Re: 15/120 NST Coil Static Gap Performance Problems

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

Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net> 

Hi Claude and Ian,

I would expect longer sparks with SRSG than a static spark gap.  A static
gap can never fire after peak where as a SRSG is phase adjusted for maximum
output which occurs after peak (the back flow of energy from the Cp into the
NST will prime the system for the next and opposite peak (don't use all of
the energy on this peak allows for a larger peak next time and so on.  The
SRSG can get Cp charged to peak voltage of the unloaded NST with twice the
capacitance than a static spark gap can. Hence, the energy per bang can be
twice that of a static gap system.  The fact that you apparently got less
than 100BPS on the static gap might mean that the Cp was a tad bit too
large.  Also, the firing of a static gap is somewhat chaotic and will not be
as smooth as a SRSG.  Before reducing Cp, make sure your safety gap is set
correctly so the NST's don't smoke.

Gerry R.


 > ----- Original Message -----
 > From: "Ian McLean" <ianmm-at-optusnet-dot-com.au>
 > To: "Claude Masetto (E-mail)" <claudmas-at-optusnet-dot-com.au>
 > Sent: Monday, February 16, 2004 3:52 AM
 > Subject: 15/120 NST Coil Static Gap Performance Problems
 >
 >
 >  > Hi all,
 >  >
 >  > I having a difficult time trying to understand this problem, so it's
going
 >  > to take a bit to explain, so sorry all in advance for the long post :)
:)
 >  >
 >  > Tuned my 6" coil last Saturday afternoon with the help of Claude.  I
don't
 >  > have a decent static gap, so Claude kindly brought along his sucker
gap,
 >  > control box which has a current meter, and an extra variac to help tune
 > the
 >  > SRSG and to control the suction to the suction gap - BTW: thanks for
 >  > Saturday Claude :-)
 >  >
 >  > Firstly, we got some good streamers on Saturday :)  Especially with my
 > SRSG
 >  > and the 62.5nF tank cap.  Some nice bright power arcs to the colourbond
 >  > roofing and overhead metal pipe.  Some out to 5 foot.  One power arc to
 >  > ground, through a vice mounted on my workbench.  The 5 footers at the
end
 > of
 >  > the day, when both Claude and I think we just about got it right,
wanted
 > to
 >  > go further.  A couple of streamers arced through a metal jerry can on a
 >  > shelf, through the half inch thick wooden shelf above it (directly
 > through,
 >  > it was no barrier at all) and upwards to the furthest point on the
corner
 > of
 >  > the ceiling 5 foot away - so I am getting very close now to predicted
 >  > output.  It was definately limited by the roofing.  I am now getting
 >  > prepared for an early evening full power outdoor test.
 >  >
 >  > I learnt a few things on the day.  Don't use GTO-15 for tank cable -
 >  > dramatic drop in output.  This was the first thing changed, for some
thick
 >  > multi-strand copper cable, and the output instantly improved.  This was
 >  > unshielded - so I am going to get some even thicker copper multi-strand
 > and
 >  > shield it myself.  I learnt not to let this unshielded copper touch the
 >  > varnished wood of the primary base (it caught on fire :-0).
 >  >
 >  > And now the mystery.  My coil didn't respond too well to the sucker
gap.
 >  > Streamers about 4 foot max.  But that's not the mystery.  No matter the
 >  > tuning, tweaking, adjusting of coil coupling, gap size,  cap size (LTR
 >  > static -at- 37.5nF or LTR rotary -at- 62.5nF, or sucker suction velocity, the
 >  > output did not improve beyond this, and the gap seemed to sputter, and
 >  > seemed to be at a low break rate (slower than SRSG at 100bps, you could
 >  > easily tell the difference between the two).  Now neither Claude nor I
 > could
 >  > understand the reason for this, so if anyone can shed some light as to
why
 >  > ????  Is my 15/120 NST bank not getting the caps charged enough ?
Current
 >  > draw with sucker gap was 15A average, tuned, from 240VAC mains
(Australian
 >  > supply).  With SRSG, tuned, that dropped to about 10A average.  This
 > sucker
 >  > gap performs much better on it's owner's (Claude's) coil.  On his coil,
it
 >  > roars like a chainsaw on heat, and the gap spark is much brighter.  On
my
 >  > coil, it is loud, but not as loud, and the spark brightness is sputtery
 > and
 >  > not quite as intense (although still very very bright).
 >  >
 >  > My coil instantly performed well on the SRSG, once tuning and SRSG
 > alignment
 >  > had been tweaked.  5 footers wanting to be longer.  Nice bright power
 > arcs.
 >  > Clean 100bps break rate.  Very loud but even sounding.  Very smooth.  I
 > like
 >  > the way the streamers seem to "snake out" of the toroid, and fork more,
on
 >  > the SRSG.  Noticed this on Claudes coil as well.  Even breakout over
the
 > top
 >  > toroid, with some arcs and streamers moving around the toroid.
 >  >
 >  > Wish I could have taken pictures.  My sister will be at my place on
 >  > Wednesday, with her digital camera, so I'll do an outdoor SRSG run in
the
 >  > early evening and get her to take some pictures of it all for me :)
 > Hoping
 >  > for 6 footers.  Wish me luck :-)  I'll get some photo's up on a Web
page
 >  > somewhere.
 >  >
 >  > Any help with the sucker gap performance problems would be greatly
 >  > appreciated.  I want to build one.  I like the more random and thicker,
 >  > brushier output (albiet shorter) it gives as well.
 >  >
 >  > Rgs
 >  > Ian
 >  >
 >  >
 >  >
 >  >
 >
 >