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Bigger & Better Toroids



---------- Forwarded message ----------
Date: Wed, 8 Oct 1997 12:47:44 -0400
From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Bigger & Better Toroids



----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Why a toroid? 
> Date: Tuesday, October 07, 1997 11:04 PM
> 
> 
> 
> ---------- Forwarded message ----------
> Date: Tue, 07 Oct 1997 19:04:16 +0000
> From: Greg Leyh <lod-at-pacbell-dot-net>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Why a toroid?
> 
> A lot of effort has been directed at fabricating toroids for TC's.
> Has anyone ever tried using a large metal disk as the top
electrode?
> A suitably sized disk would have just as much C to gnd as the
toroid.
> 
> I know that I should just try it myself, but I thought I'd ask
first.
> 
> 
> -GL

Greg,
While a large flat plate would have a really good capacitance value,
it would be plagued by the corona losses off of the edge of the
plate. In this regard, a round plate might be better than a square
plate, but both would be miserable ozone generators :(

Plan 2. Use a big round flat plate and curve it so you have no sharp
edges. You just made a sphere or an oblate shaped collector.

Plan 3. Keep the plate round and smooth and add corona protection
around the edge. You just made a toroid with a plate inside. Due to
the smaller radius of curvature of the outer toroid, the inner plate
is shielded as far as the e-field goes, so you might as well remove
the inner plate. And now you have a toroid.

Plan 4. Build a toroid that is wide but not too thick, say something
like a 36 x 6 and surmount it with a metal cylinder that has a
diameter of 30 and a height of say 20. Surmount the cylinder with
another toroid, say 36 x 6. NOW you have increased the effective
capacitance VERY cheaply with the inexpensive and easy to make
cylinder. The two toroids help prevent that nasty corona stuff. If
the corona is more than you like, then make the toroids something
like 36 x 12 and the cylinder with a diameter of say just less than
36 and a height as much as your little heart desires. 

The cylinder can be aluminum foil or flashing with a frame made of
just about anything. Wood, plastic, coat hangers, popsicle sticks,
hollow pvc pipes, 1" thick steel boiler plate. Whatever you gots that
works. Heck, on a really BIG one you can dispense with the outer
coating and just use an occasional metal rod or pipe to "suggest" the
outline of a cylinder. In this case the high voltage ionized cloud of
you-know-what will merge and itself act as the "coating" we desire.

(I notice you built a toroid using bent tubing with air spaces
between each section of tubing, so I know you are aware that such
frames are very suitable)

There are variations on the theme. Make the bottom toroid somewhat
smallish and the top toroid somewhat biggish, and then instead of
joining them with a cylinder, use a section of a cone that touches
each toroid somewhere between the high point of the toroid and the
outer edge of the toroid.

If you need greater structural integrity, then have the cylinder part
just inside the toroid. That way it will not be crushing the toroid
itself.

I'm sure you get the idea. I have never built any of the really big
humongous stuff like you, Greg, but I like to think big. It doesn't
cost me anything, and it keeps my brain cells happy.

Hope this helps.
Fr. Tom McGahee