Re: Certain s.s. phenomena; to J.F. et al

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

Original poster: "Kennan C Herrick by way of Terry Fritz <twftesla-at-uswest-dot-net>" <kcha1-at-juno-dot-com>

John Freau (& all)-

[snipped]

> >...And often I get 2 or more [sparks] at the same 
> time,
> >  i.e. during the same pulse-burst.  That's surprising since I 
> would have
> >  thought that once the first one started, then all the energy 
> would go
> >  into that one.
> >  
> >  Anyone have any light to shed on that?
> 
> Ken, all,
> 
> I've noticed that if a toroid on a spark gap coil is too small, or 
> especially if a flat disc is used as a toroid, the sparks will
> form equally spaced around the edge of the disc.  There might
> be 6 sparks equally spaced around the disc.  I assume
> electrostatic effects cause this.

I've seen that, too, now that you mention it.  A useful item to use for
that is a pizza tray.  Various sizes available up to 16" dia. with a very
smooth aluminum rim.  It makes numerous sparks all at once but, of
course, each one is pretty short.  And they are more or less equally
spaced, as I recall.

 I've also noticed that when
> a spark gap TC gives just two streamers, they are always
> at opposite sides of the toroid.  Again I assume an electro-
> static cause.  I seem to remember someone once mentioning
> some other possible cause though.  Maybe both streamers
> begin at the same time (close enough in time), so they're
> able to both form.

I haven't seen that regularity:  I'll get sometimes 2 -at- ~90 deg,
sometimes 3 within ~120 deg, sometimes 2 -at- ~180 deg, sometimes 3 more or
less equally spaced, etc.  It seems random--and usually there's just one.

[snipped]

> A number of people say the bigger the better in terms of making the 
> spark
> >  longer or fatter
> 
> Even for tube or other CW coils?  I've never heard that.  Even for 
> spark
> gap TC's bigger is only better up to a point, for a given power 
> input.

I may be mis-remembering since I haven't paid too much attention to
toroid lore as related to spark-gap coils.  I thought I'd remembered that
a bigger toroid is supposed to yield more top capacitance which is
supposed to yield a more robust spark due to its increased capability for
holding charge.

> I was thinking about the issue some more, and I think that even a
> thin corona ring about 1" in diameter placed just above the top 
> turn
> of the secondary would protect the secondary from breakdown.  On
> my 36" spark VTTC, I had to install a 1/8" dia minor diameter 
> copper
> ring above the top turn to stop the spark from flaring off of the 
> top
> turn of the winding.  The overall diameter of the ring was 1/4" 
> wider
> than the 7" diameter secondary form.  In one test on that coil, I
> installed a 3" by 12" diameter toroid, but it made no difference to
> the spark length.  I also tried a 4" by 17" toroid, but it still 
> made
> no difference.  The toroids did get warm however, due to induction
> heating I guess.  I guess this heating may have been killing
> whatever benefit the toroid may have "wanted" to produce?  Does
> your toroid heat up at all?

Not in the least but then, I don't leave the coil on for extended
periods.  That Landgren toroid is seriously massive and would take a
whole lot of power before it got warm.  If your toroids get warm, that's
quite a bit of power lost.  But that really surprises me since the
inherent resistance of a toroid is pretty low--unless it's of the
corrugated variety & perhaps imperfectly glued together.  Since power =
(I^2)R, there'd have to be a humungous amount of I running around in any
fully-metallic one.

I'm reminded of an acquaintance of mine who used to give Tesla demos. 
He'd take an aluminum ring, place it on his primary in lieu of the
secondary, and cause it to shoot up into the air when he fired off the
coil.  (But maybe I'm mis-remembering this, also)

>  Since tube coil toroids heat up, I
> would think that spark gap TC toroids would heat up too, 
> although it seems to be too slight to notice.  This heating may
> be hurting the performance slightly on spark gap TC's.  Many
> mysteries still.

It's still a black art.

[snipped]

Ken Herrick
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