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Stator and rotor scraping at one motor side only??

So at a certain rpm, I get that crazy wrrrt motor sound and after some small rpm range it goes away

This started happening on the first warmer days this year and the magnets are holding up really well as I have had this issue for 2 months and I finally now opened up the motor.

Magnets are battle hardened so idk how they menaged to go to shit…

This is literally my 5th or 6th Maytech gone to shit after less than 1000km…
Cant even imagine how often others break

Any ideas what could help?

Filing the stator a bit maybe?


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No dirt on the magnets? Hard to see on the picture

Usually metallic particles build up inside the motors and start scraping, specially it your board has them close to the ground

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No dirt, motors and closed and clean only a bit of dust was there, I will file down the stator and try again

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Worn or bend shaft?

I wouldn’t do that, this will short the lamination together and can greatly increase the loses on the motor

If it’s not that can only be the bearings

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When I put in the shaft only only a few mill in the bearing and spin, it seems to be perfectly true, also dont see a reason why a bit bent shaft would cause this issue when the motor spins alone…

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Already done it lol

I will try to check if it still scrapes by paiting the stator and then trying to spin it at the rpm it makes the noise.

Also I can just apply some insulation over again?

Why would this increase the losses?

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You could sand with a fine sand paper parallel to the laminations

The stator is made in layers insulated from one anotherto reduce the induced current loop, Eddie current loses, when you file them there is a big chance they are connected again

image

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is there excessive play when you wiggle the motor shaft against the can?
Is there excessive play when you wiggle the can or the shaft against the bearings? (can you make the can rub?)

just asking questions I’d ask myself. I’m curious about motor failures.

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The can is supported by the shaft, but only at one end. Basically it’s one big lever, so any undue force (hard drop, impact, big rocks, whatever) can bend the shaft, or the bore in the can that the shaft is pressed into. Have a look at this picture, lovingly drawn in MSPaint.

The only place the can and magnets are supported is at the red arrow. So if the shaft is bent near the red arrow, or the hole the shaft is pressed into is wobbled out, then the can will not run true.

You can also see that a very tiny bend or deviation there, can result in a significant deviation at the far end of the can.

It’s an inherent design flaw in most of the motors we use, since they are descended from motors designed for RC airplanes, where they don’t see these kinds of lateral forces.

The only motors that are immune from this weakness are inrunners, or outrunners with a third bearing to support the can’s other end such as Hobbyking Sk3 and SK8, and a few others that don’t spring readily to mind.

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Check the shaft is seated and the set screws are tight in the can. Remove, clean, reinstall

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Here you can hear the sound, doesn’t sound like rubbing against the stator so much…

Cant believe maytech didn’t fix this simple issue yet…
Maybe the new motors have the third bearing

Maytech sucks the last time really had. 6880 is crap. 6396 is running to hot, broken bolts etc.

Time to start thinking for a other supplier.

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That sound could just be a single loose winding wire resonating at certain pitches. Covering it with epoxy (sometimes called battle hardening) could rid the noise at the detriment of not cooling as efficiently.

That may not be what’s wrong, but it’s definitely a possibility. If it is that, then eventually it could cause failure after prolonged use. But this is a lot of speculation.

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Like a copper “string” in the windings?

My phase wires are already epoxied in place…

Anyways the sound got much better after i filed down around the whole motor

Im giving them another chance, if they fail on me again I will try to make a motor that will last myself haha

Magnets will be welded to the can, and the shaft will have 5 bearings from the end to the pulley :smiley:

Like I mentioned earlier, it’s a design flaw with pretty much all esk8 outrunner motors, with a couple notable exceptions that I mentioned, like the SK3 and SK8 and a couple others I don’t remember.

ALL other outrunner esk8 motors have this weakness. Torqueboards, APS, Maytech, Flipsky, all of them.

6374 and 6380 tend to have more problems than 6355s, because the cans are longer, and thus more leverage.

Motors with 10mm or 12mm shafts tend to be much better than ones with 8mm shafts because the
thicker shafts are stiffer and more resistant to getting bent.

But even a 6355 with a 12mm shaft is not 100% immune.

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I think all cans that do not have a bearing on the end of the can like those 6396 motors run the risk. However those motors overheat like crazy, maybe because they are sealed off too much?

Also about 5 bearings on the same axle, thats not really a great idea. More than two bearings on a axle cause more bearing wear because they are never totally the same, thus having one bearing spin not completely true.

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