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What's the best way to secure the ends of single layer windings on a plastic form?

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jpsmith123

Tue Sept 29 2009, 09:52PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

Well I'm ready to wind my UHMW polyethylene tube coil formers with 30 gauge magnet wire, but I'm stuck on how to mechanically secure the windings on the form.

I've seen some people just using tape on the ends, but that doesn't seem like a very elegant solution to me.

I'm wondering, what do Tesla-coilers do? Is just varnishing the coil enough? Or maybe some kind of large diameter heat-shrink tubing?

doctor electrons

Tue Sept 29 2009, 10:09PM

Registered Member #2390 Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381

Here goes! If the plastic that you are using (the uhmw) is clear, than this probably wont be what you want, if it is not clear try this.
You can use a 12 X 12 piece of double sided tack paper around the form; as long as it does not extend beyond your winding length. The paper is very thin and non conductive obviously so there will be no issue with hindering performance. Or just wind it as tight as you can and use some painters tape to hold the loose ends. Then coat it with polycrylic or polyurethane. That will hold it tight until it dries than you can finish the loose parts easily. If you wind the coil at a cold temperature and secure the ends when you warm it up the coil will tighten, thats the best time to coat it. Good luck, hope this helps!!

jpsmith123

Tue Sept 29 2009, 10:42PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

Thanks for the reply. Yes, I guess I'm going to have to coat it with something.

Has anyone ever used any Krylon "Sprayon" insulating varnish, as in the following link, and if so how did you like it?

Proud Mary

Tue Sept 29 2009, 10:55PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

I use nylon nuts and bolts with a double solder tag as anchors in that kind of work, or even a ceramic stand-off with a nut on the inside of the tube.

aonomus

Tue Sept 29 2009, 11:18PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

I've used Minwax (I think) polyurethane varnish to coat the coils, and for the end terminations I used a nylon bolt at the base to connect a terminal up. Probably not the best, but not the worst solution.

jpsmith123

Wed Sept 30 2009, 04:01AM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

Harry wrote ...

I use nylon nuts and bolts with a double solder tag as anchors in that kind of work, or even a ceramic stand-off with a nut on the inside of the tube.

Hello Harry,

Plastic nuts and bolts were one of the first things that crossed my mind...and I'll probably end up using them, but I'm hesitating a little bit as I don't like the idea of weakening the insulating system somewhat by drilling through the coil former. If it were an air-core situation of course it wouldn't matter, but with the ferrite core, grounded-foil shield and only some thin PP insulating film inside, I had hoped to preserve the integrity of the thick plastic coil former.

Maybe I can rig up some kind of plastic clamp or something and secure the wire to it.

...

Wed Sept 30 2009, 06:53AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

I just apply a patch of superglue at the end (I try to get 10 windings or so at the top/bottom and sometimes in the middle for good luck) before I apply polyurethane, and as long as you don't yank on the wire to hard it holds just fine. it also give the added benefit that if you do yank the wire to hard, you just unwind one turn

It also doesn't leave any sharp ends to cause bad e-field gradients.

Proud Mary

Wed Sept 30 2009, 01:29PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

jpsmith123 wrote ...

Harry wrote ...

I use nylon nuts and bolts with a double solder tag as anchors in that kind of work, or even a ceramic stand-off with a nut on the inside of the tube.

You can pull the larger cable ties up pretty hard with pliers. I think sometimes it's helpful to have what I'll call an initial anchor, which can hold down the end temporarily whilst glue or varnish dries and all is made safe.

Nicko

Wed Sept 30 2009, 04:17PM

Registered Member #1334 Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615

I'm a bit of a beginner at all this HV stuff, but I use that nice adhesive copper foil to place a small patch (1cm x 1cm) at the end of the winding to act as a strain relief and solder pad - terminate the winding on that and solder the flying leads to the pads also...

Proud Mary

Wed Sept 30 2009, 05:25PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Nicko wrote ...

I'm a bit of a beginner at all this HV stuff, but I use that nice adhesive copper foil to place a small patch (1cm x 1cm) at the end of the winding to act as a strain relief and solder pad - terminate the winding on that and solder the flying leads to the pads also...

That would probably be good for fine windings Nicko, but when you get onto thicker wires that you have to straighten as you turn, I'd suggest a rather stronger anchor at the end.

I've been winding some inductors for a Pulse Forming Line using 3mm enamelled copper wire, (11 SWG) and holding down the end and getting a straight pull is no easy matter for the man with ten thumbs, even though there are not many turns.

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