I don’t know why, but for some reason I was of the impression that it is really hard to re-wind one of these typical skate outrunners. Seeing how well the hall’s and wires are glued in, it certainly looks difficult to save those, but if the goal is to drive it with a magnetic encoder, then I don’t see why not.
Re-winding it for higher resistance and thereby increasing the wire-turn-count will make it easier to control, at lower amperage. Naturally the KV rating will drop in the process, but the torque should also increase.
Getting the rotor dismantled did involve some hammering on the shaft. It is a really tight fit. Overall these motors has some pretty strong magnets. Let’s see how they perform with higher resistance.
Just sharing this for future reference. I haven’t ordered the wire yet. My plan is to fit it to a vacuum device for CNC chip removal and possibly also PnP vacuum. Not sure it’s even possible, maybe if the hose for chip removal is relatively thin, to keep the airflow demand low.
It most certainly is possible to de-wind these, but man it is a paint to do. Two of the slots is pretty much soaked with epoxy, because the wires for hall-sensors and thermistor run in the grooves. Anyways, it should be pretty easy to estimate how much wire is needed…
From factory the motor had 11 wire turns (multi-threaded).
The stator is 35mm tall, and each tooth is like 3-4mm wide, so one turn is approximately 80mm of wire+. Each tooth is 11mm long, so if we use 1.2mm wire, it should be possible to wind 9 turns on first layer. Second layer can only hold 8 turns, since the space between stator teeth is so narrow close to center. We then have to squeeze 4 more turns in on 3th layer, to reach 21 turns, which should be possible by hand. 21 turns x 80mm (+/-) is 1.7meter’ish. X 4 teeth per phase is 7 meter to be safe, so 21meter total, using 1.2mm wire.
Just to clarify, the motor had 11 turns with a multi-stranded wire? Because looking at the winding it seems a lot more than 11 turns, is that why?
Are you planning to rewind the motor to achieve higher resistance?
The reason I’m asking is I got the exact same motor I was planning on rewinding to convert it to a high-ohm motor to run very slowly with high torque as a gimbal and replace the halls with linear ratiometric ones. I wasn’t sure it’s possible.
Yea, pretty much. I’m curious to see how well we can control these with higher resistance. From factory these pull a-lota-amps. Thinking to wind it up for e.g. top 10 amp?
From my quick calculation (which is be probably a little off) if you use a single-stranded 0.2mm wire you should be able to get under 10A for a 48v input. This will allow you to run it as a gimbal.
I’m estimating may be 50 turns per individual pole, 4 poles = 200 turns, each is 5cm x 2 = 2000 cm (20 meters) that’s about 10 ohms resistance.
If you put ratiometric halls gets even better, you will get three-phase sinusoidal signals to really accurately control the rotation.
I am very curios if you can pull this off, please post results.
I’m estimating may be 50 turns per individual pole, 4 poles per phase = 200 turns, each is 5cm x 2 = 2000 cm (20 meters) that’s about 10 ohms resistance for 0.2mm wire.
If you go for 1mm then you cannot get to 10 ohms. You will end with may be 20 turns
20 * 4 * 2 * 5 = 800 cm ~= 0.2 Ohm for 1mm copper wire.
