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Re: [TCML] My Hemisphere/Toroid with Unconnected Top Sphere results

Hi Peter,

I understand what you are saying, but the data is incorrect. The sphere + hemisphere/toroid does not add (as though you add the single capacitance of both). You really need a program that looks at the effective combined capacitance in situ from ground plane to top load objects, coil to top load objects, object to object, etc.

For example, a 4" x 20" toroid (by itself) raised 50" above the ground plane = 22.8pF
Stack a 2nd toroid of the same size resting on top of the first = 26.7pF
If we raise the 2nd toroid up to a 60" height, C increases = 30.8pF

When these top load objects are stacked on top of a coil, the effective top load capacitance changes again as the secondary coil and primary coil are then in situ of the objects.

In your case, the sphere will only add about 2pF of C when placed on the hemisphere/toroid and will only change Fr a few kHz (about 20kHz with your particular coil). Stacking odd shaped top load objects is something many of us have done many times over many years and we've made plenty of measurements to see the effects.

If you have a generator and scope, you should measure the change in Fr. Playing with top loads is always fun to do, but it sure is nice to take a measured Fr reading as it tells the tale.

Best regards,
Bart B. Anderson

Peter Baitz wrote:
Hello Bart,

Here's the calculation results done with deepfriedneon.com calculator for my coil, and toploads
I'm experimenting with.   As you can see if the sphere is directly connected metal-to-metal
to the secondary output like the hemisphere/toroid, or sitting atop but connected to the hemi/toroid (other than with a coil of wire or tubing or isolated) technically the topload capacitance
does change, like the following chart.   I am fairly convinced when it sits atop but is
unconnected, or connected through a coil or wire or tubing (forming a type of 'magnifier')
the topload remains that of the hemi/toroid for which my primary turns calculation comes
out to 8.8 turns, and it does work at 8.4-8.8 turns.
Using 9.822 mH self inductance, and 7.197pF (0.000007197uF) self capacitance plus the topload.

6" sphere alone 8.551pF (0.000008551uF) res. freq. is 404.676 kHz

11.125" 'hemisphere/toroid' alone 14.116pF (0.000014116uF) res freq. is 347.854 kHz

Hemi-toroid plus sphere 22.667pF (0.000022667uF)  res freq is 293.864 kHz


6" sphere alone
7.65 turns

11.125" hemitor (hemisphere-toroid) alone 8.8 turns

Hemitor (hemi-toroid) plus sphere (physically connected metal to metal) 10.3 turns (in actuality this needed a bit less) ----------------------------------------------------

So it appears to me the top sphere does change the topload capacitance
when directly connected, but not when unconnected or through
a tertiary coil - and in the latter two cases acts as a special case
"magnifier" without affecting the top load (hemi-toroid) capacitance. Just some observations based on behavior of my tesla coil, and compared to tesla calculator information. I could be wrong, still open to thoughts.
See website updates for Sept. 9 and 10 with regard to this third coil
which I found well replaces the isolated/unconnected original sphere
on top of the hemi/toroid situation.


PS: I am hoping as another next step to build a second spark gap that is adjustable so I can work with it a little.     My current 6-gap spark gap is fixed with total space just
a little less than my safety gap size, and works quite well, but will try for a better one. I may hook up a vaccum to the new one, not sure yet. I'd really hate to have a vacuum noise running too, LOL.

------------------------------I haven't been keeping up well with these posts, but regarding top load
C, I just wanted to point out that the top sphere adds only a slight increase in C. Roughly, the hemisphere is about 12pF. Putting the 6" sphere on top results in the neighborhood of 13.7pF overall. As you can see, only a slight top load change and very small Fr change. The interconnect coil adds nothing. So the system should remain well in tune in all cases.
Take care,

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