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Anyone familiar with coil winding machines ?

Discussion in 'Electronic Repair' started by N_Cook, May 26, 2008.

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  1. N_Cook

    N_Cook Guest

    My coil winder is from the 1920s and no manual and when I picked it up in a
    very sorry state, it was minus the tensioning aparatus, so never seen.
    This ETA hand winder is something like the Avo Douglas coil winder but the
    manual for that is not very helpful on picture or description, being part 30
    lost in this pic, 50K

    I made up a workable back tensioner from VCR slip clutch, lightly sprung
    pulley carrier etc but it is not very good for evening out the variation
    due to unwinding very light gauge wire from the supply spool giving a
    somewhat jerky back tension. It is many years since I was hands-on a Douglas
    and have forgotten what the mechanism is. Anyone know what the Avo system is
    or any other more reliable system. As far as I remember it was a pair of
    discs that somehow the wire passed through and the pressure between the
    discs was varied for different tension. I also seem to remember that it too
    was not very good at the very lightest gauge wire AWG40 / SWG45 and it was
    better to run through human fingers rather than the discs. At only 1 or 2 oz
    back tension it would sometimes grab onto the wire if contaminated or
    something and break the wire. But there must be better than human finger
    back tensioner.
    Is there a 2-stage spool supply process? so the wire is unwound to an
    intermediary stage at near enough zero tension that then goes to the winder
  2. bz

    bz Guest

    Many sewing machines use a similar system to set the thread tension.
    You might adapt one from a sewing machine.

    Also try looking up the patent applications for such devices, you might
    finds something helpful.


    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
  3. N_Cook

    N_Cook Guest

    I think a cross-wired memory effect has come into play.
    That pair of discs is what I've seen on a sewing machine and memory
    transfered to coil-winder m/c so probably have no recollection of what that
    Douglas mechanism was. But I do remember having to use fingers for
    back-tension as the proper mechanism , whatever it was, was unreliable.
  4. bz

    bz Guest

    One or more turns around a shaft might do the job.
    You might tear up an old hard drive and use the supports and bearing for
    the platters for the shaft variable drag on the shaft could set the
    tension for you. Somewhat similar to the drag on a tape machine.

    Another idea, how about the variable drag on a fishing reel?
    Off load your wire onto the reel.


    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

  5. Smitty Two

    Smitty Two Guest

    I've wound a coil or two; we make guitar pickups. Tensioning requires a
    bit of logic and science, but a healthier dose of black magic. We use 42
    AWG almost exclusively, and put somewhere between 5000 and 8000 turns on
    a given bobbin.

    There are happy days when you get 95% yield and annoying days when you
    get 10%. There are several components to the dereeling and tensioning
    process. I can take some pics of our machine or some copies from the
    relevant operator's manual pages in the next day or two if you like,
    with further observations.
  6. N_Cook

    N_Cook Guest

    That would be very helpful.
    Can you upload to a site somewhere? if by email, I will have to relay an
    account/address to you that does not have filters on it.

    I've had another google and not found anything useful.

    There is nothing wrong with the spool layering , it is just the natural
    marginal wedging that occurs with on unwinding, not overlaps , but just
    slight variation of a couple of ounces that would not matter if using 8oz
    of back tension or more for a thicker gauge, but 2 oz is too critical.
  7. Jamie

    Jamie Guest

    I don't know about that how ever, at work we deal with small wire and
    conductor in the area's of 40 AWG etc.. and 2 difference systems are used..
    One uses a small lever (catenary) arm with a small disc roller on the
    end of the arm along with an eyelet to keep it in the roller.
    When the wire is pulled, it pulls down on the arm which has a spring
    as part of a strap that goes around a drum that is an integral part of
    the pay off shaft the supply of wire is loaded on.

    The strap has a rawhide pad on it.. the pulling of the arm pivots on a
    shoulder bolt, the other end opens the strap to release the braking.
    Putting on a tiny air piston with speed bleeders on both ends help
    in damping the oscillation.

    The other system is just about the same how ever, we have a DC motor
    attached to the shaft with a dancer circuit. The centenary arm has a
    small POT on it that drives the DC regen drive to maintain position of
    the arm which maintains constant tension through out on the take up end.

    This works great for very fine wire and all we do is adjust the spring
    on the arm via a thumb screw and lock nut on the threads.

    The motors are 1/10 HP PM units.

    The pot's are optical types, so the movement in the shaft has very
    little drag and are smooth .

    The electronics for the Pot sensing has trims on it to adjust for
    delay, Lead, sensitivity etc.."
  8. Smitty Two

    Smitty Two Guest

    This is a motorized winder, obviously, so take whatever is applicable
    for your machine. We found that the tiniest details are important. For

    Dereeling counterclockwise, on our machine, makes a significant

    Spool diameter is important. Too large, and the wire gets tossed around
    too much on its way from curved to straight.

    It's tempting to wind with the minimum possible tension, but the result
    will be loose coils, which may or may not be an issue in your
    application. Our dancer arm is set to the minimum, but the wire also
    goes through three felt pinchers.

    Placement of felt tensioning pads is widely adjustable, and we only
    found the best positioning after much experimentation. We have one near
    the dereeler and two close to the bobbin.

    The bobbin should be dead smooth, obviously. No burrs allowed, and it
    has to run true.
  9. N_Cook

    N_Cook Guest

    Many thanks for that.
    Seems more black arts than science. I assume the black fibrous block under
    the arm in pic 008 is someone's retrofit damper like the Millenium Bridge in

    I think I would make the sprung arm out of lighter materials as I would only
    need it for 40AWG/45SWG type gauges and so less inertia there.
    Do you find a problem with dirt or grime on the felt pads causing
    irregularity problems at these light tensions ?

    I was wondering if a servo system for spool unloading to zero tension is a
    way to go. Inductively or optically, somehow monitoring the sag in an
    unsupported section of the supply wire. When in optimal band then spool rate
    say 5 second average speed. More sag then proportional down to zero speed
    and too little sag then proportional up to some system limit.
  10. N_Cook

    N_Cook Guest

    With pulling off the spool axially and vertically don't you get problems
    when the lead-out reaches the top of the supply spool? compared to pulling

    One thing i have learnt is the use of a small force gauge as used in
    checking slip clutches etc on VCRs.
    Mine is 0 to 50gm Halda / Haldex of Sweden, just make a loop in the end of
    the wire to hook into and pull for a bit, to check for tension and
    consistency on the dial.
  11. Smitty Two

    Smitty Two Guest

    Not sure whether you meant to say "as opposed to pulling off radially?"
    But in any case, I think that the way it's done on our winder provides
    *consistent* tension. As I mentioned, a larger diameter spool does cause
    problems, though.

    This pic isn't very clear, but it's a "whisker disk" that is supposed to
    sit on top of the spool to dampen oscillations as the wire dereels. We
    found it to be counterproductive.
  12. Smitty Two

    Smitty Two Guest

    Ha, I hadn't heard that bridge story! The little scrap of scotchbrite
    pad is to soften the metallic clang of the dancer arm, but in normal
    operation it doesn't hit there, anyway.
    The pads are replaced as needed, but they don't tend to collect dirt.
    I think the less technology, the better. We built a custom take-up
    winding machine for a fibre optic manufacturer, and it was fairly
    sophisticated, with a PLC controlling everything. If I had to do it
    over, I'd just use a dancer arm...

    I think one key to the success of this machine is the substantial
    distance from spool to bobbin. Nowhere is there any slack wire beyond
    the idler pulley, but the distance and widely spaced tensioners may
    allow some imperceptible stretching, and of course the idler pulley
    moves up and down slightly on the end of the dancer arm, which moderates
    dereeling variations.
  13. N_Cook

    N_Cook Guest

    But what happens for the when the spool take-off reaches the very uppermost
    turn and the wire is rubbing along the internal face of the spool and being
    pulled through a softened right angle at the the spool rim ?
  14. Smitty Two

    Smitty Two Guest

    Well, thirty five years ago I might have been able to analyze and
    quantify the physics of that. All I can say now is that it doesn't pose
    a problem. The wire is *always* being dragged against the the endcap of
    the spool, at varying angles of course, but if the set-up does have
    drawbacks they seem to be minimal. I think that without a motorized
    dereeler and a sophisticated system to monitor slack and adjust dispense
    and take-up speeds, this is the best approach.
  15. N_Cook

    N_Cook Guest

    The spool must be wound in a radial sense at manufacture, so I assumed it
    was best to take it off radially.
    If mounted vertically and pulled off vertically then its not just the
    uppermost take-off rubbing against the spool end but at the lower end, on
    every other layer, you are pulling against the remaining lay of wire.

    My method is not ideal , hence this thread. I chose mounting vertically and
    pulling off horizontally for minimum pull off variable tension.
    Mounting the spool on a pair of good quality ball races and then adding an
    ex-VCR slip clutch pair over the top. One runs with the spool and the other
    sprung tied back to frame and small weight added to activate the
    That works very well but it leaves the problem of variable lay pull-off
    tension from the spool at these small wire gauges.

    I see I have to probably increase to 3 slip/brakes. Existing exVCR slip with
    very little weight , little more than a brake, and the main back-tension
    governed by a mix of your felted clothes pegs and lightly sprung felted
    discs, separated as far apart as practical to employ inherent slight
    stretching in the wire, to even things out, as well as my existing dancer
    arm and pulley.

    Another minor problem is the final small pulley that delivers the wire to
    the bobbin. Plenty of pulleys with good quality bearings salvaged from kit.
    But they all the good quality ones have a groove at the join of the V of the
    pulley, just the thickness of this wire, so useless for this purpose. I
    assume as they are for rubber drive band use it is something to do with air
    being trapped between pulley and rubber if no such groove. I may swap to
    just a small piece of PTFE with a groove in it , extended on a moveable rod,
    instead of a pulley for final delivery.
  16. Smitty Two

    Smitty Two Guest

    I'm not quite following your last paragraph, here. Why are the good
    quality guide pulleys useless? Isn't the guide groove just what you
    want? Sounds like what we have at the bobbin end. What do you mean by
    them being for rubber drive band use?

    BTW, how are you handling the traverse motion to lay the wire neatly
    along the bobbin's length?
  17. N_Cook

    N_Cook Guest

    Most of the pulleys , that have high quality bearings, ie run true have come
    from tape players or VCRs. It seems that along with the high quality
    bearing, they have this very small groove, that honestly I've never noticed

    The pulley rim is V in section but instead of coming to a point at the
    bottom of the V they have a tiny slot perhaps 0.1 to 0.2mm which grabs on
    wire of 0.07mm diameter, due to slight imperfections or whatever.

    The traverse speed and change direction is automatic and works very well
    once the infinitely variable gearing is set and end settings positioned.
    There is a bit of a kick due to the PTO change-over action but a kick to
    slacken wire supply, rather than tighten which would be disastrous, and I
    can compensate for that , as manual , by slowing the rotation down just
    prior to flip over and hand brake slightly..
  18. bz

    bz Guest

    can you run a rattail file along there to widen/remove the groove?
    How about wrapping a few layers of TFE tape around the pulley and filling
    in the groove?

    Shapelock aka Friendly plastic could be used to mold a 'cover' for the
    pulley. Heat it with a hot air gun or hot water, it turns clear and
    mold-able. It sticks to other plastics. When it cools it is nylon hard and
    opaque white. I have used it to fix broken nylon gears in a printer and a
    broken slide bracket in my wife's sewing machine.

    bz 73 de N5BZ k

    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
  19. Guest

    I can wind a fish line.My fishing reel machine automatically does it for
  20. N_Cook

    N_Cook Guest

    I tried plumber's PTFE and it failed.
    Had another hunt through my collection of salvaged pulleys and from about 20
    they all had this tiny groove just where I don't need it.
    Never previously realised, because it is such a tiny groove, that all good
    quality small pulleys , plastic, brass or aluminium have this groove.
    Still not found the funtional reason for it.

    Took some advice from a proper mechanical engineer on how to best tackle
    turning my own small 8mm diam x 3mm PTFE pulley with a straight (un grooved)
    V cut , and will go down that root ;-)
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