The NTM Prop Drive 50-60 Rebuild Thread

Save yourself a lot of pain and maybe do the LRK wind with delta. Winding every other tooth you can’t end up too jammed.

That motor looks like a real bitch to get the wire off. I’ve had a tacon160 I gave up trying to remove the wires and it’s a paperweight forever. If u can figure out how many strands are wound in parallel and you take off all of those parallel strands together it can be a difference between night and day

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Be careful if you’re only winding every other tooth. The windings barely cleared the bell when winding every tooth on the r-spec, wouldn’t have managed it doing every other tooth.

Busy pulling the windings off the stator. It’s easier to bake the stator in an oven set to 200 degC, to soften the glue, which makes pulling the windings easier.

That said, these windings are very brittle due to the heat damage, and I’ve struggled to keep track of the orientation of the windings of each coil due to breakages, and due to the tight wind, these motors are very hard to unwrap. It seems like the winding pattern is AabBCcaABbcC though, which is simple enough.

Some numbers describing the wind on these motors:

No. of strands: 22 Gauge of single strand: 0.23 mm No. of turns per core: 9 Winding pattern: AabBCcaABbcC

I’ve been giving things some thought, and I have decided I’m going to opt for a Wye termination, because it just seems like a far better idea both in terms of space restrictions and current capacity. What I plan on doing is reducing the number of turns by about a third (for a higher Kv) and increasing the copper cross sectional area and then terminating in Wye. I should get a Kv close to 225.

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this thread is awesome.

The stator is free from windings.

To all those interested, it is a quite a serious mission with all of the glue involved, especially with the brittle burned coils.

Now to work out the wire gauge and length of wire I’ll need for the new wind. I’m going to be going with the Wye wind, 6 turns per core to get the Kv I want.

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will it make any difference that the epoxy coating on the stator is all flaked off and cracking and peeling now?

i had the green epoxy coating come off when I “unwound” as well. I picked at it and took off a whole lamination. Don’t do that. I spend many many fruitless hours trying to recoat the stators edges. I made a pie with three types of glue on top of each other: crazy glue, liquid electrical tape, Task9 polyurethane. Don’t do that. It’s definately worth the time to get some high heat epoxy. I read harbor freight has some. Rcgroups has a a thread on doing it worth reading. I also tried using super thin fiberglass which I read about there. Don’t do that either! Otherwise, if u don’t recoat all the edges well it will be a nightmare of shorts through the stator. I hate my stator now and now hate rewinding. I must have rewound it four times and shorted everytime. Coat the edges with good lighting so u can really see and get them all. My stator was harder as its already pressed on an aluminum shaft and hard to access as well but none-the-less coat all the edges well

@longhairedboy @Hummie Did you try taping the outside all the way around and then the inside? Then you could just dip it into a cup of whatever you choose to coat it with. Then peel off the tape.

I was thinking just coat it in a high heat enamel like this: http://www.homedepot.com/p/Rust-Oleum-Automotive-12-oz-High-Heat-Enamel-Flat-Black-Spray-Paint-Case-of-6-248903/202628557

Here’s what I found on ES. https://endless-sphere.com/forums/viewtopic.php?f=30&t=38873 Sprayon red insulating varnish https://www.zoro.com/sprayon-red-insulating-varnish-20-oz-s00601000/i/G1811056/?gclid=Cj0KEQjw09C5BRDy972s6q2y4egBEiQA5_guv82NXM4j5vRbPeZQYr4iaDhQqdt5NhSF6-SJBf8Hb4IaAqwc8P8HAQ&gclsrc=aw.ds

@longhairedboy Yes! Forgot to mention that re-insulating the stator is actually the next step, which I’ll do while I’m trying to source wire.

I also forgot to mention that while I was unwrapping the coils, under the two offensive poles with the burned wires, there was bare metal, which is obviously where this whole thing started. I think that some of the NTM motors suffer from poor stator core insulation, and I think that’s what caused this motor to fail.

I’ve found a couple of tips online, and I think I’m going to go with a high heat epoxy, and mask off the outside of the core as well as the inside.

I’m going to spend some time sanding off the epoxy on the top and the bottom of the core, but I won’t worry too much about in between the teeth.

Lol I bet not lol

20 stupid words

I didn’t do it that way thinking it’d be filling valuable space where there could be wire. It’s not much space but I try to over optimize :expressionless:

I suppose it depends on how viscous the insulator is…But I think if the excess could drip off it would work well that way. My guess is, people aren’t in factories brushing that stuff on.

Did some shopping for some vital rewinding supplies. Grade 3 enamelled magnet wire (more about this later), some Rustoleum high heat spray enamel, silicone lead wire, heat shrink and beer.

Black Label is a local South African favourite, and a quart is fondly referred to as ‘Zamalek’, named after the Egyptian Zamalek FC’s walloping win over local favourite, the Kaizer Chiefs. The beer is said to be as strong as the Egyptian team that night. If you haven’t tried it, you owe it to yourself to make a plan.

The stator is masked up and ready for a hit of enamel, after a little sanding. I went for the spray on over dipping, as most of the coating is intact. If I was doing a fully stripped motor, I would go for a high heat epoxy dip.

Looks like you’ll be doing a better job than me.

Strong beer I like. Here in San Francisco there’s the Speakeasy brand. Everything they make is strong. They have no story though.

Are u going to waterproof it!? I want to and figure all that needs to be done is insulate the three connections from magnet wire to whatever it is you’re connecting them to. And maybe a spraying of some of that spray on enamel for the windings just to make sure and also keep them from moving.

@Hummie Yeah, I plan on waterproofing as much as I can. What I’m planning to do is once everything is wound and the phase wires soldered up is spraying the whole thing with 2 light coats of this this enamel paint and then dipping the whole thing in laminating resin, with the inside and outside masked up as above. Should hold up to much abuse.

I’ve put on two thick coats of the enamel paint. It stacks up quite nicely, and I reckon I’ve got about 1.5mm of it on the ends and about 0.5mm on the insides of the teeth.

While that’s drying, on to discussing the winding wire.

I opted for 1.12 mm conductor diameter grade 3 magnet wire. The outer diameter is approx 1.18 mm. I based this on a calculation of the cross sectional area of the stock wind, multiplied by a factor of 1.2 or so based on what I could comfortably fit on the teeth.

The height of the conductor bearing part of the teeth was about 8 mm, and the smallest radial gap is about 2.8 mm. This leaves me with a bit of wiggle room.

I’m going for a single strand wrap. Grade 3 based on the fact that I want to never have to do this again. It’s not all that fun, as @Hummie has mentioned.

Doing three coatings of enamel or resin of some sort you say. did it ever get hot before because that sounds pretty insulating. What’s wrong with 2 or 1?

Omg this is a pain in the stator

I’m never gonna try this lol