tuning in my latest big coil (a little long)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: DRIEBEN@xxxxxxxxxxxxxxx 

Hi all,

I had a chance to try to tune in my newest big coil
project yesterday afternoon (Sunday) along with lo-
cal HV enthusiast and fellow Tesla list member Carl
Litton. We pulled it out in the driveway although I
don't think that we pulled it quite far enough from
the house :^O Anyway, we played around with tuning a
little while before we started getting anthing off of
the breakout point of the 12x56 toroid. We finally de-
cided that .2 uFD was just too much capacitor for my
15 kVA transformer to effectively charge that fast
from my 60 amp electrical service. So we removed one
of the two .1 uFD, 50 kV pulse caps and started trying
to run with just one. Things started improving at this
point ;^) We started getting streamers with the primary
tapped between the 10th and 12th turn (there is only 12
turns on the entire primary). A little more tweeking
seemed to narrow the best tuning down to the 10th to
10 1/2th turn of the primary. The primary is 12 turns
of 5/8" OD copper tubing in a spiral with approximately
1/2" turn/turn spacing and the innermost turn at 15" in
diameter and the outermost turn at about 40" in diameter.
The secondary is 1260 turns of #19 magnet wire wound on
48 1/2" of a 12.75" OD gray PVC duct pipe. The spark gap
is an asynch rotary type with infinte speed adjustment
from 0 - 3500 rpm via a variac and a FWB rectifier. The
ASRSG has 8 rotary electrodes and 2 stationary electrodes.

We were really starting to get her toward the sweet spot when
mama couldn't take it anymore and told me that I had to
stop. Toward the end though we were starting to get ground
strikes from the toroid and it's over 7 ft off the ground ;^)
I never turned my variac knob up past about 70 either (0 to
100 scale where 100= 280 volts) One thing that I did notice
is that the RSG started to quench poorly when I turned the
variac up to around 70 (an erratic popping sound with visi-
ble change in the RSG spark) That's one of the main reasons
that I didn't turn it up past 70! Toward the end though as
the tuning started to get more keen it seemed that the
RSG didn't have as much trouble quenching and it ran better
even as the varic got turned up closer to 70. It was at this
time that mama "laid down the law" though so we weren't able
to completely "tune 'er in for the sweet spot":*( I assume that
it is normal for the spark gap to have more trouble quenching
when the coil isn't properly tuned but does quench better once
properly tuned, right? And man do the 1/2"x3" long tungsten
carbide stationary electrodes and their accompanying 1 1/4"
brass square stock mouting hardware get HOT!!! I'm sure
that tends to make quenching a bit of a challenge, too!

I found out later that my garage door opener is now defunct :^(
and I'm sure it's no coincidence that it was following the
firing of the big coil :^O That's why I stated earlier that
we didn't set the coil up far enough away from the house!
We may try moving the coil to Carl's place for the next firing
as his facilities seems a little more "EMP friendly" than do
mine :^P We're hoping for 12 ft to 14 ft+ once everything is tuned
in ;^)))

David Rieben