Re: bad coil

To: tesla-at-poodle.pupman-dot-com
Subject: Re: bad coil
From: Tesla List <tesla-at-stic-dot-net>
Date: Fri, 30 May 1997 08:52:48 -0500
Approved: tesla-at-stic-dot-net
Subject:  Re: bad coil
  Date:   Thu, 29 May 1997 13:35:14 -0400 (EDT)
  From:    Esondrmn-at-aol-dot-com
    To:    tesla-at-pupman-dot-com


In a message dated 97-05-29 09:03:54 EDT, you write:

<< 
 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.
  >>
-snip-
Damon,

I did some caclculations on your coil.  Assuming your secondary is 3.0"
dia,
it should tune at about turn 7.5 with a 5 pf toroid (this would be quite
small).  With a 10 pf toroid, it will tune at turn 9 of the primary.  It
sounds like you need to add another couple of turns on the primary - or
reduce the capacitance.

I agree with whoever suggested it, you should build a cylindrical static
gap.
 It would improve your performance greatly.  With 15 kv, 30 ma you
should be
able to get 12 to 16" discharges from this coil.

Ed Sonderman