Re: [TCML] Spark gap for first TC

[jimlux <jimlux@xxxxxxxxxxxxx>]

John Byström wrote:
> Hi!
>
> I've started to build a TC as a project in school.

Excellent!
> And I've searched around about spark gaps and which who would fit my coil. 
> I don't have a big coil, my NST is rated 8kV and 50mA, so I wounder if there's best to have a single gap
> that doesn't quench as good as a gap with several in series, but that's more efficient than a multi gap.

Almost anything will "work".
I like a gap made of three pieces of 3/4" or 1" diameter copper pipe 
about 2" long arranged with the long axes parallel.  So you effectively 
have 2 long skinny gaps in series.  You have a small fan blow air 
through the pipes (along the axis of the pipe.  If you arrange them in a 
sort of squashed triangle, you can permanently mount the two end ones, 
and adjustments only need to move the middle one.

The other easy gap that works fairly well is a couple of copper pipe 
caps facing each other, with a shop vac blowing between them.

You could even do the two bolts thing, but I've found that the bolt is 
so small  (even if you use carriage bolts and the gap is the head of the 
bolt) the spark always goes from exactly the same spot on the electrode 
and you get a hotspot.  Once you get that glowing hot spot, the gap 
characteristics change (it breaks down more easily), and the output of 
your coil drops.

> Also, I've had thoughts on how a spark gap would be if you had several in parallel, instead of in series.
Series only.  Parallel gaps: When the first gap breaks down, the voltage 
across it drops way down (from kilovolts to a few hundred volts), so 
none of the not-yet-broken-down gaps will break down.

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