RE: Primary coil configuration

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

So you say to start with the secondary higher than the "correct" height,
and slowly lower it until a peak in spark length is observed?  I've not
tried that, but I wouldn't expect to see the spark length start to
decrease beyond a peak-point before getting racing sparks.

I will try this with my mini coil, and I promise to report the
spark-length vs. height results, conclusive or otherwise.

Regards, Gary Lau
MA, USA

> Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>
>
>
>
> A properly designed coil does not produce racing sparks.  Setting the
> sec coil above the horizontal plane of the pri at the correct
> distance produces a correct design.
>
> When you approach the "racing spark" mode it's because you had your
> sec too low to begin with.  If you're doing a new design, start a bit
> higher than you expect and run it up and down with a simple screw
> type brass threaded thru a brass plate.  The screw is hooked to a DC
> motor with a flexible shaft drive --- Dremel tool or even a tight
> tygon tubing will work.  Run it slowly down until you can peak the
> spark.  Go down 1/2 inch below this amount to check for a longer
> spark and then raise it up again.  Now measure it.  This is the point
> at which you hit optimum spark output which is really what we are
> trying to do here in the first place.  Absolutely no need to produce
> racing sparks and then later elevate it.  Once the damage is done ---
> it's done and only rewinding will cure it to a "like new" state again.
>
> I've done this with many different sizes of sec.  For a 4 inch size,
> which is what the experimenter was using, approx 1.25 inches is
> perfect and will not produce racing sparks.  With a 6 inch size sec
> use 2.25 inches above the pri.  No racing sparks, no damage, and no
> --- running the sec any lower will not produce any output gains at
all.
>
> Dr. Resonance
>
>
>
> >Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>
> >
> >Increasing the coupling until racing sparks occur, then backing off,
is
> >the only way I have ever heard of to set the coupling.  Since the
exact
> >mechanism responsible for racing sparks is still unknown, we are
unable
> >to predict the coupling threshold at which they'll occur.  As setting
> >the coupling much lower than that threshold will degrade performance,
we
> >strive to keep it as high as possible.  Some may consider it
"horrible
> >engineering", but it's the best that can be done.   How do you
propose
> >to determine that threshold without ever crossing it?
> >
> >I agree that running a coil with racing sparks with reckless abandon
> >will permanently damage the secondary, but I think most of us have
> >briefly coupled too high, seen the sparks, backed off, and have had
no
> >further trouble.  Or are you suggesting that a brief racing spark
will
> >permanently lower the critical coupling threshold?  An interesting
and
> >reasonable suggestion, but very difficult to prove.
> >
> >I don't know that it's ever been conclusively demonstrated that any
> >secondary sealing technique will render it invulnerable to racing
> >sparks.
> >
> >Regards, Gary Lau
> >MA, USA
> >
> > > Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>
> > >
> > > Someone advocated adjustment until racing sparks occur and then
> > > backing off. This is horrible engineering.  Once a spark punctures
a
> > > solid insulation it does not "cure" or repair itself.  Once the
> > > damage is done it is permanent unless the coil is rewound.  You
can
> > > back off the coupling to reduce sparkover, but then you always
have a
> > > weakest link in your coil system. Properly sealing the sec coil
and
> > > then not puncturing it will produce a long lasting coil.
> > >
> > > Dr. Resonance
> >
> >
>
>