Coil Form Sealing?
From: D.C. Cox [SMTP:DR.RESONANCE-at-next-wave-dot-net]
Sent: Saturday, April 18, 1998 11:26 PM
To: Tesla List
Subject: Re: Coil Form Sealing?
Avoid the polyurethane -- will crack with time and becomes unsightly. A
good sealer to use is 3 light coats of G.E. Glyptal which is available in
quarts through almost all large electric motor repair shops. Be sure to
apply to inside using a rag taped to a wooden dowel. Use xylol as the
thinning agent and strain the glyptal through standard paint filters after
stirring for 5-6 minutes with an electric drill stirrer. Glyptal may also
be used as the finishing sealer as well although if using enameled magnet
wire a better choice is Dolph's AC-43 air dry varnish. Has a.n excellent
dielectric and insulating properties. Bullseye clear shellac is also a
better choice than polyurethane as it doesn't crack either.
> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-pupman-dot-com>
> Subject: Coil Form Sealing?
> Date: Saturday, April 18, 1998 6:04 AM
> From: Esondrmn [SMTP:Esondrmn-at-aol-dot-com]
> Sent: Friday, April 17, 1998 10:17 AM
> To: tesla-at-pupman-dot-com
> Subject: Re: Coil Form Sealing?
> In a message dated 98-04-16 00:02:06 EDT, you write:
> I now have my 6" PVC coil-form. I've sanded it inside and out and it's
> drying under a heat lamp. My question is what to use to seal it with
> (before and after winding). I have oil based polyurethane and spar
> I'm leaning towards the polyurethane since a test shows it is thicker
> adheres better to the 200 oC magnet wire. Although the spar varnish has
> proven to be very durable on previous projects. What are your
> Almost forgot to say that I will keep the secondary turning on the
> jig while the sealer dries.
> Brian B.
> I used a 6" dia pvc form prepared as you described. I used oil based
> polyurethane and applied about 5 coats on the bare form and them applied
> 6 coats over the finished windings. You are correct, keep the form
> prevent sags and runs. Don't use a heat lamp to accelerate drying, it
> air bubbles to form in the polyurethane.
> Ed Sonderman