Re: Sword-like VTTC spark pix at my website

["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 2/9/01 9:43:45 AM Eastern Standard Time, tesla-at-pupman-dot-com 
writes:

> Nice photos John!
>  
>  I'm glad to have seen this really unusual spark in your pictures- I never
>  quite knew what you meant before.  My coil does not exhibit this
>  phenomenon, but I use a horizontal breakout and a larger topload.   With
>  smaller CW coils, I can get a single vertical strand of arc into air (the
>  811-a coil schematic at www.angelfire-dot-com/electronic/cwillis/811acoil.html
>  will do this) but the appearance is not the same.  I think that by using
>  vertical breakout, heated / ionized air rising through the electric field
>  can strongly contribute to discharge shape and length, maybe forming a
>  bubble or column of warm, rather conducting gas over the topload for the
>  next spark to "aim into."    I'll have to make some adjustments and see if
>  I can reproduce the effect on the staccato 833-A coil.

Hi Carl, all,

Thanks Carl for the nice comments.  I just did a test with my coil.  I placed
a large steel nail leaning off the top of the toroid to the side as a breakout
point.  It's angling upwards at about a 20 degree angle from the horizontal.
I obtain the same swordlike spark as before, except the sparks are aimed
at 20 degrees from the horizontal, exactly following the angle of the nail.
So it seems that the spark works the same vertically or near horizontally.
I didn't try exactly horizontal.
>  
>  One interesting effect I do see on the 833-A coil are sparks that have
>  "knots" or beads in them, in some cases the beads seem to be actual
>  looping-back of the discharge around a 0.25" radius or so.

I've seen the knots or beads in some of my tube coils, but not so large
I don't think.
>  
>  On the subject of tube coils, I feel the irrepressible urge to build
>  another 'un soon- for some reason, classwork just doesn't provide many
>  thrills in life. So I'm planning to go with a push-pull oscillator, with
>  4CX300's or similar (if I can afford them) or some "no-name" tubes from a
>  diathermy machine I recently sacked.  My goal is to make a "half-wave"
>  coil, with two secondaries base-fed off coils tightly coupled to the tank
>  inductor.  MMC capacitor.   I'd like to include a "super staccato" cathode
>  grounder and the good old level-shifted supply.  If you (or any of the
>  other tube coilers) have tried "half-wave" tube coils I'd be interested to
>  know.  Also, if you have advice regarding using the ceramic tubes I could
>  use it- I have always stuck with glass before.

I've never made a half wave tube coil, and I've never tried the ceramic
tubes.  I know they need a lot of air flow through the fins, and metering
is essential, because you can't judge by "plate redness" I guess.

John Freau

>  
>  Thanks for posting those pictures- they have certainly made a worthy
>  conversation piece!  
>  
>  -Carl Willis
>