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Method to secure windings of PI coil

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  • Method to secure windings of PI coil

    Hey all,

    I've just dreamed up a rather brutal method of securing PI coil windings (before placing into a housing) without using any adhesives/resins, therefore avoiding any additional capacitance.

    Recently I've been winding up a bunch of coils using litz wire - enamelled copper served in silk. When hitting the wire end with a 350C iron, the enamel and the silk quickly melts off at the solder point - however, just up a little from the solder joint, the silk seems to melt and amalgamate, creating a very rigid casing around the wire - and if two sections of wire are contacting when this happens, the wires seem to become fastened together with the melted silk. The enamel below is still perfectly intact when this occurs.

    My suggestion here is to wind up a coil and hit it with the SMD blower to see if I can get all of the individual windings to meld together, and form a rigid coil without any adhesives/resins. I figure that if using the silk that's already around the wire to fasten it, then I wouldn't be introducing any more capacitance than the silk was already introducing in the first place, hopefully achieving the same rigid effect as coating it in resin - giving it a longer service life, and reducing wire movement/noise when the coil is bumped on a tree or rock. I expect this would work well on flat/spiral, spiderweb and basket coils, a mono bundle coil might be a bit thick.

    Has anyone attempted this?

    Would the silk's dielectric properties change once melted and prove my whole idea wrong?

    If this is all new to everyone, I'll be happy to sacrifice some litz to give it a try. I'm just nearing the end of my spool and don't particularly want to waste it if someone's already tried this and failed before me!

    Looking forward to your thoughts!

  • #2
    Magnet wire is available with an additional "bonding coat" that can be used to fuse the wire bundle together in a similar way. The bond coat can be activated with either alcohol or heat. Heat activation is usually accomplished by running a high current through the coil and the wire heats up and melts the bond coat without affecting the insulation coat. This way you can bond even thick bundles. The current is controlled by monitoring the delta resistance of the coil which tells you the temperature. Probably the same technique will work on the silk.

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    • #3
      Originally posted by Carl-NC View Post
      Heat activation is usually accomplished by running a high current through the coil and the wire heats up and melts the bond coat without affecting the insulation coat.
      Thanks Carl, that sounds like a fantastic method.

      I'll do a test with the hot air gun, and another by heating the wires electrically. The only issue I can foresee with electrical heating is that the flying ends of the coil wire will also be heated and encased in the melted silk, removing all flexibility. I'll need to ensure everything is positioned perfectly for attaching the coax prior to applying current.
      Last edited by fo0bar; 12-20-2020, 07:01 AM. Reason: word

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