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Coil Winding motor rpm & torque needed?

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  • Coil Winding motor rpm & torque needed?

    I was wondering what the coil winding motor RPM range needed is for winding coils? In contemplating what I have available in my equipment pool to draw from, I have a couple Bruel & Kjaer chart recorders, which have motor couplings on the side to drive their stand-alone oscillators and filter sets. The RPM range available on these is 120 RPM down to 0.0036 RPM, in step sequences of 120>>36>>12>>3.6.....0.0036 RPM. Motor Torque spec limit is 1.7 (0.2Nm). With a maximum speed of 2 revolutions per seconds, is this adequate? It also has an internal cam switch for sending out pulses. I'll have to look at the manual to see if it's directly related to shaft rotation....1 pulse per rotation or what?

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    Logic is an organized way of going wrong with confidence

  • #2
    I'll take the easy question. Is the motor speed fast enough? I reckon that depends on how patient you are. Say you want to put 5000 turns on a humbucker bobbin... 5000 turns x 1minute/120 turns = just under 42 minutes per bobbin.



    • #3
      120 RPM is mighty slow.

      RJB is right, it would take all day to wind a set of pickups with that. Maybe a set of pulleys are in order



      • #4
        I didn't stop to work the math. Never having done any of this, and thinking about just how fast do you spin an obround coil form while trying to guide the wire as what would seem the tension varying at every rotation, it made me wonder just how fast you would run the coil form, with a much higher range of motor rpm. Good answers. I'll move past the B & K boat anchor and see what else I have. Any idea about the necessary motor torque needed?
        Logic is an organized way of going wrong with confidence


        • #5
          Back in the day, circa 2005, I built a research winder that would spin the bobbin at up to 1200 rpm, which was fast enough for me.

          The motor wasn't all that large. Used a Globe Motors model IM-13 (12 volt) long-stack with ball bearings, part number 405A6109-2. Cost $36 for new from Arrow Electric, as I recall. It's 6.7 watts, with 2.5 inch-ounces of torque.

          Also had some mechanical components to get from motor speed to bobbin speed, and for the counter and rotation sensor.

          Sewing machine motors work well, but are actually overkill.

          People who wind coil after coil like to go more like 5000 rpm, but it takes some practice to go that fast without too much wire breakage.


          • #6
            I played around with these when I developed and built my winder about 13 years ago. I built mine with a nice industrial Baldor DC motor and speed controller. It'll adjust smoothly from zero to about 2600 rpm. Over the years, I've found that I like to wind my coils at 1000 to 1200 rpm. That seems to be a nice working range. I typically wind 5000 turn coils, so each one takes around 5 minutes total. Not too tedious and boring. If you run faster than that, centrifugal force starts becoming a real problem. The center of oblong coils want to swell out. You have to use higher tension to keep the coils tight and neat. And that brings in more problems with the slightest blip snapping the wire.

            Unless you are trying to go real high production rate, I'd design your machine to go 0 to 1200 rpm. And having good electronic control that will go right down to zero is very useful. I always start my winds doing the first layer at around 60 rpm, just to make sure it's all seated and laying correctly, then speed it up.

            Motor torque required? Just about nothing. I generally wind at about 25 gm of wire tension. At maybe 1/2" average bobbin radius, that's....just about nothing. Almost all of the horsepower you'll need will be for driving your mechanical feed mechanism or mechanical counter, if you are using them.


            • #7
              Many thanks for your input above. That gives me a lot to go by. The need isn't immediate, but something that will come together in the next year, probably. Besides pickups (I'm a bass player), small audio transformers, inductors as well. Lots to learn and take in from all of you guys who've been at this for a good long while. Looking forward to it.
              Logic is an organized way of going wrong with confidence