Re: [TCML] Sphere Topload Coil

[bartb <bartb@xxxxxxxxxxxxxxxx>]

I understand your reasoning, but I'm simply looking for those big sphere 
top terminals (not necessarily if their good or bad). And I should add, 
the coil I saw with a big sphere might surprise you (really surprise 
you)! I've run a 20" sphere myself in the past. But it's been so long, 
I'd really like to get some data from people that actually stuck with 
it. I didn't. I simply ran it, had fun, and that's about it. I remember 
it taking my larger 13" coil to get breakout. My smaller coils just 
couldn't without a help, and even that was hard pressed.

I also am fond of the toroid configuration for geometric and surface 
field reasons. But due to the coil I'm looking at (a huge sphere), my 
concerns are valid and I'm contemplating a multi-sphere configuration 
versus a single sphere (something similar to Terry's Piranha Coil).

Take care,
Bart

Peter Terren wrote:
> A big sphere is a poor termination for a TC.  I never use it. The 
> simple reason is that the high breakout voltage mean that sparks will 
> come from the sharpest curvature ie at the junction of the coil and 
> sphere or from the coil itself down to the primary.
> You will not see a sphere performing with sparks 2 or more times the 
> length of the secondary because of this UNLESS it has a breakout point 
> but then you are defeating the purpose of a sphere.
> If you want to have the lowest chance or primary strikes then a large 
> toroid on a smaller one is the most practical and allowed me to get 3 
> times secondary length with a SGTC.
>
> Peter
> www.tesladownunder.com
>
> ----- Original Message ----- From: "bartb" <bartb@xxxxxxxxxxxxxxxx>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
>
>
> > Hi Everyone,
> >
> > Sometime back (quite a while I guess), I remember photo's of a pretty 
> > good sized coil with a large sphere top terminal (I'm thinking about 
> > 20" diameter). For some reason, Gary Lau comes to mind but I'm not 
> > sure. I'm curious of big sphere's and the system that drove them. I'm 
> > looking at breakout voltage as based on surface field strength and it 
> > would be nice to know a little something on the basic specs of those 
> > coils.
> >
> > So if anyone meeting those specs isn't too busy with life, please 
> > post some specs. I don't need the whole gap scene or anything of that 
> > nature. Just the basic secondary, top load, cap, and power supply 
> > data. Also, was a breakout point required or not would be nice to know.
> >
> > Reason: I'm advising someone regarding a rather large coil with a 
> > very large sphere. From my calculations, the sphere I think is too 
> > big for breakout on it's own. Calc's are one thing and those of you 
> > well experienced with sphere's may help fill the gap of uncertainty.
> >
> > Thanks,
> > Bart
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