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RE: drying coil forms




This is just a thought, but would it be possible to make a formless secondary?
I would envisage the process going something like this:

        1. Wind coil on carboard tube of appropriate dimensions 
        2. Epoxy/Varnish with lots of coats (enough to hold shape) 
        3. Soak coil in water (or whatever) to disolve cardboard form. 
        4. Sand & coat inside for extra support for wire. 

Any thought? 

Justin G. 

-----Original Message----- 
From: Tesla List [<mailto:tesla-at-pupman-dot-com>mailto:tesla-at-pupman-dot-com] 
Sent: Thursday, 6 January 2000 12:35 
To: tesla-at-pupman-dot-com 
Subject: Re: drying coil forms 

Original Poster: "Reinhard Walter Buchner" <rw.buchner-at-verbund-dot-net> 

Hi Rob, all, 

> Original Poster: "ROBERT CRESSLER" <59CREROB-at-MENASHA-dot-com> 
> acrylics (cast,extruded) are indeed hygroscopic , for comparison 
> rigid PVC has a water absorption of .04-.4%  and  acrylics with 
>.2-.3%  (wt. gain after 24hours per ASTM D570). This has come up 
>before and I am still unclear as what dictates (or why)  a superior 
>coil form.To really confuse   me the dissipation factor at 1Khz 
> for acrylics is .02-.03 and PVC is.009-.017 !!?? 

Well consider the length of the E-Field lines in your secondary. 
I think some 500mm is an okay average. Now consider your 
PVC pipe wall thickness. Some 5mm maybe. So you are 
loosing AT MOST 1% in your coil former. Nothing to really 
worry about, I would say. Your gap is -by far- much lossier. 

Personally I donīt think the material is THAT important. There 
are a few that I would stay away from (such as cardboard), 
because of its (non) resistance to flashovers. In contrary to 
some on this list, I think preparation of the former and really 
embeeding the wire in epoxy and / or PU varnish is MUCH 
more important if your coilīs former is too survive a flashover. 

My primary tilted away once during a run and I got massive 
flashover between primary and secondary. I switched off 
immediately, and found......... nothing, not a single mark. Iīm 
pretty sure my magnet wire would not have survived this, if 
I hadnīt coated it 5x (3x epoxy and 2x PU varnish, including 
sanding in between). Plus the glass hard surface looks just 
great. 

Coiler greets from Germany, 
Reinhard 

(Gee, Iīm really flooding the List today, ainīt I ;o))