RE: A photographic tutorial of Pancake Coil winding...with movies...(fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 21 Jun 2007 22:25:02 +0000
From: Jeff Behary <jeff_behary@xxxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: RE: A photographic tutorial of Pancake Coil winding...with
    movies...(fwd)

Hi Dave,

I'm not sure which coil you are referring to.  The coil shown at:
http://www.electrotherapymuseum.com/2007/9inPancake/index.htm
is a flat spiral secondary, 300 turns of 26 AWG, and a 2 1/2 turn primary of 
3/4" tall flat ribbon.
Its a Pancake 100%.  The discharger was made as a tube, and this will later 
have a plastic tube inserted over it to act as a discharger post..with a 
polished sphere on top.

If you were referring to the "multilayered" Pancake Coils shown, these are 
also still called "Pancake Coils".   In the small "Violet Ray" machines they 
appear taller than wider (which seems out of proportion for the term) with 
many more turns per layer, but the concept is the same.  The only difference 
is that the number of layers extended out only to an inch diameter instead 
of 7 or 8", etc.

To give you an example, the Campbell Electric X-Ray machines (first built in 
1901) used a Pancake Coil seen here:
Machine:
http://www.electrotherapymuseum.com/2006/CampbellE/index.htm
Unpotted Coil:
http://www.electrotherapymuseum.com/2006/DPancake/index.htm

The unpotted coil is from a near identical model that needs restoration.  I 
am going to photograph a cross section of this coil that we made (waterjet 
cut), it was actually burned out.  The person who last owned it virtually 
destroyed the entire apparatus.

The secondary coil contains approx. about 5 dozen layers of wire, each with 
around a dozen turns of wire.  The wire is space wound and heavily insulated 
between layers.

The coil I am constructing as a demo will produce a very similar spark a few 
inches longer than the Campbell but it will be a flat spiral instead of 
multi-layered to keep it simple..  It'll have 1/3 of the wire but will need 
a bit more current too.

The term "Pancake Coil" is curious.  It wasn't until the late teens and 
early 20s that we began seeing the Tesla Coil we think of today.  Most of 
the early machines and books in the US referred to Pancake coils as "Tesla 
Coils", and cylindrical coils as "Oudin Resonators".    The whole topic of a 
definition for Tesla Coil is a lengthy discussion in itself!   From 1891 
until the 1930s it changed completely every 5 years or so.  (Even the term 
"Oudin Resonator" changed about every decade)   In Europe the definitions 
were equally as confusing.  For the first 20 years or so in Europe a "Tesla 
Coil" referred to any coil where there wasn't a ground or common connection 
with a Primary coil, other than coupling!

Ol' Nikola didn't have the time to correct everyone.  But we did give 
everyone an earful in July 1919:
http://www.electrotherapymuseum.com/2006/ElectricalOscillators/index.htm

Noone has ever been able to tell me why the Nikola Tesla Museum chose to use 
different photos
when reproducing this article.  Have a look for yourself!
http://www.electrotherapymuseum.com/TeslaArchive/ElectricOscillators/index.htm

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


>From: David Thomson <dwt@xxxxxxxxxxxx>
>To: 'Tesla list' <tesla@xxxxxxxxxx>
>Subject: RE: A photographic tutorial of Pancake Coil winding...with
>     movies...(fwd)
>
>Hi Jeff,
>
>What you have here is a combination flat spiral and tall solenoid coil.
>Bart just pointed out that the metal pipe you are using acts like a
>waveguide, or third coil.  It would be more appropriate to call this a
>combination coil, rather than just a pancake coil.
>
>You should be able to change to quality of the spark output by changing the
>tube length.
>
>BTW, I like your winding technique with the roll of paper.  Have you
>considered using a roll of electrical tape?
>
>David W. Thomson
>
>
>

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