RE: Please Advise

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com> 

Hi Emmett:

Are your caps really rated for 2600V each?  If so, your cap looks great,
I just haven't seen a voltage rating that high.

I agree that you could do with a significantly larger toroid.  Assuming
everything else in your coil is good, you probably could do with at
least a 6" x 24" or 30" toroid.  If you ask me how I know, the best I
can say is it's a gut feel based on my experience.  Sadly there is no
known formula for calculating the optimal top load size, and the right
size can make a world of difference.  Generally, performance improves as
the top load size is increased, up to the point where it will no longer
break out without a breakout point.

Increasing your top load size will also allow you to use more turns on
your primary, resulting in lower losses in the gap.

A 3/8" total gap for a 12kV power supply may be pushing things a bit.
I'd recommend checking that with just the NST hooked up, that the gap is
on the verge of breaking down.

Regards, Gary Lau
MA, USA


Original poster: "Emmett Secrest" <secrest2032-at-msn-dot-com>

First let me say Happy New Year to everyone on the list. I added a
second
NST and additional caps to my coil tonight. I had to decrease the tap
point
from the 7th turn to the 5th for estimated best performance. I am
getting
roughly 5' streamers with frequent strikes to the strike rail. I had one

primary hit but it didn't cause any damage.  I repositioned my strike
rail
and did not get any further strikes to the primary. I have not changed
my
coupling or Toroid. I get multiple streamers of 4 to 5 feet and in quick

succession. My question is whether I should increase the size of the
Toroid?  I presently have one  that is d=4 D=16.  Please correct me if I
am
wrong but it seems I read that if there are lots of streamers being
produced it means the breakout voltage required for the Toroid is small
compared to the amount of voltage being delivered. If this is the case,
then wouldn't a larger Toroid have a higher breakout voltage point and
then
for a given voltage supply produce less numbers of streamers that are
longer?  I was considering making a d=6 by D=16 Toroid.  Any suggestions
as
to a better size would be appreciated.  These are the spec's on my coil:

(2) 12/60 NST's
(2) strings of eight .15 uF LTR 2600v MMC's
RQ Gap w/ fan ( 3 gaps of 1/8" each)
15 turn primary of .25" cu tubing w/ .25" spacing between turns
4.5 dia. secondary  22.5" winding length/ 22 AWG
pri. even with bottom of sec winding
2.5 spacing between pri. and sec.
bottom of Toroid 1" above top winding of sec.

Thanks for your help.  It is due to everyone's kind assistance that I
have
successfully built my first coil and I am sure that with your help I
will
get the bugs out of my recent upgrade.


Emmett