Re: Another toroid question

In a message dated 12/24/98 12:29:12 PM Pacific Standard Time,
tesla-at-pupman-dot-com writes:

<< Original Poster: "Jon Rosenstiel" <jonr-at-pacbell-dot-net> 
 Hi, I'm fairly new here, have been lurking for a couple of weeks, this is my
 first post. I have been playing with a couple of small coils, (1.75 inch and
 now 4 inch secondary). I am powering them with a 15kV, 60mA neon, but I am
 not using any higher that 40Vac input to the xfmr due to my inadequate
 capacitor, (correct capacitance, just not enough dielectric).
 I have been following the discussion on toroids, has been quite helpful to
 me.  My question is: What is the effect on total capacitance of stacking one
 toroid on top of another? Do you add the two capacitance's? It would seem
 that some surface area is lost where the toroids contact and that would make
 the total capacitance somewhat less.
 On my 4 inch coil I have achieved best performance so far, (15 inch sparks
 to a grounded wire), by stacking a 6" x 19" on top of a 4" x 15.5" toroid. I
 wanted to know the total capacitance.
 This stuff is really exciting, I'm having a ball!
 Thanks, Jon Rosenstiel

Congratulations, sounds like you have the addiction now.  Your 19" toroid
probably adds about 20 pf of capacitance to the secondary, the 15.5" torord,
probably about 15 pf.  If you lay one on top of the other, the new total won't
be much higher than the original amount for one - my guess would be the total
for both laying on top of each other would be 25 pf.  I use dual toroids on
both of my coils, one reason is to yield larger capacitance but an equally
important reason is that it increases the distance between the primary and
where the sparks come from, which will be the upper toroid.  On my 3.0" dia
coil, the two toroids are separated by 6".  On the 6.0" dia coil, that 33" and
40" toroids are separated by 16".  My notes say the total for this type of
configuration will be 65 to 75% of the combined total of both toroids.  I
can't find the source for this number but I believe it.

Ed Sonderman