Re: Gore's Ball

[William Beaty <billb@eskimo.com>]

On Wed, 16 Jul 1997, Brad Shue wrote:

> Herb,
> 	I think he is refering to a variation on a "rail gun" that uses
> the magnetic fields produced by a flowing current to cause an object to
> move.  We do this with a Pasco magnet, 2 brass rods and a slider that
> slides down the rods when current from a battery flows through it.

Yes, the force from a current in a loop of wire makes the loop expand, and
if a roller is placed on a pair of rods connected to a battery, the roller
will move away from the battery such that the area of the loop is
increased.  If a kilojoule/kilovolt capacitor bank is the power supply,
hide behind thick walls before throwing the switch!

The effect is different (and stronger) if the roller/cylinder is itself a
magnet, with alike poles on the end faces and an opposite pole on the
cylindrical surface.  Direction of rotation then is dependant on polarity. 
This constitutes the opposite of Faraday's homopolar disk generator: a
homopolar motor!  Cylindrical homopolar devices are topologically
identical to two stacked Faraday Disks on a common shaft, with brushes
only on the edges of the disks, and b-fields along the disk axes and one
magnetic pole between the disks.  I encountered these things in Charles
Yost's ELECTRIC SPACECRAFT JOURNAL, which publishes weird and interesting
discoveries made by "fringe" researchers. 

I built one tri-polar homopolar roller by gluing two .75"dia x .375" 
Neodymium disk magnets together with alike-poles facing, wrapped with tape
to increase the diameter, then jammed within a short copper pipe.  (If I
ever dropped the thing, the magnets would probably launch out like
bullets!)  If I recall, it took 10 or 20 amperes to make it roll along the
rails.  The force was constant, so when I tilted the rails at an incline,
the roller would sit still, or would drift along if bumped, as if local
gravity was at an angle.  Odd to watch. 

The device in the ESJ was a pair of parallel steel disks an inch apart,
disk planes horizontal, with the edges acting as the "rails" and the
rollers adhering to the steel.  Several tripolar homopolar rollers were
placed to link the disks together.  The rollers repel each other and adopt
uniform spacing.  When many amps is run from disk to disk, the rollers
collectively drift along.

Why do all this?   BECAUSE!   ;)

One thing I always meant to try: build two tri-polar cylindrical rollers,
place them on parallel conductive rods at enough distance so their fields
do not interact, then push one along and see if the other responds.  One
will act as a homopolar generator and create large amperage at fractional
voltage, the other is a homopolar motor.  How efficient are they, how
close is the in/out coupling?  The rods would probably have to be wetted
with mercury in order to eliminate the large resistance at the contact
points.  If big ones were used as the wheels in each car in a train, then
the cars would need no physical coupling, and if one was dragged along,
all the others would move as well.

......................uuuu / oo \ uuuu........,.............................
William Beaty  voice:206-781-3320   bbs:206-789-0775    cserv:71241,3623
EE/Programmer/Science exhibit designer        http://www.eskimo.com/~billb/
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