Re: Redesigning/tuning a coil

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

Original poster: pepperman-at-SoftHome-dot-net 

Thanks for the suggestions--it sounds like using a sloped primary is
more complicated than I thought, so I think I'll go ahead with the flat
primary.  It sounds like it'll have plenty of coupling anyway.  I also
appreciate the ideas for the spark gap and short run times to keep
the caps cooler.

Dr. Resonance, I'm afraid I didn't understand what you were
recommending with testing the primary--you said:

"Also, a flat test "scrap wire" primary with 25-30 turns can be quickly set 
up with some slotted scrap
cardboard for a quick test of your entire tuning range.  Keep your sparkgap
setting tight (under 0.100")and your variac below 30% until you find the
best pri resonant point."

How would using a temporary 25-30 turn primary help find the
resonance frequency for the final ~10 turn primary?  Were you
suggesting using normal insulated wire (e.g. 12-14 AWG) for the
test coil--and if so, how would you recommend varying the tapping?
I'm afraid I don't understand what you're suggesting here.

(To everyone): there's something else I'm curious about--how well
do you think the coil would run if it was tuned up to use the existing
8" x 23" toroid, rather than replacing it?  I know there are more
ideal ratios (e.g. 5" x 20" or 6" x 26"), but how do you think the 8" x
23" would perform?  Would it be too big for the 15/60 NST?

If it wouldn't do well, what other size would you suggest for one
made of corrugated aluminum ducting?  Also, a related question:
once you've curled the ducting around, what do you use to attach
the two ends?  I've read some comments about aluminum foil tape
disrupting the normal spark pattern, so I was hoping to avoid that...

Michael Johnson