RE: [TCML] Coil forms, any good?

["Lau, Gary" <Gary.Lau@xxxxxx>]

If the pipe were 100% PVC, there would be no problems.  But with either thin or thick wall PVC, one runs a small risk of there being a spec of conductive flotsam just beneath the outer surface that could cause a short between the potential of a few turns.  If you stick a light bulb inside a piece of thin wall pipe you may see this.

But I've used nothing but PVC pipe and never had a problem.  For the majority of us that pay for pipe, PVC is the only economical choice.  I don't know if thin or thick walls alter the risk of conductive flotsam.  I was able to do the light bulb thing on a piece of very thin-wall 4" SDR pipe, but I've not seen 6" pipe thin enough to be translucent.  Odds are it will be just fine.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of otmaskin5@xxxxxxx
> Sent: Tuesday, January 15, 2008 6:07 PM
> To: tesla@xxxxxxxxxx
> Subject: Re: [TCML] Coil forms, any good?
>
> Hi Gary, just to confirm what I hear you saying...thick walled PVC secondary form
> doesn't have any downside with respect to its electrical properties - it's just a matter
> of adding unwanted weight to the system...Is that correct??
>
> Reason I'm asking, I've got some 6" heavy-walled PVC I can use.? But if it hurts
> performance, I'll have to track down some thin-walled pipe.
>
> Thx, Dennis Hopkinton MA
>
>
> -----Original Message-----
> From: Lau, Gary <Gary.Lau@xxxxxx>
> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> Sent: Tue, 15 Jan 2008 2:46 pm
> Subject: RE: [TCML] Coil forms, any good?
>
>
>
> The only credible reported difference in secondary form materials so far as
> losses are concerned have been in the paper-based "Sonotube" concrete forms.  It
> wasn't the paper, it was the unknown binder that was believed to be responsible
> for the losses, and even then, the losses were theoretical based on (I think)
> ringdown measurements.  It was felt that such losses might only be an issue on
> CW or solid state coils.  The many, many pig-powered Sonotube coils that work
> just fine are evidence that it's not a deal breaker.
>
> There was also a report that PVC pipe often contains random debris that in at
> least one instance, proved to be conductive, causing a secondary short.  PVC
> itself is just fine though.
>
> I think there would be no measurable performance difference between the
> materials you mentioned.  I would base the choice on material strength,
> machinability, color (aesthetics), will glue and polyurethane stick to it, and
> weight.  I would choose the thinnest wall that's structurally adequate, but only
> to minimize weight.
>
> Regards, Gary Lau
> MA, USA
>
> > -----Original Message-----
> > From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> > Behalf Of Tesla
> > Sent: Tuesday, January 15, 2008 1:59 PM
> > To: tesla@xxxxxxxxxx
> > Subject: [TCML] Coil forms, any good?
> >
> > Hi all.
> >
> > I have just struck a little bit of gold, I now have more or less
> > unlimited supply of
> > coil forms in glass fabric, cotton fabric and paper. The resin in
> > these forms are some of the
> > following: Phenolic, Epoxy, Melamine, Silicone and Polyester.
> >
> > Are they all good for winding coils on or are there some that i should avoid?
> > Also if they're good, does the thickness of the wall(RF losses)
> > affect the coil performance
> > with these materials?
> >
> > Of course i have seen several on the web using fiberglass so i guess
> > that should be ok
> > but what about the other materials?
> >
> > Any input appreciated as i can get any diameter in any length for
> > free. Lucky me....=)
> >
> > Thanks!
> > /Matt
> > www.tesla.nu (in Swedish)
>
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