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Re: [TCML] Coil forms, any good?

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

> The only credible reported difference in secondary form materials so far as
> losses are concerned have been in the paper-based "Sonotube" concrete forms.
> wasn't the paper, it was the unknown binder that was believed to be
> 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
> to minimize weight.
> Regards, Gary Lau

> > 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

> >
> > 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,

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