bad coil

To: tesla-at-poodle.pupman-dot-com
Subject: bad coil
From: Tesla List <tesla-at-stic-dot-net>
Date: Thu, 29 May 1997 07:44:20 -0500
Approved: tesla-at-stic-dot-net
Subject:  bad coil
  Date:   Wed, 28 May 1997 01:29:20 -0400 (EDT)
  From:  Damon Burke <damon-at-portal.stwing.upenn.edu>
    To:  tesla-at-pupman-dot-com



Hello.. I'm writing to you for help with my coil.  I read alot of online
material, searched through alot of web sites, and downloaded many
programs
so i could start building my tesla coil.  I finally finished it and
despite my accurate construction (or what I considered rather accurate)
i
find my coil arcing nearly 1/2" to a ground wire at the most.  I made my
primary tap moveable so i could attempt to tune the coil, but anywhere i
move it i get the same results.  Here is my coil specifications:

I'm using a standard 120v 60hz input with a 15kv 30ma neon transformer.
I have gto wire running to all my components.  The entire set is built
onto a wooden cart for portability.  Parallel to the transformer is my
safety gap set to 3/4" (recommended by chip.)  Also parallel to these is
my static gap.  I'm using 8 gaps with somewhere between .01-.02 inch
gaps
(recommended by the teslac program.)  The gap was designed by placing a
strip of tin sheeting on a piece of wood and screwing it down in 9
places.
Between the screws i used a hacksaw to cdut a groove through the metal.
This gave me about 1/16 of an inch gaps.  I then turned the little
strips
of metal to close the gaps to their recommended gap sizes.

Parallel to all of these of course is my cap/coil combination.  I have a
wooden box with three sheets of 1/4" thick window glass.  I have 10"x10"
aluminum foil on each side of the glass.  Three of these are parallel to
each other bring me to just under .004 uf (the recommended capicatance
for
my coil is .0038 according to the teslac program.)  My primary coil is 8
turns of 1/4" copper tubing with 1/4" spacing.  My first tap is on the
very inside of the coil (soldered in place) and the other one is on a
moveable mount somewhere between the 7th and 8th turns (as recommended
by
the teslac program.)  My secondary is 24 gauge wire on (can't remember,
either 3" or 4".. i believe 3") plexiglass tube.  The coil winding is
12"
high.  The bottom of the secondary lines up about the same height as the
primary (which is a flat spiral.)  

The secondary has a wire that goes out the bottom to a ground rod sunk
6'
into the ground.  The top end  wire goes to a toroid made of 4" diameter
aluminum dryer duct material.  I didn't have alot of information on the
toroid so I used what i had and made a donut out of it.

Here is a drawing of my coil design

                                    _____
+----+-----+---+---| |--+-------   (_____)
|    |     |   |        |      o      8
|    |     |   +---| |--+      o      8
|    |     |   |        |      o      8
           :   +---| |--+      o      8
T          :                   o      8
           :                   o      8
|    |     |                   o      8
|    |     |                   o      8
|    |     |                   o      8
+----+-----+--------------------      8
                                      |
^  Transformer      ^ Capicators     ---
                                     \ /  <- ground
     ^ Safety Gap
  
           ^ Static Gap


I have placed a few small flourscent tubes near the coil, and they glow
quite well.  I can gring a ground wire close to a tube about a foot form
the primary and pull a 1/4" arc from it!  If i put the secondary near
the
primary i don't get any arc from it.

If anyone out there has any ideas what i'm doing wrong please let me
know.
Also: what is involved in tuning a coil.. what items should i look to
modify first?

Thanks in advance for the help.

Damon