Hi Scot,
I'll add my 2 cents.
I built a rotary once comprised of small electrodes (3/16"D)
protruding out about 1.5". The electrodes were screwed into one side
of the disc. The disc was metal. The problem I had is that when the
voltage went high enough, the arc would travel down the electrode and
across the wheel to the other electrode (or attempt to). This was
"drawing the arc" mechanically from one electrode towards the next.
When I realized what was occurring, I decided to use an insulated disc
(no copper ring) and let the arc pass through the electrode placing my
stationary electrodes on each side of the disc rather than on the same
side. I think my problem was mainly that quenching was poor. I suspect
quenching is also part of your problem here, but not sure.
Are you able to arc the distance if the rotary is not spinning and the
rotary electrodes are positioned equal distance away from the
stationary electrodes? Giving that a quick test may help determine if
you are truly arcing the distance or if your drawing the arc across.
When running, it may quench before it reaches the next electrode in
which case may appear like a static gap. I think if this is the case,
the next electrode may not fire and then the following electrode has a
very high voltage which conducts, this time drawing the arc all the
way to the next electrode. And then we start over again. Sort of a
very erratic running situation at that point.
Throwing some food for thought out there.
Take care,
Bart