Stories from the 4th

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

Original poster: "Jason Johnson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <hvjjohnson13-at-hotmail-dot-com>

Hello, been a long time since I posted but thought I'd share a few bits
to the list about coiling on the fourth.

I ran my coil for several hours on both Thursday and Friday nights, and
quite a crowd gathered both times (probably 30+ people, most of whom I
don't even know). I did a few demos with flourescent tubes, nothing
spectacular but everyone loved it. I put one light on top of the toroid
and after ~2 minutes the light bulb blew into three pieces (it broke
where it contacted the toroid, the arcs melted right through the glass),
much to the crowd's delight.

I ruined my secondary coil towards the end of the second night, it had
virtually no insulation on it (just enough poly to hold the windings
on), and it arced to the primary coil just a few inches above the base,
which blew 5 turns completly apart (there was already a burnt spot
there, and I've been running the secondary coil for just over 3 years,
it was just one of many small burnt spots). I knew that there was no fix
to it, so I just ran it until the PVC caught fire. Oddly enough there
was little degredation of performance, perhaps only six inches of spark
lost (not too much from ~6 feet of spark on average). This made me make
the decision to upgrade the whole coil, which I started today.

The all metal rotary gap logged several more hours over the two nights,
putting the gap that was supposed to instantly fry itself to well over
100 hours of very satisfactory performance. I just finished upgrading
this gap by drilling out the end of the brass stationary electrodes and
press fitting some 3/32" thoriated tungsten electrodes in there to
improve heat handling capabilities of the stationary electrodes. This
will also decrease dwell time from 754 usecs to 597 usecs, which
probably will have no noticeable effect, but we'll find out.

I'm moving up from a 4.375" x 23.75" coil wound with 28 gauge to an
8.25" x 32" coil wound with 21 gauge. I cut my capacitor bank down to a
3x5 array today, to give me 198nf instead of a 3x9 array for 110nf. The
transformers will be the same with 2 unballasted MOTs in series for
4800volts, and the gap will be the same, except the modifications noted
above. This should increase max spark length to about 104" from the
previous best of 78" based on my calcs and design changes. I should have
the coil done within a day or two of my next trip to the home depot.

Can I push 8+ feet of spark on a 120 volt 20 amp breaker? We'll find
out, but I may have to plug the rotary gap into a different circuit.


<< Jason R. Johnson >>
G-3 #1129
The Geek Group
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