RE: mini coil

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

Original poster: "sundog by way of Terry Fritz <twftesla-at-uswest-dot-net>" <sundog-at-timeship-dot-net>

Hi All, Robert

  Good move!  I personally ran coils wound on 2" id PVC, from 9 to 13" long,
and learned much more about tuning and tweaking that I ever did on a bigger
coil.  Plus, a 10 pound spool of wire will last you *quite* awhile winding
coils that small.  While a 12kv (a single 12/30 works great) tranny is good,
I've gotten the best results from a 9/60.  Small, low powered systems are
the best way to do the "What If..." experiments.  OBITS also perform well in
small coils.  The advantages
  - wire lasts longer.  Only a few hundred feet on each coil.
  - tranny, caps, and setup is smaller. Easy to store.
  - less crash and bang than a large system.  a 12' streamer is Loud, a 12"
streamer is much quieter
  - Cheaper!!  2"id pipe runs me ~$5 for a 10' length. You can build an MMC
for just a few bucks!
  - easy to experiment with.
  - less RFI than a large coil, though it *CAN* cause some serious problems
if not grounded properly.
  - doesn't need a dedicated RF ground.  I got same length streamers with no
ground, a good ground, and a sheet of foil (1'x3') put on the concrete
garage floor.
  - Easy to take places
  - you won't mind smoking a 2" secondary as much as you do a 4,6, or 8"
one.
  - dealing with less power makes it safer. It's still a dangerous hobby, so
don't get complacent.
  - you'd be amazed how much power a well-designed 2" coil can process.

Downsides
  -  it's small...small arcs aren't as impressive as big arcs
  -  some ppl have difficulty fabricating the small parts for these coils
  -  you'll still probably manage to kill a few trannies on 'em (see terry's
NST filter)
  -  small coils seem to make a *ton* more ozone than large coils.
Ventilation is a must!

I'm sure there's more downsides, but I can't think of 'em right now.

Now, my personal advice (been there, done that, got the T-shirt, as in
~15-20 small coils build and burned).
-  Go MMC.  Play with SW caps once or twice, then go MMC.  My 9/60 uses 3
strings of 13. Garry F. uses the same thing (how's it working still Garry?).
Works like a champ.
-  Use a flat primary.  1/8" copper tubing is the best, but bare copper wire
will work. I don't recommend PVC house wire, as I find it a hassle to tap it
a zillion times, and stripping 20-30' of insulation is not my idea of fun.
12-10ga wire is fine.
-  Tap from the bottom.  Cut the holes in the bottom of the primary table
and tap from underneath, an alligator clip works fine for small coils (no
flames for that pls, it works great).  When you start loading up on topload
on a short coil, the tap becomes a target if it's sticking up.
-  Decouple, tune from the outside in, couple closer.  You'll save a lot of
secondaries that way.
-  Magnifiers work fine despite being tiny.  No real performance difference
I could see, but it looks cool :)
-  buy a small spun toroid if John F. still has them. They work beautiful on
small coils. (I got 4 of 'em)  You'll build your own too, use aluminum tape
and burnish it down.
- *never* let anybody tell you a small coil can't throw long sparks.  I've
gotten white-hot 25-30" sparks from a 9/60 on a 2x13" coil.  Scary
performance from a tiny coil.
- make a jig to wind secondaries. A piece of threaded rod, some 2x4's, a
handfull of nuts and washers, and 2 endcaps (don't fit 'em too tight), add a
variable speed drill, and you're all set.  be sure to build something to
hold the wire, and keep good tension on the wire (pinch it with cardstock of
cardboard to tension it and save fingers!)  The easier they are to wind, the
less fear you have of experimenting.
-  don't run the wires inside the form unless you install baffles. it'l
flash over almost guaranteed.
-  do it "high quality."  cutting corners or taking shortcuts will not pay
off.  If anything, small coils are more sensetive to flaws and shartcuts
(sharp bends of wire, kinks, etc), because you've got a lot of HV in a small
space. Take the time to do it smooth and right :)

That bug zapper tranny probably wasn't designed for the continious use a TC
tranny will see (most bugs go BZAP! in short order, expect palmetto bugs.)
I don't know how long it'll work in a TC, but I believe others have used
them sucessfully.  An OBIT or ignition coil/runcap/dimmer switch make great
trannies for the <100watt range.  I use a 9/60. (raw power for a tiny coil!)
I'd scrounge up some OBITS for it.


  Now, all that being said, don't play with the streamers. Don't let others
play with the streamers. They still hurt ;)  You'll find that small coils
are a real blast to tinker with, can run for insanely long runs (till the
ozone, noise, RFI, or Significant Other see fit to end the run), barring
tranny death (again, terry's NST filter).  Nothing like kicking back with a
cold coke watching streamers wander around.  ~20 min is my record on a 9/60.
Caps were warm to the touch.


 Welcome to the world of Lilliputians!  Can't wait to hear about first
light!
					caio!							Shad

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Tuesday, February 20, 2001 6:52 PM
To: tesla-at-pupman-dot-com
Subject: mini coil


Original poster: "R Lunsford by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<Millipede-at-carolina.rr-dot-com>

Hello,
 I am going to go miniature for a bit. I want to use my old bug zapper xfmr
to
run a coil. Unfortunatly, I have no idea what the voltage or current on the
secondary is.
 So, here is my dilema. I need to know if anyone has ever tried this...or a
cheap way of checking the outputs so I can go ahead with this project.
 Thanks,
Robert Lunsford