RE: [TCML] Tesla's spinning egg of Columbus

[William Beaty <billb@xxxxxxxxxx>]

On Sun, 16 Nov 2008, Lau, Gary wrote:

> I've not studied the topic beyond a casual interest, but the choice of a
> toroidal core seems curious to me.

It Tesla's induction motor stator.  I suspect this whole idea was Tesla's,
dating at least back to his DC motor work for Edison corp or perhaps
earlier.  It's in his patent drawings ...but did any earlier inventors
already use the idea?  It comes from an odd viewpoint, using coils 90deg
from usual orientation, so I wouldn't be surprised if NT was the source.

  Patent dwg 381968
  http://upload.wikimedia.org/wikipedia/en/thumb/7/7a/RMFpatent.PNG/222px-RMFpatent.PNG
  http://www.pbs.org/tesla/res/381968.html

Rather than building a horseshoe-style electromagnet as a DC motor's
stator coil, instead use a closed iron ring and place the motor's rotor
in the center.  Such redesigned electric motors would then become
cylindrical devices.  This breaks with most earlier traditions of
employing large U-shaped or bar-magnet electromagnets extending out the
side of the motor, see for example

  Edison dynamos
  http://images.google.com/images?gbv=2&hl=en&q=edison+dynamo

Wind your stator coil on the ring, but split it into two separate
windings, each covering half the ring, then connect them so they create
alike magnetic poles adjacent to the end of each winding.  The flux spews
out of two spots on the ring and extends across the center.  Then add a DC
motor rotor/commutator inside the ring.

A "small" change is to use four AC coils with 90deg phase, and suspend a
copper-covered iron rotor in the center like so:         :)

  http://www.teslasociety.com/pictures/bday19.jpg

  http://www.sciencemuseum.org.uk/images/object_images/535x535/10323397.jpg

  http://www.electrotherapymuseum.com/2006/LIPhotos/Jane/billwysockcopy.jpg
  http://www.electrotherapymuseum.com/2006/LIPhotos/InductionMotorFront2.jpg
    (from http://www.electrotherapymuseum.com/2006/LIPhotos/index.htm)

The Columbi Egg was of course an induction motor demo, and it displayed
the induction motor stator Tesla used in his prototypes.

> Isn't the point of a toroidal core,
> to as completely as possible, contain all of the magnetic flux (so the
> egg would see very little of it)?

If the goal was to replace the traditional bulky U-shaped motor core with
a compact ring core which tightly hugs the motor's rotor, everything
becomes clear.

More old motors:  http://www.sparkmuseum.com/MOTORS.HTM



Separate question:

If Tesla redesigned Edison's motor product line, then walked away
over the $50,000 "joke"  ...what exactly did Tesla design?   I've never
heard anyone ask this question, much less answer it.   I strongly suspect
that Tesla got rid of Edison's "skeletal-U" stator shape:
http://www.antiqbuyer.com/ARCHIVEPICS/cc_motor.jpg
and replaced it with cylindrical stators.

If so, then not only did was Tesla responsible for the induction motor,
but he's responsible for the cylindrical shape of ALL electric motors.


(((((((((((((((((( ( (  (   (    (O)    )   )  ) ) )))))))))))))))))))
William J. Beaty                            SCIENCE HOBBYIST website
billb at amasci com                         http://amasci.com
EE/programmer/sci-exhibits   amateur science, hobby projects, sci fair
Seattle, WA  206-762-3818    unusual phenomena, tesla coils, weird sci
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