[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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



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
>
>
>
>
>
>
> _____________________________________________________________
> Washington DC's Largest FREE Email service. --->
http://www.DCemail.com <http://www.dcemail.com/><http://www.dcemail.com/>--->
A Washington Online
Community Member --->
> http://www.DCpages.com <http://www.dcpages.com/> <
http://www.dcpages.com/>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla

_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla

_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla


_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla