To buy or make a coil winder?

[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!