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Re: SPARK GAP QUESTION
---------- Forwarded message ----------
Date: Mon, 06 Oct 1997 11:10:39 -0700
From: Bert Hickman <bert.hickman-at-aquila-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: SPARK GAP QUESTION
Tesla List wrote:
>
> ---------- Forwarded message ----------
> Date: Sun, 05 Oct 1997 19:34:40 -0400
> From: Richard Staron <rstaron-at-widow.aracnet-dot-net>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: SPARK GAP QUESTION
>
> Hi there and thanks for taking time to read my post.
>
> I am using a 15KV-at-30ma neon transformer with a .005 ufd cap, an 18" x
> 4 3/16" diam secondary and tapered primary -at- 18" diam 1/4 copper tubing.
> At present I am getting 28" sparks using a 2 gap spark gap contrived of
> 3 3/4" ball bearings set to a total gap of .240"
>
> I have built an 8 gap spark gap using 9 pieces of 3/4" diam s 1" l
> solid brass rod. Each gap was set to .030" and ends polished . Each
> electrode was supported on ceramic standoffs and gaps were accurately
> measured for parallelism and spacing.
>
> Question: I have tried both gaps, the 2 gap and the 8 gap with and
> without air blowing over them and I see no difference in
> spark length or spark strength. Can anyone make a comment
> or give direction as to the possible reason for this?
> I have kept everything the same except for changing the
> different type of gap.
> (I tried reducing the spacing of the multi-gap to .025" and
> found that the spark length did reduce in length.
>
> Looking forward to any comments, ideas, theories or lies :)
>
> Richard
Richard,
The breakdown voltage for both gap systems will be approximately the
same, although the 8 gap system will tend to have a more repeatable
breakdown voltage. Assuming similar breakdown voltages, the initial
"bang" energy stored in your tank cap will be similar , and your peak
output voltage will tend to be similar.
Normally, forcing air (or vacuum) through the gaps will help prevent
reignition of the gaps once all the primary's energy has been
transferred to the secondary - "quenching" the gap, and trapping the
energy in the secondary. If you're seeing no difference between the
different gaps with/without forced air, you could be running at a low
enough power level combined with a relatively low coupling coefficient
so that no additional effort is required to ideally quench your system.
Try lowering your secondary a bit (a LITTLE bit at a time!) and re-run
the experiment using your 8 gap system. You should reach a point where
you'll see significantly improved performance when using forced air
through the gaps. Do this in a darkenned room so you can closely watch
for excessive secondary:primary corona or turn-turn flashovers. If you
start getting flashovers across the secondary winding or from the
secondary to the primary, you'll need to raise the secondary a bit. You
want to run with the most coupling you can within the limits of your
coil's insulation and gap quenching capabilities.
Safe coilin' to you, Richard!
-- Bert --