Subject: Coil stuff
From: Craig Shields <cshields-at-tyrell-dot-net>
Date: Tue, 4 Oct 1994 19:32:14 -0500 (EDT)
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Just got done reading your last message. Sounds like your coil
works pretty good. How what is the milliampres rating of your
neon sign transformers? I have 3 15KV neons, total of 120 ma.
I'm using 2 of the big TCBOR caps in series, for a total of
.018 capacitance (each cap is .036 because I got 30 mil plastic
instead of the 60 mil....but it has worked out OK). Best
output I've seen is 32" to ground. The streamers average around
2 feet. If you have 120ma or so of current, you could probably
get this much or better.
I used SAE 30 motor oil to fill my caps, and it's worked fine
so far. I know it's really pushing the limits though with the
30 mil poly. I heard that too, about these big caps will fail if
you try to run them without oil. Wouldn't recommend it <G>
On the series gap, the ball berings sounds like a good idea, but
they probably need to be larger so they don't heat up too fast.
I saw a video of a guy's coil using large 2" berings and vibrating
them with a small motor to keep them from building up too much
carbon during a run. He had them mounted in a plastic pipe, with
a blower going thru it to cool it off. Seemed to work good.
The spark gap I use is based on a TCBOR video design. I use 5
sections of 1" copper pipe, cut to be 3 inches long. These
are mounted side by side on a plastic base, with about a .020 gap
between each for a total of 4 gaps. So the gap surface is about
3" long, and I mounted the whole thing on it's side, so the pipe
sections are vertical. I tried using 5 gaps of the same distance,
but the coil seems to work much better at 4 gaps .020 each. By
only running the coil for max 30 seconds, the gap doesn't seem to
get hot enough to affect performance. Performance does go down some
when the gap gets dirty. It has to be cleaned once every couple
I agree with you on the gaps being large and a flat surface. I really
like the copper pipe gap, mainly because it's cheap, but also because
it does have a good size sparking surface.
My experiments also have shown the "directional" effect you noticed
on your torus, where the streamers seem to favor one direction rather
than being evenly distributed. But, in contrast to your experiment,
I could turn my torus and change the direction of the sparks. Seems
like there are certain spots on my torus that favor sparks more or