Re: PVC drain pipe toroids - was foil-covered inner-tubes for large toroids?

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Original poster: "S&JY" <youngsters-at-konnections-dot-net> 

Dave,

I built a couple of toroids from 7" od flex drain pipe (purchased at a
plumbing supply store).  About the smallest center to center diameter one
can make with it is 37".  Assuming the "bendability" roughly scales, then a
12 inch drain pipe could be bent into a 12/7 x 37" = about 63".  I think you
would have a tough time achieving a 54 inch c-c diameter, especially since
the larger pipe probably has greater wall thickness.

Joining the ends is a tough proposition also (e.g. to keep the ends
parallel).  I used about a 4 inch length of the drain pipe, and cut a slot
through it about an inch wide along the axis.  This allows it to be
compressed inward so it can slip into the two ends, then expand into the
corrugations.  Then put in a bunch of sheet metal screws to secure it.  This
makes a strong light-weight joint.  One has to rig up some crossed loops of
rope or twine to get the ends to align parallel and pull toward each other
while fastening the ends together.  The toroid looks like a race track while
doing this, with the joint in the middle of one of the long sides, then you
have to bend it out to be round afterward.  Would be much easier if two
people did the deed.

--Steve Y.
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, October 26, 2004 5:31 PM
Subject: Re: foil-covered inner-tubes for large toroids?


 > Original poster: "David Rieben" <drieben-at-midsouth.rr-dot-com>
 >
 > Hi Dave,
 >
 > Thanks for the pointers :^) I have seen websites where they did use
 > the flexible PVC drainage pipe for the toroid form. I think 4" is about
 > the largest that can be found at Lowes, at least locally (Memphis), but
 > I have seen the same kind of pipe that looked to be 12" in diameter
 > at a farm/tractor supply place. That would give me the minor diameter
 > that I'm looking for but I wonder how managable this stuff would be
 > to try to bend into a "donut" shape? It looks like it would be consi-
 > derably  more unwieldy than the 4" stuff :^O Any more pointers
 > on that issue? I'd love to be able to make a say 12 x 54 or so
 > toroid for a large toroid capacitance is the key to making HUGE
 > sparks, assuming you have the power to push them and that should
 > not be a problem here as I have a 10 kVA and a 15 kVA pole
 > transformer at my deposal. They are both 14,400 volt units. I
 > suppose that I could stack 2 or more 4" thick toroids to get an
 > effective larger minor diameter but I'd rather have one larger
 > minor diametered toroid.
 >
 > Thanks,
 > David Rieben