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RE: Spheres vs Toriods



Quoting Marcus E Young <E.Young-at-mailbox.uq.oz.au>:

> I must add here, that while spheres are a 'bad' terminal 
> capacitance to use under most conditions, one interesting 
> phenomena I noticed using a nice shiny sphere was the 'single 
> tenticle effect'. Something that doesnt occur on torroids to 
> the same extent. One long streamer (discharging into air) 
> 'swinging' in a random fasion all over the place.....walk up 
> cautiously and outside strike distance of course, and sometimes
> you can coax the  streamer to swing round and 'look you in the
> eye' so to speak.....quite entertaining! If you have never 
> tried it before, its worth a go just for the effect! Keep those
> torroids for the big sparks though!!

I too have messed with this effect on a 4 inch sphere discharge
terminal (flag pole top). I spent about an hour playing with the
effect (input to the system 720 watts, the discharge was produced
on an extra coil topped with a 4" sphere... base fed with one end
of a bi-polar coil!). Aside from the fact that the system was
simply exciting, the singular spark was quite an attention
grabber. A swirling, whirling, vortex of electrical fire; I have
seen smoke and flame whirl and swirl in similar patterns, but
this system would produce a continous single spark that would
dance like Sheba of the desert.

*****************************************************************
Pasted in....

7) The spark from the extra coil behaves strangely a lot of the
time. Because it is not affected by the emf of a primary it
cruises slowly around the spherical discharge terminal. I have
seen it stop in one place for as long as a minute with the split
streamers wavering at the tips. And because there was no primary
circuit nearby, and the transmission line had a low potential, I
felt comfortable sitting next to it and observing the slow moving
streamers. The streamers spun internally like a vortex. When the
spark began to move it revolved around the sphere in the same
direction as the internal spin. It was quite beautiful.

*****************************************************************
My ignorant wanderings/suppositions as recorded four years ago:

Imported text from a letter sent to Richard Hull in 1992:

I hate to wander on but this last note might interest you. I was
firing an old, bare ended, 5" coil (610 turns, 5" dia. coil form,
38" winding length, ~577 KHz) in a bipolar configuration. About
three turns tapped on an 18" dia. primary, turns widely spaced at
two inches, .009 capacitance. No spark from the ends???? I still
can't figure this out unless the coil was operating as a half
wave, with the ends nodal points, but this is the first time I
have ever experimented with (or seen) a bipolar fired coil. 

Anyway, as soon as I tried to pull some spark off of one end I
got discharge at both ends (about four inches) and was able to
tune it in. Equal spark would issue from both ends as would be
expected as long as there was a draw on it. That spark would
disappear from both ends when the ground wire was moved away. 

No load or draw on either terminal of the coil = no spark, any
load or draw on either end produced equal spark at both ends.
This is important. I can only guess (maybe you could enlighten me
here a little also) that the coil switches from half to quarter
wave operation with a load. The coil was without a doubt in
fairly good tune (my specialty), but it was hard to be exact as I
was jury rigged with the secondary between two saw horses and the
primary balanced on old wood blocks setting precariously on the
narrow secondary (Alex style?) (A joke Alex!). The whole thing
threatened to collapse at any second.

This does have a point by the way. 

I loaded one end of the bipolar coil with a transmission line
(and the opposite end produced a feeble discharge with the
transmission line alone) and bottom fed an extra coil. The extra
coil in this case was a 4" coil, 20 inches of winding, 520 turns
of thin insulated wire, ~770 KHz, top loaded with a 4" sphere. I
got a good 18 inches of spark off of the top of the extra coil.
This spark was a healthy, thick, bright spark. The opposite end
of the 5" bipolar showed a 1/4 wave resonance by producing a thin
crackly 4-6 inch spark that brightened only when a ground wire
was used to draw it off, it never exceeded 8 or so inches when
being pulled, and never had much power. 

The coupling on the 5" coil, fired bipolar, I can only assume was
loose, so I assume the frequency in the bipolar coil was true.
The fact that the system produced no spark what-so-ever when
fired with just bare wires on the ends tells me there were no
harmonics present in the bipolar coil used to feed the extra
coil, at least before the transmission line was connected. The
transmission line was short, but long enough to remove the extra
coil from any significant inductance from the bipolar
primary/secondary. A grounded probe used to draw spark from the
transmission line barely pulled anything at all, yet I was
pulling a stronger and stronger spark off of the extra coil as I
moved the probe up the windings, clearly showing a substantial
VSWR rise to the top turn.

There were really several interesting things about this system:

1) The mirror spark produced at the unloaded, free end, of the
bipolar coil. Any draw or load on either side of the bipolar coil
always produced spark of exactly the same intensity from the
opposite end. The extra coil acted on the mirror end of the
bipolar coil as if a ground lead were in it's place drawing off
spark. 

2) The fact that the bipolar fired coil produced no spark at all
without a load or draw on a terminal. (Half wave nodes? I know
nothing about bipolar coils and I don't know if this is normal.
I,ve read that bipolar coils act as two mirror quarter wave
coils, but then the ends of the coil are usually loaded with a
terminal of some type, or a line is brought together to draw
spark; this bipolar coil ended with bare wire at both ends as it
was fired).

3) The transmission line from the extra coil was removed from the
extra coil base and used to draw spark from the free or "mirror"
end of the bipolar coil, shunting the coil for maximum spark. I
was only able to pull 12-14 inches of spark from the bipolar coil
alone. Part of the problem was that the transmission line became
lossy (corona loss) as the line was lengthened and supported by
insulators, and the nodal point broke down some. The free or
"mirror" end of the bipolar coil began to discharge before the
wire was brought around, and as the transmission line had to be
supplied with equal voltage at 1/4 wave resonance it meant I lost
a couple of inches of spark. Yet I could pull 20 inches, or more,
of spark off of the extra coil using a ground. One thing I did
NOT try was to draw spark from the mirror end of the bipolar coil
to the extra coil. I just thought of that. Hmmmmm....

4) I did note that the bipolar coil alone, with a lead from one
end to the other produced 12-14 inches of spark (if that) yet
when the extra coil was connected to one end, producing 18 inches
of spark, the mirror end of the bipolar coil was putting out 4-6
inches of discharge at the same time. The total spark the system
generated was increased to two feet (free end of the bipolar coil
discharge plus the extra coil discharge).

5) There was no common ground to connect the extra coil to, so I
was unable to find out if the extra coil would resonate through
inductance/ground excitation.

6) The spark in the extra coil was cut off completely when a
ground was used to draw the discharge off from the mirror end of
the bipolar coil. Yet without the extra coil on the bipolar coil,
drawing spark off one end produced spark on the other end! The
spark drawn off the free end, with the extra coil on the other
side, was much greater in strength than the system produced from
one terminal without the extra coil at the opposite end. This
spark looked just like the spark produced across both terminals
of the bipolar coil fired alone. 

7) The spark from the extra coil behaves strangely a lot of the
time. Because it is not affected by the emf of a primary it
cruises slowly around the spherical discharge terminal. I have
seen it stop in one place for as long as a minute with the split
streamers wavering at the tips. And because there was no primary
circuit nearby, and the transmission line had a low potential, I
felt comfortable sitting next to it and observing the slow moving
streamers. The streamers spun internally like a vortex. When the
spark began to move it revolved around the sphere in the same
direction as the internal spin. It was quite beautiful.

Now I know this letter is getting too long....

Richard Quick


... If all else fails... Throw another megavolt across it!
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