Re: Winding secondaries

["Malcolm Watts" <M.J.Watts-at-massey.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Ken,
        I spacewound a largish secondary in the following 
manner:

     I bifilar wound same gauge wire and turned the 10" form 
over by hand. I had endcaps with dowels fitted to allow 
suspension of the form between two chairs (in the crooks) as I 
wound. With the finished winding secured at both ends, I stood 
the form upright and let one of the wires go from the top. It 
self-unwound partwat down the form. I then sprayed the now 
spaced portion of the winding with electrical varnish and let 
it dry to touch before getting rid of the unwound wire and 
doing the same trick again for the next portion.
    The next coil I spacewind will have the spacing wire wound 
back onto the original reel rather than cut into pieces. It 
will be trickier to avoid disturbing the spacing however.

On 4 Jul 00, at 16:58, Kennan C Herrick wrote:

> I'm in the process of building a couple of conventional secondaries (as
> contrasted with my existing "pie"-wound one) in order to compare their
> effectiveness using my solid-state primary apparatus.  Thought I'd ask
> around as to ways in which to do this.
> 
> I am using Sonotubes--one 10" and one 12"--and I intend to wind 22 ga.
> (0.025", 0.6 mm dia.) onto the 10" and 18 ga. (0.06", 1.5 mm dia.) onto
> the 12".  I intend to wind the wire over double-sided sticky-tape
> (polypropylene cloth with rubber-resin adhesive) to keep it secure.  I've
> already contrived end-closures and intermediate stiffeners for the
> Sonotubes and I have coated them with a water-repellant that I'm pretty
> sure will not overly reduce the adhesion of the tape I plan to use.
> 
> I'll probably wind the 22 ga. without spacing as it's
> enamel-covered--although I have some doubts about that because excessive
> volts/turn may well punch through that minimal spacing.  But my 18 ga. is
> bare and so I will need spacing for it.

I don't think you need to worry. I've tested polyesterimide 
wire to 4kV between two touching pieces for that gauge or 
thereabouts using a high frequency supply and I'm pretty sure 
TC voltages rarely if ever hit 1kV/turn for the size range you 
are talking about.   

> I have made a rudimentary winding machine but the wire will be
> hand-guided during the winding process.
> 
> I have in mind two ways to attain spacing with the 18 ga. wire:
> 
> 1.  Wind it simultaneously with 0.028"-dia. monofilament fishline,
> providing about 0.025" or so spacing.  Not having ever done this, I see
> it as a bit of a chore, to say the least.
> 
> 2.  Wind on first, a polypropylene twine of about 0.08" dia., to form a
> spiral track.  Then on top of that, wind on the 18 ga. wire,
> giving--again--a spacing of about 0.025".  I forsee that method as being
> somewhat easier since only one wind at a time need be attended to.  I
> would expect the twine to be held sufficiently well in place by the
> sticky-tape so it would not be displaced by the subsequent wire-winding. 
> I envision the slight springiness of the twine as being advantageous in
> keeping the wire turns tight, over time.
> 
> I'm wary of gluing the wire in place with subsequently-applied varnish or
> the like:  I feel that anything organic through which a spark might pass
> is inevitably going to leave a carbon track that will promote subsequent
> corona or worse.
> 
> I've not gotten to the point yet where I will try out the two methods, 
> so I'm very interested in receiving comments anyone may have as to what I
> have in mind.  Any advice derived from sad experience, any suggestions as
> to better ways to do it, etc. would be most welcome.
> 
> Respond via the List so that all & sundry may be enlightened!
> 
> Ken Herrick

I've considered twine and had a preliminary go using it but 
don't like the results. Fishing trace might be useful if you 
do the coil in sections, removing the trace and varnishing the 
winding to hopd it as you go. I wouldn't leave the spacer in 
there either.

Regards,
Malcolm