Re: Secondary winding frustration: how to do it

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

Original poster: "Scott Hanson" <huil888-at-surfside-dot-net> 

Mike -

A hand-held coil with a synch rotary gap? I'd be interested to hear more
design details. Are you proposing that the entire coil assembly (HV
transformer, tank cap, rotary gap, and primary/secondary coils) is small
enough to be hand held? Powered via an extension cord? Please provide a more
detailed description, and post photos during construction. When do you
anticipate having it running?  Personally, I can't see any benefit to using
#39 AWG wire in a secondary of this size, but if your design calculations
indicate that this is the optimum for your system, press on.

As to your winding problem, feed spool inertia is too great a problem with
smaller gage wire (<#29 AWG), especially if you are working with a 7.5 or 10
Lb spool. Instead of trying to get the spool to rotate, simply set the spool
upright below your winding jig, and feed the wire up through the center of a
plastic funnel that sits on top of the spool. The large end of the funnel
needs to be slightly larger than the flange on the spool. Now the funnel
pinches the wire against the spool flange, and the weight of the funnel
controls winding tension. Make sure that there are no burrs or nicks on the
edge of the spool flange that might catch the wire. If necessary, you can
tape small weights to the funnel to adjust tension. There must be some
tension maintained on smaller gage wire at all times, or it will kink
because of the 'twist" imparted to the wire as every turn exits the spool.

On another subject, you previously posted (10-4-03) some information on a
Tesla coil you had made using a 90kV, 270ma  X-ray transformer charging a
bank of five-hundred (500) Cornell Dubilier model 943 capacitors (5 strings
of 100 capacitors). I am unaware of anyone else ever successfully using 90kV
in a Tesla coil tank circuit, and would be very interested if you could
provide a detailed description of the entire system, its performance and the
types of problems you encountered during debugging this system. Of course, a
few photographs would be worth a lot of verbiage.

Regards,
Scott Hanson

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, January 02, 2004 7:57 PM
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.
 >
 >
 >
 > ---
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 >
 >