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Re: well, this is interesting

Subject:      Re: well, this is interesting
       Date:  Tue, 6 May 1997 08:17:40 +1200
       From:  "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Organization: Wellington Polytechnic, NZ
         To:  tesla-at-pupman-dot-com


Hi William, 
             there seems to be a clear answer to your conundrum....

>   From:   "William Noble" <William_B_Noble-at-MSN.COM>
>     To:  "Tesla List" <tesla-at-poodle.pupman-dot-com>
> 
> 
> well, I learned a few things tonite - maybe even some make sense.  I
> added 
> some capacitance to my new coil - I started from .001 mica and added a
> .001 
> 14.5KV capacitor made by Plastic Capacitor company (it's about 1"
> diameter, 8 
> inches long, encased in glass) - sparks went from dinky little 3 inch
> sparks 
> to really nice looking 18 inch sparks with lots of forking.  So, adding 
> capacitance is good, and the little Plastic Capacitor unit is good too -
> it 
> warmed up just a bit in a 20 to 30 sec run (about as long as I can run
> with my 
> half done RQ spark gap with no fan) - it felt like it raised up about 5 
> degrees or so.
> 
> I also learned that the toilet float I used for a top capacitor (a
> plastic one 
> with some aluminum foil wrapped around it) keeps a charge - I got a
> small 
> shock when I went to dismantle the coil - I don't quite understand this
> since 
> I thought it would be grounded through the secondary (the low side of
> which is 
> grounded), but the connections were't the best, so maybe there was an
> open 
> circuit???
> 
> What I don't understand is the following - when I doubled the tank 
> capacitance, I would have thought I would halve the tank inductance to
> keep LC 
> about constant and maintain resonance with the secondary.  But I found
> that 
> with .002 uf it was best on turn 13 (I only have 14 total turns on a 1/4
> inch 
> {50 ft} tubing flat spiral primary), and with just the .001 mica
> capacitor it 
> seemed to like fewer turns - my notes say that with the same secondary 
> configuration (toilet float on top, etc) I got best performace at turn
> 8, and 
> with no top capacitance, best was at turn 13.  does this make any
> sense???

Yes. In doubling the capacitance you only doubled available energy
(assuming cap voltage was the same), so the clear answer to why you 
got 6x the spark is that the coil wasn't in tune originally. A lot 
more primary L would have been needed for the smaller cap.
 
> And, can I expect still better performance by adding more primary 
> capacitance?? (input xformer is 15KV 30 ma neon) - it would seem so....

Absolutely! According to my calcs, you need about 5nF for optimum use 
of the transformer.

Malcolm