Direction of Winding

To: "'Tesla List'" <tesla-at-pupman-dot-com>
Subject: Direction of Winding
From: Tesla List <tesla-at-stic-dot-net>
Date: Tue, 18 Aug 1998 08:42:44 -0500
Approved: tesla-at-stic-dot-net

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From:  FutureT-at-aol-dot-com [SMTP:FutureT-at-aol-dot-com]
Sent:  Monday, August 17, 1998 1:26 PM
To:  tesla-at-pupman-dot-com
Subject:  Re: Direction of Winding

In a message dated 98-08-17 10:23:14 EDT, you write:

<<snip>  so I can put some
> effort into my NST unit. Have now 2 x 12kv/30ma NST's on the 4" coil but
> I'm still not exceeding 12" - 14" sparks. Can't think of any reason for
> the poor results. Question :-
> Does direction of winding affect coil performance. ie Secondary wound
> clock wise and primary the same direction which is my present situation.
> Or does the primary have to be wound anti clock wise??. The other reason
> could be my toroid which could be too small. (9" dia using 1.5"
> corrugated PVC tube.). My spark gap is a static gap using 8 1/2" Cu
> tubes 1.5" long and spaced 0.015". Should I use more gaps??. Have bought
> some 22 gauge wire for a 6" coil which may perform better. I plan to
> have a total winding height of 18". Any comments??.  snip
 

> Regards to All
> Pete Scully >>

Hi Pete,

Welcome back.  I would expect the spark to reach at least 3 times
the toroid dia, for that power input, but it would depend on the capacitor
size too.  Winding direction doesn't matter for a normal TC.  Some have
said that in a close coupled set-up such as a magnifier driver, that the
windings
should be in the same direction.  The proper spacing for the gaps, will
depend on the size of the capacitor, which will determine how much
resonant charging is occuring.  That's if you want to use resonant
charging which stresses the NST's somewhat.  In an early test of a
TC with a 12kV, 30ma NST, I got 24" sparks with no toroid at all, my
cap was .0084uF in that test.  0.0084 is a little large for that NST, but
it worked because it was an old fashioned NST that was robust.  I do
not use this NST on my new 42" spark TC which uses an ordinary
modern NST.

On a 7" by 19" secondary, I got some sparks jumping from top
to bottom along the winding, as I raised the power input, so I like to
make the coils at least 23" or 24" long.  But under certain conditions,
the 18" coil would be OK.  I did some recent tests where I got 20-
something inch sparks from a 3" by 9", secondary, but this was on the
verge of breakdown...I was testing the capabilities of small coils, etc.

Regards,
John Freau