RE: Secondary winding frustration

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

Original poster: "John H. Couture" <couturejh-at-mgte-dot-com> 


Resistance is normally not an important parameter in the frequency equation,
however, it can become a factor with TC's that have many secondary turns.
The complete frequency equation is

      Fr = (1/pi)(sqrt((1/LC)-(R^2/4L^2))

It is obvious from this equation that resistance is a factor with long wire
lengths. In fact as the resistance is increased the frequency decreases and
approches zero as shown in my TC Construction Guide. One of my early TC
computer programs took this limitation into consideration. As the secondary
turns were increased the resonant frequency was reduced.

John Couture

-----------------------------------


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Friday, January 02, 2004 10:58 PM
To: tesla-at-pupman-dot-com
Subject: Secondary winding frustration


Original poster: "RIAA/MPAA's Worst Nightmare" <mike.marcum-at-zoomtown-dot-com>

In the pursuit of ever longer sparks (and for a challenge) I'm building a
hand held TC (a la BH-10 vacuum tester only bigger) with a high surge
impedence to lower sync rotary gap losses. Realized really high
voltages/low currents (30kv+ 10mA) are out of the question for a portable
handheld unit due to weight, so I decided to canibalize 1 of my other coils
for its 120-7500/40 nst's. Anyway, I have a winding jig rigged that's
adjustable from from ~10-120 rpm assuming I don't go over the 90 vdc rating
of the motor. I'm attemping to wind a 3.75 od acrylic tube with 19" of 36
awg (175 tpi/~3300 turns according to my wire table). I was going to use
39awg, but that would have made the Fres down to less than 87 khz with my
8" sphere (want it to where it barely breaks out or doesn't without a
breakout point, hope that's big enough) and out of range of the primary.
Anyway how is this stuff kept from breaking when winding? It's hard to find
tune the tension to where it's tight but not stretching. I don't want a
solder joint (or lots of them) in the middle of the coil so every time it
breaks I have to start over (aggravating if this happens with over 1000
turns already on it). I'm thinking of adding another moter to unwind the
roll (fresh so weighs 10.5 lbs and has quite a bit of inertia). I can't
imagine how a commercial winding machine does a clean job of this. Any
ideas/suggestions appreciated. Up till now I've never dealt with anything
smaller than 30awg.