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Re: My Primary Coil disaster



Original poster: "David Speck by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dspeck-at-relex-dot-com>

Patrick,
Copper has an annoying habit of work hardening -- the more you bend it,
the harder, and more brittle it becomes.  You can draw the temper of the
copper by heating it with a propane torch, and letting it cool slowly in
still air.  It is not necessary to achieve a red heat.  The annealed
tube will become buttery soft, allowing you to salvage the material you
have.  However, after a couple of bends, it will harden again.  

Try to arrange your work process to absolutely minimize the number of
times you bend any portion of the tube.  You can straighten the material
you have by annealing it, unrolling it as straight as you can make it,
annealing it again, then clamping one end in a well anchored vise, and
pulling hard on the other end with a big pair of vise grips.  You will
feel the copper stretch a bit, and virtually all the kinks and
irregularities will fall out of the material.  You will have to anneal
it again before you will be able to wind it successfully.  

I would suggest winding a close spaced coil, with each turn touching the
previous one, on a smooth cylinder of the appropriate size, and then
just stretching the coil along its axis to get the vertical spacing you
need.  I'd install coil supports with semicircular notches along the
outside edges from the inside of the coil, and let the natural rigidity
of the material keep the coil against the supports.  You can use nylon
tie wraps to hold the tube against the forms if necessary.  If you try
to pull the tube through a series of holes, like threading a shoelace,
you will never obtain a useable coil.

HTH

Dave

Tesla list wrote:
> 
> Original poster: "Patrick Bloofon by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <transactoid-at-home-dot-com>
> 
> Okay, this whole tesla coil thing has not been going my way. First, the wire
> breaks while winding the secondary (perhaps you've seen my post...). Now, my
> primary coil is all but an expensive hunk of copper.
> 
> I cut out and drilled 5 really nice offsets. I mounted them onto a
surface, and
> began feeding 1/4" copper tube through it, starting from the outside.  After
> about 5 loops, the tubing was so bent, twisted, and demented out of shape I
> couldn't go any further.  Loops were overlapping and the tube was flexed in
> multiple planes (ie, bent side to side as well as up and down...). I'll
try to
> get some pictures up so you can see this mess.
> 
> What I'd like to know is:
> 
> -Are there any good ways to re-bend or straigten the copper tubing when it is
> in such a state? (ie, is this thing salvagable)
> 
> -Seeing as my method of winding failed miserably, I'm guessing it's not how
> others do it. What is the "proper" way to wind it?
> 
> PS. This copper tube is extremely expensive where I live. The cheapest I
found
> was $30 for 50 feet.  Home Depot doesn't even carry it around here.
> 
> Thanks,
> "A very frustrated coiler",
> Patrick
>