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PVC, Re. Bert's response on Pyrex


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From:  Alfred A. Skrocki [SMTP:alfred.skrocki-at-cybernetworking-dot-com]
Sent:  Tuesday, March 03, 1998 3:14 PM
To:  Tesla List
Subject:  Re: PVC,  Re. Bert's response on Pyrex

On Wednesday, January 14, 1998 6:10 PM Eleanor Flood
[SMTP:eflood-at-bellsouth-dot-net] wrote;

> Tesla List wrote:
> 
>  Heck even well
> > > baked out cardboard tubing that is saturated with polyurethane and allowed
> > > to dry under heat is superior to glass!
> > >
> > <SNIP>
> > 
> > Alfred,
> > 
> > Got to disagree with you a bit here, Alfred. The difference in
> > dielectric loss between PVC and glass is really not all that great...
> > and Pyrex (at about 30) is actually about 1/4 as lossy as PVC. Even soda
> > lime glass is only 1-2X as lossy as PVC. While using glass, or PVC for
> > that matter, as a dielectric in a Tesla Coil tank cap would be quite
> > lossy, use of this material in a coilform is a significantly different
> > application. PVC, although quite lossy, makes an excellent coilform due
> > to it's excellent insulating properties after proper pre-treatment. Its
> > dielectric loss properties have relatively little practical impact on
> > secondary Q when compared to other losses in an operating system
> > (streamers in particular...).
> > 
> > Jim, your Pyrex coilform will work just fine.. and may actually have a
> > higher Q than if you wound it on PVC.
> > 
> > At no loss for words in Illinois...  :^)
> > 
> > -- Bert --

I have to disagree with Bert! First he is compairing PVC to Pyrex which IS 
NOT what I was talking about!  I have built secondaries out of; open wood 
frames, cardboard, PVC, polyethylene, plexiglass, vicor glass, and Pyrex 
glass. I found that IF you bake out the cardboard and then saturate it with 
polyurethane it has less losses than ANY glass or even plexiglass and is 
second to Polyethylene! The key factor is the cardboard MUST be totaly 
dried out befor being sealed in with the polyurethane.

> We are now using afore mentioned coated cardboard tubing for secondary
> coil.  Planning a PVC one shortly. Note a reference to proper
> pre-treatment. Please, how?  

Coat the PVC with polyurethane inside and out before winding the secondary 
the coat again when done.

> Plan to make coil as open air as possible by cutting slots lengthwise in
> PVC about 1/4' apart, this is just a thought, would it be worth the
> trouble?

NO! If I understand you correctly you are talking about laying the wire in 
precut groves in the PVC, this will increase the distributed capacitance 
and thus lower the secondary output.

                                       Sincerely

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