To buy or make a coil winder?

[SurreyNick]

As I suspected a number of the old 1920s/1930s transformers I have don't work. The thing is they're really nice and, if affordable, I'd like to rewind them. I'm guessing it'll be cheaper for me to do them myself than commission someone to do them for me, especially if I then decide to sell them on. The question is, do these cheap (see pic) Chinese-made coil winders work OK and are they fit for purpose? At £20 including P&P (Amazon UK) I probably couldn't make one, such as Yorkie's nice homebrew jobbie, any cheaper.

Does anyone have any experience of these machines? The one and only review wasn't complimentary!

Thanks

Nick

   

[Alan Douglas]

For that price you couldn't go wrong but I surely wouldn't want to wind an audio interstage transformer that way, with (say) 10,000 turns on the secondary.  A foot-controlled high-speed winder is far better; you'll definitely wish you had both hands free to feed the wire.

[Radio Fixer]

I agree with Alan, having wound interface transformers with a total of 15,000 turns. No way would you want to do this with a hand winder. And you seem mostly interested in radios from the late 20's to early 30's and these are the most likely transformers to need a coil winder for. This is simply because the wire gauges used are very fine so 'green spotting' is much more likely to O/C the wire.

'Green spotting' maybe caused by electrolytic action according to some and is more common in anode windings than grids so I'm told.

Gary

[SurreyNick]

OK guys, thanks. I will take your advice and avoid a hand cranked winder. Which means of course that I will have to make one.
Now, where did I put that design of Yorkie's?......
Nick

[Yorkie]

I think the one that you’re referring to Nick at £19.99 is this one, which is made of plastic and has two iffy reviews:

http://www.amazon.co.uk/Merry-Tools-HK-T..._4?ie=UTF8&qid=1437037837&sr=8-4&keywords=coil+winder

This one at £29.99 looks to be made of metal. Can be hand or motor driven up to 2,000 RPM. Two ratios 1:8 and 1:5. Counter goes to 99,999. Max coil sizes 150mm diam, 100mm long:

http://www.amazon.co.uk/990723A-Winding-..._2?ie=UTF8&qid=1437037837&sr=8-2&keywords=coil+winder

Looks quite a good bit of kit and has two five-star reviews.

As Gary says, the wire for inter-valve transformers is exceedingly fine and most transformers have fallen victim to green spot corrosion. Quite a challenge to rewind, but Gary built a winder to do that, which was published in two parts in the BVWS Bulletin some years ago under the heading ‘Making a Coil Winder (mostly from the junk box)’, which I shamelessly copied and also had published I the Bulletin. Gary adapted a battery powered drill to drive his winder – I used a sewing machine motor and controller.

One of the challenges is the feed reel arrangements. You need a smooth feed, with the wire very slightly under tension so that it doesn’t ‘whip’ or go slack at any point, and the distance from the feed reel to the coil former needs to be say 45 cms or so, so that the angle at which the wire traverses across the coil from the feed reel isn’t too acute. As to guiding the wire onto the coil, I  used two shafts with pulleys and a handle to move the wire back and forth to try to get the layers as even as possible, but really, the wire has a mind of its own, and all you can hope for is to wind as much wire as can be accommodated onto the former as neatly as you can without and breaks, and hope that it comes as close as you need it to the resistance required. In my case, I was lucky – it was a field coil with about 2kms of wire and need to be 2,000 Ohms. It was spot on, but given that it wasn’t a transformer, the issue of ratios didn’t arise, so a bit of leeway wouldn’t have mattered.

It's an intriguing topic which often crops up, and those that have the ability and inclination have devised complex winders programmed by  PICs to traverse back and forth, laying turns side by side, taking account of the wire gauge. Coincidentally, there was such a winder described in an 11-page article in the Summer 2015 BVWS Bulletin - a marvellous affair with a control board and unit with twenty push-buttons to program the number of turns, wire gauge, coil length etc. I found the article a little confusing - not just because of the complexity, but that it was about an original hand-cranked winder using one of the mechanisms you referred to, and a newly designed  winder - 35 pictures in all and two circuits.  A great deal of thought, ingenuity and commitment, which goes way beyond my overall capabilities and needs, but all very fascinating, and deserving of much credit to the designer. I do marvel at the ingenuity and inventiveness of others who are rather higher up the food chain then Me!

[SurreyNick]

Actually David, I'm hunting around for your homebrew design as I thought that might suffice for my needs
Nick

[Alan Douglas]

Regarding the feed, I have always put the supply spool on the floor between my feet and taken the wire over the top flange. There's no inertia to worry about. The upper flange does need to be smooth enough to not snag the wire. For large (ten-pound) spools I have a urethane-foam sleeve that is a loose fit around the flange, to provide just a little drag to keep the wire from tangling.

[Radio Fixer]

David said: "Gary built a winder .... which I shamelessly copied and also had published in the Bulletin."

But yours was much better built than mine, partly as its always easier to improve something but also because you are better and do a neater job on mechanics than me. So copy that one Surrey. N.

Gary

[Refugee]

I have a coil winder under construction that is based on a Kenwood chef food mixer.
The counter is electronic and in the event of a power cut will loose the count. It makes up for this as it has a relay that closes at a preset count giving an auto stop feature.

[SurreyNick]

....So copy that one Surrey. N.
Gary

I will Gary....if I can just find the damn instructions! I'm sure David gave them to me some months ago.
Aargh! Will someone please buy my house so I can get organised again.
Nick