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What caused this?

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I have this HW Xerun V10 G3R from a used car I bought and this happened…. 
the rotor just shattered… I was using it into my 01e drifter and I did notice it to be hotter than the prior motors ive used in the car… is it still worth changing the rotor? 
 

IMG_5040.jpeg

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Odd!  So what am I looking at there?  Has the magnet completely exploded?  I can only imagine that would happen if the magnet got out of balance at high RPM, and broke apart.

What's going on with the rotor?  Is that part with the spiral on it a magnet, or part of the shaft?  Or perhaps that part is the magnet, and the stuff around it was some kind of ceramic?  I've never seen a rotor completely apart before so I don't really know what all those different materials are.

The only reason I'm here is because I had something similar happen 2 years ago with an old 9 turn Etronix Photon motor.  Half-way through my final at Revival 2022, it started making a seriously loud screeching sound - like the gearbox was failing.  I figured with a noise like that it wouldn't get to the end of the lap, but it just kept going.  I even noticed that it was slow to accelerate, like the pinion was slipping, but it was still reaching high speeds on the straight.  There's no way on Earth a slipping pinion should have lasted as long as it did.  It got me through several laps and completed the race.

When I stripped it down I expected to see a jammed bearing or something, but I actually found the adhesive that secures the magnet to the rotor shaft had broken (probably due to heat), and the magnet was spinning on the shaft.  I did try putting it back on with epoxy but when I tried it last week it had failed again, I guess the heat of a few gentle runs and the cold of winter has broken it again.

Interesting to see if something similar has happened here, and if it's cause the magnet to go out of balance or clout the windings and shatter.

I'm guessing that motor isn't vented, so it's not a foreign object that's got in there and smashed it?  What's that solid-looking thing inside the can just to the right and just below centre?  (immediately up from the solder mark at the bottom?)  Looks like a small screw.

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1 hour ago, Mad Ax said:

Odd!  So what am I looking at there?  Has the magnet completely exploded?  I can only imagine that would happen if the magnet got out of balance at high RPM, and broke apart.

What's going on with the rotor?  Is that part with the spiral on it a magnet, or part of the shaft?  Or perhaps that part is the magnet, and the stuff around it was some kind of ceramic?  I've never seen a rotor completely apart before so I don't really know what all those different materials are.

The only reason I'm here is because I had something similar happen 2 years ago with an old 9 turn Etronix Photon motor.  Half-way through my final at Revival 2022, it started making a seriously loud screeching sound - like the gearbox was failing.  I figured with a noise like that it wouldn't get to the end of the lap, but it just kept going.  I even noticed that it was slow to accelerate, like the pinion was slipping, but it was still reaching high speeds on the straight.  There's no way on Earth a slipping pinion should have lasted as long as it did.  It got me through several laps and completed the race.

When I stripped it down I expected to see a jammed bearing or something, but I actually found the adhesive that secures the magnet to the rotor shaft had broken (probably due to heat), and the magnet was spinning on the shaft.  I did try putting it back on with epoxy but when I tried it last week it had failed again, I guess the heat of a few gentle runs and the cold of winter has broken it again.

Interesting to see if something similar has happened here, and if it's cause the magnet to go out of balance or clout the windings and shatter.

I'm guessing that motor isn't vented, so it's not a foreign object that's got in there and smashed it?  What's that solid-looking thing inside the can just to the right and just below centre?  (immediately up from the solder mark at the bottom?)  Looks like a small screw.

The gray thing you see inside the can is the material that came off the rotor itself... magnets seems to be intact

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I just did a bit of searching online, and it turns out brushless motor magnets are usually ceramic.  Surprised me as I didn't realise you could get a ceramic magnet.  So, it seems your magnet has destroyed itself somehow - maybe excess heat cracked it or denatured the glue and caused it to vibrate on the rotor.  It's a strange one though, I've never seen that before.

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55 minutes ago, Mad Ax said:

it turns out brushless motor magnets are usually ceramic

I would have thought they were neodymium magnets.  Brushed motors have black ferrite magnets. Those are also called ceramic magnets.  Because brushless could only have a smaller core, I always imagined the core was stronger neodymium. (Unless they are called ceramic too?).  I'm learning something everyday!

 

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I've only heard some stories about rotor blowing up on Castle motors due to crazy power.

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