Hi Jim,I have a question about your gap. The tapered air blast is focused directly into the gap between electrodes, but is there any airflow over the brass dowels themselves? It's interesting to me as it appears the air is being used to force quench the gap as opposed to just cooling it. I suppose the gap tips are being cooled, but if I'm understanding this gap air blast setup correctly, it appears the electrodes are staying cool due to quenching and not by "convection".
Have you scoped the gap to look at energy transfer waveforms (quenching)? I suspect it is quenching at the 1st primary notch. There are of course other aspects to consider such as actual power delivered to the gap, but your gap seems to give a ray of hope for solid stock electrodes. In my case, I attempted to cool solid brass round stock (1/2" x 3", several in a multi gap setup). They got hot quickly and performance dropped fast. The difference is that I was attempting to cool the brass stock itself. Due to the poor thermal cooling ability of solid stock, I failed even with a high air flow. I then tried larger brass stock (5/8" diameter). It took a little longer before sparks diminished, but I realized it was simply due to the fact that larger solid stock took a little longer to heat up at the same power level, but it eventually did, and air just would not balance out the heat at my power level. Then I decided to design for large surface area and fast heat up (which also cools fast, so balance and control is easier to obtain). Thus, large copper cylinders. The difference was amazing and confirmed with a 30 minute run! I was running probably higher power at 180mA in all these attempts.
But, your gap is different in that it is blowing directly on the gap itself and "maybe" this is affecting quench times?
Regards, Bart
Jim Mora wrote:Hi Bert,Please define big and power. My 15/120 used two 1" brass dowels 2" long each spaced about .5" if I recall (end to end). They were threaded and therefore easily adjustable. They would run 5-10 minutes and not get hot and cleaningoff the Zink oxide we have talked about was occasionally needed for bestperformance. The faces were polished. And the air blast was very focused on the gap and velocity enhanced by the fire hose like tapered nozzle which had2.5" input to .5" out tapered over 12" and set very close to the gap.
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