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Re: Fiat PVC, Fiat Lux

At 09:36 AM 7/4/99 -0600, 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 
>afterward? 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. 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.

Yuri,

Here's what I did with my 6" secondary -

I sanded down my PVC until I couldn't see any lettering, then 
washed it down with a hose and wiped it down with a cloth,
inside and out.

I then stuck the form into a box with a lamp and let the 
entire form dry thoroughly for 3 days. Some people stick 
the form into an oven (if the form will fit) and use a low 
temp for a few hours. 

Once dry,  I went ahead and put one coat on the inside of
the pipe with polyurethane varnish. After that dried, I mounted
it on a homemade coil winder with a handle on one end, spun 
it and put several coats of more polyurethane varnish (oilbase 
only, don't use a water base) over the outside of the form, 
while spinning the form the whole time so the coats would go 
on evenly. After the varnish dried, I then wound  #22 magnet 
wire onto the form. I didn't sand the wire since that would 
remove the wire's thin enameled insulation, and isn't a good
idea.

I tried using hot glue to get the first turn to hold, but the hot 
glue wouldn't stick to the varnished surface, so I used 
electrical tape and it worked well. After the wire was wound,
I applied about 10 coats of spray polyurethane over the wire.

I buried the wire under the varnish with applying several 
coats. This protects the wire, minimizes corona, and 
protects the coil form itself from any bumps or mishaps.

I used silicone glue to put the two end disks on just inside the
form. The idea about sealing the ends of the form is to keep 
any possible avenue of a spark or arc from entering inside of 
the coil form, plus it keeps out additional moisture. I didn't drill 
any holes in my coil form but elected to use the Richard Quick
method for fastening the RF ground wire to a wide copper strip
at the base, and will spiral the wire up the top for the toroid. 

I built a coil winder out of 2 x 4's for the uprights and a 2 x 8" 
for the base. I used a 3/8" threaded rod to hold the form, and 
a 5/8" wooden dowel to hold a spool of #22 magnet wire. I 
used a window crank for the turning handle. I cut out two disks
for the inside of the form and ran the 3/8" threaded rod through
that. My girlfriend helped keep tension on the wire as I turned 
the form. This worked OK, but if I had to do it over again with
this setup, I would have bought two PVC end caps that fit the 
6" coil form and it would have held it much tighter. I only secured
one wooden disk on the rod by itself, so I could get the coil form 
on and off the threaded rod on the free end. Once the form was 
on the rod,  I tightened the other disk. I learned it's better to keep
the wire spool at a distance away from the coil form as if it's too 
close the wire has a tendency to try to get tangled up in itself.
#22 magnet wire is real springy, so if you take a break while
winding, make sure you tape down your last few turns with
electrical tape to keep it from unwinding.

Gary Lau used a drill with a variac, so as to vary the winding 
speed. That's a good way to go. Just put a rod through the form, 
chuck it into the drill, clamp the drill down, force it on and use the 
drill and the variac to do the work. That's the method I'll use on the 
next secondary I wind. :-)

It would be a good idea to give yourself a little extra room at the
bottom of the form that isn't wound. This will give you room for the 
RF ground and will provide some height for the primary-to-secondary 
coupling.

Don


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"Resistance to tyrants is obedience to God" - Thomas Jefferson