RE: [TCML] racing arcs

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

Hi Dan,

Regarding your racing sparks with the sync RSG -

> As I advanced the SRSG, the sparks grew & increased until I
> reached a point where I developed racing sparks. Back off a couple of
> degrees and everything was fine. One of the list gurus explained to me
> that by changing the point on the sine wave where the RSG fires also
> changes the inductance of my NST secondary thus changing the tune of the
> entire system.

That doesn't make sense.  The inductance of the NST secondary in no way affects the resonance of the TC primary or secondary, and I can see no way for the NST secondary inductance to vary, based on timing of the gap.

I think what happened is one of two things.  As you delay the SRSG timing, the bang occurs later in the charging cycle, so the bang-voltage increases and performance increases.  Any secondary is only good for a certain bang-size, so it's possible that you may have increased the bang voltage beyond that point.  But more likely, SRSG's have a strange mode of behavior, where if you advance the timing too far, the gap misses firing at a presentation.  But the energy in the cap is not lost just because the gap wasn't quite ready.  That energy is saved in the form of current in the NST secondary inductor, and in the next charging cycle, the energy from the missed bang is added to the energy in that charging cycle, resulting in a MUCH higher voltage bang at the next presentation, and this is what will cause the racing sparks.  Just back off a little on the RSG timing and that fixes it.  SRSG timing is VERY critical, so having a live, variable RSG timing adjustment is really good to have.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Daniel Hess
> Sent: Saturday, March 08, 2008 9:12 AM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] racing arcs
>
> Hi Phil;
>
> Never experienced racing arcs? You're obviously not trying hard enough!
> ;-)
>
> There are two ways I can 'make' my 6" x 24" secondary produce racing arcs
> although it's not something I'm eager to do deliberately as they can be a
> fast-path to send your coil into the afterlife.
>
> The first was when I was attempting to set coupling at what Malcolm Watts
> called the magic K values of .22. (Magic K values are where the coupling
> is specifically set to transfer energy from the primary to the secondary
> coil in whole, complete cycles, maximizing efficiency.) Greg Legh once
> posed a simple method to measure K with what he called the suicide cord
> method. I had already achieved .18 K this way and the time and trouble was
> worth it considering the performance improvement I gained. But when I
> tried to couple at .22 I got racing sparks out the wazoo! I've since
> learned that coupling this tight is nearly impossible to achieve with a
> classic two coil setup.
>
> The second way occurred when I graduated from a RSG to a SRSG. My SRSG
> could be advanced/retarded, on the fly, with a stepper motor lead screw
> arrangement. As I advanced the SRSG, the sparks grew & increased until I
> reached a point where I developed racing sparks. Back off a couple of
> degrees and everything was fine. One of the list gurus explained to me
> that by changing the point on the sine wave where the RSG fires also
> changes the inductance of my NST secondary thus changing the tune of the
> entire system. This aspect of using SRSG came as a complete surprise to
> me. For those on the list more knowledgeable on this, please feel free to
> amplify on the subject.
>
> Daniel Hess

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