New coil

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

Original poster: "John Richardson" <jprich-at-up-dot-net> 

Hello,

Well, last night I fired up my new 4.5" coil, and
performance was great for a first fire, but I do have a few questions and
comments for the list.  Here's the specs:

Secondary:  4.5" OD PVC with 36" of heavy build #24.  Set 1" above primary,
last winding 3" from top of form.  Total pvc length 42".

Primary:  14 1/4 turns of .25 Cu tubing.

Toroid:  Quick lash up of 4" dryer duct.  24" by 4".

Gap and cap bank:  8 942 CD's in series mounted next to a five segment
copper pipe gap blown with a small muffin fan.  Everything mounted on two
sandwiched 8 by 11 cutting boards.

Transformer: Transco 12/60.

Upon first fire up, I tapped at turn 14 1/4, as I usually start from the
outside in when first firing.  This happens to be the number of turns I
wound up with before running out of a full roll of tubing.  Instant multiple
streamers, maybe four or five at a time, with the longest consistently
hitting the 36" mark.  Within a minute or so, a capacitor lead arced to the
muffin fan, killing it.  I set up another fan, and proceeded.  Within
another minute, I heard a sound like a rifle shot every 15 seconds or so.
Turns out the last capacitor in the bank was arcing to a bolt which joins
this same cap to a lead to the primary.  The arc had to jump over an inch,
and I figured that since both the last capacitor and the wire going to the
primary SHOULD be at the same potential, I wouldn't have a problem.  Why did
this happen?  Even though there is a hole in this cap, there was no loss in
performance.  I am obviously going to need a larger topload, and was
thinking of going to a 6x30 for the final configuration, judging from the
length and amount of streamers I presently have.  Do you guys think I should
add a few more turns to the primary, taking into consideration the larger
topload and future dedicated 15/60 NST?

A few comments on the physical design of this unit.  The whole primary base,
including the primary supports, are made out of plywood, so to those who
feel that HDPE or similar is required, don't be afraid to work with wood if
that's all you have.
Remember to keep lots of spacing between components, or you will have arcing
problems like I had above.  Also, don't bend the tubing unnecessarily, or it
becomes very hard, and you will set new records for profanity.  For those
who are wondering how to anchor threaded rods for screwing on the topload
and the bottom to your base, try what I do:  Cut two wooden discs that will
fit snugly into your form.  Epoxy the first one in about two and a half
inches below the end of the form.  Drill a centered hole in your other disc,
and four or five random holes along its perimeter.  Mix up a batch of
fiberglass resin, and pour it over the first disc.  Place a length of
threaded rod thru the center hole of the last disc, and anchor with nuts on
both sides.  Slowly push it down into the form until the resin starts to
squeeze up thru the outer holes.  The disc should now be about a half inch
from the end of the form.  Thread the winding thru a small hole in the form,
and anchor with another nut.  Finish off by filling the remainder of the
space with more resin, submerging the wire and last nut.  Both ends
shouldn't take more than fifteen minutes total, excluding resin drying time.