Re: Fiat PVC, Fiat Lux
Tesla List wrote:
> Original Poster: Yuri Markov <wmondale-at-hotmail-dot-com>
> I finally got a nice clean 4-inch wide PVC pipe, and 22 gauge magnet wire to
> wind. This new secondary will replace my insult to the hobby of Tesla
> coiling, my 2-inch cardboard wrapping paper tube, 30-gauge wire seconday.
> This time I'm going to get it right. Everything. But first I need to know
> what everything is. So far I've sanded the pipe down to a fairly smooth, not
> at all shiney surface. Should I continue sanding with fine paper until it is
> really quite smooth? As smooth as it was before? Next, I know that I have to
> coat the pipe with something before winding. What is this magical substance
> that I should use? Will it go on nice and evenly, or will I have to re-sand
Yuri, There is no magical substance use nothing at all, or perhaps a light wipe
down with some acetone to remove any grease or fingerprints. Acetone is a weak
solvent for PVC. It will smooth out small imperfections without making the
sticky. Acetone will attack styrene plastic. A dull finish on the pipe is not
cause for concern.
Some of the older books advocate a tacky coating of varnish to keep the wire
down as it's wound. Don't do it! Those folks had their books "ghost written,"
because the author's hands are permanently encased in varnish, or their coil
forms have more bumps than Mount Rushmore. Coating the form, and attempting to
wind on a tacky surface, is inviting problems.
> Next, I assume I wind the wire. (Yawn... I wish I had a lathe...)
> Then am I meant to put another coat of the magical coil coating on top of
> that? Sand? Does it matter if it's nice and shiny in the end? How do I make
> sure I don't sand the enamel off the wire? Please help.
A little time preparing to wind a secondary helps. First, build a jig to hold
the form. Make something that will allow you to turn the coil with one
lay on wire with the other. It takes less time to build a jury-rigged lathe,
than it takes to wind a coil without something.
Keep a few cut pieces of masking tape ready to anchor the wire if you need to
take a break. Hot melt adhesive, or fast setting epoxy, are excellent for
anchoring the bitter ends of the wire to the form.
An outer coating is not necessary if the winding is fair (smooth, tight, no
overlaps). It will make the coil more rugged. I generally use one, but it
detract slightly from performance. Use a clear oil-based, varnish, shellac, or
epoxy coating. You can sand between layers, if you want to achieve a thick,
high-gloss, coating. Use fine sand paper, not emery cloth. The particles in
emery cloth are conductive, ditto with steel wool. Avoid sanding the
the wire. If you build a motorized winding lathe, the lathe can be used to
the coil slowly while the coating hardens, and will prevent running.
Performance-wise, I'd rate shellac high, followed by phenolic varnish, then
polyurethane varnish, and lastly epoxy and polyester resin. The best looking,
and most rugged coating is probably epoxy. Avoid using lacquer, the
lacquer may cause the enamel on the wire to dissolve or wrinkle.
> Also, I am vaguely
> aware that I should make the coil airtight with a plastic disk on each end.
> Why is this necessary? What are the advantages of an airtight coil form?
> And, last of all, can I attach these disks using hot glue, or is that a
> no-no? I apologize if I've asked too many questions in one post. Answers to
> some, or preferably all of these questions would be appreciated and
> eternally helpful. Thank you.
It isn't necessary to hermetically seal secondary coils. There is a slight
chance of having a corona or arc form down through the center of the coil form,
but it isn't likely. If you should use a piece of wood in the end of the coil,
to hold the coil upright, you do run the risk of creating a path for internal
arcing. Hot glue is fine for attaching disks to the forms.
All sizes of plumbing PVC pipe have "construction" caps made for them.
thin plastic disks designed to fit the inside diameter of the pipe to
temporarily keep construction debris from contaminating pipe, that is installed
on a construction site. The caps are cheap and intended to be discarded. The
four inch size costs about 17 cents. They make excellent end caps for coil
Hope this helps. take care,