Bent motor shaft?

[amstel78]

I was inspecting all four motors closely today and noticed the bell housing on the rear starboard leg motor seems to have a wobble. It's not loose but when turning it slowly by hand, the gap distance between the bottom plate and the bell housing changes as the housing is turned.

I took all props off and ran the motors and could not feel any unusual vibrations. The shaft itself does not look like it rotates off axis either. Placing a thin rigid piece of plastic against the shaft while spinning doesn't reveal any strange vibrations either. The external temps of each motor as measured with an IR temp gauge all show within a few tenths of each other.

It's a little disconcerting to see the bell housing do that, but everything else about the motor looks fine. With the blades on and the motor turning, there are no extraneous vibrations and the blades track straight.

Unfortunately my dial indicator is broken so I can't measure runout of the shaft. Without that, the only thing I can think of at this point is that if the shaft isn't bent, the bell housing itself isn't true or isn't mounted well.

Can the housing be removed by unscrewing the two torx screws on the prop mount?

Should I be concerned?

 

[amstel78]

Found my other dial indicator (digital) that measures up to 1/10,000 of an inch.

The shaft itself is true with absolutely zero runout. Quite impressive really. The bell housing on the other hand does. In fact all four have a little with the worst around 0.004".

I guess I can relax a little then [emoji23]

 

[Deleted member 103366]

I would be concerned that DIY investigations that involve dismantling anything would invalidate warranty. You say the "gap distance between the bottom plate and the bell housing changes as the housing is turned" is there a corresponding rise and fall in the outer edge of the top face of the motor. Putting a pencil tip against the base of the bell and turning the motor can you see any axial (ooops meant radial) run out?

Edit

Ah answered whilst I was typing

 

[bumper]

In order to remove the rotor (bell housing), you need to dismount the motor from the arm in order to get to the bottom of the motor. The rotor shaft goes through a bearing at the top of the stator and another at the bottom where it is secured under the motor place by a small "C-clip". In my experience the shaft OD to bearing ID is a tight.

Note this is on a M2P, but they are probably the same or similar.

 

[amstel78]

I would be concerned that DIY investigations that involve dismantling anything would invalidate warranty. You say the "gap distance between the bottom plate and the bell housing changes as the housing is turned" is there a corresponding rise and fall in the outer edge of the top face of the motor. Putting a pencil tip against the base of the bell and turning the motor can you see any axial run out?

Edit

Ah answered whilst I was typing

I'll have to somehow rig my dial indicator holder to see if there's any runout at the top of the propeller plate as indicated in your diagram, but based on what I'm seeing, my guess is the housing itself or the way the housing is attached to the "armature" mount isn't exactly true.

I was more focused on the shaft itself but since the props aren't technically attached to the shaft, i have to wonder if the minute runout in the housing is anything to be concerned about.

And no, I won't be dismantling anything. At least not as long as my warranty and Refresh is still valid. It was more out of curiosity that I asked. I've rebuilt plenty of small brushed electrical motors, nitro motors, and even a twin turbo AMG V12 once, but never experienced a modern micro brushless before. They're pretty neat but I have no idea how they go together. [emoji848]

Anyway, since the axial runout on the housing seems to be minor, until I figure out a good way of measuring lateral runout, I can only assume it'll be minor (if any) as well. FWIW, I don't feel any lateral movement.

I've only had one minor incident with my MA2 where it clipped my living room wall about 4 feet of the deck. I didn't even break a prop, but still, paranoia can run rampant after that. [emoji23]

 

[amstel78]

In order to remove the rotor (bell housing), you need to dismount the motor from the arm in order to get to the bottom of the motor. The rotor shaft goes through a bearing at the top of the stator and another at the bottom where it is secured under the motor place by a small "C-clip". In my experience the shaft OD to bearing ID is a tight.

Note this is on a M2P, but they are probably the same or similar.

Cool. Thanks for the insight. Much obliged.

 

[DanMan32]

I had an issue with one of my P3 motors. It had some play which I thought was the bearings but when I worked on replacing the bearings, I think I found really the bell pushed up a bit off the shaft.

 

[boblui]

Out of curiosity I have checked the centricity of one of the motors of my M2P. Not perfect but certainly no issues.

 

[amstel78]

Out of curiosity I have checked the centricity of one of the motors of my M2P. Not perfect but certainly no issues.

Thanks for the video. Your findings are similar to mine as far as bell or rotor housing goes. The actual shaft on my motor in question exhibits no runout though which is surprising.

What is the brand or model number of your dial gauge? I have to replace my analog one which has since stopped working.

 

[boblui]

What is the brand or model number of your dial gauge? I have to replace my analog one which has since stopped working.

The brand is Interapid, Swiss made. I bought it some 25 years ago ......

 

[amstel78]

The brand is Interapid, Swiss made. I bought it some 25 years ago ......

Thanks. Found them online at McMaster. Not sure if the new ones are still Swiss made so I'll research a bit more.