Re: the cure for racing sparks

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

Original poster: "Steven Ward by way of Terry Fritz <twftesla-at-qwest-dot-net>" <srward16-at-hotmail-dot-com>

Hi Doc,

Im not positive that you understand all of the circumstances.  Im using the 
9 turns with the extra inductor, but i need such a small extra inductance 
the just running wire to the inductor and back brings it in tune(no extra 
turns added).  So this would suggest that i only need to add at most 1 more 
turn to bring it into tune.  So does the primary still seem to be the 
culprit??  There is a tad roughness on the base of the sphere, but the 
sparks that jump down do not appear to come from the sphere, but the last 
few turns on top, and travel all the way down the coil.

But you know what, i just realised that the last time i ran it, it didnt 
have any problems for a good few minute runs.  GEEZE!  ive been so busy 
lately that i totally forgot that i added a layer of polyurethane, and ran 
the coil again!!!  I dont even know why i wrote the above paragraph!!  The 
mind is a strange thing (especially mine lately).  I suppose the above 
paragraph may hold since im not sure how long my quick fix may last, and i 
may run into the same problems.  Sorry to anyone i confused with this 
email!!

Steve Ward


>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: the cure for racing sparks
>Date: Wed, 10 Jul 2002 19:30:51 -0600
>
>Original poster: "D.C. Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
><DR.RESONANCE-at-next-wave-dot-net>
>
>
>
>Steve:
>
>Two things come to mind.  First, racing sparks are usually caused by either
>too small a toroid on top which provides ineffective electostatic field
>control down the coil and second, the usual culprit, not enough available
>inductance in the primary (too few turns) to hit the proper tuning point.
>You are tuning at the wrong primary resonance point.
>
>A 12 inch sphere is adequate, but keep it as close to the winding as
>possible, ie, no more than 1/4-1/2 inch away.
>
>A second note is that you may be "overcoupled" which causes the
>"double-hump" on the freq, ie, splitting the res. freq. into two different
>freqs which beat against each other.  Try elevating your sec. coil. or
>moving your primary further out.  With this size coil we get 28 inch sparks
>(our model M-20).  The sec. is elevated 1 full inch above the primary coils
>horizontal plane and the pri to sec coilform spacing is also 1 inch.
>
>The first thing to do is get rid of your present primary and set up some
>scrap 12 AWG house wiring on cardboard (cut slits for the wire).  Set up
>this test with about 30 turns and adjust tuning with variac at 30 % and 
>your
>spark gap set close together.  In many cases the racing sparks are caused
>because you simply do not have enough available primary turns to find the
>tuning point.  After tuning carefully with scrap wire you will find the
>correct tuning point and then it's time to replace it with your beautiful
>primary.
>
>I would be willing to bet when you do this you will hit the proper tunig
>point and then the racing sparks will go away totally.  Remember, they only
>occur when you are grossly out of tune.
>
>Dr. Resonance
>
>
>
>
>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: <tesla-at-pupman-dot-com>
>Sent: Tuesday, July 09, 2002 12:18 PM
>Subject: sparks along secondary
>
>
> > Original poster: "Steven Ward by way of Terry Fritz 
><twftesla-at-qwest-dot-net>"
><srward16-at-hotmail-dot-com>
> >
> > Hi everybody
> >
> > Does anyone know how to cure those pesky arcs that travel over the 
>entire
> > length of the secondary coil??  Ive coated my coil several times with
> > acrylic spray, and its helped a little.  My problem is that i use a 
>sphere
> > (12" diameter) because its the coolest damn thing ive ever used for a
> > topload!  My coil is powered with a 12000v 40ma(modified) NST.  My cap 
>is
>a
> > GE bank for a total of .0136uf at 30000vdc.  I have a 9 gap static gap
>with
> > a blower.  A 9 turn flat spiral primary(12" outer diameter) and an off
>axis
> > tuning inductor.  My secondary is wound on some kind of HDPE (i think)
>tube
> > that is only about 1/32" thick(low losses!).  Its 3" in diameter, and
>wound
> > 14" with some 28g magnet wire.  Atop sits a 12" sphere about .5" from 
>the
> > windidng.  At times the arcs reach about 30" or so!  This sphere has the
> > coolest breakouts ive seen yet.  It takes a few seconds, then WHAMMM!!! 
>a
> > huge 28" arc will jump out into the air.  But lately ive been
>experimenting
> > and it seems that it likes to just jump down the side of the secondary
>coil
> > if it cant breakout of the sphere.  Anyone know how to fix this??  Would
> > putting plexiglass discs around the coil help??  Ive seen this on big
>coils
> > but not on anything my size.  Any thoughts are welcome,
> >
> > Thanks,
> >
> > Steve Ward.
> >
> >
> >
> >
> >