Re: First Light in Oz and topload question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Gregory Hunter by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>

Hi Stacy,

I once built a 4.5" x 24" coil based on a 15/30 NST.
10" to 11" sparks is a bit less than I would have
expected from your coil. I have a couple of ideas. For
one thing, lack of breakout might indicate an oversize
topload. Try a smaller one. On a coil this size you
might have better results with a spherical terminal
instead of a toroid. A 6" diameter plastic ball
covered with foil stuck on with spray glue makes a
cheap discharge sphere.

The next suspect is your spark gap. A single static
air blast or sucker-type spark gap might improve
performance a bit. If nothing else, the single static
would make gap adjustment simpler and more consistent.
Gary Lau has the neatest and most efficient example of
the two-horned sucker gap I've ever seen. It's such a
simple design it should be easy to copy.

Third suspect is the saltwater cap. Obviously a low
loss plastic film cap would be better. However, even
the beer bottle cap can be improved. My own beer
bottle cap has never exhibited any RF heating even at
power levels up to 7.5KVA. I seem to have found a
brand of bottle well suited to RF work (quite by
accident). Also, you might want to experiment with
different numbers of bottles to find the optimum
primary turns / capacitance ratio.

With a bit of tinkering & refinement, sparks in excess
of 18" is a reasonable goal.

Best Regards,

Greg
http://hot-streamer-dot-com/greg

--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "Stacy Gillett by way of Terry
> Fritz <twftesla-at-qwest-dot-net>" <sgillett-at-hotmail-dot-com>
> 
> Hello all,
> 
> I posted here a few months back with some questions
> before I started 
> building my first coil, and fired it up for the
> first time tonight.
> 
> Specs are:
> 
> * 15kv/30ma NST
> 
> * safety gap for protection (set so that it barely
> doesn't fire with only 
> the trannie connected)
> 
> * RQ/TCBOR gap with 11 electrodes of 1 1/4" dia x 3"
> long copper tubes  
> (each gap spaced at 0.028") plus microwave oven fan
> for cooling
> 
> * 8 x 12oz beer bottles for capacitor (approx 6nf)
> 
> * 14 turn flat primary with 0.375" turn-turn spacing
> and 7" inner diameter 
> (wound with insulated 5AWG wire)
> 
> * 4" x 20" secondary wound with approx 700 turns of
> 22AWG magnet wire
> (secondary Fres is about 300kHz with the toroid on
> top)
> 
> * 4.5" x 10" toroid (florists' foam sanded into
> toroidal shape then wrapped 
> with Al tape)
> 
> Using a breakout point on the toroid, tapping into
> the 9th turn on the 
> primary gave the best sparks (around 10" or 11"
> long... though still a bit 
> shorter than I expected).  However, what surprised
> me was that there was 
> absolutely ZERO breakout without the breakout point
> attached (even though I 
> thought that my topload was relatively small and
> sized correctly for my 
> charging circuit).  Does anyone have any ideas as to
> why this would be the 
> case?
> 
> Also, I found that running with all 10 gaps caused
> the safety gap to fire 
> every few seconds... reducing this to 9 gaps solved
> this problem (I don't 
> fancy burning up my trannie!)
> 
> Next step from here... maybe put another 15/30 in
> parallel and add another 8 
> beer bottles (MMC is out of my price range at the
> moment)... this might fix 
> the breakout problem.  A MOT doubler supply might be
> worth a go as well...
> 
> Thanks again to all who post on this list... I don't
> know how I would have 
> built my coil without the information in the Pupman
> archives !
> 
> Stacy Gillett
> Victoria, Australia
> 
>
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> Get your FREE download of MSN Explorer at
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> 
> 
> 




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