RE: [TCML] Poly thickness (does matter!)

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

Hi Woo,

I reviewed your experimental write-up at http://www.audiotesla.org/corona%20experiment.htm

The thing that strikes me is that in the before and after photos under "The Results", the spark length in the After photo appears to be significantly shorter than in the Before photo.  The Before photo shows the corona skirt and racing sparks, and this would all be consistent with either less power being applied, or reduced couping in the After photo.  This makes me less than certain that conditions were actually identical.  But I can fully appreciate the difficulty in duplicating conditions over such a long interval.

While strong evidence might persuade me to think that some coating types might affect the tendency to develop racing sparks, it's a stretch to suggest that spark length might be significantly affected.  It's my understanding that the E-field surrounding the secondary and top-load is governed by the geometry of conductors, not insulators.

The photographs you took are an excellent diagnostic tool.  It's a shame that most common digital cameras can't achieve the equivalent film speed of ISO 1600 without being overwhelmed by noise.  Your images clearly show that the toroid is too far from the top of the secondary to adequately shield it and prevent the corona skirt that begins at the top of the secondary.  I would wager that if you added a very small toroid just above the secondary, it would eliminate the skirt, and permit a higher coupling before racing sparks occur.

Regards, Gary Lau
MA, USA


> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of dr.hankenstein@xxxxxxxxxxxxx
> Sent: Saturday, July 12, 2008 6:14 PM
> To: Tesla Coil Mailing List
> Subject: [TCML] Poly thickness (does matter!)
>
> Gary,
>
> I beg to differ with you on this point. I used to think the same thing until we did a
> recent experiment: I refinished an old secondary, one I had been using for 14 years
> and was astonished what 20+ coats of fresh polyurethane did for the coils
> performance. Noted was the elimination of a "corona skirt" under the gradient ring
> (top load). The occasional racing sparks have been eliminated not to mention I now
> have the closest coulpling possible with this coil. I used to use a 1" spacer under
> the secondary to decouple the coil. Spark length has increased 4 to 6" as well. For
> more details, please check out the article I wrote on this experiment at:
> http://www.audiotesla.org/corona%20experiment.htm
>
> Regards,
>
> Woo
>
>
> > [Original Message]
> > From: Lau, Gary <Gary.Lau@xxxxxx>
> > To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> > Date: 7/1/2008 10:01:59 AM
> > Subject: RE: [TCML] Poly thickness
> >
> > I'm not convinced that coating a secondary with anything significantly improves it
> electrically.  Mostly it's to keep the windings from shifting on the form, and to
> provide a small amount of armor should something bump into it.  And probably
> most importantly, it just makes the coil look nice and shiny.  No matter what one
> coats the secondary with, it's still vulnerable to racing sparks if it is overcoupled.
> >
> > Regards, Gary Lau
> > MA, USA

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