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Rimfire motor mystery?

Old 10-19-2018, 05:08 AM
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scattermaster
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Default Rimfire motor mystery?

So,
I've been running the Rimfire motors for the last 3 or 4 years because that's what all the fastest guys are running. Along with the rest of their power set up.
The motors usually run normal when they're new, but sooner or later they all seem to develop a noise. When running on an airplane it sounds like a growl.When I have one out of an airplane and hold it up my ear, it makes a clicking/ticking noise. I've been told by more than one person that it's my bearings. Well, I've bought bearings from 3 different suppliers and changed them out numerous times and it never seems to fix the noise. I always end up giving up and just buying new motors. I'm getting tired of that. Does anyone know what's going on with these motors?
Bearings?
Last night I decided to try an experiment. I took all 3 ball bearings out of a motor and made some bushings out of a ptfe/acetal plastic to take their place. The fit on the bushings is perfect, there is NO side play.
To my surprise, the noise is still there. I can turn the motor slowly and in one spot there is a definite click. So it would seem like a magnet is moving but it doesn't click everywhere in the rotation (like 360 deg) I have taken a knife blade and pried on the magnets and I can't make any of them move.
There is a fairly large space between the magnets and the armature, so it seems highly unlikely that they are hitting.
Does anyone have any ideas?
thx,
Jim

Last edited by scattermaster; 10-19-2018 at 05:13 AM.
Old 10-25-2018, 10:16 AM
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GSJames
 
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Let me know if you figure it out, "Inquiring minds want to know..." See ya next week.
Old 10-25-2018, 05:30 PM
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scattermaster
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Originally Posted by GSJames View Post
Let me know if you figure it out, "Inquiring minds want to know..." See ya next week.
I looked and looked and looked for loose magnets and I just can't find any. I'm at a loss.
I did learn a couple of interesting things though.
1. Someone told me that the magnetism alone would hold the motor together while it's running. Like, you could in theory run without the retainer on the rear end of the shaft.
Well I tested it and NO you can't! As I advanced the throttle, I watched the outside of the motor move farther and farther forward until I was afraid it was going to come apart. SO, don't try this at home folks. (I beat you to it)
2. The plastic bearings ran at full throttle for about a minute then suddenly the motor slowed down very rapidly.
After I shut it down, it was very tight and squeaked when I turned it. When I tore it down though, the plastic bearings were perfectly fine all except the very front of the front one. Not sure why it failed there. Maybe I made it too tight.
Note to the peanut gallery,
I had no intention of racing it that way, it was just an experiment. Just to satisfy my curiosity. The original bearings are back in place.

Last edited by scattermaster; 10-25-2018 at 05:52 PM.

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