RE: (Fwd) RE: Longitudinal Waves

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "David Thomson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>

Hi Al,

I did calculations on the spiral coil before I wound my first one.
Independently I discovered the maximum inductance for a given length of wire
for a spiral coil would have the average radius at 4/3 of the width of one
side.  I was about to wind such a coil when I began noticing that every
single one of Tesla's spiral coils both in photos and in illustrations, were
wound from the center out, with no inner radius.

I will still wind a maximum inductance coil sometime to see what effects it
has.  Thanks for bringing this up.

Dave

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Tuesday, February 12, 2002 9:36 PM
To: tesla-at-pupman-dot-com
Subject: Re: (Fwd) RE: Longitudinal Waves


Original poster: "Alfred Erpel by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<alfred-at-erpel-dot-com>



Howdy All,


    Duane A. Bylund shows in his book Modern Tesla Coil Theory published in
1990 on page 50-53, for close wound pancake coils,  in order to maximize the
inductance, you should wind a pancake whose inside radius is equal to
.466666 times the outside radius. A pancake coil with any other ratio can
give you more inductance but at diminishing returns. For example, if you
start with wanting a pancake coil with outside radius of 7 inches then your
inside radius should be 3.26 (i.e. 7*.466666). A simple formula could be
developed to calculate the optimal radii based on wire length and wire
diameter. Other formulas could be derived based on desired inductance, etc.

Possibly winding a pancake secondary coil to these specifications would
sharpen up any effects you may observe. I am speaking instictively here
only, without any basis in theory, but it seems to me that winding a pancake
all the way to a point  in the center (even though it looks cool) will
dampen or "sponge" out effects because you are so far away from the ratio of
maximum inductance for minimum conductor.

Regards,

Al Erpel