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Electric Stunt => Gettin all AMP'ed up! => Topic started by: Joe Yau on February 21, 2017, 11:01:22 AM
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I have a Cobra 2826-12 that the shaft has gain some play from side to side.. I didn't notice that when it was new. but otherwise works fine. Is this normal ? or I should replace the bearings.
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Does the motor run OK? Does the prop angle change significantly when you wiggle it that way? Can you feel a gravelly feeling when you turn the motor, or is it smooth aside from the normal cogging? Does the spinny* part of the motor rub on the stay-put part of the motor when you're pushing and pulling it while turning it? Or is it just a side to side translation of the prop?
I suspect that a certain amount of wear-in is normal. Ball bearings in general offer you a choice between high friction with good locating, or low friction and a bit sloppy. So you actually don't want the tightest fit in a motor. "Noticeable play" is hard to quantify, though, because there's slobs out there that would only notice play in the bearings when the motor fell apart, and there's uptight detail-oriented guys who might notice a few thousands of an inch of play that no one else could perceive.
On the plus side, I'm pretty sure that changing out the bearings in these motors is fairly easy -- just get a set from Boca or Cobra, press out the old ones, and press in the new.
* I believe in using precise engineering terms at all times
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I just felt the shaft in a brand new motor. It has 0 play. A how-too change bearings video is at:
https://www.youtube.com/watch?v=3RJQfbzXNjQ&index=12&list=PLMy5bnpkH-HyH5P8-atqqnYQEsFlmwR8j
I think the Cobra motor has a snap ring that needs to be removed in order to pull it apart. A pain to say the least. Does anyone know of a good source for a snap ring pliers?
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I would say if it's perceivable without equipment, it's time to change the bearings.
He knows more than I do about this. BTW.
Does anyone know of a good source for a snap ring pliers?
Not specifically, but Amazon, Wholesale Tools, MSC, Eastwood, and a whole raft of other suppliers should have them. The real question (which I can't answer) is who makes the best pliers -- once you know that there's probably a dozen places to get them.
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I change mine with any perceptible change. The EFlite bearings I use get changed out pretty regularly.
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Does the motor run OK? Does the prop angle change significantly when you wiggle it that way? Can you feel a gravelly feeling when you turn the motor, or is it smooth aside from the normal cogging? Does the spinny* part of the motor rub on the stay-put part of the motor when you're pushing and pulling it while turning it? Or is it just a side to side translation of the prop?
The motor seems to run o.k., if you push on the tip of the spinner to side to side, there's about at least 1/16" play. and there's a slight gravelly feel when you flip the prop. but goes away when its running. there is no rubbing within the motor. and the cogging seems normal.
I would say if it's perceivable without equipment, it's time to change the bearings.
MM
I most likely will.
I just felt the shaft in a brand new motor. It has 0 play. A how-too change bearings video is at:
https://www.youtube.com/watch?v=3RJQfbzXNjQ&index=12&list=PLMy5bnpkH-HyH5P8-atqqnYQEsFlmwR8j
I think the Cobra motor has a snap ring that needs to be removed in order to pull it apart. A pain to say the least. Does anyone know of a good source for a snap ring pliers?
Thanks for posting the video. I had it apart once already.
I have seen those small snap rings plier at KMS tools.
I change mine with any perceptible change. The EFlite bearings I use get changed out pretty regularly.
I have an E-flite 32 on my Legacy, and has well over a hundred flights so far.. and still seems fine.
Thanks all for the replies! H^^
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The motor seems to run o.k., if you push on the tip of the spinner to side to side, there's about at least 1/16" play. and there's a slight gravelly feel when you flip the prop. but goes away when its running. there is no rubbing within the motor. and the cogging seems normal.
Oh, God -- yes! Change it out! I was thinking maybe you were feeling a little 0.005" ticking. Gravel and 1/16" of travel means the thing is about to fall apart.
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Oh, God -- yes! Change it out! I was thinking maybe you were feeling a little 0.005" ticking. Gravel and 1/16" of travel means the thing is about to fall apart.
Thanks Tim. I guess I'll have to change it out.
Joe