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Success with Synchronous rotary gap.
---------- Forwarded message ----------
Date: Mon, 20 Oct 1997 21:34:35 +1000
From: Peter Electric <elekessy-at-macquarie.matra-dot-com.au>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Success with Synchronous rotary gap.
I have recently completed a synchronous rotary gap for my 6" TC.
Previously it was running a forced air quenched, single stationary gap
and I was getting an occasional 39" strike with 15kV 60 mA on my 6"
coil.
Initial results with the rotary were very poor. It would run evenly at
about 1/4 power but as soon as I went higher, I got continuous arcs
across my safety gaps and not much spark. On the weekend, Rod, Jason and
myself fired up Rods 12" coil with his pole pig and after getting only
fair results with his non-synch rotary, we connected my little synch
rotary up. The results were spectacular but short lived! We had great
white snaking arcs everywhere, but the polythene rotor promtly melted
and the 1/4" dome nuts threatened to launch themselves across the room!
We have since taken a few electrodes out of Rods rotary to get it as
close as possible to 100BPS (50HZ mains) and now it runs nicely every
time it drifts in and out of phase. I believe Rod is aiming to convert
it to synch operation this week. Anyway, I thought it was a great
afternoon's coiling and they were certainly the hottest sparks I've seen
for a while!
I have since got the rotary running nicely on my coil also. Previously,
I had been running the trannies and safety gaps in parrallel with the
rotary. After repairing the rotary, I rewired my coil to place the cap
across the trannies and the results were better but now I got arcing
around the stationary gaps. I eventually discovered that the phase of
the rotor had to be shifted a full 90 degrees (from what we had used on
Rods coil) and the gap now runs sweetly with a very even 100 Hz buzz.
Also I now get no arcing across the safety gaps and even the resistors I
have across the filter chokes run cooler. It seems from all this that
placing the gap across the trannies might be good for staionary gaps but
is no good for rotaries. Also the peak of the AC cycle is substantially
phase shifted, possibly because of resonant charging effects. I am now
getting regular 40" strikes, not a match for John Freau's efforts yet
but I think some more tuning and playing with coupling might improve on
that. Also I am only running 11 nF as opposed to 13 (according to the
formula) so resonant charging is probably not optimum. Anyway, many
thanks to John Freau's excellent posts on synch rotaries - I'm now a
great believer in the synch spark gap!
Do many of you guys that run pole pigs use synch gaps, and if so were
they a big improvement?
Cheers,
Peter E.