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electricpete

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Reply with quote  #16 

You get involved in some interesting ones all right, Oli!  I have to admit I don't follow a lot of the cases you post because they get complicated quickly. 

Going from cold to hot they see much higher vibration but no change in detectable resonance‚Ķ that supports the idea that the thermally-expanding rotor may be in an axial bind. When they inspected the bearing and didn't see any skidding... did they see anything to indicate the bearing was carrying axial load,  like unusual wear/discoloration on the roller edges and race flanges?   If not, what parts do they think are contacting axially to restrain the expansion?

The other thing that comes to mind is a rotor thermal bow. That doesn't readily explain the upper bearing temperature, but who knows maybe the angle misalignment of the cylindrical bearing during severe bow causes heating (it's a longshot, I know). 


OLi

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Reply with quote  #17 

No damage found on the rollers anywhere.
Only idea currently is uneven radial-axial contact btw. rotor halves, internal surfaces either pure mechanical and or in combination with resulting uneven current flow.
It is the only identified difference so far btw. the only good motor and the multiple bad motors. 
"Mating" ends of the rotors have 0.4mm spacing all around in the good rotor, all others are irregular and at places very small around the circumference.
In the good motor the rotor current need to go down to the shaft I guess or do work like a proper separate std. rotor, in rotors that get in contact at a diameter or radial point(s) current goes other ways I guess or are there no currents so it is pure mechanical contact and bending?
True, that bending may be giving the overload that increase bearing temp. 

Well you do need to do en effort to keep up the image of a GhostBuster :-).
On the other hand we call this kind of jobs as "Wild Goose Chases" so maybe we are GeeseBusters?


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