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RE: Latest coil
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.
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 polypropylene
>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 wired
>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, freshly
>soldered and re-painted. More racing sparks and some that jumped
>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 dropped,
>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