I fired up my rotary spark gap this weekend. Performance is disappointing.
Construction: The wheel is 10.0" dia. Lexan (polycarbonate). There are 8
electrodes composed of 1/4" stainless steel acorn nuts connected by a 1/4"
stud. They are set in 1/2" from the outside edge of the wheel. The
stationary electrodes are 1/8" tungsten. Since the wheel is not perfectly
true and the acorn nuts are not all exactly the same height, there is some
small gap between the electrodes. I set them up so they just barely do not
hit. There is probably .005 to .010" clearance. I'm not exactly sure what
RPM I am running at, I had trouble getting consistent readings with my
tachometer. It is turning fast enough to sound like an airplane motor. I
tried different speeds as well. I have not got my fan that I plan to mount
in the cover box yet so I am running it out in the open for now.
I thought hooking it up correctly was to simply place it in series with my
existing cylindrical static gap. I tried this first. It would only fire
intermittently and the secondary of the coil produced weak, short discharges.
The cylindrical gap at this point was electrically folded in half. Then I
shorted out one set of gaps so I had only two gaps on each side, in parallel.
Same result. Next I tried removing the static gap and using only the
rotary. Same result. Next I removed the resistive load in series with the
welder. Same result. I tried varying the setting on the welder and it did
I noticed that I can finallly control the input voltage to the pig. It does
not "clamp" at 125v like it used to with the static gap - which we concluded
was shorting out the pig secondary due to it's inability to quench properly.
I still did not exceed about 10,000 volts because I am using my homemade
capacitor. (My new commercial cap should be here today or tomorrow.)
Do you have any ideas? I don't know why this is not working as I thought it
would. I expected the same or better performance than I had with the static
gap - and the ability to control the primary pig voltage. I seem to have
control over the pig primary now but the rotary gap hardly works at all. It
fires very inconsistently, maybe on a 10% or less duty cycly. I had longer
discharges with a static gap and a 12kv 60ma neon transformer.
Thanks, Ed Sonderman