Re: Toroid Design

[FutureT-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

In a message dated 8/29/00 5:50:32 PM Pacific Daylight Time, tesla-at-pupman-dot-com 
writes:

> Original poster: "Ted Rosenberg" <Ted.Rosenberg-at-radioshack-dot-com> 
>  
>  Hi toroid builders out there....
>  Since I am wrapping mine tonight or tomorrow, I just thought of a question.
>  Is there any difference/benefit/negative from using a 4" compressed 
aluminum
>  duct with a wider diameter (ie 24") or a 6" duct with a slightly smaller
>  diameter (ie 18")  assuming the pF is, of course, equal for the top load
>  figure in Wintesla.
>  Don't use the specific 18 or 24. they are only approximations for this
>  question.
>  
>  Almost finished...whew! Gotta buy beer  :) Betas smoke anytime!
>  
>  Ted Rosenberg

Ted,

I think the most important figure for max spark length is the minor
diameter.  For instance the 6 x 18 toroid may give a longer spark
than the 4 x 24 toroid.  I'm basing this on the behavior of spherical
toploads, which a thick toroid is tending towards.... shape-wise.

But let me say that I have not really done much testing or
research in that area, but it is an interesting question which I've
wondered about also.  Another piece of evidence which suggests
that the minor diameter is most important is the fact that a
smooth toroid gives longer sparks for the same size.  All that
is affected by a smooth toroid is the breakout voltage.

Furthermore, all of the above assumes that the coil is being
driven with enough power to break out of the toroid ROC in
question, etc. 

Another issue is that a smaller toroid, (18" in the example) should
still be rather wide relative to the secondary so that the toroid's
capacitance will not be shaded too much.

In a way, larger ROC, and smaller major diameter go hand in
hand since less Ctop permits a higher voltage to build up, but
only if the larger ROC is used.

I too would be interested to hear if anyone has analyzed this
issue more completely.

John Freau