98 Bottles of Beer on the Floor...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Gregory Hunter by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ghunter31014-at-yahoo-dot-com>

Dear List,

I've been up to some tinkering with my 6" x 30" Tesla
coil since I added the 81nF beer bottle cap.  Oddly
enough, the coil seems to perform better with the old
static spark gap instead of the 10,000RPM ASRG.  I
always assumed the rotary would be superior.  The
static gap I'm referring to is a Gary Lau style
two-horned single static gap mounted atop a vacuum
cleaner motor.  It's a heavy-duty unit made of 1"
copper pipe and fittings.  Another peculiar
thing--opening the gap to the widest setting capable
of reliable firing does not give longest sparks. 
Spark length peaks when the gap is closed down a
little below maximum firing width.  The coil also
sounds better--smoother I guess.  Maximum measured
spark length so far is 72 inches.  I think I saw some
longer ones, but the longest one I actually checked
with a tape measure was 72".  The bottle cap boxes
took several hits from long streamers that curved way
out and down, like big hoops.  It each case, the pole
pig safety gaps fired, but coil operation was not
interrupted.  Sure was fun watching the show.  Sorry,
no pictures yet.  I'll get to it soon.

Out of curiosity, I tried powering this setup with my
twin MOT ballast, which only puts out about 4800VAC. 
I used the two MOTs straight, with no extra ballast
and no RF filter.  I removed the shorting wire and
plugged the coil tank circuit straight in to 4800VAC. 
I had to close the gap way down to get reliable
firing.  Breakout from the 4" x 20" drainpipe toroid
was a bit iffy, so I sat a chunk of brass rod on top
to help it.  This elicited a short, thick, very
intense blue streamer, which shot up to connect with
the attic door.  The spark gap made an evil, very
loud, mechanical grinding noise.  Gap current must've
been hideous.  It reminded me of something.  I was out
in my yard one day when a big residential pole
transformer died a couple of blocks from my house.  I
heard an incredibly loud BRAAAAATTT!!! as the pole pig
gave up its smoke (and my power went off for half a
day).  That's what the spark gap sounded like with
straight MOT power.  I didn't like it.  Best measured
spark length in this mode was 36".  That doesn't seem
very long considering the power level, but the
streamers were very thick!  I replaced the shorting
wire across the MOT terminals and put it back to work
as a pig ballast.  4800VAC is just too low for my
liking.  This might be an interesting application for
a triggered spark gap.  A TSG would allow a wider gap
opening for improved quenching & cooling without
giving up reliable firing.  Just a thought.

For the 240VAC/20A I'm drawing from the wall, 72"
isn't long enough.  I'm getting multiple small
streamers and only few big ones.  Clearly I need a
bigger toroid.  I'm thinking along the lines of a car
tire inner tube.

Best Regards,

Gregory R. Hunter
http://hot-streamer-dot-com/greg


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