Re: Secondary wire & insulation
Subject: Re: Secondary wire & insulation
Date: Mon, 9 Jun 1997 03:30:02 +1000 (EST)
From: Rodney Graham Davies <Rodney.Davies-at-anu.edu.au>
To: Tesla List <tesla-at-pupman-dot-com>
On Sat, 7 Jun 1997, Tesla List wrote:
> Subject: Re: Secondary wire & insulation
> Date: Fri, 6 Jun 1997 20:03:51 -0700 (PDT)
> From: "Edward V. Phillips" <ed-at-alumni.caltech.edu>
> To: tesla-at-pupman-dot-com
> "Of course the best way is to use a
> lathe (expensive)or make a winding machine."
> Watch out on using the lathe. It is almost impossible
> to stop in time when something goes wrong with the winding,
> as it usually does (at least for me). A hand-cranked winder
> consisting of n othing more than a piece of threaded rod
> mounted in simple bearings (ev en wood) and end pieces which
> fit the tube work just great. It only takes an hour or so
> to wind a pretty big coil, and you can't get in trouble. Particularly
> if you keep pre-cut masking tape handy to hold things in place
> when you have to stop. Look at some of the TCBOR videos for
> similar arrangement.
Ed, you're right that it's important not to get into trouble on a lathe.
All of the coils I've wound I've done on lathes utilizing the
to move up the winding length while winding the wire on in a nice
I've found that hand-winding is a very good method, providing tension is
The beauty of doing it on a lathe is that you just get the first couple
of turns happening, then sit back and watch it wind!
Then, a very nicely wound coil comes off! ;-)
One thing I actually do when winding is apply the poly-ethylene in a
I build a "bath" box which is about a foot longer than the secondary and
about 1/2 a foot wider. Then I pour in the poly-ethylene into the bath
and prop it up so that the bottom of the coil (lying sideways) is about
1-2" under the surface of the liquid.
This allows for the inside, aswell as the outside of the coil to be
"bathed" in the liquid, hence applying a coat to the inside and the
outside of the former for the entire length.
This enables a nice even application of poly-ethylene while winding is
This is also neat in the sense that "soaks" in between the wire and the
former (and the turns) evenly, also helps to hold the turns in place.
Once the winding is complete, I let the coil almost dry so it's just a
little 'tacky' to touch. I then wipe it quickly with a soft cloth dipped
in cold water and squeezed so that the cloth is 'just damp', as to
any dust particles before re-application.
Then I rig up the bath and let the coil rotate in that for about half an
or so to soak up another layer.
I repeat this process until you can look along the windings and not see
any bumps from the turns - basically, perfectly smooth.
I then let it dry (while the lathe is in motion) so that it dries evenly
and you don't get blobs and dribbles of poly-ethylene forming all over
Perhaps a heat lamp or a warm-air fan blowing across could enhance
and setting of the windings, although I've never used either of them
But I've found that by using this (fairly involved) technique, the
secondaries I've produced have been of excellent quality, never broken
down by discharge and have virtually minimal RF losses.
I also use clear poly-ethylene so that it leaves a brilliant copper
(I also use enamel-coated copper winding wire).
This usually takes 1 week or so to do this, but it's worth it!
My formers are usually PVC pipe - well prepared and sealed.
I'm next going to try out 15-20" Sonotubes... I like big coils!
Anyway, just thought I'd share my secondary constructions with