[TCML] Coil forms, any good?

[mark olson]

>
>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
>
>
> >
> > 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
>
> > > 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?
>
> > >
> > > Thanks!
> > > /Matt
> > > www.tesla.nu (in Swedish)

Hi Matt,

Glad to see that you "struck gold", just avoid the forms that contain it 
(gold).

I wonder if a metal detector, such as the ones that a woodworker would use 
before risking his planer knives,
would be of benefit here.

When  I performed my first NST rebuild the other day, I needed card board 
shims.  Being new years day,  I
found some fireworks paper that I thought would be suitable.  I carefully 
dried it in the microwave and inspected it.
What I found was a visibly high metal foil content, which I verified with 
my "megger".  Needless to say, I searched
out another substitute (fiberglass mat saturated in paraffin).

Just my two cents,

Marko