spacewinding techniques..RE: Designing BIG Secondary Coil

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Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

At 11:58 AM 9/9/2002 -0600, you wrote:
>Original poster: "Malcolm Watts by way of Terry Fritz 
><twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
>
>
>
> > How are you accomplishing space winding?
>
>Bifilar wind two lengths of the same gauge wire. Fix at both ends.
>Stand the coil upright, then let one of the lengths go. It neatly
>unwinds/unpeels itself to part-way down leaving the spaced wire
>intact. Some spray varnish applied to the exposed winding holds it,
>then you can snip another length and let it unravel. I ended up with
>a bundle of various lengths at the base of the coil, some of which I
>re-used for other projects. The ideal would be to unwind the spacing
>wire back onto a reel but great care would be needed not to disturb
>the wanted winding.
>      I am planning to wind two others, one 10", the other 12"
>sometime in the future using much the same techniques. This time they
>will be using thinwall pipe left over from a construction project at
>work.

A cheaper approach to the bifilar winding technique is to use nylon 
monofilament fishing line as the second "wire" for spacing.  You can just 
leave it on when you are done, or not, depending on your feelings about its 
RF and HV properties (nylon IS hygroscopic..) .  You can get cheap 
monofilament in a variety of sizes to allow customizing the interwinding 
spacing.  There are also all manner of less expensive wires to use in a 
sacrificial way than copper.. iron baling wire springs to mind.

Now, someone just has to turn up a "pounds test" to "monofilament diameter" 
table or equation, and we're all set.

"Weedwhacker" cable might also work as a spacer, but I suspect that it's 
more expensive than fishing line (although... in a big spool, maybe not). 
Some of the more sophisticated (expensive?..I haven't checked) weedwhacker 
line is square or triangular in cross section, which might make for nicer 
windings.  The stuff should be "real cheap" because it doesn't cost any 
more than round monofilament to produce, and is probably less well quality 
controlled (nobody is going to whine about losing the big fish or the 
smoothness with which the line comes off the spool).