Re: wood core coils

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Steve Greenfield by way of Terry Fritz <twftesla-at-qwest-dot-net>" <alienrelics-at-yahoo-dot-com>

--- R Heidlebaugh <rheidlebaugh-at-zialink-dot-com> wrote:
> Wood can be made to work for a while, but it will
> fail. spasks an wood makes
> carbon. Carbon conducts electricty.

If you are replying to my post, yes I found that out.
:') I was also probably overpowering a small coil, it
was about 12 inches, 10 inches wound length using 32
gauge wire (only had to start over once due to
breaking!) with a small round drawer pull for the top,
driven by a 15KV 30mA neon sign transformer. When I
had it tuned just right I was getting 2 to 4 inch
branching sparks into the air, nothing compared to
what I've seen others do since then but at the time it
impressed the heck out of me. For about 1 minute, then
the core failed and it burned a small hole down the
center of the wood core to ground.

> Use white PVC
> plastic pipe to avoid
> trouble that is common to wood and cardboard.
>     Robert H 

Something that has been bothering me. I've seen people
refer to PVC as being able to absorb water, and
suggest baking it to drive the water out and then
giving it coats inside and out of sealant
(polyurethane or laquer, clear only). I also recall
long ago seeing an article in the ARRL magazine where
someone had used PVC to make loading coils for a
multiband dipole antenna, and when he keyed up a KW on
it the coils failed by arcing a path across the PVC.
He had a photo of the PVC cores with the wire removed,
and there was the classic branching pattern burned
into the PVC.

So does PVC really able to absorb moisture? Perhaps
this guys antenna cores failed because he didn't seal
them. Has anyone tried ABS black pipe, or does the
black come from carbon for color? Just as a quick test
for insulation, I was in the hardware store last night
and rubbed my cotton/poly shirt sleeve on some PVC,
black ABS and grey (ABS?) plastic electrical conduit
and then tested it with the hair on the back of my
hands.

The concept being that if it was truly nonconductive
then the static charge I had just caused should stay
long enough for me to feel it. And if it was even
slightly conductive it should leak off too fast for me
to feel it.

Grey plastic electrical conduit passed with flying
colors. White PVC I could feel the charge but not as
much. Black ABS was inconclusive.

My original intention was actually for a Van de Graf
generator, but this got me to thinking about Tesla
coil cores.

So, can anyone state with authority whether or not PVC
will absorb any moisture? And whether or not black ABS
sewer pipe is suitable for Tesla coil cores?

Thanks,
Steve Greenfield

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