Re: Low output coil

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

Original poster: John <fireba8104-at-yahoo-dot-com> 

Hello Christoph Bohr,
After re-examining my coil I've decided to redo some things.
I'm going to go with a inductively ballasted 4 MOT stack (9600VAC) and I am 
going to build a terry brake sync gap. The ceramic cap bank is in fact a 
problem, it over heats to the point where caps set on fire. This is going 
to be replaced with a ploy cap. The secondary circuit of this coil is in a 
word strange. At first I had a K of about 1.3 than I lowered the secondary 
to increase spark length( which it did, only a few centimeters). K is now 
at an unbelievable 0.48-0.5.The reason for this probably has something to 
do with a modification I made to my secondary. I added another small 4 turn 
coil above the main secondary coil( maybe I turned it in to a magnifier. 
Don't know for sure).  The coil is in tune(1/4 wave) at 363kHz. I don't 
know how you came up with 287kHz, but thanks for crunching numbers anyway.
Thanks,
John




Tesla list <tesla-at-pupman-dot-com> wrote:
Original poster: "Christoph Bohr"

Hello John!

lets got through this step by step, I think I have at least some
ideas...

 > Transformer
 > 120v 60Hz
 > 2 Mots stacked for 4800vac

This can be done, but with this fairly low voltage/ high current
you need sufficient primary capacity to take advanteage of the
power. Another problem might be, that your simple gap might not
be able to quench properly. Did you check your quenching with a
scope ?? might be woth a try.

 > I think I'll try to build a sync gap

good idea, but there are good static gaps, too. A multi sectioin
gap with the same airflow will work much better from my
experience.

 > Tank Cap
 > 5 in series 25 in parallel 125 total
 > Each cap 0.01uF 3KV
 > 0.05 uF 20% tolerance each cap

this should be sufficient for much more output. I don't think
there is am problem if they are low loss, high current and don't
heat up.

 > Primary
 > Secondary...

OK, I cut that of for better readability ;-)
I put your data into a tesla calculator and received different
results:

it says your coil should be in tune at 237.28 KHz with the
primary tapped at the 6th turn, maybe you tuned you coil to
another mode than 1/4 wavelength.

 > 1/4 inch above primary

looks pretty close to me, but might work; you might try rising
the topload but watch out that you don't get racing sparks.

 > wound on power line grounding insulator

wow....thats real HV stuff but I am not sure if this has good a
RF dissipation factor, maybe someone else can help you here.

This is just what I think, I am not too good with this
calculation stuff, but improving your gap will almost certainly
improve things.
Maybe with some pi! cs ( how components are hooked up ) and more
data ( how high is the secondary rised above the primary...and
you according K ? ) me and others could find out more to help
you. At least you build you cloil and have something to
experiment with so I think you will sure and up with a satisfying
result after some improvements ;-)


Hope this gave at least some new food for thoughts

play safe and good success.

Christoph Boh