Bigger top = bigger sparks

From: 	Bert Pool[SMTP:bertpool-at-flash-dot-net]
Sent: 	Saturday, June 28, 1997 8:10 PM
To: 	Tesla List
Subject: 	Bigger top = bigger sparks

We just had an excellent Tesla magnifier run, with measured sparks 11 
feet in length.  We were running a 62 inch diameter toroid with an 8 
inch cross section stacked on top of two 36 by 8 inch toroids.  The 
first time we ran the big top, we were out of tune, and some violent 
interturn sparking shorted out and effectively destroyed our two 
layer extra coil.  We added one turn on the primary and replaced the 
extra coil with our single layer unit.  This is the first time we've 
had sufficient power and tune to use the large toroid, and it  was 
nice to get it to run.  We shot some excellent video, and even had 
had one guy with a stereo camera positioned on top of a steet metal 
roof with 10 and 11 foot sparks hitting the edge of  the roof about 
two to three feet from the cameraman's feet.  I have to give Jerry 
David Gore credit, he held his ground, so to speak.  His camera and 
tripod were picking up so much EM field that he couldn't touch his 
camera, so we isolated him with a sheet of plexiglass and he was able 
to take some shots - we hope they will be good ones.  The video 
from the roof looking down into the big sparks was great.  Our 
longest run ever was 4 and 1/2 minutes exactly; and that is a very 
long run for a coil.  If you have anything weak in the system, an 
extended run will show it up.  We checked our stationary electrodes 
on the rotary gap - they got too hot to touch, but not hot enough to 
damage the gap frame.  We also lost a welder when we tried to 
parallel it with our first welder.  There were instant balls of 
molten metal splashing out of the inside of the welder - not a good 
sign, so we never got to push the extra power we wanted.  Max kva 
measured at the wall was about 12 kva.  Oh yeah, we had to replace 
the 3 inch diameter corona ring on top of the secondary with a 7 inch 
cross section toroid 30 inches in diameter.  We needed some field 
shaping at the top of the secondary, and we also found we had to 
raise this toroid about an inch to prevent strikes from the 
secondary to the primary.  Our flat aluminum flashing transmission 
line has been stiffened by stapling some 8 foot long wood strips 1/2 
inch by 1/2 inch to the back side; we did this to prevent the 
transmission line from "flagging" when breezes blow through the yard.

Bert Pool