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Re: 16" Pancake Coil discharge photos

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Jeff,
Nice spark pics for a flat coil (some of the best I've ever seen)! As I've been contemplating the Tesla design, I've been observing as many photos as possible of the large flat coil. Oddly enough, the coil is only 86 or 87 turns of large wire (cotton insulation) about #8. The spacing between turns edge to edge to about .37 with a self resonant frequency at 200kHz and what must be a very high Q. 
I've started collecting runners but not sure I will take the Tesla 
route as far as wire size (it will look very Tesla, but will have 
some technology updates). I was figuring on #18 with about .25" 
spacing which is nearly 1/2 Fres of Tesla's coil and 3/4 the Q (but 
still very high). Tesla actually bored out the runners to accept the 
cotton winding. It's hard to detail the securement, but appears to be 
a bonding of some type. I will go a different route. My coupling will 
be very high (0.5 or greater) and without any chance of flashover. 
The secondary winding will be a true test of patience. I really want 
to strive for nice curves and not some octagonal winding (easier said 
than done).

It appears I'm free now to start building this coil as I just 
finished a coil for a neighbor/friend.

Take care,
Bart

Tesla list wrote:


Original poster: "Jeff Behary" <jeff_behary@xxxxxxxxxxx>

Bart,


The largest flat spiral coils I've made were 24" and 48" diameters - 
very different though!

The 24" coil used 1mm thick x 25mm PVC "edgebanding" for insulation 
between the turns.  It used 30 AWG wire.  I tested it at 7500V .032 
mfd with a 5-series tungsten spark gap for approx. 4 seconds - I got 
an amazing 24"+ spark from the top when the whole coil died 
instantly from an internal short due to the PVC interleaves not 
giving a sufficient insulation.  It was fun while it lasted.

The 48" coil was originally a primary coil for a 10.75" OD 3 foot 
tall secondary coil.  (Odd size, but worked well!).  The coil was 
48" OD 12" ID with around 25 turns of solid 10 AWG wire.  For the 
flat experiment I used the outer turn as the primary and the inner 
turns as the secondary.  I was getting powerful 4" sparks from a 
simple 15kV 30mA neon and a two-quart leyden jar.  This was years 
before I started making Pancakes...

I also have two 18" diameter coils with 1" IDs wound with 10 AWG 
parallel stranded wire, asbestos coating (?or something similar?).
These were more for demonstrating inductive effects...there is a 
frenchman W. H. Guilleminot that did a lot of research in flat coils.

He wrote a few books in the 20s.
I have one translation that I have to scan for the site...


I have another 18" diameter flat coil wound with 21 AWG wire.  It 
gives 8" arcs, but works better as a P:S for my Pancake magnifier 
system.  One day I attached a wire leading to a 5" diameter x 24" 
tall helix coil (close wound 24 AWG) and saw 4 foot arcs from the 
top to the ceiling of our spare bedroom!  That was a surprise.

http://www.electrotherapymuseum.com/2006/18inPancake/index.htm

http://www.electrotherapymuseum.com/Forgotten_Tesla_Technologies/Magnifier_Pancake_System/index.htm 


Tonight I finished a replacement coil for the floor model demo unit 
- it is about 14" in diameter, and this time cast it into a glass 
lamp shade so that I could see all of the windings were permeated 
completely.  I used a mixture of linseed oil and beeswax that 
hardened to a consistency of peanut butter.
In initial testing I was getting nice crackling 6" sparks and no 
signs of breakdown whatsoever.

For more on Pancake Coils in general, check out these pages:
http://www.electrotherapymuseum.com/2006/PancakeCoils.htm


There is a lot of general information, but I haven't updated it with 
coils made in the last months...

Jeff Behary, c/o
The Turn Of The Century Electrotherapy Museum
http://www.electrotherapymuseum.com

_