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Re: How do sparks propagate, anyway? (toroid)

Subject: Re: How do sparks propagate, anyway?
  Date: Fri, 9 May 1997 16:39:39 -0400 (EDT)
  From: FutureT-at-aol-dot-com
    To: tesla-at-pupman-dot-com


In a message dated 97-05-08 23:57:54 EDT, you write:
>snip
<<  Why do many coilers  report that a larger toroid increases 
>the striking distance of their  coils,  given that increasing
> Coutput always decreases the output voltage? 
> (I am assuming that the striking range is increased by more
>than just  the  increase in toroid radius.)
 > 
 > -GL
 
> Greg,
 
>An interesting question for sure! I'm assuming you're refering to cases
>where the tank C, gap breakdown voltage, and incoming power levels
> are not changed. I suspect that part of the reason has to do with the
>enhanced capability of a larger toroid to provide minimal voltage drop
> while supplying high-amplitude current peaks that occur during
> propagation/growth of the streamers. A larger "chunk" of toroid
> capacitance would permit a greater reserve of charge to be available to
> support further propagation. Although the larger C would also reduce
> maximum voltage, I suspect this is of secondary importance AS LONG
>AS the voltage is high enough to initiate and maintain streamer
> production. This may be why lower Z ( or relatively higher self-C) coils
>may see reduced benefits from oversized toroids.
 
>Have to think about this a bit more...
 
>-- Bert H --
  >>
 
Bert, Greg, All,

Here's some other musings and observations:
I've noticed also, that if a larger toroid is installed, and if power is
rather limited (but kept the same as it was), the sparks lose their nice
blue-white "thin" nature, and take on a purplish, fluffy look when the
larger
toroid is installed.  In spite of this, the sparks tend to be a little
longer.  For instance, the sparks may increase from 45" (small toroid)
to 49"
with the larger toroid.   Of course if plenty of power is available,
then the
sparks using the larger toroid may become even brighter and whiter than
with
the small toroid.

If power input is higher, then the larger toroid seems to give more of a
benefit.  It seems very hard to push long sparks out of a small toroid. 
I
wonder if PART of the reason could be because more streamers tend to be
produced when the toroid is small.  Multiple streamers definitely seems
to
reduce spark length esp. when power is limited.   It may be for this
reason
that some coilers seem to benefit from using a very long "rod type" take
off
point on their toroid, which forces it to produce only one streamer. 
They
may be "compensating" to a degree for a too-small toroid.

Another thing I noticed is that in many cases, the spark length is equal
to
about 2 to 3.5 times the toroid diameter.  It seems difficult to go
beyond
this ratio.  It would seem that very large, high powered coils CAN go
beyond
this ratio; consider for instance Golka's impressive coil output with NO
toroid.  Maybe as you said Bert, these large coils have so much self C,
that
they perform as if they had a built in toroid more or less. (At least I
think
this is what you're saying, correct me if I misunderstand.)

Another thing to consider is that larger toroids working with LIMITED
power
inputs, tend to degrade the quenching which would tend to REDUCE the
spark
length (maybe if the quench wasn't degraded under these conditions,
spark
length gains would be even better?)  

I suspect that there is also a relationship between optimal (or at least
useable) toroid sizes and break-rate, due to "growing of sparks"
effects, but
I am just starting to look into this.  Here we're back to that age-old
question; is big bang/ low break-rate better, or small bang/ high break/
rate?  We know that quenching is easier using the small bang, but what
is not
so clear is how growing of sparks and therefore overall resonator
"efficiency" is affected. 

After all this, let me say, Bert, that I tend to agree with your
comments
about energy storage in the toroid, and that total energy in the toroid
and
sparks may be more important than having the highest voltage.   I just
though
I'd share these additional musings and observations.  With all the
creative
folks on this list, someone should be able to come up with a set of
experiments that will prove or disprove the various theories and
speculations. 

Towards optimal coiling,

John Freau