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Help! Radial motor rattles after crash

hitjim

New member
#1
I've been helping my son learn to fly with a FT Simple Cub on power pack B.

He nosed it into the ground after barely missing it the first time and stalling. Maybe 10-20ft height. Maybe at a ~70deg angle.

The motor seems to still be balanced just fine. There's no play on the shaft or outrunner.

When I'd spin it by hand, there was a faint rattle. When I'd spin it up anchored on the ground, it went away. But we'd hear it rattling most of the time in the air.

Flight times and performance don't seem affected. Again, everything runs smooth and balanced, it just doesn't sound like it.

I opened it up, blew it out with air, and inspected the windings etc - nothing out of the ordinary (that I could see, anyhow). I wonder if it's a slightly damaged bearing or something?

Is it worth the time/sweat to try and source and replace a bearing on one of these motors? Or should I just fly with it until it becomes a problem?

I replaced the motor already. But if it's good to fly until it gets much worse, maybe I'll just make this the "trainer motor" :p
 

"Corpse"

Well-known member
#2
I've been helping my son learn to fly with a FT Simple Cub on power pack B.

He nosed it into the ground after barely missing it the first time and stalling. Maybe 10-20ft height. Maybe at a ~70deg angle.

The motor seems to still be balanced just fine. There's no play on the shaft or outrunner.

When I'd spin it by hand, there was a faint rattle. When I'd spin it up anchored on the ground, it went away. But we'd hear it rattling most of the time in the air.

Flight times and performance don't seem affected. Again, everything runs smooth and balanced, it just doesn't sound like it.

I opened it up, blew it out with air, and inspected the windings etc - nothing out of the ordinary (that I could see, anyhow). I wonder if it's a slightly damaged bearing or something?

Is it worth the time/sweat to try and source and replace a bearing on one of these motors? Or should I just fly with it until it becomes a problem?

I replaced the motor already. But if it's good to fly until it gets much worse, maybe I'll just make this the "trainer motor" :p
Try putting a big prop on it and seeing if the tips of the prop are off kilter. That's a better way to check alignment than looking at the shaft.

As long as it works I wouldn't throw it out. Sounds like you have a loose bearing or something like that. As long as it runs smoothly you should be fine.

Happy flying!
 

Ketchup

4s mini mustang
#3
I feel like it might be a bearing, but I am no motor expert. If it is a bearing though, you should still keep the motor. I have a plane that still runs with really worn bearings (it is a quad motor on 4s but I can still hear the bearings in flight). I don't know what happens when the bearings get "too worn" though.
 

PsyBorg

Wake up! Time to fly!
#4
Did the "E" clip pop out of its groove or even snap off completely? That would allow the prop to pull the bell forward and the only thing holding it in is the magnets?
 

BATTLEAXE

Well-known member
#5
The only physical point of wear or failure will be in the bearings. The motor itself should last for a long time unless physically damaged, like a bent can or shaft. If you say the shaft isn't bent then the only thing to look at will be the bearings. For a decent motor like the radial i would say it is worth it to get new bearings which should be able to be found online through sites like bangood or aliexpress. Bearing generally price out to 5-10 bucks for a pack of ten. the motor should have two bearings in it leaving you with 5 full bearing changes. Now here is the question. Would you rather buy 5 radials at say 25-30 bucks a pop or get 5 radials out of a $10 pack of bearing and just take the ten minutes to replace them?

If it was a bunch of cheap Racestar motors you have then yea I would say it is just easier to get new motors. But in your case i would be shopping for new bearings. And yours might not need to be changed right away if they are just making noise and there is no difference in performance. But keep in mind that they wont get better on their own, they don't heal. So you will need bearings at some point in time. Might be a good idea to take the motor apart, see what size you need, and re-assemble then order new ones. By the time the bearings come in the mail, you have them on hand when you need them.
 

cranialrectosis

Well-Known Member
Mentor
#6
Both @BATTLEAXE and @PsyBorg have points, but neither have mentioned the possibility of a loose magnet or debris in the bell.

To replace bearings or examine the inside of a bell you will have to remove the E clip. If you don't have a clip, @PsyBorg is right and you need a new one.

Put the motor in a plastic bag to remove the clip. If the clip springs off at high velocity, bounces off your eyeball and buries itself in the rug, the motor is toast until you replace that clip. Remove them with caution. E clips are notorious for heading for the stars the second you let them.

Seriously. Remove E clips with the whole motor in a bag. It is truly amazing how far they can fly and/or roll.


Open up the motor and test the magnets with a gentle probing with a toothpick or toothbrush. Look for scratches on the inside of the bell or on the magnets to indicate that something is loose in there. Blow out any sand using moderate pressure or a soft toothbrush. Use a good epoxy to re-attach loose magnets and take your time. Gluing your motor bell in place or gluing a magnet in such a manner that the bell won't seat ruins your motor.
 

Merv

Well-known member
#8
All good ideas, those rattles are tough to track down.
Sometimes a piece of grit can cause a lot of noise. I’ve had had luck taking a motor apart and using an old toothbrush to remove any foreign material. A brush may be more effective then compressed air.