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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
bertpool-at-flash-dot-net