[TCML] New Double Toroid idea works!

[FIFTYGUY@xxxxxxx]

Remember when Scott Bogard wrote:
 
>Adding a top load lowers the tesla coils resonant frequency, what about  
adding a bottom load?  Would 
>putting a toroid or some kind of  capacitor between the coil and ground 
lower the coils resonant frequency?
 
    At first glance it didn't seem like much of an  idea. But it *did* get me 
to thinking:
 
>Could one run a "transmission line" from the  topload to another  toroid 
some 
>distance away? And then use breakouts on this  second  topload to force it 
to 
>act as the main discharge point? Seems safer  and  easier than a magnifier 
>configuration, but with all the  spacing  benefits. Plus easier to make and 
>transport two separate  small toroids than  one big one.

Bart didn't think much of this:
 
>Not sure. I doubt it. The transmission line would likely be the  breakout 
>point if of a 2 coil 
>systems normal turns. Note in maggy's, the driver has >only 200 to 300 
turns. 
>The extra coil is the high turn coil. If the driver 
>had high turns, the transmission line would be a  serious breakout problem. 
>
>
>What appears good in visualization is rarely true  in reality (physics is 
the 
>cause).
 
 
    Well, guess what? It works *very* well, thank  you!
    I've been having chronic problems with my Pig SISG  killing itself by 
secondary strikes hitting the electronics under the primary.  So a few weeks ago, 
I set up my "extra" toroid and gave it a try!
    I kept my "good" toroid (very smooth home made 8" x  36") over the 
secondary. I had a spare "ugly" 8" x 36", so I located it at the  same height, but 
70" away (center-to-center, so 34" edge-to-edge). I put the  "extra" toroid on 
a piece of 8" PVC pipe. I connected the two with a piece of 4"  OD aluminum 
flexduct.
    Despite the much smaller radius of curvature, at no  time did any 
streamers come from the 4" flexduct.
    With a breakout point on the "extra" toroid, all  the streamers came from 
the extra. When I started pushing way too much power  into the coil, a few 
streamers occasionally came from the main toroid to an  unlucky piece of nearby 
plywood sheeting. But one doesn't usually put 8 kVA into  a 6" non-maggy coil 
with an 8x36  toroid!
    Yes, I had to re-tune because of the extra topload  capacitance. This was 
actually quite convenient. For one, it allows you to  significantly increase 
the topload without having to resort to a single,  awkwardly large toroid. 
Stacking toroids vertically seems to allow only minimal  gains because they get 
"lumped" electrostatically. 
    Sure, you decrease the Cprim/Csec ratio which  theoretically lowers the 
voltage gain. But at the same time, I've heard the  larger Csec mitigates 
harmonics, stores more charge before breakout, and  increases the discharge current 
during each bang. 
    With no other modifications other than adding the  extra toroid and 
retuning, I'd say the spark length increased 10-15%. It was  noticeable, and 
surprising. Maybe it was really due to lower losses in the SISG  from a lower Fres 
and lower primary current. All I know is that it definitely  helped!
    Not willing to leave well enough alone, I decided  to move the primary 
tap back to fewer turns, and increase the primary cap for  more power. That's 
how I ended up running .150 uF of primary cap, and  blowing up another SISG 
section. Maybe when I hook up the 12" coil and I  can get the Fres way down, I'll 
push it to .300 uF and see how long  things last...
 
-Phil LaBudde
Center for the Advanced Study of Ballistic  Improbabilities



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