Re: [TCML] max performance per secondary diameter/resonate inductor.

[Phillip Slawinski <pslawinski@xxxxxxxxx>]

Scott,

I don't think there is any table that shows a maximum spark length vs
secondary diameter.  That's only one parameter in a long list of parameters
that determine the maximum spark you can get from a coil.  The limit to the
spark length you can achieve with a particular secondary will depend on the
voltage stress seen across the secondary, and on how you control this
stress.

For a while I have been working on a coil specifically designed to return a
large spark length to secondary length ratio.  So far I've reached 5.3333X
(54" vs 12" secondary).  The secondary diameter is 3.5".  I had to take many
steps to ensure that the coil form did not break down internally, or
externally.  In addition I had to make sure that the coil would not
continuously arc between primary and strike rail.

Much of what I saw in testing agrees with what John says below.  My coil can
not run at low break rates, it just flashes over.  Also the coil has to have
a pretty massive top load (18"x4.5") considering the size of the coil to
achieve 54".  Before I put the larger top load on the coil the sparks were
not able to reach as far.  In the case of my coil bang energy is independent
of break rate.  Running at a higher break rate allows me to run larger bang
energies due to the spark loading bringing down the top voltage of the coil.

-Phillip Slawinski

On Mon, Jul 19, 2010 at 17:27, <futuret@xxxxxxx> wrote:

> Scott,
>
> Generally speaking, you should be able to get longer sparks from a given
> secondary size at high bps compared to low bps.  This is because the
> bang size is much smaller at high bps (for a given input power) so it
> stresses the secondary less.  The ability of a secondary to survive high
> input power should depend more on the length of the coil than on the coil
> diameter I would think.  Much also depends on the type of wire insulation,
> number of turns, secondary coating,  toroid size, presence of a corona
> ring on top of the secondary, shape of the primary, etc..   On my old
> research coil which had a 4" x 23" secondary wound with 28awg wire
> running at 120 bps, I began to get racing sparks when the sparks reached
> about 56" or so.  I don't remember if I experimented with higher bps with
> that coil.  I don't know of any tests that anyone ever did to compare
> how a given coil stands up to low bps vs. high bps, for a given spark
> length.
> I would think that high bps might tolerate a smaller toroid size also for
> a given spark length, because the high bps should be able to create
> longer sparks via bang-to-bang spark growth compared to a lower bps
> coil for a given input power.  I don't know of any tests that were done
> specifically to test this idea.  (one of the things I never got around to
> testing).
>
> Richard Hull's Nemesis secondary was 14" x 46" I think, and he
> got 15 foot sparks.  But it probably could have given longer sparks
> if he had the space since the secondary didn't show any signs of
> breakdown.  He was operating at around 400 bps probably.
>
> Cheers,
> John
>
>
>
>
>
>
>
>
>
>
> -----Original Message-----
> From: Scott Bogard <sdbogard@xxxxxxxxx>
> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> Sent: Mon, Jul 19, 2010 5:06 pm
> Subject: [TCML] max performance per secondary diameter/resonate inductor.
>
>
> Greetings all,
>   Ok finally got my 4-inch coil back up and running after a year, got sick
> of burning out MOTs and decided to use only two (surprisingly my spark gap
> manages Ok despite being less than a work of art.)  Current results is 54
> inch max spark frequent strikes up to 51 inches (a personal record for me
> using a coil this small, and a record for my efficiency by Freau number of
> all my coils so far) now I'm space limited unless I roll it outside so I'm
> fairly pleased with the performance, half the voltage, assuming double the
> current, twice the arc length. Anyway my question is this, is there a table
> someplace that will demonstrate the longest practical arc-length per
> secondary diameter, I don't think I can expect to get much more out of one
> this small, let alone using only 4kV input and a cap way to small for
> resonate (I have to be running nearly 700-800bps to get the results I do.)
>
>
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>
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