Re: RE- Secondary wire & insu

Subject:  Re: RE- Secondary wire & insu
  Date:  Fri, 6 Jun 1997 03:35:01 +0500
  From:  "Alfred A. Skrocki" <alfred.skrocki-at-cybernetworking-dot-com>
    To:  Tesla List <tesla-at-pupman-dot-com>

oN Wed, 04 Jun 1997 08:07:00 GMT Robert Michaels
<robert.michaels-at-online.sme-dot-org> WROTE;

>         -- Making a space-wound coil using a closed loop (as a
>                 spacer) with a weight attached is effective, but I'd
>                 scarcely say it is "easily" done.  In fact it precludes
>                 any machine or power-driven winding of a coil.

Before I got my lathe I wound all my coils by hand and I never found 
any difficulty in using a closed loop with a weight as a spacer, but 
then I learned how to cut threads bare handed with a file so I guess
it's a matter of ones background.

>                 In my experience, the closed, weighted loop is best
>                 made itself of magnet wire.

That I agree on! The best is to use the same wire your winding the 
coil with. I also feel it's important to have a sticky base to wind 
on so the spacing wont be for nil! I like thin double sided tape to
give the coil form some tackyness, I usualy lay it on length wise on 
the form and space them every 2 inches around the form.

>         -- To compare wire enamels of 1907 (or whenever) to those of
>                 1997 is truly to compare persimmons and mangos.
>                 "Back then" they were little more than furniture
>                 varnish, their high-frequency electrical characteristics
>                 were ...?!?!?.   Today, wire enamels are specially
>                 designed and formulated for optimal electrical
>                 characteristics; it's a whole technology in itself.

I agree that for 'normal' use todays enamels are far supperior to 
those of 1907, but in a Tesla coil it's totaly different! I would 
still have to agree with Stanley Curtis and say there is NO 
insulation aside from distance that will insulate the high frequency
high voltage. I still have several pounds of double cotton coated
wire and have wound identical coils with it and present day enamel
coated wire and the secondaries wound with double cotton coated wire
perform much better than the otherwise indentical coil wound with 
MODERN enamels. Since the cotton is known to be a poorer insultation 
I can only assume the supperior performance is due to the cotton 
holding more of the polyurethane insulation I coat all my coils with.

>         -- In all but the highest powered Tesla coils, the volts-per-
>                 turn of the secondary is apt to be below the breakdown
>                 voltage of the wire enamel.
>                 Consider:  A 500-Kv coil having a thousand turns
>                            in it's secondary  (Love those round num-
>                            bers!).   That's 500-volts/turn.

Huh! Accept for my very first coil (somewhat of a disapointment) I
NEVER use more than 600 turns on a secondary and of lately I a 
getting better output with no more than 300 turns! This means my 
coils would require a bit over 3 times the dialectric strength in the 
wire insulation than your example.

>                         Which means, the wire enamel must withstand
>                         250-volts. Not a major challenge for today's
>                         wire enamels.   Comprendo, compadre - 250-v.?

In the comparasin to the coils I wind I would need over 1700 Volts of 
insulation and I haven't found any enamel wire that holds up at that 
voltage to R.F., this is why I space my turns otherwise my 
secondaries would all short out the first time I fire them up!

>                         (Hint: Adjacent turns have  =two=  layers of
>                         wire enamel between them, one on each of the
>                         two wires:  500/2 = 250-volts. )

Again comparing that to y typical coils would still require over 800 
volts insulation and that is expensive in thin coatings!

>         This is not to say Mr. Skrocki (or Mr. Curtis) is wrong.  Not
>         at all.  (If nothing else, DCC wire really looks cool when
>         wound into a coil -- and I favor gutta percha myself! - ooohh!).
>         I'm just here to say that wholesale dismissal of the
>         entire field of modern wire enamels may be a bit hasty.
>         (That, and use a weighted loop of  =wire=  when space-winding
>         that coil).

I wasn't making a wholesale dismissal of modern enamel insulation, I 
was just pointing out that with the more efficient coils being built
there is no commercialy available insulation that will hold up with 
out spacing the turns and personaly in comparing identical 
secondaries with bare wire, modern enamel and double cotton coated
(all being coated with polyurethane when done) the coils wound 
with double cotton coated wire perform better ie. longer discharge, 
thicker sparks and more branching.


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                           Alfred A. Skrocki
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