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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