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I've been winding a guitar pickup and occasionally there will be knots in the thread of enameled wire from my spool. Some of them are loose enough that I can untie them, but there are some really tight ones that if I were to try and pull the ends apart, the thread would break and I would have to start my process over.

My assumption is that, given that a pickup is usually a couple thousand feet of wire, that one or two few-inch knots in the loop are negligible - that they would add some unwanted resistance and/or leakage current(?) but wouldn't be enough to impede current from driving through the loop when the guitar strings are plucked. But I'm not actually sure.

What are the effects of having knots in a solenoid or wire loop?

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  • \$\begingroup\$ I'm just wondering how you manage to tie wire in a knot while winding a spool unless your knot isn't a knot and is a looped kink. \$\endgroup\$ – DKNguyen Sep 7 '20 at 14:26
  • \$\begingroup\$ @DKNguyen I'd been wondering that myself. It's almost like if I unwind too much wire at a time and don't leave enough tension it forms its own loops that get stuck through each other once I tug the wire again \$\endgroup\$ – Nick Nagy Sep 7 '20 at 14:33
  • \$\begingroup\$ Am going to call it a "kink" rather than "knot" (a knot must be untied, a kink can be straightened). The problem with copper wire is work-hardening. Un-kinking work-hardens them more - the wire gets brittle and prone to breaking. Murphy says, "a multi-layer winding will break exactly where the buried wire emerges from the spindle - unrepairable". Been there more than once. \$\endgroup\$ – glen_geek Sep 7 '20 at 15:15
  • \$\begingroup\$ I imagine it is because the wire is being twisted as it is wound on. It might help to unwind a lot of wire at a time but keep tension near the winding point so the wire has slack to rotate itself out of torsion as it comes off t he reel and is wound on, and feel/check rotation/twist of the wire as you go. If it were flat wire or square it would be super obvious. \$\endgroup\$ – DKNguyen Sep 7 '20 at 15:16
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The radius of curvature on the knots is very tight so it's possible the insulation is damaged. The insulation has to be damaged in two places for there to be a short so you're probably okay, but it's not ideal.

Do not pull wire off the edge of the spool, unwind the spool, or you'll get a lot of kinks.

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  • \$\begingroup\$ Yeah, it was a sloppy winding job on my part. If this pickup ends up failing I will definitely be smarter about my re-attempt. \$\endgroup\$ – Nick Nagy Sep 7 '20 at 15:10
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My assumption is that, given that a pickup is usually a couple thousand feet of wire, that one or two few-inch knots in the loop are negligible

The knots will have no-appreciable effect given what you have described. They are more of an annoyance to getting a smoothly wound coil but that's just a build-issue and won't affect performance.

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  • \$\begingroup\$ Thank you! That was my hunch but would have been disappointed finding out I'm wrong the hard way. Ironically, about 10 minutes ago I snapped the wire by mistake anyways... whoops. \$\endgroup\$ – Nick Nagy Sep 7 '20 at 15:07
  • \$\begingroup\$ This isn't really a complete conclusion. While a knot's tiny reverse length has no real effect, consider that the mechanical disturbance is a great place for insulation failure leading to shorted turns, wire breakage, and will disrupt the form of the coil overall. You may have enough turns that a short is survivable, and the disruption of form may go unnoticed... but really, knots are best avoided. Try putting the spool on a holder. \$\endgroup\$ – Chris Stratton Sep 7 '20 at 15:08
  • \$\begingroup\$ Ah, thanks! Yeah, it was a sloppy job on my part. Looking into spool holders right now. \$\endgroup\$ – Nick Nagy Sep 7 '20 at 15:12

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