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

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 3/17/01 7:46:45 PM Eastern Standard Time, tesla-at-pupman-dot-com 
writes:

> > Do the sparks move around the toroid surface from place to place
>  > as the coil runs?  They do this on a spark gap TC with a smooth 
>  > toroid.
>  
>  Yes, they do.  Not "frantically" but seeming to pause near 1 spot or
>  another for brief periods.  And often I get 2 or more 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 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.

The sparks from a spark gap coil also move around slowly 
on a smooth toroid.

>  > My guess is that the smaller toroid would protect the secondary
>  > just about as well.  Not too small though...  let's see.  Your coil
>  > secondary is 1 foot in dia (?).  Maybe a 4" by 16" toroid would be 
>  > very 
>  > effective also.  Even a 3" by 15" should be good.
>  
>  Very likely.  I use 6" x 24" since that's the bulk-buy Landgren size.  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 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?  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.

I seem to be implying above that larger toroids are not of much
benefit on a tube coil, but I'm not really sure about that.  In any
case I do gain about 1" of spark length when I use my 1.5" by 6"
toroid on my small tube coil which gives 19" sparks.  I always
retune as needed for all tests.

> --but I don't see a whole lot of difference between the
>  smooth 6" x 24" and my prior 4" x 15" corrugated one.  My $190 may have
>  gone mostly for beauty.

Well beauty is important too, and the smooth toroid lets the sparks
move around as you mentioned, instead of getting stuck on the
ridges. 

John Freau

>  
>  Ken Herrick