Strange Spark Phenomena

From:  gweaver [SMTP:gweaver-at-earthlink-dot-net]
Sent:  Friday, January 30, 1998 11:46 AM
To:  Tesla-at-pupman-dot-com
Subject:  Strange Spark Phenomena

> I fired up my tiny 1.5" TC today.  I changed the sphere from 2" to 4".
> Changed the cap from .0014 uf to .005 uf.  Changed the spark gap from 4 gaps
> .025 each to 3 gaps .025 each.  Moved primary tap from turn 5 to turn 3.
> Spark output increased from 3" to 6".  The power supply is a furnace
> ignition transformer 6K 20 ma.  120 watts.
> The output spark is strange.  I have seen this phenomena before but haven't
> thought much about it until now.  The first 2" of the output spark is very
> thin, the next 2" are very hot, thick and blue, the last 2" are very thin
> like the first 2".   How can a spark that is all one continuous spark be
> made up of 3 sections?  How can the center 2" of the spark be hotter and
> thicker than the ends of the same spark?
> Gary Weaver

>Take a length of nichrome wire, attach it to two clip leads and turn up
>the voltage. The center will be glowing red hot while the ends are dull.
>Simple heat-sinking effects.

>Your sphere is a heatsink. The place where the arc strikes is a heatsink.
>I am assuming that you are drawing the arc to a grounded wire.

>Besides the heat-sinking effect, there is also the increased heating
>effect that comes from being surrounded by other hot objects. The
>objects in the center will be much hotter than the objects around
>the periphery.

>I'm not saying these are necessarily the reasons for your strange
>arcs. I do not know all of the conditions under which these arcs are
>occuring. But I do know that at low powers you can see things that
>are greatly masked at high powers. And vice versa.

>Do the arcs exhibit the same peculiarities both when striking to a 
>ground and when just brushing out into the air? If they exhibit them
>ONLY when arcing to a ground, then the above effects are probably
>at work. If not, then something else is probably at work here.

>Hope this helps.
>Fr. Tom McGahee

>I too have noted this on a number of occasions with a lot of 
>different systems (easy to see at low power). My reading of it is 
>that a streamer issues from the terminal and a close enough object
>(either simultaneously or when the terminal leader gets close enough 
>to the target (cf. lightning)) and the two meet in the middle where, 
>presumably, the highest concentration of energy is. Any 
>advance/correction to this anyone?


>I see these kinds of effects often with tube coils and the effects 
>vary with tuning, coupling, power input, etc.  In one case, the 
>sparks were 21" long and the first 10" were thick and fuzzy, and
>the upper part of the sparks were thin and pointy and straight.  By
>varying the tuning, the sparks could be made completely fuzzy, or
>completely pointy.  It's all very weird and I don't know if spark gap
>coil spark appearances are controlled by the same factors as tube
>coil sparks.  This whole question of spark appearances is an 
>interesting, and as far as I know, an under-explored area of coiling.

>John Freau

>I use this phenomena sometimes for tuning at low power.  Instead of tuning for
>the longest spark, which involves moving the ground target numerous times, I
>just tune for the longest white hot spot in the middle of the discharge spark.

>Ed Sonderman

This is very interesting.  All 4 observations sound logical. I think these
strange sparks are telling us something but I don't know yet what it is.  2
out of 4 people have observed these strange sparks change appearence when
tuning the coil.  Maybe it has something to do with having the coil tuned
correctly.  Maybe its something different like having the capacacitor value
sized correctly for the total system.  Or maybe its something else and maybe
its not even important. I noticed one time on another coil a 12" spark was
made up of 5 sections and had 2 hot spots spaced about 3" apart.  Could this
strange spark have something to do with how the spark gap fires or how many
times the gap fires during the length of one discharge spark from the toroid.  

Does anyone know how may times a spark gap will fire compaired to the number
of discharge sparks from the toroid?  Is there one discharge spark from the
toroid for each time the spark gap fires or does the spark gap fire several
times for each discharge spark?  

A variable capacitor could be put in parallel with the fixed capacitor.  The
cap could be adjusted to see the effects of the discharge spark.  Moving the
primary coil tap a little at a time should show the exact same results.  But
this would not be true if the primary coil and capacitor have to be sized
correctly with respect to each other.

Gary Weaver