flat vs angled primary
From: Mad Coiler [SMTP:tesla_coiler-at-hotmail-dot-com]
Sent: Friday, April 17, 1998 10:53 AM
Subject: flat vs angled primary
I have recently built a new flat spiral primary coil for my small 3"
diameter TC. Previously I had a vertical helical coil (wound strait up).
The old primary was 5 turns of 1/4" copper tubing, and for my previous
setup was tapped at about 4.5 turns and the coil produced about 15"-21"
sparks. This setup is seen in the pictures that is on Chip's webpage.
The main problem was that with only 5 turns I couldnt put a bigger
topload on the coil. Also, there was always a problem with primary to
secondary arcing, even with the 6" PVC sheilding. Safety gaps accros the
NST seemed to be firing too often for my taste.
I built a new primary, flat spiral, #12 solid wire, about 12 turns
spaced at about 1/4" between turns. With the same setup and the new
primary coil (after tunning) the coil produced just a couple inches less
thean old coil. One thing I noticed right away is no safety gap
activity. I brought the gaps about 1/8" closer and still no firing of
the safety gap. My next test was to take off the 10" sphere I had and
put on a larger toroid. I took the top half of the sphere off so the
toroid could sit on the bottom half that was already connected. With a
6" x 22" aluminum ducting toroid, (after retuning) the output increased
to 29" sparks. There was still no safety gap firing. I guess I should
try and bring the gaps a little closer. I think this coil is about at
max because the secondary is only 15" tall and the 29" sparks are
looking as though they want to come out of the top and bend around
almost getting back to the primary.
I was wondering why the helical primary caused much more safety gap
firing. I thought of two possibilities. One was just because there was
slight corona discharge between the pri and sec coils that could be
placing an unwanted potential in the primary circuits. The other was
that the helical coil was more tightly coupled to the secondary and that
the secondary could then be inducing a higher current into the primary
circuits by mutual coupling?
Comments are appreciated,