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

[johnbrooks@xxxxxxxxxxx]

Quarqster there is (or was) some one useing the "Cam" style,,
about an hour construct and hookup,controll 20 feet away,think about it.
j 

On Tue, 07 Jul 2009 04:20 -0700, "Quarkster" <quarkster@xxxxxxx> wrote:
> DC:
> 
> Sorry, its still not clear how you are moving the secondary vertically
> for 
> dynamic coupling adjustments. Previously, you said that it was done using
> a 
> "flexible shaft coupling attached to the base of the secondary".
> 
> In another post, you stated that you were "driving the secondary up and
> down 
> via some thick walled Tygon tubing".
> 
> Now, you are are saying that there is a motor-driven right-angle gearbox 
> that "runs the 3/8" brass rod up and down".
> 
> A few specific answers might help everyone visualize your actual setup:
> 1. Since the output of the right-angle gearbox is just a rotating shaft, 
> what converts this rotation to linear motion that would move the brass
> rod 
> up and down? It would seem more logical to have the brass rod simply
> rotate, 
> with a fixed nut mounted in the bottom of the secondary.
> 
> 2. How are the secondary coils being supported and guided (and restrained 
> against rotation) while moving up and down? Obviously they cannot be just 
> hanging on the end of a flimsy 3/8" brass rod, especially  a 24" diameter 
> secondary that must be at least 60" tall and possibly weigh a hundred
> pounds 
> or more?
> 
> It would really be helpful if you could provide a detailed description of 
> your setup. As always, a few photos would be worth a thousand words.
> 
> Regards,
> Herr Zapp
> ----- Original Message ----- 
> From: "DC Cox" <resonance@xxxxxxxxxxxx>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Sent: Tuesday, July 07, 2009 7:10 AM
> Subject: Re: [TCML] Sudden and unexplained destructive racing spark 
> flashovers
> 
> 
> > It's a right angle drive driven by a small 50 rpm gearmotor.  It runs the
> > 3/8" brass rod (sec ground) up and down vertically.
> >
> > It allows you to find the optimum sweet spot in only 5-10 minutes of
> > experimenting while the coil is continuously running.
> >
> > D.C. Cox
> >
> >
> >
> >
> > On Mon, Jul 6, 2009 at 7:29 PM, Jim Mora <wavetuner@xxxxxxxxx> wrote:
> >
> >> 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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