[TCML] Envirotex Lite , High Torque drive

[Steve Ward]

>
>
> Steve Ward recently (7-27) posted a message about a secondary of his that
> was initially coated with polyurethane varnish, then overcoated with
> Envirotex Lite.
>
> However, I doubt that Steve would be willing to bang on the coil with a
> plastic mallet to check adhesion between the epoxy and the underlying
> varnish.
>
> I think that if you carefully clean the coil before applying the epoxy, you
> will get adequate adhesion.
>
> Regards,
> Herr Zapp
>
>


Yeah, i wont be intentionally testing the adhesion any time soon ;-).  But i
*have* been pretty rough on my secondary that i wrapped with glass fiber
cloth soaked with envirotex as the resin... not to mention that i later
spray painted it blue ;-).

I do find that even the run-off of envirotex onto my garage floor (which is
relatively new and clean) can be peeled off if you pry up the edge with a
flat-bladed screwdriver (i am happy for this).  I dont think epoxy of this
type ever *really* gets a great bond to the material.  Some of my older
epoxy coils did show signs of de-lamination from the magnet wire where they
had been bumped against a hard surface.  This is now the reason that i still
use a layer or more of PU varnish on the magnet wire directly (to serve as
*some* form of extra insulation that will flex some) and then the epoxy is a
thick top coat, almost like wrapping your secondary with a big sheet of
plastic.  The benefit comes from having a thick *void-free* insulator
surrounding the secondary coil, so that the arc current heating is spread
over a larger volume of material, making it less likely to burn through.
Admittedly, my epoxy coatings are literally filled with tiny air bubbles, so
for this reason i do 2 coats to reduce the likelihood of it breaking down a
thin spot in the epoxy where a bubble might be.

Anyway, i always wipe the surface with a rag saturated with isopropyl
alcohol, i think i read this in the envirotex instructions.  Light sanding
might help too, provided the coating is thick enough for that without risk
of damaging the wire.

Steve