[TCML] Envirotex Lite , High Torque drive
quarkster at att.net
Wed Jul 29 21:23:50 MDT 2009
I think the difference may just be in our application methods.
I haven't actually cross-sectioned one of my epoxy coated coils and directly measured the coating thickness, but by visual observation, and measuring the circumference of a coated coil, I "estimate" that the coating thickness is at least .04" to .05" thick.(single application). This is enough to completely "level" the surface of a coil wound with #26 AWG wire, and gives the appearance that the wire is embedded under a fairly thick clear plastic sleeve. This is MUCH, MUCH thicker than even multiple coats of insulating varnish.
As you and Dr. Hankenstein have noted, this thick an insulation layer significantly increases the coil's resistance to "racing arcs'" and damage from streamer hits.
I find that I can increase the coupling on a coil once it has been epoxy coated, without any risk of flashover or racing arcs. On one coil, I increased the coupling pretty significantly, and during initial testing found corona literally spraying from a near microscopic pinhole in the coating about half-way up the secondary. I think this is a good indicator of the voltage stress that ws present at the surface of the windings, and I'm sure that the coil would have suffered flashover without the coating. (The pinhole was easily repaired with a tiny dot of resin.)
--- On Wed, 7/29/09, Steve Ward <steve.ward at gmail.com> wrote:
From: Steve Ward <steve.ward at gmail.com>
Subject: Re: [TCML] Envirotex Lite , High Torque drive
To: "Tesla Coil Mailing List" <tesla at pupman.com>
Date: Wednesday, July 29, 2009, 12:52 PM
> I definitely WOULD NOT try to use a "putty knife" to spread the resin; use
> a 4" wide "foam paintbrush".You are not "trowelling on" the resin like a
> thick coat of stucco on a wall, you are applying a thin coating that
> eventually coalesces into a very level, very uniform, very smooth layer. Use
> just the very tip of the foam brush, gliding gently against the surface of
> the windings. After the entire form is coated, the final smoothing pass is
> made with the tip of the foam paintbrush just barely touching the form.
> I evaluated many types of applicators/spreaders for applying the resin, and
> the foam paintbrushes work best by far. A distant second best are the
> knife-edge rubber squeegees used for fiberglass cloth/polyester resin
> laminating work.
I find that a good straight hard edge is quite effective at spreading the
epoxy with the correct technique. I think our philosophy for using epoxy is
different, however. I tend to go for a *very* thick coating and risk having
some slight surface imperfections (such as thickness inconsistency), but
with the benefit of an electrically robust system. A really thin coat of
epoxy is not much better than urethane varnish.
I hear a lot of guys go "yeah, my coil survived some flash-over too, i just
had to wipe it down and recoat the burn area", and i think to myself... i
didnt have to do ANYTHING after my flashovers because there was NO damage to
Not to say that you couldn't put on a bunch of thin epoxy layers using the
foam brush method. I find the wide putty knife to give good control over
the epoxy when putting on HEAVY coats that naturally self level better than
thin coats where the application has to be much cleaner from the start. In
fact i would agree, a putty knife sucks if you are doing thin coats of
epoxy, but i found the foam brush to be too difficult to control the spread
of a thick epoxy coat.
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