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RE: [TCML] Sudden and unexplained destructive racing spark flashovers



I've always wanted to put real-time coupling adjustment on my coil, but never got around to it. I was always afraid to simply set my secondary on my primary base, so you can see how mine is supported:

http://www.classictesla.com/hot-streamer/adam/bigass_coil/coil09.jpg

All I'd have to do is add another baffle inside, where the windings begin, and attach a linear actuator, like what is used to move 7' satellite dishes. I'd add three rollers to the bottom of my primary base, to guide and center the secondary. If my secondary is too heavy, I could always raise and lower the primary, though that would take a little more effort to raise and lower four supports simultaneously.

Adam

--- On Mon, 7/6/09, Jim Mora <wavetuner@xxxxxxxxx> wrote:

> From: Jim Mora <wavetuner@xxxxxxxxx>
> Subject: RE: [TCML] Sudden and unexplained destructive racing spark flashovers
> To: "'Tesla Coil Mailing List'" <tesla@xxxxxxxxxx>
> Date: Monday, July 6, 2009, 9:29 PM
> Hi DC, Et Al
> 
> I don't understand your dynamic coil height changer. I have
> been doing it
> the hard way (round PE or plexi spacers). I would like a
> dynamic method to
> raise the secondary of my future VTTV 6" acrylic .125" form
> which will be at
> least 2" into the 8" solenoid. It would be nice to vary the
> height rather
> than spacing for my 12".125" PVC coil. Neither coils are
> grossly heavy.
> 
> Jim Mora
> 
> How other do it are welcome. I suspect a longer former at
> the bottom for
> stability is part of the recipe. Thoughts? 
> 
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx
> [mailto:tesla-bounces@xxxxxxxxxx]
> On Behalf
> Of DC Cox
> Sent: Sunday, July 05, 2009 9:04 AM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Sudden and unexplained destructive
> racing spark
> flashovers
> 
> I'm just reporting from practical experience in coil
> building.
> 
> If you exceed 0.14 in classic type coils, especially around
> 0.18 and above,
> racing sparks will occur.
> 
> There is no reason to exceed this coupling value.  If
> you do your output
> sparks will diminish in length, not grow.
> 
> I've attached a flexible shaft coupling to the base of
> various sec coils and
> dynamically elevated and lowered them while the coil is
> running.  Various
> size coils, 4" dia to 24 inch dia.  In all case max
> spark length is achieved
> around 0.12 to 0.14 range.  I've carefully measured
> the k value at the
> setting that we achieved the long spark length for a given
> coil.
> 
> Oddly, it appears to be nearly a linear relationship. 
> A 24" dia sec
> performs best with 9" of elevation.  A 18" dia. sec
> performs best with 6.5
> inches of elevation.  9" dia sec works best with 3.25"
> of elevation.
> 
> At around 0.18 to 0.2 range most coils started to exhibit
> signs of excessive
> corona and occassional flashovers.  I've repeated
> these experiments with
> coils sizes ranging from 4" to 24 inch dia and the results
> seem to be the
> same.  Excessive coupling produces diminished output
> spark lengths.
> Carefull measurements with oscopes indicated the
> frequencies were starting
> to split indicating power was being wasted by not going
> into the fundamental
> resonant freq of the sec inductor.
> 
> Dr. Resonance
> 
> 
> 
> 
> On Sun, Jul 5, 2009 at 3:15 AM, Dex Dexter <dexterlabs@xxxxxxxxxxx>
> wrote:
> 
> > It's an experimental fact that too high coupling can
> be the cause of
> > flashovers and racing sparks but...The point of max
> potential is at the
> > terminal (top load) of the secondary in 1/4 wave
> resonance coils.Typical
> > couplings used (0.1-0.2 range) can be hardly 
> high enough for the point of
> > max potential to be shifted somewhere else.Perhaps you
> are referring to
> > increased secondary local voltage gradients vs higher
> coupling
> > instead?That's a different thing and more possible to
> occur I think.
> >
> >
> > Dex
> >
> >
> > --- resonance@xxxxxxxxxxxx
> wrote:
> >
> > From: DC Cox <resonance@xxxxxxxxxxxx>
> > To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> > Cc:
> > Subject: Re: [TCML] Sudden and unexplained destructive
> racing spark
> > flashovers
> > Date: Mon, 29 Jun 2009 20:19:02 -0700
> >
> > Over coupling is one cause of racing sparks.  It
> produces more than one HV
> > point near the top 1/4 of the coil which can cause
> local ionization and
> > eventual flashover in this area.
> >
> >
> >
> > Dr. Resonance
> >
> >
> >
> >
> >
> >
> >
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