Re: 6" spark

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Hollmike-at-aol-dot-com>

Hi Saun, 

>
> I was able to attain a 6" spark from this, not very impressive.  And, holy 
> gajeebers!  This thing is loud!  Today I'm going to make a Richard Quick 
> spark gap with a fan.  I'm hoping that will quiten things down and make a 
> bit of a difference in spark length. 



You're getting sparks, so can't be too far off.  Coils are loud, so I don't
have a feel as to whether yours is abnormally loud or not.  Gap could be a tad
wide, but don't know from what you have said.  Having a series of gaps cannot
hurt.  Probably 3-5 electrodes will do for your setup at 9 kV 

>
> I have used no protection on this whatsover.  I am considering putting a 
> safety gap on the NST but am not sure if I really need this.  Is NST failure 
> a common thing on such a small coil?  Will a safety gap really help? 



When I am playing with a temporary setup, which I do often, and am feeling too
lazy to include a nice TF filter,  I at least put a 25 W , 1k ohm resistor on
each output terminal of the NST.  I figure that provides at least some level of
protection.  I got the idea that this might suffice because I got some great
parts from a large spark source spectrometer, which included what appeared to
be a trigger for the spark.  It consisted of a NST, a 500pF /50 kV  door knob
cap and a spark gap.  The NST had a power resistor coming from only one side of
the :NST output.  I am only guessing that this was a trigger, but it looked
very much like a tank circuit set up without the primary coil.  The deal is
that this thing was used well over 20 years on a daily basis and the NST is
alive and well,  so the resistor seemed to be enough protection. 

>
> Any suggestions on creating a bigger spark?  I have plenty more NST's 
> available to me, but would prefer to have all other components working at a 
> good efficiency first before jacking up the power.  Realistically, what size 
> spark could I expect from such a setup if it were running at a good 
> efficiency? 
>
> One other thing.  I notice on my SWC that there is arking in one of the beer 
> bottles.  The spark is actually inside the bottle.  I can't understand why 
> there would be arcing inside the bottle.  All that is inside is a brass 
> electrode and the salt water.  Since the electrode is already touching the 
> water, I'm not sure why I would see sparking.  Of course, I don't want to 
> stick my head close to this thing while it's on for further examination ;-) 



A certain amount of corona losses are to be expected with SW caps,  but I have
not heard of internal arcing before.  Did you float oil on top of the water? 
this may help.  Also,  you could make a series/parallel bank of the SW caps to
achieve the same capacitance and cut the voltage stress in half for any one
bottle.  It is hard to say.since I cannot tell if you have done this already
with the 12 in use.   It is also difficult for me to know if you are really in
tune for the same reason.  You could be running at a harmonic.  If you could
measure the caps I would not be difficult to calculate this. 
>
> Appreciate all the advice. 
>
> Shaun R. Phelps 



Not too much help, but wishing you all the best, 
Mike