Rewinding motor tips

I wanna try my hand at rewinding a fried motor. It’s a maytech 6355. I’ve read a handful of articles and watched videos but have a couple questions here. One: how do I remove this PCB top?


Two: Theres some glue/adhesive around some of the coils, is there something I can soak this in to remove the glue and keep everything in tact? Acetone?


I read on an old thread that someone put it in the freezer with penetrating oil to get the stator out but I’m still not sure how to remove that PCB board on top or how that functions exactly with the motor as a whole unit. Any tips welcome, thanks.

@MysticalDork I feel like you may have some knowledge…:sweat_smile::sweat_smile:

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@whaddys I’d guess the PCB is held in by that aluminum piece with flats on it. Looks like it’s threaded on.

As for removing the windings, I’ve seen people use solvents, heat, brute force or a combination. It’s not easy to do when they’ve been glued in securely like that.

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Is there any particular consideration/danger in soaking it in acetone? Also do you know what purpose that PCB serves? It seems to be in all the 63xx motors I’ve seen but not in smaller ones.

The PCB holds the hall sensors and usually a thermistor too.

Acetone will probably be okay, it might take the epoxy off the steel laminations, or not. Might not even soften the epoxy on the windings, for all I know. Be careful with solvents, they’re usually flammable and volatile. Really easy to have a fire.

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I know when I was rewinding a transformer, it had been dipped in some resin or other that made it impossible, so I resorted to cutting off the protruding windings, then pounding out the remainder in the grooves with a punch and a hammer. It was a slow, labor intensive but very satisfying process. :smiling_imp:

If the acetone does remove the epoxy on the windings, it will probably remove the epoxy on the laminations as well, and it may turn back into a pile of individual laminations that need to be assembled again. If so, remember to insulate them before reassembly - ideally you want no electrical continuity between each lamination and its neighbors. They usually are coated wit ha thin layer of lacquer before being assembled.

Do you mean the lamination on the stator, so there’s no continuity between the stator and the phases? I read an article saying to coat the stator with liquid paper.

The material the motor is dipped in is an epoxy. I don’t think it will respond well to acetone, but more importantly like @MysticalDork said, you’re likely to take more apart than you really need to. You’ll want to know the number of turns and gauge of the wire used to wind the motor before you rewind it in order to have the right material for the job, and the pattern used to wind and terminate the wire is key as well.

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If you look at your second pic, each layer of metal making up the stator is a separate piece of metal. Those are the laminations. The whole thing usually doesn’t separate into laminations unless you do something to unglue them, like use a solvent.

What you read, about using liquid paper, is to avoid creating a short between the wire you are winding with and the laminations/stator. This is common at the corners where you bend the wire around, as these edges can be sharp and cut the wires coating. The whole stator is usually coated with a baked on powder coating that makes the surface less sharp at those edges. Again, you might find that acetone removes this material.

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heat works well for softening the winding epoxy and then unwind if you can or cut.
don’t pull so hard that you pull up the stator laminations at the top and bottom of the stator.

if you do end up with a bare edge that the rewind will have to go over its difficult to get a good coating of a resin that will stay on and might be easier to use tyvex paper or something. usps has the envelopes for free and glue it over the bare spot. you have to get all spots the wire goes over covered or its easy to short and you will be pisssssed.

if the lrk winding will fit that is an awesome easy winding. and if terminated wye a hair better

its a nightmare trying to figure how many turns and wires are in parallel and easier to get it all off without thinking about it in my experience, carefully, and just rewind first with a super thin wire that will be easy to put on and you can test the kv, figuring how many turns you really want, and then rewind with the thickest wire that will do it for you. maybe you know this already. and youre going to want to put another layer of resin back on after winding and fix down all wires

its hard to tell if your motor rewind is wound without shorting either to other phases or within the phase or to the stator (which isn’t a complete short but a half short and not too bad). a resistance test with a multimeter will tell only so much and a good inductance meter is the easiest way to see it all and you can get them for like 20 bucks. L/C meter

im pretty obsessed with winding motors. if you want to talk about it you can message me…or I could clutter the site up for days

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hell yeah thanks @Hummie, you will most certainly get a PM from me over the next week I’m sure! I was going to count the windings and pay attention to the pattern when unwinding but I may just arbitrarily cut off the wire and do a whichever winding is easiest, lrk you say? I haven’t read about that winding pattern yet only delta and wye.

I think I’ll pass on the acetone as to not potentially fuck up the laminations.

lrk is the winding and wye is the termination. lrk is failproof as youre winding every other tooth only, strangely, and you just wrap the tooth, filling the two slots beside, with as much as you can and you don’t need to make considerations for the windings beside.

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That, and if the individual laminations come apart, you should insulate every one of them from their neighbors If it were me, I’d probably use some insulating epoxy spray I discovered at my previous job. You want no electrical continuity between your wires and the stator, and if you put one multimeter probe on say the top layer and the other on the next layer down, you should get no continuity there as well. (Some continuity is usually unavoidable due to friction and scraping as you reassemble the layers, but you want to absolutely minimize it.)

Ideally I don’t want these individual laminations to come apart though I’m guessing, correct? Seems like that would save me quite a headache (or learning experience depending how you wanna look at it =/)

That is correct. if they come apart it’s not the end of the world, but it can be a bit of a pain.

Is 18awg acceptable for rewinding? image

@whaddys You have to calculate the space you have and the number of windings you want and pick the wire size that fills as much space as possible without being too much.

Don’t use that wire at all though - it’s not insulated, it’s bare copper.

Also, it’s usually easier to use multiple thinner strands than one fat one, because it’s less of a pain to bend.

I thought you watched a bunch of rewinding videos? This is all basic stuff that should have been covered from the get-go!

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Hahah no I did not read anything other than thicker wire for higher KV. Clearly I need to do more HW. THANKS @MysticalDork if you have any essential literature you can send my way I’d love the reading material.

I guess I’ve read more about specific winding types and terminations, and how they affect motor performance. Nothing about the electrical physics behind it though, that would obviously be good stuff to know. Essential stuff to know and both have some pretty in-depth information about winding schemes. This instructable also has loooots of very detailed information and links and equations and and and.

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you strip it yet?

I would skip calculations based on your measuring of space as its hard to really measure accurately and the difference between wire sizes is small. Easiest is just do the lrk winding with any thin insulated wire (magnet wire being best) quickly and give it a spin on the bldc tool to make sure you got the winding done right and you can see what the kv is. Then when you figure how many turns of wire you want, for your desired kv, find a wire that you can wind that will be thick enough that it just fits in and does that.

you can put a very thick wire on by tying the end to a hook and pulling it on from the other end. I find doing multistrand a pain and its unlikely to yield as much copper fill or give as nicely made coils that produce as good a field. count how many turns are on a tooth from the opposite side the wire ends and starts are. the goal is of course least electrical resistance for most inductance, so fat wire in nice coils.

with the amount of space in that motor case you have lots of room for the endturns, or copper sticking out the top and bottom of the stator, and I’ll bet you can jam the can with a huge amount of wire. it will be bulging so much I bet the sensor board maybe would be a limitation. id forget putting it back on if so but to each their own.

you cant see what the electrical resistance of the motor is now, or maybe someone else has one and you could find out (wouldn’t trust the manu number) and you could compare it to what you end up with as shown also on the bldc tool. or weigh the motor now and weigh it after you strip it and weigh it after you rewind. and you’ll want some thin high heat epoxy to fix the windings down. Id get omega brand unfilled stuff in the envelope as its easy, heat it up to make it thinner, and try to get it all in there as best you can. and make sure where the wires come out of the motor is well protected.

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