A Special Project
Dedicated to Brian Foley and Frank Jones:
Portable 1 1/2 KW Bipolar Pancake Coil / Unipolar Tesla Coil
85 pounds, complete.
Over the years two people have been unusually generous and supportive of
my experiments. When I ran out of energy or money,
these two would always manage to throw a box in the mail and surprise me
- end mills, wax, bolts, nuts, "stuff" of all varieties
that kept the creative juices flowing and my feeble mind active!
In Brian's case, a wealth of machinist treasures so that I have no
excuses not to build anything...and in Frank's case, tubes
and books, and manuals and things to open and exclaim "I HAVE TO
This isn't an overly complicated project, but one that I really enjoyed
making. The 25 pound oak box was made for $10
in oak floorboards from Habitat For Humanity!
The wax poured Pancakes are made from discarded candles Brian sent last
Wiring components in the backyard.
Yes, its sitting on Mejla's little red wagon (barely).
What am I gonna do?
The power transformer is my "Super MOT" invention - two
MOTs cut in half and welded together.
One primary coil, two secondary coils. Input is 1 1/2 KW, ran
directly from 120V 15A line.
Output is 4kV at 300-500mA (depending on the size of transformers used,
shunts removed, etc.)
Not bad for something found in the trash!
The condenser is a 40kV .06 mfd Maxwell Cap donated generously by Brian
Maxwell cap can be seen in the compartment to the right. This
thing is a beautiful monster of a cap!
Connections are with 3/8-16 bolts! In front of this the Super MOT
(to the right) would be installed.
In front the primary coil can be seen with the double throw single
pole knife switches (sent by Frank)
that would select which coil to power. The box was made from
4" oak flooring, two slats glues together and cut 90°.
The corners of the box are 3/4" square oak dowels. The
internal compartments are made from 2x4 and 2x6
unplaned oak planks from an old hardwood pallet. The Pancakes are
housed in their own box, actually cherry floor boards
previously recycled from a neighbour's project...
First light: Tesla/Oudin Coil
Secondary coil is 18" of 27 AWG on a 4.5" form.
6" diameter topload, with 1/16" rod for breakout point.
Output is approx 24" hot brush discharge.
Dischargers made for Pancakes. Secondary coil can be removed from
Primary on the uni-polar section
for low voltage d'Arsonval experiments. Powerful bipolar high
frequency arcs can be experimented with by
tapping this coil for experimental arc lighting, RF heating, etc.
These experiments were done on the same coil but only 450 watts of
power! Iron rod and RF arcs.
2 Series Stationary Spark Gap. 3/4" Tungsten, 6061-T6
Aluminum, 304 Stainless Steel.
7 Inch Pancake Coils, roughly 350 turns each.
I made an oak plywood over for this box, but need to do a bit more
trimming to make it fit.
The dischargers are made from bakelite tubing (canvas, donated by my
Dad), and some delrin. The center rods are old arc carbons,
copper clad, and the tops are brass knobs (temporarily). I need to
replace them with some proper spheres...
Regardless, they work. Are noisy and fairly evil arcs!
Discharge Balls are 11" apart
Suddenly I hear the theme song to
"Doofenshmirtz Evil, Incorporated"...
Left: Heat Lightning, a common occurrence
in South Florida.
Right: Another common occurrence here! Pidgie in her bouncy
seat! I need one of these too.
(C) Jeff Behary, 2010