Anyone have any tips on rewinding MXUS 3k?

There are a couple of hub motors around here that have been run too hot and then left to stand resulting in blackening of the windings in one particular area.

One is an MXUS 3k and another is a similar clone. Needless to say they don't work any more due to current leakage between the wires..

Is the solution as simple as resoaking the windings in varnish to restore the insulation, and if not can anyone point me to a resource which might help me to get started with understanding the rewinding process?

Thanks

Your motors are most likely toast. I woudn't try the varnish trick because it would be at most a temporary fix and the motor could easily short out again, blowing your controller. If you elect to rewind the motor, you'll have to pull out the old wire and make a chart of how it was wound.
Next, you would buy some same-gauge wire and rewind it as it was.
I have rewound a few small brushed motors and it was not a fun experience. If you decide to go the rewinding route, be prepared for several hours of work. Make sure you fill in your chart accurately to prevent a miswired, malfunctioning motor.

Finally, whether you have rewound your motor or simply bought a new one, you'll want to install a thermistor or similar heat sensor in the motor. When I got my hub motor, it was the very first thing I did. You simply run a thin wire into the motor through the existing bundle, and then solder a thermistor between that wire and the sensor board's ground terminal. Make sure to add heatshrink before soldering and hold the thermistor in place on the windings with either epoxy or silicone. Set the temperature limit to 100°C and you'll never burn another motor again.

Having taken a closer look it’s not going to be feasible to recoat the wiring so a rewind is my best bet. Have looked into it and it’s really not all that complicated. A couple hours work to save hundreds of dollars on a new wheel seems like a good payoff to me.

There’s 750g of 0.5mm copper wire in the MXUS, 250g for each phase. I found this winding calculator which showed me how to arrange the windings.

http://www.bavaria-direct.co.za/scheme/calculator/

As I unwound the dead motor I checked against the diagram produced by the website and the pattern matches up. The only hard part I can see will be working out how long to make the wires. The ones in the 4T Mxus (16x4) are about 8.75m so 8.75x16x3=420m total, but to wind for 5T that figure is going to be larger.

If a motor has melted it's insulation from a overheat situatuon then it's a fair assumption that the magnets have been exposed to heat well above their 120c max recomendation.
What does this mean for their health? The magents field strength will have reduced resulting in a motor with less initial torque, lower power handling, and a higher kv per volt applied.
Save yourself the time and trouble if its overheated then its junked, bite the bullet before you waste cash.

I am going to do the rewind, so I'm looking for tips to do it properly, not naysayers telling me not to bother. You haven't seen the inside of either motor. There is only damage to one of the phases so its more likely a malfunction than overuse.

If I get them working its a bonus if I don't I have learnt a new skill. The cost of the wire required is negligible.

So any tips from anyone who has rewound an MXUS or similar motor?

I'm not a nay sayer, I do a lot of motor work and could give some good point's specially on coil layout minamizing end turns and soldering to enamelled wires but I've give my 2 pence and rather than give assurance you insult so all the best butty, if your looking to rewind what do you need to know that you already dont just replace what you take apart or change the turns to suit your needs.

LOL. Charming.

I haven't done it before so I don't know what I need to know and was just asking for some help...

I won't reply through PM to your baiting, I offered my advice don't like it then that's your problem not mine.
Pictures of the issue may have help show your situation more clear in the beginning.
I advised on your discription same as another member as it's a common occurrence if you say it's salvageable then you do that but I'm not naysaying but offering advice.

If you believe the magnet ring has no major weaking and want to do a rewind then try match it exactly as it come off or a known factory wind, Its all done by machine so manual is hard work and needs a good clean clear area, its best to sort the phases individual and take the time along with the sore fingers.
Sort the phase lengths wrap individual coils, use a mild caustic soda solution and dip the ends of each phase in to clean the enamel off and solder the phase wires on if it's a wye motor centre tap them or mate the ends if it's delta, U only need to make a wye connection internal and the core is free of the motor so it's a easy motor to rewind obviously get your length and add some on not to fall short, with it being wound already that should be easy enough.

I'm not looking to fight I don't want to see you waste money on a motor with heat damage to the laminations and winding's do a continuity check of the lams see if they short out the magnet's are harder to check with out a gauss metre and factory data and I can't help you with that my motors back together and staying that way it's a bitch to get that rotor out.

It seems kind of odd that only one phase was burned. In other burned motors I've seen, all three were charred and black from sustained overheating.

After you rewind your motor and add a thermistor (highly recommended), make sure that your controller is not "single phasing" the motor. Single phasing is what happens when one wire is disconnected/loose and only one phase is energized. The one phase takes 3x the normal power, and the others are unloaded. If you notice your motor vibrating excessively, there's a good chance that you're single phasing it.

Also I like the link that you posted to the motor calculator. It'll come in handy if/when I wind my motor for a higher top speed.

I've gathered a bit more information on the laminations of brushed dc motors vs brushless ac turns out AC lam's are not always insulated as the oscillating current keeps the eddys small or so I've learnt, but you seem to have snapped gone quiet and not looked back bit like my missus really.
It takes a little willy to kick off and were all capable of that, but it takes man sized girth to apologise.

Ok lets get on with it. I would very interested in seeing and reading about these to an end result . Good luck being a little Chinese girl or you need to do 5 in one hour.

Replace all phases not just one because often these motors have questionable workmanship with the windings from the factory. You also don't know the insulation grade. If you want to get hot enough to demagnetize the thing, go with polyimide / high temp magnet wire...not all magnet wire is created equally.

Some cautions for the disassembly: Take care not to fold up any of the steel laminations or create any more shorts between the layers than you have to. You may need to replace the halls. Take care with packing the wire, it's a lot more difficult than you'd think and it can be easy to short the wires to the stator particularly if you don't apply a protective coating like the user above suggests.

It will take you a lot longer than 2 hours but I endorse this project. No sense paying for a brand new motor when only some wires need changing.

One last note, you may have damaged the halls too so if you replace those be careful to avoid damaging the stator when removing / replacing.

I was dead careful removing my stator after cracking my a2b motor case, Even then there was a little graze to the laminate on one side of the motor, with out and industrial strength clamp and hydraulic puller it's damp hard to get that rotor out, It's not happening by hand.
I used a 3 jaw puller to pull the magnet ring over the stator then away from the motor after removing one of the side plates but the one bearing is not a good enough guide you must be careful especially on placing it back on or it could lose your fingers easily.

I kept my fingers outside the ring and let it suck on to the stator then convince the side covers back on, try not to lose the brass washers inside keep it all organised and you should get a result.

I'd focus on the mxus and see what you can get if there's good pull at the magnets with a bit of steel then it should be good to rewind if the theory I've read is correct, So good luck no hard feeling's and I'm not a naysayer lol, if anything I drag things well past their death to my own cost, but through personal experience and wasted cash on scooter motors I give the response that I did.