deg angle,
gravity would cancel the linear motor force. In that case a gentle shove
would make the cylider roll either uphill or down.


I never tried mounting any rotors with bearings and brushes (I just drew
diagrams of such things.) Since the voltage is so low and the current is
so high, any normal brush will become the major load in the circuit. If
you want to run these devices as proper motors and generators (with power
on the order of 1w - 10w), you'd need liquid metal brushes. Rolling a
copper cylinder on some steel rails worked OK, but I kept having to sand
down the steel to prevent bits of oxidation from creating heat (creating
spot-welds!)

PS, try supergluing a pair of NIB magnets with faces repelling! If you
first make a slip-fit plastic tube, and use a C-clamp, it becomes
feasible. I filled the ends of the assembly with glue too, since I had
visions of the magnets coming out like bullets if the glue should ever
crack.




At 1:12 AM -0700 on 6/4/02, William Beaty wrote
Hi Wojciech!

This regards your article "Unconventional Dynamo" in TPT April 2002 p220


Very interesting device you have there. I've seen that demonstration in
the past, but not such a simple version. (Actually, you can make yours
even simpler. Replace your array of magnets with a tripolar magnet: south
on both ends and north pole in the center, using a stack of disk magnets.)

This sort of device is closedly connected with Faraday's Disk, also known
as the Homopolar Generator or "HPG." Some hobbyists call these by the
name "N-machine." Another variant is called "Alexander's Wheel."

A few years ago I built various versions of these and made some GIF
diagrams. Take a look:

Two Faraday-disk generators
http://amasci.com/graphics/nmchcyl1.gif

Merge the two generators to create a cylindrical HPG
http://amasci.com/graphics/nmchcyl2.gif

Slotted-rotor self-excited HPG motor or generator (no magnet used)
http://amasci.com/freenrg/chevron.gif

The magnet feels no torque. The external circuit is the "stator."
http://amasci.com/freenrg/N_MACH1.GIF

Faraday's disk, but where's the rotor? Where's the stator?
http://amasci.com/freenrg/N_MACH2.GIF



Here is a book about this topic:

The Homopolar Handbook
http://www.amazon.com/exec/obidos/ISBN%3D0964107015/


Here are other things I tried back in 1992:

Rather than a wire loop, enclose the whole magnet within a metal
cylinder. The generator still works. This was suggested in
Charles Yost's hobby journal ESJ, "Electric Spacecraft."

Rather than using bearings and two brushes, place the cylinder-assembly
upon two rails. Connect your ammeter across the rails. When you
force the cylinder-assembly to roll along, the meter detects the current
being created.

Instead of a generator, RUN THE DEVICE AS A MOTOR. Connect a power
supply to the rails mentioned above. Up to 30 amperes is required. The
cylinder-assembly will begin to roll along. Reverse the current, and it
rolls the other way.

Something I did not try: make TWO rail assemblies and TWO cylinder
assemblies. Connect the rail assemblies together electrically. Now,
when you roll one of the cylinders, it generates a large current, which
should run the OTHER cylinder like a motor! Push one, and the other
one moves. Or push the second, and the first one moves. (Does this
actually work?) It's a motor/generator pair.

In my version, I glued two 2cm neodymium supermagnets together so alike
poles were face-to-face. This creates a cylinder magnet with one pole on
the side of the cylinder, and the other two opposite poles on the ends.
This I placed within a copper tube, then rolled the copper tube on
parallel metal rails.

These devices are very strange. When operated as a generator, motions of
the magnet do not create any DC. When operated as a motor, the magnet
does not spin. The torque appears between the "rotor" conductors and the
connecting wires. If you hold the "rotor" still, and instead rotate the
brushes and the ammeter around it, you will create just as much current as
when you hold the brushes and ammeter still and instead turn only the
rotor.

(((((((((((((((((( ( ( ( ( (O) ) ) ) ) )))))))))))))))))))
William J. Beaty SCIENCE HOBBYIST website
billb@eskimo.com http://amasci.com
EE/programmer/sci-exhibits science projects, tesla, weird science
Seattle, WA 206-789-0775 sciclub-list freenrg-L vortex-L webhead-L


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Chuck Britton Education is what is left when
britton@ncssm.edu you have forgotten everything
North Carolina School of Science & Math you learned in school.
(919) 416-2762 Albert Einstein, 1936


(((((((((((((((((( ( ( ( ( (O) ) ) ) ) )))))))))))))))))))
William J. Beaty SCIENCE HOBBYIST website
billb@eskimo.com http://amasci.com
EE/programmer/sci-exhibits science projects, tesla, weird science
Seattle, WA 206-789-0775 sciclub-list freenrg-L vortex-L webhead-L