Re: [TCML] Poly thickness

["David Rieben" <drieben@xxxxxxxxxxx>]

Hi Bart,

Agreed. And I might also add that while space
winding the secondary does reduce the inner turn
ditributed capacitance (which is a good thing), it
also notably reduces the secondary inductance
(which is a bad thing). The bottom line is that
unless the secondary is space wound, the poly
coating really only offers external physical pro-
tection, locks the coil into place, and adds asthe-
tics to coil (which IMHO are good reasons to
apply poly coatings to your secondary coil liberally)
Anyone who has had a secondary coil to slide
down the form like a slinky after a few hours of
winding the thing knows what I'm talking about
here!

I seem to recall back in my early days on this
list, around 2000 I believe, that the school of
thought on this list at that time was to space
wind the secondary coil to reduce the aforemen-
tioned distributed C. Now it seems that we have
finally "wised up" to the fact that the increased L
is a good trade off for the increased distributed
C with close wound secondaries for maximum
spark length vs. available power.

David Rieben



----- Original Message ----- 
From: "bartb" <bartb@xxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Tuesday, July 01, 2008 11:14 PM
Subject: Re: [TCML] Poly thickness


> Hi David, good question.
>
> From a voltage per turn and performance standpoint, no, it makes no 
> difference. The insulation on the magnet wire is the voltage standoff 
> layer, even with a coating (unless space wound). Terry Fritz wound a 
> couple coils with saran wrap (probably Glad cling-free wrap) and they 
> performed flawlessly (no goo to seep into the windings). He put it there 
> basically to keep the windings in place.
>
> It is nice to coat a coil with a clear coating (which seals out moisture, 
> holds the windings in place, allows handling of the coil, and a little 
> help from dielectric mishaps). I personally will always coat my coils for 
> these reasons. I put on enough coats until the winding ridges are no 
> longer noticeable (smooth finish). That is my basic target for "enough" 
> coats. The thicker the application, the less coats that are necessary.
>
> Space winding a coil will certainly add to standoff voltage, but 
> considering the volts per turn, it's not necessary to space wind a coil 
> (and there is no benefit in performance).
>
> Take care,
> Bart
>
> david baehr wrote:
> > with a 'tight' wound coil,..is a coating really helping much?  The 
> > windings are touching...
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