Spool brake band for winding machine

I wind electromagnets somewhat often with a crappy desktop lathe and a parts counter. I've decided I want to setup a carriage to move the wire back and forth and keep the buildup of wire even. With that comes the potential for higher winding speeds now that my fingers won't be involved.

The trouble is I may be using fairly thin wire on fairly heavy spools, and to have a static brake to slow the roll enough with feed changes would be hard on the wire. I will of course be using minimal acceleration, but still.

Anyway, I want to mount a potentiometer on a tension sensing arm and send that amplified signal to a beefy solenoid or torque motor that can put tension on a brake band, and I'm unsure of materials to try.

The only similar thing I've done is put a piece of spring loaded felt on a ball bearing hamster wheel to fix overspeeding issues.

If I had to guess I'd start with a felt band on an aluminum wheel.

To give a sense of scale the breaking strength of the wire is 11 pounds and the spool weighs 80 pounds. Slow acceleration of the spindle is easier to achieve than slow deceleration.

Ive made small ones for microphone transformer winding.

I arranged the band brake so that as the tension in the wire increases , so it pulls a pulley down, in this case, and releases tension iin the band brake . Similarly, the brake band should be arranged so that the friction force tends to release the brake , so that you don't get snatching .

I'll try and find a picture.

Bill

Alternatively, if you can , set the reeel on its side and allow the wire to pull off the side. This will remove the spool mass from the equation, but cause a twist in the wire that can be a problem.

Look at the way tension is held on undersea cable layers. The same method is used on smaller wire eg 26 AWG.

Years ago my son wanted to build a Tesla coil for a school science project. This was a 6" diameter plexiglass tube four feet long. I think it had something like 10,000 ( maybe more I can't remember ) turns of wire on it. I used the longitudinal feed on the lathe to lay the turns down evenly and mounted an old Pflueger fishing reel on the cross slide ( I just tightened down the grub screws of the QCTP tool holder on one of the "feet" of the reel used to clamp it to the rod). I used the drag on the reel and put one full turn around the spool. I clamped a dowel to the follow rest for the stock spool. Worked very well and was so much fun I was sorry when I was finished.

This is the only pic I can find of the wire tensioning part in action.

The box would normally contain a small spool ( on its side so the wire rolls of its edge) , but here I'm unwinding a small inductor (for some reason??)

The things to note is that the large brake drum revolves clockwise (as seen in the picture) and that the brake band (blue) wraps counter-clockwise from the fixed point, so friction against the drum tend to pull on up on the spring and release the brake.

And, the roller that senses the wire tension, pulling down ,also releases the brake. The spring captive end is in an adjustable slot.

Bill

Watch some of the videos here. I think you will see how the process is conducted.

https://www.youtube.com/results?search_query=bachi+coil+winding+machine+

Tom