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RE: Gary Lau's gap
I switched to a Lau Gap with good results. I have 40 in sparks using 0.017
uF SW caps and about 1.3 kW input. However, with close spacing, I will
suddenly lose breakout, followed by an audibly "faster" sounding SG
discharge which continues to increase until its almost a continuous sounding
arc. Obviously at this point quenching is virtially non existent. Input
power rises and I have to shut down. Running of the airflow with no SG
discharge for 10 s to 1 min seems to clear the problem for a while, but its
getting worse. Reducing the power by opening 3/4 of my ballast switches (HW
elements) will not restore quenching once its lost. Wider gap is less
sensitive, but mine will not fire at the lowest power setting.
I'm using 3/4 Cu pipe end to end with no fittings. I thought ionized air
was being trapped in a boundary layer and killing the quench, but I have to
shut off HV for much longer than I would expect for this failure mode. My
Cu electrodes are becoming dark and eroded which may be a factor. RIght now
I'm down because the washtub sprung a leak, when I'm up agin, I hope to be
instrumented for measurements thanks to Terry and his excellent Mk I fiber
optic VI probes. Y'all missed the bargain of the century.
I still want to know if I'm in the ballpark with 40 in from my SW cap
system, running from a 70:1 PT, about 1.3 kW thru the xformer, maybe 2-3 kW
in ballast.
Will
ps Gary is it OK with you to post this type gap on my site ?
> ----------
> From: Tesla List[SMTP:tesla-at-pupman-dot-com]
> Sent: Sunday, November 01, 1998 00:27
> To: tesla-at-pupman-dot-com
> Subject: Gary Lau's gap
>
> Original Poster: Gary Lau 31-Oct-1998 1742 <lau-at-hdecad.ENET.dec-dot-com>
>
> >Original Poster: Bert Hickman <bert.hickman-at-aquila-dot-com>
> >
> >Chris,
> >Welcome to coiling, Chris!
> >Some quick suggestions:
> <snip>
> >3. Go to a vacuum gap (either multiple parallel copper pipes or to Gary
> >Lau's style single-gap vacuum gap) to improve quenching performance.
> <snip>
> >-- Bert --
>
> Thanks for the referal, Bert! But I do have to caution potential users
> of my single gap of one thing relating to quenching. While I have not
> yet tried to confirm this with a scope (on my list of things to do), I
> suspect that my single gap, while being a better performer than my RQ
> gap, may be actually exhibit inferior quenching. I draw this
> conclusion by noting that my capacitor runs much warmer with the single
> gap, all other things being the same. I suspect that the inferior
> quenching may be the thing that caused my extended foil cap to fail. The
> thing that inspired me to try a single gap was Terry's paper comparing
> single and multi (aka TF) gaps. Although Terry didn't use any sort of
> forced airflow, his measurements showed that at higher couplings, the
> single gap produced higher secondary currents but with inferior
> quenching. See
> http://www.peakpeak-dot-com/~terryf/tesla/experiments/sgap/sgap.html
>
> So, while sparks may be better with a single gap, it may be much harder
> on one's caps and NST.
>
> Gary Lau
> Waltham, MA USA
> http://people.ne.mediaone-dot-net/lau/tesla/tesla.htm
>
>