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Re: [TCML] Low Power Coil Questions

Hi Guape,

I would say that you're getting very good results for what it is.  Here are
the things I would recommend for improving performance.

1. The biggest improvement would be switching from salt water caps to a
polypropylene MMC.  Losses in the glass dielectric are very high.

2. The spark gap - It's very possible that your brass acorn nuts are in
fact brass-plated white metal, which erodes very fast and leaves a
sharp-edged crater at the point of arcing.  The sharp edge reduces the
breakdown voltage of the gap, and the edges get hot which impedes
quenching.  Kudos to you for adding the forced air cooling - this makes a
big difference. But instead of using the acorn nuts that have a single
point of arcing, I would recommend using a cylinder gap made of copper
pipes, that arc along the length of the pipes.  There is some debate over
using multi-segment gaps or single segment gaps.  I favor single segment
gaps with a vacuum cleaner motor to move a lot of air - construction and
adjustment are easier and I believe losses are lower in single segment gaps.

3. The fact that you see multiple streamers from the toroid suggests that
you could use a larger toroid with fewer, longer sparks.  Bigger toroids
ALWAYS result in longer sparks. The down side is that a bigger toroid is
more difficult to build, and can't be done in isolation.  If you make a
bigger toroid, you'll have to accommodate the lower resonant frequency by
having a larger primary, which brings us to...

4. Bigger IS Better on all TC components.  One should use the largest
primary capacitor that the NST is capable of charging to have the biggest
possible bang size.  For a 12/30 NST @60Hz you want about .01uF, although
it's not critical like a resonent frequency. Same applies to primary and
secondary size and inductance, subject of course to resonance constraints.
Bigger components result in lower frequencies which have lower losses.
Both your primary and secondary sound like they would benefit by having
more turns.  Primary currents, and hence losses, are lower with higher
inductances.  It soon becomes a choice between a smaller, more portable
coil vs. a larger, bulkier and better performing coil.  But be warned -
step 4 is a slippery slope and you may embark on a never-ending quest of
constant upgrades.

Regards, Gary Lau

On Wed, Feb 1, 2017 at 6:34 AM, Guape Sinnelag <amn1t3@xxxxxxxxx> wrote:

> Operation gif (breakout) - https://postimg.org/image/u8vnbn0el/
> Operation gif - https://postimg.org/image/fkhxyauhp/
> Spark Gap -  https://postimg.org/image/d1aaf2kj1/
> Underneath -https://postimg.org/image/o6vbdklsh/
> Specs:
> 12kV 30mA NST
> Salt Water Leyden Caps x 9(.007mF)
> 5 bolt (w/spherical brass nuts) spark gap
> 10g insulated wire @ 4.3 wraps/10" diameter primary
> 19g @ ~550 wraps/4"x21" secondary
> 12"x1.5" toroid
> RF ground - 3x 3' Aluminum rods ~10' from coil
> This is my first coil. I've been doing research for a few months now and
> started tinkering on a failed exciter. It lit a CFL but was quite
> dissapointing. But I didn't deter and tried Flybacks. That was a headache
> and a half and finally found me a local NST. It is the only $ spent on the
> coil aside from Aluminum Tape. Salvaged TV magnet wire etc. So I severely
> limited what I could do. But I wanted more of a proof of concept. And after
> months of research and fails, I got a start of a coil.... Many, many
> revisions later I have this! I'm quite happy with it. And has sparked a
> hobby that I can already tell might be borderline obsessive. But as I'm
> planning a new one already...
> Is this acceptable length spark for 360w?
> Is there any small things I can do to improve its spark length (aside from
> the obvious caps, secondary, etc)?
> General criticism on setup and things to look at. Are my wires too long?
> Solid vs Stranded? Minor details overlooked  by a novice.
> There is so much conflicting thoughts on things such as secondary windings,
> sec diameter, etc, when trying to design a coil idk what is what.
> If I used the same NST and pulled no punches on the components what could I
> be looking at? what about thoughts on windings? I was thinking 1600(26awg)
> on 4". But then I found conflicting thoughts. I guess I'm looking for
> thoughts. I've read 100s of pages on coils. And I have a fair grasp of it.
> But with all things experimental different people have different ideas.
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