RE: Latest coil

Hi Malcolm:

When I was running with the .02uF cap, I was using a single-segment static
gap, and I had measured the firing voltage as 24KV.  More recently I have
switched to a synchronous RSG, 120BPS, and increased the cap size to .03uF.
I have yet to measure the firing voltage and have not yet done too much in
varying the rotor phase, still waiting for my HV probe to arrive so I can
scope these things rather than stabbing in the dark.

Regards, Gary Lau
Waltham, MA USA

		Original Poster: "Malcolm Watts" <malcolm.watts-at-wnp.ac.nz> 

		Hi Gary,
		             A couple of questions:

		> Original Poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com> 
		> Hi Alan. All,
		> I don't yet have any answers to your racing sparks
problem, but if misery
		> loves company, perhaps I can offer you that.  I'm in the
process of
		> converting from my static gap to a sync RSG.  I had been
getting nice 60"
		> arcs from my 4 1/4" secondary, power by a 15/60 NST and a
.02uF cap.  I
		> upped my cap to .03uF so as not to over-volt it, and I too
am now seeing the
		> racing sparks (who coined that name anyway?), and also
have a burnt spot at
		> the base of the secondary to mend.  And I tried raising
the secondary, still
		> got the sparks.

		Was your gap set to the same voltage as when you ran with
		20nF cap?  If not, what was it set to (by comparison if
voltage not 

		> Right now I'm waiting for a HV probe that I ordered so I
can scope my cap
		> charging and phase, perhaps that will show up something.
I'll let you know
		> if it does.
		> Regards, Gary Lau
		> Waltham, MA USA
		> >Original Poster: ajones-at-pointlink-dot-net 
		> >
		> >Hello everyone. I thought I would post a little about my
latest coil.
		> >The primary is flat with 3/8" tubing with slots in the
form to allow
		> >tapping from below. The secondary is an upside down
		> >trash can that measures 14" diameter on the bottom and
13" diameter on
		> >the top and wound with 18gauge magnet wire for 24-1/4"
winding length.
		> >Two toroids are being used, a corrugated drain pipe
wrapped with tin
		> >foil that measures 4"x33", and two flexible ducts taped
end to end for
		> >7"x 40". I am using two of the H&R transformers that are
		> >anti-parallel for 10kV 300ma. Six sets of polypropylene
caps, .013uF
		> >each for .078uF or so total and a sync-gap. This isn't
quite resonant
		> >yet, but will soon be larger than resonant.
		> >
		> >The first run was just to see that everything worked.
There were
		> >serious racing sparks and as I found out, several spots
had burnt.
		> >Some turns had to be removed on the bottom and the other
spots had the
		> >burnt insulation scraped off and were coated with model
paint. Trying
		> >again the next night, one of the repaired spots burnt
again and three
		> >turns had to be removed. But there was a ground strike
before shutting
		> >down that I later measured at 80". Or 3.2 times the
winding length.
		> >Pretty decent, but will have to get better :-)
		> >
		> >I setup again tonight with the newly repaired secondary,
		> >soldered and re-painted. More racing sparks and some that
		> >straight down to the primary from the lower toroid. Since
I have never
		> >had these kinds of problems, I didn't really know what to
do. I have
		> >only run with crappy capacitors before that wouldn't let
the power out
		> >to the coil and these polypropylene caps are working
great. I tried
		> >raising the secondary some more to reduce the coupling.
It was now
		> >1-1/2" above the primary, but still had the racing
sparks. The only
		> >other thing I could think of was to lower the toroids
some. Now the
		> >racing sparks have been eliminated. But the spark length
		> >probably from the reduced coupling. I'll try increasing
the coupling
		> >in a few days and see if the spark length comes back up.
		> >
		> >So, any comments or suggestions? All welcomed.
		> >Thanks,
		> >Alan Jones