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Message-ID:	<51505B7A.8060202@ecosensory.com>
Date:	Mon, 25 Mar 2013 09:13:14 -0500
From:	John Griessen <john AT ecosensory DOT com>
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To:	geda-user AT delorie DOT com
Subject:	Re: [geda-user] Magnetic Exercise Bike design with a stator and rotor
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Reply-To:	geda-user AT delorie DOT com

On 03/24/2013 03:58 PM, Rob Butts wrote:
> One plastic disc is fixed and the opposing plastic disk is allowed to rotate 30 degrees providing the variable magnetic field and
> variable resistance.  I have not been able to simulate the resistance I believe because I'm not providing the same rotational
> velocity of the aluminum disc.

Sounds like the out of alignment of the discs makes the field vary from weak to strong.
To have strong fields, each magnet needs to be straight across, (through the aluminum disc),
from another with same polarity direction.  Then induced currents flowing in circles around the strong field area
counter subsequent motion by a force of their own.  I've never quite grasped how that force stays local
to any place in the aluminum plate though...perhaps inertia of electrons?  Else moving the path of the high
eddying current is more resistive than the eddy path?  It's all so circular!  I feel like researching
and reading about it instead of doing my taxes...

What do you mean by simulate?  What velocity can you get?

Some decent velocity is needed for small inexpensive magnets.  I've seen a demo
of eddy current braking done with a pendulum hung plate, then a slotted plate
for comparison, where the opposing magnets were very massive and with iron looping
around to make a complete magnetic circle path with two short gaps, ( where the aluminum
plate moved).  It would slow the pendulum in one stroke by 4/5ths.  It must have weighed
80 lbs.

An alternator will need velocity also.  Bicycle gearing can get you velocity.

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