'Universal Coil Winding Machine' (David J Gingery)

[David G4EBT]

There have been posts recently about simple coil winding, and I thought I'd mention again the little hand-operated machine designed many years ago by David J Gingery for making 'wave wound' coils, which might be of interest to a few on the forum. I'd mentioned my intention to make one of these simple machines in a thread back in 2010 (now closed):

https://www.vintage-radio.net/forum/...ad.php?t=52988

I did make the machine, as I know others on the forum have. It didn't cost me anything other than 67p for the Tesco calculator to count the turns - everything else was from my scrap-box. But as I mentioned in the earlier thread, the downfall is the need to use Litz wire as enamelled wire won't form the wave-wound turns correctly - the turns just slip off. Litz is prohibitively expensive, and so for that matter, is cotton covered wire, and Litz has the added problem of difficulty in making soldered joints unless it's solderable. I did however get hold of a reel of 45 SWG 'cotton' covered enamelled wire, (though the cotton isn't cotton as such because when the soldering iron is applied to it, it dissolves and enables the wire to be tinned).

My original intention was to wind a replica Repanco DRR2 coil to build the 1959 BBC Focus Radio out of curiosity, but instead, I wound the coil by hand, having borrowed a DRR2 to check the inductances. (It came with a poor diagram in which the sketch gave a misleading impression of the size of the various windings). I built the 'Focus' which confirmed what I'd suspected - basically, it's a crystal set with a two transistor amplifier tagged on, so while it had sufficient volume for headphones, it had extremely poor selectivity. As the BBC layout was very untidy I designed and etched a PCB for it. The coil did it's job fine, but I must say that any lad who bought the bits out of his pocket money back in 1959 - if he succeeded in building it and getting it to work from the untidy instructions - would have been greatly disappointed, and far from being encouraged to get into electronics, would I think have been put off. At that time, circuits for simple one-valve TRFs abounded and could have been built more cheaply, and with much better results. I'll perhaps elaborate on that in another thread.

Be that as it may, today, I've finally got round to winding a test coil on the David Gingery machine using the 45 SWG 'cotton covered' wire, with reasonable results. I wound 500 turns onto a 12.5mm Paxolin former, which turned out to be 105 Ohms, and 4mH. (The resistance of the wire is 4 Ohms per Metre, so the coil consists of approximately 26 Metres). I deliberately made the width of the coil narrow (5mm) to see whether or not the turns would slip off the edge of the coil when several layers have been laid down. I suspect that slightly thicker wire might give better results, but that's a matter of conjecture.

Incidentally, the inductance of this test coil is far greater than would be needed for a DRR2 coil, in which the three windings are 30uH, 70uH and 170uH.

As to the little coil winding machine, I dispensed with the 'Tally Counter' used as a turns counter in the original design as it needed too much pressure on the button to operate it. Instead, used a pocket calculator and fitted a cam and micro-switch, which I wired across the '=' button on the calculator. I guess it's common knowledge that if you press 1 + + = on a calculator, every time the = button is pressed thereafter, it will increment up: 2,3,4 etc. Hence, by putting a switch across the = key on the calculator PCB it will count the turns each time the switch operates. However, having since made a motor driven winder to wind an 18,000 turn field coil, I've discovered that a calculator will only work on a winder which runs at less than about 150RPM, after which it defeats the ability of the counter, but that's on no relevance to a hand-operated winder.

I've attached pics of the hand- operated winder that I made, the test coil I wound today, and the data sheet on the Repanco DRR2 coil, on which I've annotated comments based on my experiences with that coil.

There is a youtube video of the David Gingery winder in operation here:

http://www.youtube.com/watch?v=FIOocMoRsYQ

Hope that might be of interest to someone.

[Nickthedentist]

Very nice.

I have also seen those cheap pedometers that were all the rage about 5 years ago used as turns counters, BTW.

Nick

[David G4EBT]

They're 'buy one get one free' at Mountain Warehouse currently Nick so I've got a couple to experiment with to see if they suffer from the same problem as pocket calculators when used at above about 150RPM as a turns counter - a purpose of course for which they aren't designed. (But the screwdrivers aren't designed to get lids off tins of paint yet they work well enough!). Pedometers have a 'step' function to record the number of steps taken as well as the distance travelled. It works by a small weight on a light spring bouncing with each step, shorting out two contacts. Hence, if a micro-switch is wired across the contacts, each time it is shorted in the 'step' mode, it will count up. (to 99,999). (The reading is stored and can be retrieved). I'm sure they'll work well enough for a hand-operated winder such as the Gingery one.

I've also managed to find a proper mechanical 'shaft counter' which I've ordered online, which has a 6mm diam shaft to try with my motor-driven winder, and await its arrival. That will work up to 350RPM, which hopefully will be satisfactory. I primarily built that winder for winding a field coil, in which the actual number of turns is of little relevance - all that was needed was that it was 2,000 Ohms. However, to wind RF coils or transformers where the inductance and turns ratio are important, then a turns counter comes into its own, especially if repeatability is desired.

[Mark James]

This looks like a potential project! Camden no longer stock David Gingery's book. Before I order it from the USA - does anyone have a copy that they would be willing to part with?

Mark

[Lloyd 1985]

That's a really nice looking little machine you have made there!

I could really do with a coil winder, I recently had a blocking oscillator transformer fail in my Philips 385U tv, and my attempt at rewinding it on my lathe (turned by hand..) was entirely useless!

This could also be used to make up the EHT overwind on a Bush TV22 LOPT, I think I'm going to have to try building one of these, if I can find the book!

Regards,
Lloyd.

[David G4EBT]

I've been winding a few test coils to see how this little machine performs and what adjustments to make in its use.

For anyone who has built but not yet used one of these little winders or who might be thinking about building one, a few more comments and pics about my experiences might be of interest.

Firstly, the rate at which the 'waves' arise is dictated by how close the rubber tyred drive disc is either towards the outer perimeter of the coil drive disc, or more into the centre. The rubber tyred disc and the one that it drives form what might be termed a simple 90 degree 'bevel drive'. The closer to the edge of the drive disc, the fewer the waves - the nearer to the centre, the more acute the angle of the waves. The shallower the angle, the greater the risk of turns slipping off the edge of the coil as the layers build up, though the type of covering (silk, cotton etc) and the gauge of the wire will have a bearing on this.

With a shallow angle the turns lie closer together, which increases the inductance for a given number of turns, but on multilayer coils the risk of turns slipping off the edge of the coil is greater. Today I've wound a coil with the drive disc more into the centre, which increased the rate of the weave and makes the angle of weave back and forth more acute, and I had no difficulty winding a coil of 500 turns, without any slippage of turns. I'm sure I could have increased the number of layers without any problems. However, the downside is that because the turns are more widely spaced one from the next, this has a bearing on the inductance. I'd fitted another cam which affects the width of the coil - this one enabling a 12mm width of coil whereas the one referred to in my first post was just 5mm wide. Though this second coil more than twice the width of the first, and had 500 turns like the first one, the resistance of the wire was almost the same (100 Ohms) but due to the less dense weave pattern, the inductance was only 3mH as compared to the smaller, but more tightly woven first coil, which was 4mH.

I've attached a few pics to help make more sense of the above.

Two black rings caused by the drive tyre will be seen on mating disc - the outer one shows the positing for the tighter weave (closely spaced turns) - the inner black ring shows the position of the tyre for the looser weave with wider spaced turns. The extent to which the cam disc is offset from the centre dictates the extent of the left and right hand throw if the wire guide, and hence, the width of the coil. The one show is for a 12mm wide coil.

I've also attached a pic of this latest coil.

The last pic shows the weave of the coil taking shape after 50 turns have been wound on.

As I have a lathe and a half decent scrap box, whilst it did take several hours to make the winder, it cost me nothing. It needs only basic metalworking skills and I guess it would be possible to make one without a lathe with a bit of improvisation. Useful for anyone who hankers after making replica Denco coils and the like, and once the parameters have been worked out, I guess that fairly consistent repeatability could be attained. The downside is finding suitable wire at anything like a sensible price.

I'm not winding these test coils to any great purpose - just to familiarise myself with the capabilities of this handy little gizmo and to confirm that it isn't just a novelty but does work as well as the youtube video suggest. I should add perhaps that the inductance of these test coils is far higher than that required for say a replica Repanco DRR2 coil (DRR2: 'Dual Range Reaction 2 Waveband'), in which the highest inductance - that of the long-wave winding, is only 1.5mH, the MW being 170uH and the coupling coil 145 uH.

Hope that's of interest to someone.

[JHGibson]

These simple hand powered universal coil winders are known as Morris coil winders. They often come up on ebay.
John.

[Radio Wrangler]

I'm beginning to wonder if a seriously universal coil winder could be made with a pair of stepper motors, one driving the coil former, the second driving a screw and nut drive for the reciprocating arm which directs the wire. This could be programmed to step slowly for checking, and to do wave or parallel winding and to handle various gauges.

David

[Terry_VK5TM]

That has already been done.

Nuts & Volts magazine for June 2005 had an article describing exactly as you suggest.

It also had software to run it via a pc (through the parallel port) that calculated length of wire needed, turns per inch and all sorts of other things.

Terry VK5TM

[FRANK.C]

Hi David
I have a home brew coil winder that uses a stepper motor to drive the transverse. I had though of driving the coil being wound with another stepper motor to make it as you say "universal" , But went against this idea as any stepper motors that I have seen have limited speed compared to what one would normally wind a coil at. I also prefer to twiddle controls to set things up rather than punch numbers into a micro controller.

Frank

[David G4EBT]

Thanks for reading the thread and for your comments guys. All clever stuff - I've seen some impressive youtube videos of winders that lay turns side by side, with the wire guide traversing back and forth, taking account of the length of the coil and the wire gauge used. For wave wound coils as opposed to 'solenoids' an endless source of free Litz or DCC wire is called for to experiment with, and lots of free time. It isn't going to happen!!

[dominicbeesley]

This is all making me think I ought to pull my finger out, my current coil winder is not quite as professional looking...

Got me out of a hole yesterday, going camping and my generator packed it, I made a new magneto on it yesterday.

[David G4EBT]

It's true that book used to be obtainable in the UK from Camden Publications - it's where I got mine from, but not any more it seems. However, it is still available, along with lots of other interesting 'home workshop books' from David Gingery Books in the USA. David Gingery was famed for using ingenuity and inventiveness in making workshop equipment from scrap - the sort of chap I think most of us would warm to. Sadly, he passed away in 2004, but the bookstore still continues.

The coil-winding book is $8.95, the shipping cost is unfortunately double that - $16.75. Total $25.70 = approx. £15.50 at current exchange rates.

http://gingerybookstore.com/CoilWindingMachine.html

Incidentally, it's my understanding that to wind 'solenoid' coils - that's coils in which the turns are close-wound in layers with the wire guide traversing evenly back and forth - requires a heart-shaped cam to guide the cam follower. The best example of the commonplace use (at least in yesteryear, if not today) of a heart-shaped cam to accomplish this task is that of the sewing machine bobbin winders as shown in the attached pic. I don't know if the original 'Morris' winder had such a cam - maybe anyone who has such a winder and has put it to practical use can comment on that?

A heart-shaped cam will enable wire to traverse back and forth evenly, but for turns of wire to lay neatly side by side requires a worm drive of some kind that takes account of the width of the coil and the gauge of the wire. That needs to happen with accuracy or the turns will soon start to ride over each other and look no more neat than had the wire been guided back and forth by hand. My main aim was to make a winder that will make wave-wound coils and the little Gingery/Morris job does that with no dramas.

Hope that's of interest.

[David G4EBT]

Originally Posted by JHGibson

These simple hand powered universal coil winders are known as Morris coil winders. They often come up on ebay.

That's true John, and I know of three UK vintage radio enthusiasts who have each acquired one, though at what cost, I know not. They command high prices - that most recent two I can find on internet went for $300 US and $160 US respectively, which would incur substantial shipping costs to the UK. Unless they came in 'under the radar' as sometimes happens, they would doubtless also incur UK Value Added Tax at 20%, a Post Office fee of £8.00 for collecting the tax, and possibly import duty too. (If so, how much duty is anyone's guess - the HM Revenue & Customs have 14,000 categories of goods on which varying levels of duty are levied).

It would be lovely to own one of these delightful little original machines, but not at any cost - I think my upper limit would be £50 or so. It isn't going to happen!!

[Neil Purling]

It would be wonderful to be able to 'book' the manufacture of an alternative to a dual or single range TRF coil with reaction. The function of the completed coil is what matters, not whether the result looks like a equivalent product offered by Denco, Repanco or whoever. Therefore a coil that gives controllable reaction with a 500pf variable capacitor, as they are easiest to source from a scrap chassis.

[Sean Williams]

I wonder if a windscreen wiper motor could be used as the traverse drive - the pivot point could be made adjustable which would adjust the pitch of the wave?

[David G4EBT]

I can update what I wrote in post #13 about the non-availability of the book by David Gingery; 'How to Build a Universal Coil Winder' from Camden Publications.

I've just received their latest catalogue and it now lists the book at £7.95 plus£1.95 post in the UK.

http://www.camdenmin.co.uk/collectio...al-coil-winder

The book consists of 28 pages of detailed drawings and construction details of how to build one of these dinky little hand winders. Mine cost me nothing - it was all built from my scrap box.

The attached pic shows the front cover of the book.

As an aside, the website is well worth a browse - especially under 'Electrical', which has intriguing books such as 'How to build a Magneto Magnetizer' (re-vitalising magnets and creating new ones etc), 'How to Run Three Phase Motors on Single Phase', 'Electrical things that Boys Like to Make' (well at least they did back in 1954 when the book was published and I was fifteen!). Also lots of stuff on model engineering etc.

(Any discussion on those topics is of course not appropriate in this thread, and is for info only here).

Hope that's of interest.

[SurreyNick]

Thank you David. The book is now on my Christmas list. Hopefully my wife or one of my kids will get it for me, along with the parts
Nick

[FrankB]

Dave's book used to be available from Lindsey Publications, along with many other really good DIY books. ( I spent hundreds of dollars with Lindsey on books) I am given to understand that Lindsey Publications has now ceased operation though.

[Mike Phelan]

Camden still have it, as David says. Their catalogue is well worth asking for.