Slow Building Streamers

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

Original poster: "Harold Weiss by way of Terry Fritz <teslalist-at-qwest-dot-net>" <hweiss-at-new.rr-dot-com>

Hi All,

Have any of you had a coil that would slowly build up streamer length on 
it's own?

My 15" coil, with no variac, just an on/off switch, would start with short 
6" streamers and build up the length over about 15-30 sec, to 3.5-4'. Specs 
as follows:

Form: 15" OD 5/8" wall PVC sewer 40" length
Turns: 545 #14 155 Nythane mag wire
Winding length: 36 5/8"
Sec AGL: 25"   (above ground level)
Torrid: 20 X 5" spun Al
Hight above sec: 2 1/4"
Fres: approx 120Khz (wire length calc)
Pri ckt: series (gap accross xfmr)
Cap: 5 X .010 uF 100 KVDC (Fair Radio)
Gap: series, 3 gaps, 1/2" carrige bolt shafts with rounded
         and polished tips, 3/8-1/2" total gap
Discharge path wire: dual #14 15KV GTO stranded wire
Other HV wiring: #14 15KV GTO
XFMR: dual 15/60 NST
NST filter: RCR, 1.3K 53W ww, 250pF (Ceramite),
                1.3K 53W ww
PRI: flat spiral
PRI supports: acyrlic (bronze smoked)
PRI OD: 30 1/4"
PRI ID: 19 1/2"
PRI turns: 9
Conductor: 3/8" Cu tubing
Spacing: 1/4"
PRI-SEC spacing: 2 1/4"
SEC above PRI: 1 1/4"
RF ground: power ground
Base construction: Plywood/2x2, glue and pegged,
                              no screws, casters and xfmrs
                              bolted/T nut
While tunning this coil, I had arcing between turn 9 (end of pri) and turn 
8, with tap set at turn 6. I had racing sparks also.  To stop the arcing, I 
shorted turns 7-9 together, which resulted in the elimination of the 
racing.  I noticed that the racing would only occur while 8 and 9 
arced.  When the two wern't arcing, no racing.  The ideal tunning point 
seems to be at 5 7/8 turns, although I made my tap lead too short to hit 
it. ( I can hit 5 6/8 and 6, and can hit the outside in all sectors but 
that one. ) I also found I had 15A breakers in the garage, which cut run 
time about 10 sec.  The sound of the spark gap echoing off the neighbors 
house, sounded like someone firing a .22LR machine gun.  It had the cadence 
of an M-60D firing at 650-700 rounds per minute. ( ex-Army helo 
crewchief)  Max streamer length about 2 1/2'.

Once I got this coil to the theatre, I had a 20A breaker and isolated power 
ground.  The stage added another 3 1/2' of hight above the reinforced 
concrete floor.  The power distro had GFCI outlets at 20A.  I had a number 
of GFCI trips with both the coil and Jacob's ladders I was using.  Every so 
often, the coil would trip the breaker before it would fire the gap.  I 
think one of the NSTs has a intermittant short in the primary.  Luckily it 
hit every show cue perfectly for that wonderful simultanious gasp of the 
audience.  In the still air of the theatre, streamers could grow to 3 
1/2-4'.  This is where I noticed the slow streamer growth.  The torrid was 
too small, giving lots of breakouts that grew in length, almost like I had 
a variac, and was ramping up the power slowly over about 15-30sec.  The 
only difference was the sound of the gap remained the same throughout this 
time.  Gap temps after 1min were warm but not uncomfortable to touch.

Any ideas on what's causing this?

David E Weiss