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smooth sphere vs unsmooth sphere
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From: Mad Coiler [SMTP:tesla_coiler-at-hotmail-dot-com]
Sent: Wednesday, March 25, 1998 6:15 PM
To: tesla-at-pupman-dot-com
Subject: smooth sphere vs unsmooth sphere
To all coilers,
For the last few months I have been running my small 3" classic coil
with two metal salad bowls for the HV terminal. The salad bowls were
placed on top of each other as to make a sphere. This setup costs about
$2 and works great. For a long time I kept hearing how a smooth topload
will outperform one that has edges. So I borrowed a sphere from one of
those Van de Graph (I hope I didnt misspell that too bad) generators
that were just sitting in the phsysics lab without any insides in them.
The two different spheres were approximately the same radius. First
results: after tunning at lower power levels I turned the power up. It
seems the curvature wasnt enough for breakout on the smooth sphere and
instead arced from near the base of my sec coil to my pri coil. I then
placed a bump on the surface of the sphere by taking a small nut and
taping it to the surface with aluminum tape. I went over this a few
times with some more aluminum tape so it has no sharp edges and is
fairly smooth, protruding about 1/2 inch. I then ran the coil slowly up
to full power and it arced out from the bump and actualy rised off the
bump and traveled slightly up the side. Befor (with the salad bowls)
there was an edge all around the sphere and the arc would come out all
sides at once. Now most of the power is in one big branching arc. Arc
length increased from about 18" to 24". The pictures of mine on Chip's
site (www.pupman-dot-com) is of the salad bowl topload and the edge is
clearly visible with the arcs comming out all aoround. I probobly wont
have any better pictures for some time. And the performance increase
might even be more than is stated above because the primary tap is at my
last turn and might need more turns.
Tristan Stewart