It looks more like metal oxide as a result of the prop clips vibrating against the out runner.
If you remove the clips you'll likely see the wear that is occurring.
Hey We,I apologize for sounding totally ignorant but outer runner ? I will look that up and into it . I do long runs and fly it up to 2 miles away from me doing photos on my job site. I don't need to have parts failing on me. thanks for a place to look.
jwt, I see where your clips contact the outrunner, that there is more what looks like dust (oxide) on the area that has the most load transfer, usually a bearing loosing grease will be flung (the grease) 360 and I think almost all the grease would have come out of the vent holes. Question: Do you leave your props on all the time? Because I don't have that and I take my props off to store the AC in it's case, therefore the higher load area is present only when flying. Just wondering if leaving them on could cause this condition.Do they look like what I have showing on my P4?
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I've got 42 hrs on my motors.. I've had little streaks showing on the top of a couple of motors... Perhaps the bearings are leaking?
It started showing up 20+ hours ago. Everything runs fine. No strange noises etc....