Hi Jeff,
If you were getting strikes from the top of your winding to the
bottom, this sounds like "racing sparks". Racing sparks may occur
as lower energy sparks between various portions of the secondary
winding, or they may span the entire winding as a hot flashover.
They are usually a sign that your primary:secondary coupling (k) is
too high. Excessive coupling is often a problem when using an
inverted conical primary. There can be other causes as well, These
include using a bang size that is too large for your secondary's
power handling capability, accumulated dust or debris on the
secondary that abnormally increases the surface E-field, or using a
toroid that has too large a minor diameter that doesn't break out
on its own.
Reliable operation of a simple two-coil spark-gap coil also becomes
more challenging as you approach a 3:1 spark length to coil length
ratio, especially if your secondary also has comparatively small
diameter. A coil that seemingly operated just fine with an NST bank
may become overpowered when migrating to a distribution
transformer. Pig-powered coils generally perform better, and more
reliably, with larger-diameter secondaries. Longer-term, consider
migrating to an 8 - 10" diameter secondary.
Near-term, try decreasing your coupling coefficient to prevent
possible winding damage. Elevate the secondary (versus the primary)
in increments of 1/4" until racing sparks stop. Also consider
reducing bang size by either reducing spark-gap length or reducing
your tank capacitance. Add a two-part coating (such as Envirotex
Light) to increase voltage breakdown capability if your secondary
winding is not already coated. Carefully inspect and clean your
secondary with a dampened cloth and repair any damage. Coated coils
often retain significant surface charges, making them powerful dust
magnets after TC operation. When cleaning your secondary, remember
to continually ground yourself to prevent charge building up on
YOU. This will prevent you from getting bitten by a painful ESD
event - a rite of passage for many coilers... :^)
Carefully watch the coil in a darkened area as you ramp up power/
Look carefully for any abnormal corona off the top portion of the
secondary winding, the primary, primary tap, or strike ring. Fix
these problems, if necessary, before running at full power. If your
toroid pair is too high, you'll see corona from the top of your
secondary winding. Adding a small copper or aluminum tubing corona
ring at the top of the winding, lowering your existing toroids, or
increasing the outer diameter of your larger toroid will eliminate
this.
Good luck and safe coiling to you,
Bert
Jeff Miller wrote:
Where then should the ring be put ? Right below the Toroid or
right above the top last turn . There is about a 2.5 inch tall
area where it could be put. Again the strike were from the top of
the winding to the bottom
Thanks ,JM
On May 14, 2012, at 9:59 AM, Carl Noggle<cn@xxxxx> wrote:
You shouldn't lower your toroid, because if it is less than
about half of the winding diameter away from the coil top, it
will act as a shorted turn and reduce your performance. You
can make a turn around the top of the coil with 1/2 inch copper
tubing right next to the wire, but leave a break of 1/8 inch or
so to avoid the shorted turn. Connect this tubing to the top
of the secondary. Hopefully this will stop arcing from the top
turns.
Good luck---
Carl
Hello everyone, Tried my tesla this weekend at our annual
pig roast. Work our great, was able to light up 20 4ft and
one 8 ft fluorescents. I did have an issue when I let it
stand alone and break out. Every once in a while I would get
a secondary strike from the top of the coil winding a few
turns down to, it was hard to tell either to the primary or
to the very bottom of the secondary where the lead goes to
gnd. It is a 6.25" secondary with two toroids, a 3x12 and a
6x24. If you were to look straight at the coil the bottom of
the 3x12 Toroid is about 2.25 inches above the top of the sec
winding. In your opinion could this be the problem, the
Toroid being too far above ? If so I could cut it off, but a
lot of work. What would happen if I wrapped 2" wide foil tape
around the top of the form, have it about 1/4" above the top
of the form, fold that 1/4" over the form, then put my
toroids back on . The folded in lip would then make contact
the the 12" Toroid .
Need some help
Thanks ,JM_______________________________________________
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