Re: New 4" coil: R.Hull and CSN, Secondary Varnish

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi All,

I use off the shelf spar varnish. It's flexible, doesn't take long to build
a nice thick coat if desired,
and I have never had a shock on a coil (sonotube, pvc black or white) using
spar varnish. One benefit to
this type of coating is the ability to peel off an area around a shorted
turn should a coil need repair.
It does not penetrate between windings as well as a thin urathane might,
but it provides a nice looking
coil, excellent insulation, and has withstood temperatures from both
extremes (Minnesota to California).

Here's a link to a page discussing the differences between several
different coatings and some of what
goes "into" varnishes, polyurathanes, resins, etc. May even provide a hint
as to the "shock theory" (keep
an eye on the dryers).

http://members.aol-dot-com/woodinfo1/varnish.htm

here's a photo of a coil with spar varnish on it (to give an idea of the
finish).
http://www.classictesla-dot-com/photos/tgk/85.jpg

Take care,
Bart

Tesla list wrote:

> Original poster: "Jeff W. Parisse by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <jparisse-at-teslacoil-dot-com>
>
> TCML,
>
> We use a custom two part epoxy from 3M that sets up with a consistency
> similar to that of a "superball" (I may be showing my age here (40) but
> do they still make superballs?... It that a valid reference?) Anyway, it
> sets up semi-hard but very tough (it's bouncy!), moisture resistant,
> rated for HV electrical use and (of course) expensive as heck
> ($250/gallon kit).
>
> Given that hardware store brand two part (i.e. not specifically
> electrical potting resin) seems to work on small and medium sized coils
> (thank you Alan Yang), I'm sure that a local plastics supplier that
> supplies two part resins for casting purposes, surfboards, etc. can
> either suggest or whip up a softer alternative that's not electrically
> rated but nonetheless will still work and be less expensive.
>
> We haven't noticed the "secondary after shock" with the 3M coating
> either. My hunch is that the rough micro surface of the semi-hard resin
> is less of a capacitor plate (yes I meant plate) than the glass like
> surface of hard resin. I'm sure I'm starting a new thread in which I'm
> not qualified to contribute so I'll just leave it at that.
>
> Thermal expansion/contraction is rather profound with copper. Got to
> keep those windings in place!
>
> Jeff Parisse
> www.teslacoil-dot-com
>
> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>
> I will definitely second what Charles says here!
>
> Coil forms expand and contract with temperature and seasonal weather.
> They can easily shrink enough such that a slight tap will cause all the
> loose wire to "fall".  Just a thin coat of spray poly can prevent a
> destroyed
> coil.   guess how I know all this ;-)