Re: Toroid Design

To: tesla-at-pupman-dot-com
Subject: Re: Toroid Design
From: Bert Hickman <bert.hickman-at-aquila-dot-com> (by way of Terry Fritz <twf-at-verinet-dot-com>)
Date: Thu, 24 Dec 1998 08:55:35 -0700
Approved: twf-at-verinet-dot-com
Tesla List wrote:
> 
> Original Poster: Esondrmn-at-aol-dot-com
> 
> In a message dated 12/22/98 11:17:06 PM Pacific Standard Time,
> tesla-at-pupman-dot-com writes:
> 
> <<
>  Ed,
> 
>  There's several different kinds of ducting material out there. One kind
>  (which sounds like the material you used on your dryer) has a spiral of
>  springy wire with either a metalized mylar or very thin aluminum foil
>  wrapped around it, and an 8' length is scrunched down to abot 4" long.
>  You DON'T want this stuff. The right material is more like a thinwall
>  (0.005"?) aluminum bellows that's fairly stiff and is shipped somewhat
>  compressed. The 8" diameter material I purchased was about 2-2.5 feet
>  long, but would stretch out to about 7-8 feet. It will dent if you poke
>  it hard enough or drop the toroid, but otherwise is pretty robust.
> 
>  It's also very easy material to work with. I used a small piece of
>  rolled galvanized steel (also in the heating and ventillation section)
>  about 3" wide to fit tightly in an open end, putting it about 1/2 way in
>  and then taping it in place with aluminum tape. I slipped the end of the
>  next piece of ducting over the 1 1/2" that stuck out of the other duct,
>  and taped the joint, and then carefully smoothed out any protrusions.
> 
>  I used a couple of 14" pizza pans spaced about 3" apart via three 2" PVC
>  pipes for my center, but for a larger center I'd use the same approach
>  that Chuck Curran recommended by using some 1" aluminim foil covered
>  insulation board used in home construction. It's cheap and light weight.
>  Just remember to make good electrical contact between both the top and
>  bottom foil layers and the toroid. You'll nd up with a toroid that's
>  light wieght, works great, and is very inexpensive. Heating and
>  ventillation suppliers should carry the ducting material in up to 18"
>  diameter.
> 
>  Good luck, Ed, and let us all know how the bigger toroid works!
> 
>  -- Bert --
>   >>
> 
> Bert,
> 
> Ok, thanks, this is the material that I was thinking of.  It does sound
like a
> quick and relatively inexpensive method to make a large toroid.  My old
method
> of covering every square inch with the aluminum tape would be expensive
for a
> toroid this large - it would require many rolls of tape.  I will make one as
> you have described.  This one inch thick insulating board with aluminum on
> both sides, does this stuff come in 4 x 8 foot sheets?
> 
> It should have this complete in a couple of weeks, as time allows.  It
will be
> a few months before I can test it however since I can only run the coil
> outside.
> 
> Ed Sonderman

Ed,

I believe it comes in 4' x 8' sheets, but I haven't actually used this
material myself. Perhaps Chuck Curran can provide some more information
on this material.. ?

-- Bert --