1515 Rattling Sound - Bearings going?
 

Just been checking a motor I am selling and noticed that when it spins on its own, it sounds like something is rattling.

The motor isn't that old, and has never been abused. I've taken it apart and there is nothing wrong with the rotor or the windings.

Only thing left is the bearings, but they seemed ok when I took it apart.

To turn the motor it's pretty stiff, quite a lot more than my other 1515 and the 1717. Also, it rattles when it spins.

I made a video explaining the problem, and yes I know about how you shouldn't rev them with no load, but it's only running 4S, so it shouldn't over rev.

http://www.youtube.com/watch?v=kApiCymFVnY

What can I do in getting replacement bearings. Will Castle warranty replace things like that? If so will I have to send it off?
I would rather avoid sending it off as it takes ages. If I have to though I will just buy my own but can someone tell me what size, and how to remove the old ones.

Thanks

Anyone?

Found the bearings are 5x16x5mm

How do you replace them? I can get them out the end bell, but I can't get them out the cap...

It sounds to me like something is dragging.

When you took it apart, might you have swapped the brass spacer bushings front to back?

I put them back just as I took it apart. If I put them back the wrong way round would the shaft not be able to move back and forward a significant amount?

Took it apart again to check and the smaller length brass spacer is on the front (pinion side), the longer one is on the back.

Is this correct?

Did it look like anything was rubbing or in the motor?

Nope, motor is spotlessly clean inside.

There are no scratches on the rotor and all in internals look fine.

Humour me a moment:

with the rotor removed, use a pencil or pen to spin the front & rear bearings- do they feel rough or like there is some play or slop in any direction?

And just for the record, you really shouldn't be sticking things into your bell end to start with! :lol:

Oh Neil you are such a wit!

I have tried that and both bearings are perfectly smooth to turn.

As for play, the one in my bell end :yes: ... is fine. The one in the end cap also seems to be fine, I can't feel or see any movement so I really don't know what's going on.

Took my other 1515 apart and to my surprise it has a different type of spacer.
The front one is the same thin brass spacer, but on the rear it uses two chunky brass spacers, with two O-rings inbetween.

Why is this?

And why the hell is my other motor making that noise when it spins?

OK so, after a bit of research, I tried several combernations.

I labled the motor with the problem as bad, and the one I know that works good.

bad rotor + good can = buzz + stiff to turn
bad rotor + bad can = buzz + stiff to turn
good rotor + good can = quiet + easier to turn

So, this leads me to think it must be a problem with the rotor.
Being stiffer to turn is just the magnets in the bad rotor are better I am guessing.

The buzz however would be one of two things, either the rotor is unbalanced, or there is something on the rotor hitting the can, maybe kevlar strands?

I have inspected the rotor and there are some tiny kevlar fibres coming off, but surely they could not cause all that noise...

Did you try good rotor + bad can- if there was no buzzing with that combo then that would point to the bad rotor being the issue, though whether it is something serious, or just the kevlar threads flapping a little, that's another question ( tint bit of CA glue to stick the threads back down maybe & then re-test? )....

Just tried the good rotor in the 'bad can' and it's fine, so yes it's definitely the rotor, not the bearings or anything.
I will try gluing down the strands :)

Haven't got any super glue, but to be honest I don't think it will make a difference. The rotor does have a few tiny loose strands on it, can they cause any problems or is it acceptable?

Also, is a slightly unbalanced rotor acceptable and am I just worrying over nothing?

Please, can anyone tell me if a slightly unbalanced rotor acceptable, (if it is that what is causing the noise in the video)?

Patrick isn't replying to my PM, nobody's replying to this topic and Castle won't reply either :S

You can test if the rotor is ( badly ) unbalanced or not yourself- you just need some bearings and a non-magnetic stand to sit either end of the rotor on to spin it- a couple bits of wood with a V-notch for the bearing to sit in would work.

Also, consider that is the rotor was unbalanced enough to be a real problem, then the whole motor would vibrate like your mobile phone as it spins. If it just sounds a little off and isn't vibrating, and the temps are fine when you run it in a model normally, I wouldn't really worry so much- chances are it would have failed/shattered or turned into a washing machine full of bricks by now if it was a serious issue..

I did try testing to see if it was really unbalanced by using your method and it was fine, but then again it's not going to pick up small imperfections.

It doesn't really vibrate much, no more than my other motors, it just makes that noise.
Temps are fine too. Think you're right about if it was a serious issue something would've broken by now, so I imagine it's fine. I just wanted to be sure as I've sold it lol, and don't want get a reputation for selling bad stuff.

Cheers Neil

Just got a PM from Patrick and he says he is sending me a new rotor!
Castle ROCK!