Re: Static gap BPS, was Static Spark Gap

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

Original poster: "Peter Lawrence by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Peter.Lawrence-at-Sun.COM>

Terry,
       according to your NSTStudy tables, using my 9-30 NST, and taking into
account your point about Watts I get:

	8.8-nF (res)	200 BPS, 143 W  ->   .7 J/bang
	12-nF		120 BPS, 117 W  ->   .975 J/bang
	18-nF		60 BPS,  88 W  ->  1.47 J/bang

(I think I'm doing the math right, Watts / BPS -> J/bang ?)

I expect the 200 BPS to be variable in bang size since its semi-chaotic
so spark length may be hard to predict, but the 120 and 60 BPS should (?)
be fairly synchronous and hence stable and predictable...

If we can extrapolate J.Freau's formula, 60bps should give 22% longer spark
than 120bps in this setup (sqrt(1.47/0.975) = 1.22).

I built an MMC with four strings selectable in parallel, each with 4.8-nF,
so I can try  4.8,  9.6,  14.4, and 19.2 nF. My strings should be a wee bit
longer to get the capacitance down to 8.8, 12, and 18 nF, but the enclosure
has already been built, next time...


-Pete Lawrence.



 >Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
 >
 >Hi Peter,
 >
 >At 12:01 PM 4/24/2003 -0700, you wrote:
 >>Terry,
 >>       I also see from your chart (NSTStudy.htm) that with the 12/60 NST an
 >>18-nF results in 120 BPS, and 26-nF results in 60 BPS. It seems to me
 >>that one of these would be "better" in that the chaotic behavior might
 >>deteriorate into a stable synchronous firing.
 >
 >All the waveforms are, at least theoretically, repetitive but perhaps over
 >many cycles.
 >
 > From the other numbers on the charts, like 'real primary cap power', it
 >looks like the power to the coil drops quite a bit at 60 BPS.  I think the
 >problem is that with larger caps you can't charge them to full voltage.
 >
 >
 >>In my case I am using a 9-30 NST, so I see from your chart I can get 120 BPS
 >>with 12-nF, and 60 BPS with 17 or 18-nF. I'll try that at home tonight.
 >
 >The power seems to drop from 107 to 89 watts.  But give it a try and see
 >for sure.
 >
 >
 >>This seems consistent with my memory that at 2*Res (17.84-nF) I get a
 >>very very distinct 60-Hz machine-gun-fire sounding result from my static
 >>gap TC. I've always disliked that sound and avoided it, but it also seems
 >>to give nice long streamers. This seems consistent with the notion that
 >>the primary capacitor is consistently charging up with two full half
 >>cycles for a large bang size.
 >
 >It "might" be acting sort of like a sync gap LTR system there.  Gary Lau's
 >coil seems to do that.  Hard to say for sure since a small change can
 >affect things quite a bit.
 >
 >
 >>It seems from looking at your chart that 2*Res Cap value is pretty close
 >>to the 60 BPS value, is this consistent or a coincidence, and should this
 >>be the "recommended value" for static gap TCs.
 >
 >Doubling the cap to go from 120 to 60 BPS makes sense to me.  I would think
 >the performance would be worse at 60 BPS though.  Try it and see...  The
 >dwell timing is very near zero there, so it may indeed jump to a sync LTR 
mode.
 >
 >Cheers,
 >
 >         Terry
 >
 >
 >
 >>-Pete Lawrence.
 >>
 >>
 >>
 >>
 >> >Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
 >> >
 >> >Hi Gary, Dan, Daniel and John,
 >> >
 >> >Ok, here is the long explanation ;-))
 >> >
 >> >Daniel and John have a 12kV/60mA NST and they are using 11 series 0.15uF
 >> >MMC caps.  They want 200 BPS operation from an RQ style static gap (I am
 >> >not sure why).
 >> >
 >> >First we find their primary cap value which is 150nF / 11 = 13.63nF which
 >> >is a resonant value.  This is shown in Mark's excellent Geek Group cap
 >> >chart at the chart at:
 >> >
 >> >http://hot-streamer-dot-com/temp/MMCcapSales.gif
 >> >
 >> >I do assume their firing voltage is 12000 x SQRT(2) = 17.0kV.  If it were
 >> >more or less, that would affect BPS.  But 17kV would be the normal value
 >> >one would want to use.  Now the only thing left to do is a giant laborious
 >> >computer study...  But I already did that a year or two ago, so it's all
 >> >done ;-))
 >> >
 >> >http://hot-streamer-dot-com/TeslaCoils/Misc/NSTStudy/NSTStudy.htm
 >> >
 >> >If we look up the 12/60NST at 13.6nF we won't find it.  However, the 
values
 >> >are just the 12/30 NST numbers doubled (or, 1/2 the 12/120 
numbers).  Given
 >> >some losses, the real resonant value is 13.262nF for a BPS of
 >> >200.0454153.  Of course, in the real world, that may vary like 
+-10BPS.  If
 >> >we look at the other resonant BPS rates we see:
 >> >
 >> >NST             Resonant BPS
 >> >15/60           193.575
 >> >15/30           201.149
 >> >12/30           200.045
 >> >9/30            200.253
 >> >12/120  188.98
 >> >
 >> >So for whatever reason, static gap resonant cap NST systems run very very
 >> >close to 200BPS.
 >> >
 >> >See, I didn't just make it up :o))
 >> >
 >> >If the cap is LTR, then it is in sync with the line frequency and it 
should
 >> >fire at exactly 120 BPS.
 >> >
 >> >Cheers,
 >> >
 >> >         Terry
 >> >
 >> >.........
 >
 >