RE: spark gap

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

Ouch!  The suggested method of setting the spark gap width is a
sure-fire way to kill an NST.  Yes, the performance will be very good -
the wider the gap, the better.  But the voltage may far exceed what the
NST and cap can withstand.

The correct way to set the gap width is to disconnect the primary tap,
so that the gap is across the NST output and the cap/primary are
effectively out of the circuit.  The gap width must be set so that it
just begins to fire with maximum Variac AC in to the NST.

With a 12/120 power supply, attention to airflow through the gap is
vital.  With that much power, more than a gentle wafting through the gap
is needed to keep it cool.

Regards, Gary Lau
MA, USA


> Original poster: Just Justin <rocketfuel@xxxxxxxxxxxxx>
>
>
> Hi Tim,
>
> My coil is similar in specs, although only 60mA instead of 120.
>
> I found that I've had the best luck with 2 gaps out of 6 available.
> The way I set them is similar to setting a safety gap: open the gap
> until they stop firing and then close it back just a wee bit.  (For
> the safety gap you would keep it at the just-barely-not-firing
> distance).
>
> The width of the gap will determine the voltage that the tank cap
> is charged to before discharging through the spark gap.  In my
> (limited) experience, a wider gap makes loud bangs that are 'hotter'
> and more randomly distributed.  A narrower gap makes more of a
> high pitched buzz as the breakdown frequency goes up (the tank cap
> can be charged to the breakdown voltage several times in 1/2 of a
> 60Hz AC cycle).  Also with the narrower gap, I tend to get a streamer
> that stays 'solid', and wanders around rather than the random sparks
> jumping around erratically.
>
> My gap pieces are approx 1"x6" copper pipe and they seem to stay cool
> with a microwave-sourced fan blowing out the sparks.
>
> I also found that I got much better results with a 6" minor diameter
> toroid, perhaps you would as well.
>
> happy coiling,
>
> Justin
>
>
>
> On Thu, Jan 19, 2006 at 11:35:13AM -0700, Tesla list wrote:
>  > Original poster: Timjroche@xxxxxxx
>  >
>  > I'm running:
>  > 12kV 120mA NST
>  > .03 uF 45kV maxwell tank cap
>  > 12 T .25" tube .25" spacing primary
>  > 4.343" OD 28awg 17" lng secondary
>  > maj. dia 17" min dia 4" toriod
>  >
>  > What is the best place to start a static gap?  I have . 5" solid Cu
>  > (12 pcs. 4" long), .5" tube, 7/8" tube, and 1.125" tube...is hollow
>  > better? bigger dia?
>  > What about length? my 7/8" (6 pcs. 6" long) better than .5" 3"long?
>  > can you have to many gaps? i.e. total gap=.5",  2 tubes?, 6
> tubes?, 12 tubes?
>  >
>  > thanxs
>  > Tim
>  >
>