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Forced Air (was: Re. need some input)
>Original Poster: "Reinhard Walter Buchner" <rw.buchner-at-verbund-dot-net>=20
>>I've had good results with both single and multiple gaps. But in both
>>cases, it's VITAL to observe that the electrodes be rounded and smooth on
>>all arcing surfaces, and that the arc channel have forced airflow through
>>it. Don't even bother if there's no airflow, performance will be
>>terrible. - Gary Lau
>I have heard/read this several times, just like not using Al in a spark
>gap, but I do it anyway, and get good results o:). The 22mm Cu/Al
>static gap, I am using now (41"+ output), has absolutely NO forced
>air flow across it. I am using 10 gaps total, tho (for 7.5kV rms). I do
>agree with you that the surfaces should be rounded and smooth (this
>gives a more consistant breakdown voltage as compared to a sharp
>edge). However, (I don=B4t think you mean this) a polishing is not
>necessary as the surface will erode over time anyway (and this
>doesn=B4t seem to hamper performance at all).
>I tried a single gap (similar to yours) with pressure (not vacuum!)
>quenching. I got pretty rotten results, tho. I tried different spacings
>and different pressures, but I never achived the same (or near the
>same) results I get with my super-simple Cu/Al gap. I continuesly
>find that multiple spark gaps outperform single gaps by a WIDE
>margin (at least for me).
The diminished performance when airflow is stopped was nothing less than
striking with my single gap, but less pronounced with my 12 x .03"
RQ/TCBOR multi-cylinder gap. Terry reported that his multigap using
something like 7 mils per gap needed no airflow at all. So it may well
be that the larger the individual gaps, the more important it is to use
forced air. What were your individual gaps? If you are using 7.5KV and
10 gaps, it was probably quite a bit less than my .03".
And I agree, no polishing is necessary.
I suspect that the optimal static gap configuration may lie somewhere
between a single gap (lowest gap losses but worst quenching) and 10-12
gaps (better quenching but higher gap losses). And since the individual
gaps would be necessarily large, forced air would be important. So many
things to try, so little time...
Regards, Gary Lau
Waltham, MA USA