the cure for racing sparks

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

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.
>
>
>
>
>