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Re: Secondary coil form questions

Tesla List wrote:
> 
> > Subject: Re: Secondary coil form questions
> 
> Subscriber: bert.hickman-at-aquila-dot-com Tue Feb 11 23:18:03 1997
> Date: Tue, 11 Feb 1997 12:38:47 -0800
> From: Bert Hickman <bert.hickman-at-aquila-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Secondary coil form questions
> 
> Tesla List wrote:
> >
> > Subscriber: ccrochet-at-premier-dot-net Mon Feb 10 21:37:34 1997
> > Date: Sat, 8 Feb 1997 09:29:15 -0600
> > From: Chris Crochet <ccrochet-at-premier-dot-net>
> > To: tesla-at-pupman-dot-com
> > Subject: Re: Secondary coil form questions
> >
> > At 11:25 PM 2/7/97 -0700, you wrote:
> > >Chris,
> > >
> > >One of the highest Q coils I ever wound was on 4" diameter styrene with a
> > >.030 wall thickness.  I never coat my coils with anything any more.
> > >
> > >Yes, make them thin walled tubes from the lossest loss material possible.
> > >Avoid coating, if possible.  This assures highest Q!...  If that is what you
> > >are after!
> > >
> > >Richard Hull, TCBOR
> >
> > Thanks!  I will consider the use of styrene in my 1st design.
> >
> > Is there anywhere a database or program which would show the theoretical 'Q'
> > of the same secondary wrapped on many different types of plastic coil forms?
> >
> > Chris C.
> 
> Chris,
> 
> Not that I'm aware of. However, as long as you pre-treat the PVC by
> drying it and coating the inside and outside with polyurethane, your
> coil's performance will be excellent. ABS, polystyrene, HDPE,
> Polycarbonate (Lexan), Polypropylene, PMMA (Plexiglas), or glass-epoxy
> coilforms can be used as-is with no pretreatment required. Stay away
> from cardboard - it won't withstand the voltage levels.

Bert,

Although I agree with Richard that cardboard is definitely not the ideal
material to seek for secondary forms, I used 20" Sonotubes for the
secondary forms on my half wave twin coil and have not had any voltage
breakdowns in over three years of operation. The only coating used on
the windings is two or three light coats of shellac to hold the wire in
place, not for insulating purposes.

BTW, I did wind the secondaries on my twin in opposite directions, but
it is not necessary. A classic horizontal half wave coil's secondary is
wound in one direction, as is the primary, and they fire from one end to
the other just fine, right? A half wave twin coil is nothing more than a
horizontal coil that has been split in half and stood up on end. I just
had to mention this, I didn't see it come up in any of the posts. 

Happy twin coiling,

Ed Wingate


> Q is governed more by the wire size, form-factor (height versus
> diameter), and operating frequency than by the material used for the
> coilform itself.
> 
> -- Bert H --