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Re: drying coil forms
Tesla List wrote:
> Original Poster: Justin Gould <justing.mrl-at-dubbo.nsw.gov.au>
>
> Does anyone have any experience with secondary forms made from other
materials?
> For example, would a perspex (plexiglass for those in the US) be a feasible
> solution?
I've used glass. To make small jars with children for classroom use.
Tall jars.
An 18-inch Galliano bottle (shaped like the Transamerica pyramid, and gently
faceted). But I've never gotten nearly the spark length-per-coil-height
that others
on this group claim and show photos of. I'm told I shouldn't use glass for my
capacitor dielectric, and I'd been doing that. And I'm told that a coil
must have a
big torus at top, and I never got good results by top-loading, but that
might be
because I didn't know you have to blow out the spark gap or stretch it among
smaller gaps so it blows itself out.
Never mind. The reason --I was told-- not to use glass in the capacitor has
something to do with RF loss that translates into heat in the glass-- I only
noticed that as a problem when I tried a teevee flyback at much higher
voltage than
my neon sign transformer (the capacitor starred and popped inside). But glass
doesn't need drying and it's a great dielectric. It should work perfectly
for a big
coil form. The problem is-- where to get a big, perfect, glass cylinder?
I had a plan that I never pursued, in which I'd wind a coil on PVC
pipe, then
slip it inside another, larger pipe, bake it at just under the thermoplastic
softening temperature, fill /both pipes/ with oil and seal up the ends. I
wonder,
has anyone tried that? It seems like it would solve a lot of coil-ruining
arcing
problems.