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Re: My Primary Coil disaster



Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Bob Bozarth by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jbdetails-at-prodigy-dot-net>
> 
>     Due to similar problems I'm sure happen to many "coilers", does anybody
> out there know how to anneal copper? I've seen aluminum annealed using
> acetylene, but not sure of the process. I noticed in an earlier post to this
> thread Ed Phillips said something about annealing copper with a torch.
> Personally, I would be really interested to hear some details on the
> subject. Any help there Ed?
>     Thanks,
>         Bob Bozarth
>         Experimenter

	Annealing aluminum is a complicated process which depends on the alloy,
and I don't know anything about it except that the "big boys" do it with
time-phased heating and quenching.  In some cases at least annealed
aluminum aircraft rivets are kept cooled by liquid Nitrogen prior to
use.  Cooling copper simply involves heating to red heat and then
cooling.  In the process an oxide coating will form which can sometimes
be cleaned up pretty well by simply dunking the red hot metal in water. 
Two problems with long lengths of copper tubing.  First, you can't heat
them with a torch except in a limited area and there is a problem anyway
with heat conduction away from the area you are trying to heat.  I have
found an oxy/acetylene torch to work better because of its higher flame
temperature.  Second problem is getting rid of the scale which forms
without bending the tube enough to start work hardening it again. 
Chemical means (hydrochloric acid or even the stuff often sold as
'concrete cleaner') will eventually dissolve the scale but leave the
surface a kind of soft pink velvet.  That can be fixed nicely by
polishing with fine steel wool, if you take care not to bend it very
much.  I have used this process in winding "radio coils", usually only
10 turns or so on a form typically 3" to 5" diameter, where the length
of tubing to be handled isn't too great.  For a TC primary it would be a
harder deal because of the much greater length.

	For almost any coil wound with large diameter conductors, whether solid
or tube, the idea of winding the stuff around a form first and then
forming your coil later makes life a lot simpler.  I usually use a form
enough smaller in diameter that when the stuff expands it just slips on
the real form with only slight additional expansion.

Ed