Re: Toroid or sphere?

[FutureT-at-xxxxxxx (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

In a message dated 11/21/00 2:26:00 PM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:

> Original poster: stanmoore-at-mindspring-dot-com 
>  
>  What effects do a toroid provide, or produce, over solid sphere?  I am 
> building
>  a small tesla coil, 18" secondary, and was planning to use a 1-1/4" ball
>  bearing for the termination of the secondary.  I was planning to mount the 
> ball
>  bearing on top of a stud, that I will thread thru an insulator on top of 
the
>  secondary.  Any inputs are appreciated.
>   
>  Thanks,
>  Stan

Stan,

Toroids give better field control at the top of the coil, and help
prevent breakout from the top coil turns, and reduces corona
in that area.  That's a pretty small ball you mention.  I know a
fellow who built a small TC using salt water caps, a static
gap, and 15/60 NST, and a 4" ball on top.  This coil gave nice
22" streamers.  The coil was not super-efficient though, an
efficient coil would give 65" sparks using that NST.  A toroid
would not have helped the coil much though.

Ball electrode can form straight single streamers that come
straight off the top of the ball at times, if the ball, and other
conditions are right.  Toroids throw the sparks outwards.

The correct ball size depends on the power and efficiency
of the coil.

John Freau