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Re: first, second and third light of a flat coil



Original poster: "marc metlicka by way of Terry Fritz <twftesla-at-qwest-dot-net>" <mystuffs-at-orwell-dot-net>

Paul, Bart, All

Tesla list wrote:
> 
> Original poster: "Paul Nicholson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>
> 
> Hi Marc,
> 
> > I wound a somewhat conical primary that hangs under the secondary,
> > 70 deg. angled inward, 11 turns at 20" in.
> 
> Can you give us more details of the primary, and its position
> wrt the flat secondary?

I glued popsicle sticks extending from the underside of my paneling
coilform, These are set at a 70 degree angle inward toward the center.
The primary windings are of 18g mag wire with the first turn starting 1"
from the base and a spacing of 1\2" between turns, 11 turns total.
My thinking in using the inward angle was that it seemed to look like it
would give me the best interaction of the flux field lines cutting
across the secondary? For tapping i just scrape the enamel off were i
want to place a tap.


> 
> > Racing arcs along the sec. windings are a real problem.
> 
> At what firing voltage does the trouble start?

I'm using a 12\30 nst and tsg, a 22nf cap gives what looks tuned the
best at 7 turns. This could be a little wrong because i just couldn't
keep the racing arcs down. The racing arcs extend in a radial pattern
from the inner turns outward to the outermost turn like spokes in a
wheel. There are many of them at once, they are very strong blue\white.
I tried extending the center bolt to three inches and placing a 6" spun
toroid on it to shield the inner turns hoping i could get topload
breakout instead of racing arcs. It seemed to help some with a fuzzy
corona like discharge from the toroid as the tap\tune started to come
in, then the spoke arcs would start again. I also tried one of those
expanded aluminum down spout screen units for a topload, These look like
a 150w light bulb that is made of expanded metal, i was starting to get
1"-2" leaders from this along with the radial spoke arcing, this is when
i noticed the massive amount of carbon pinholes in the center windings.

  What are your
> primary cap and tap settings?  You'll need to retune by 20% or 30%
> between the rim-grounded and center-grounded configurations.  Do
> the racing arcs form at a particular radius on the coil?

The spoke arcing would very within the inner turns of a 2" diameter
circle, not always coming from center bolt out but sometimes from 1\2"
to 1" away. 
Bad news now because the inner 1" or so turns have been burnt so bad
that i had to remove them, I will have to rering the operating
parameters for this coil before we can do more modeling on it, sorry
Paul.

It was somewhat my fault for not setting up a ground rod to allow the
discharge an easy path or contact surface, i should have done this
rather then trying free air discharges right from first light (hind
sight 20\20). It was very exciting experimenting and am looking forward
to more.

I have since removed the inner turns and i put a layer of pvc tape
across the coil to try to give some insulation to the 28g mag wire in
the windings to try to curb some of the arcing. I will also use a variac
to bring tank voltage up slowly from 9kv up to the 12kv.


> 
> It would be nice to model this situation.

I am hoping that i can remove the primary easily so i can ring out the
new L-R and fres due to new 8 7\8" winding area extending in from the
original 20" diameter, If not no biggy, the primary was only hoaky'd
together for a start.
I should have a few pics on my site by the time this is posted:
http://www.fortunecity-dot-com/meltingpot/syria/1210/index.htm
Follow site map to "flat coil" page.

More to come soon,
Marc M.
Geek #1055
(PI geek)


> --
> Paul Nicholson
> --