RE: Scott's 4 incher?

Per Bob Thaden's request, I am providing specs on my  " 4 inch coil " setup.

Bob wrote;
>Would you be so kind to give us the low-down on your 4 inch coil?

>sec height:
>sec gauge wire:
>sec form material:

First let me point out that I have 2 secondaries in this size range, neither of
which is exactly 4" OD.  The first one is as follows:

3.75" OD x 14.5" winding with 24 gauge magnet wire.  It is wound on a
polyurethane sealed cardboard former.  The wire goes inside of the tube to come
out the top on a ceramic insulator.  It comes out the side at the bottom to a
screw terminal.  The wires inside have been carefully sealed with a insulating
material, silicone and latex tubing, I believe.  This coil was an early coil
built by Mark Graalman that he no longer used.

The second one ( actually the original ) was made from plans from Information
Unlimited.  I made it before I tried to understand Tesla resonators and their
properties, so many things were not done as they should be.  These plans were
also used to make the primary and the rest of the coil system.  These plans were
seriously lacking, from a performance standpoint.  But, it is where I started.
The secondary from these plans are as follows:

3.5" OD x 10" winding with 26 gauge magnet wire.  It is wound on a cleaned, but
UNSEALED, PVC former.  The wire again goes inside the former and comes out the
sealed bottom and top.  The bottom wire is connected to the house ground and the
top to the toroidal terminal.

The performance of both coils isn't too bad.  Both have some design limitations,
but work well.  The 3.75" OD coil made by Mark Graalman is the better performer,
and the one I use on this system.

>prim type:
>prim dimensions:

The primary is made of common 12 gauge house wire.  The first 6 turns are
bundled with the insulation of the wire left intact.  The diameter of the first
6 turns is 6" to the center of the bundle.  This acheives a high inductance in a
small package.  The last three turns are bare, spaced .25" apart, for tuning.
They are also .5" lower than the first 6 turns.  This tank circuit is grounded
on one side.  It is not a floating type primary.

>cap type:
>cap size:

The capacitor is a commercial Tesla tank pulse discharge capacitor, .005 uF with
a 10000 VAC rating.  It is made by Condenser Products.  I also have a homebrew
vertical plate cap with a 12000 VAC rating and .0056 uF that I can use with this

>spark gap type:

The original spark gap was an adjustable single static gap.  I varied from the
original plans and used tugnsten carbide as the gap material.  It survives the
best.  However, this gap's performance still stunk.  Ionization and lack of
quenching hurt the coil performance badly.  I have since changed it to a 6 gap
vacuum type spaced at .020" each.  This gap gives excellent quenching and
performance.  It also is dependable, unlike the original static gap.  I doesn't
seem to suffer from oxidation too badly.  I have only burnished the gaps once
since I made it.


I have several toroids, but I typically use my 2 -  8" x 2" units.  One is a
solid cast aluminum unit made by a friend.  The other is an old homemade unit.
It is made of automotive flexible exhaust tubing bent into a torus.  I can use
one, or both.  All I have to do is change the tune.  The performance is the
same, with 1 or 2.  So typically, I just use 1 toroidal terminal.

>HV supply:

This is where my current power supply lacks.  The original power to this coil
was a single, 23 mA -at- 6000 VAC neon, single pole type. This transformer doesn't
have 2 high voltage outputs.   With the vacuum gap, it gave 10" discharges.  I
have since come across 5 other transformers of the same rating.  I have 6 units
in parallel providing power, for up to 24" discharges, on a good dry day, with a
perfect setup.  18"-20" would be more typical.


There are no filter capacitors being used with this coil.  I have a filter choke
only.  It has 25 turns of magnet with on a phenolic rod, 1.25" in diameter.  The
winding is 1.25" long.  This system is run on the house ground, an 8' x .5"
diameter copper clad rod and the water pipe.

There you have it.  That is my 4" coil set-up.

Scott Myers