Stuck motor ?

[richandhiscat]

Flew the mini 2 today, about 20 minutes altogether, then went on to the next location and one of the rear motors wouldn't start - the prop moved with the draught from the other three before they cut out, and didn't seem to be stuck. Tried it about four times with no luck, but when I got it home it worked fine. There was no error message, but I had landed it on a wood chipped area previously - could a small amount of debris have caused it (couldn't see anything), or did it overheat?

 

[Yorkshire_Pud]

Tiny debris can jam the motors, the clearances inside these motor are minute.
It might be an idea to take the props of all the motors (KEEP THEM IN THEIR PAIRS) then turn the drone upside down, put the top of the motor to the mouth of a vacuum cleaner nozzle and slowly rotate the motor to suck anything out of the motor.
If you do the latter BE SURE to refit the props to the correct motors, more than on person has fitted props to the wrong motor and when they are run up they attempt to push that motor DOWN. The drone is likely to flip if this is done.

I suspect you would be more likely to get a warning about the motor's control chip, ESC?, over heating than actually overheating the motor.
I have seen ESC warnings after holding the a Mavic Mini whilst giving it full throttle. I believe Phantom 3's could cook the relevant ESC if the relevant motor jammed and the drone continued to try to drive it, so I am wary of those warnings and switch the drone off and let the drone cool off.

 

[eEridani]

Just tossing out ideas here...

Another possibility since the stuck prop was freewheeling (not actually stuck), is the debris dislodged shortly after the warning - which was likely flagged at power-on testing (that short glitch of all the props). But a second power-on startup attempt should have worked.

Other things that happen to electronics is broken wires at flex points. Unfolding and folding the arms can make failures intermittent; fails one time, works the next.

 

[old man mavic]

@richandhiscat do try to have the props unfolded before you start the motors ,this puts a lot less strain on them as they begin to rotate,with regards to cleaning them with a vacuum ,just remove the props from one motor at a time and reattach that pair ,before moving on to the next motor ,that way you completely avoid mixing them up ,and just as an aside ,if you ever manage to just damage on prop of a pair on one motor ,always replace both props to maintain balance ,and that way you know both of them have the same flight time on them

 

[cheddar-man]

@richandhiscat do try to have the props unfolded before you start the motors ,this puts a lot less strain on them as they begin to rotate,with regards to cleaning them with a vacuum ,just remove the props from one motor at a time and reattach that pair ,before moving on to the next motor ,that way you completely avoid mixing them up ,and just as an aside ,if you ever manage to just damage on prop of a pair on one motor ,always replace both props to maintain balance ,and that way you know both of them have the same flight time on them

Ahhh, words of wisdom from the Old Man, follow and keep safe!

 

[richandhiscat]

Thanks everybody for your advice.

Took it out next day and it worked fine, no problems. Took it out this morning, and it wouldn't start again - rotated the prop, turned it upside down and tapped the bottom of the motor and that seemed to fix it, worked fine again.

 

[old man mavic]

@richandhiscat ,because it still has some sort of issue with that motor ,if you have refresh or other insurance cover ,then if it were me i would be thinking about getting it replaced,before it causes the drone to drop from the sky

 

[Faster]

Agree with @old man mavic . I wouldn't try to fly again; your drone will be totaled if the motor stops in the middle of a flight. I will try to replace under warranty. If the warranty expired, I would send it to a reputable repairing shop for fixing.

 

[Yorkshire_Pud]

A third for Old Man Mavic's suggestion.

But a question, is it possible for these motors to stop in such a position that the rotor is perfectly positioned so that the electro-magnetic fields of the poles can not cause the rotor to move?

I have the recollection of seeing that happen on a 'simpler' motor, if that motor's rotor was given the slightest nudge that motor would start running and continue to run perfectly normally

 

[cheddar-man]

Thanks everybody for your advice.

Took it out next day and it worked fine, no problems. Took it out this morning, and it wouldn't start again - rotated the prop, turned it upside down and tapped the bottom of the motor and that seemed to fix it, worked fine again

Thanks everybody for your advice.

Took it out next day and it worked fine, no problems. Took it out this morning, and it wouldn't start again - rotated the prop, turned it upside down and tapped the bottom of the motor and that seemed to fix it, worked fine again.

Remove props. Get good vacuum cleaner suction at the top of motor and rotate it many times by hand, there is obviously something in there that keeps jamming it! If under any sort of warranty get it replaced.

 

[cheddar-man]

A third for Old Man Mavic's suggestion.

But a question, is it possible for these motors to stop in such a position that the rotor is perfectly positioned so that the electro-magnetic fields of the poles can not cause the rotor to move?

I have the recollection of seeing that happen on a 'simpler' motor, if that motor's rotor was given the slightest nudge that motor would start running and continue to run perfectly normally

Simple answer, no. They are basically a three phase motor and I’m pretty sure that scenario just cannot arise!

 

[old man mavic]

@Yorkshire_Pud an interesting theory ,but i think that as the ESC controls the rotation of the motor, by the fact that there are three wires feeding current to the windings ,that it would also jolt it to move in the correct direction
i am sure a member with more knowledge will be along soon to put us right

 

[Deleted member 154384]

Here in Italy I have heard of people who have encountered a similar problem with the engine, practically as in the photo the crankcase is not perfectly aligned and this causes a slight rubbing of the magnates with the crankcase itself. check this too to make sure you don't have this problem.

 

[cheddar-man]

If the motor was badly misaligned with the casing it would rub all the time, not intermittently. There is no

Here in Italy I have heard of people who have encountered a similar problem with the engine, practically as in the photo the crankcase is not perfectly aligned and this causes a slight rubbing of the magnates with the crankcase itself. check this too to make sure you don't have this problem.

View attachment 145514

If the motor was badly misaligned and rubbing on the Casing it would be stiff all the time, not intermittently.
If there is not debris inside the motor then you need to look one step back, at the ESC. This controls every function of the motor and a lose connection/defective component.

HERE is a very clear description of how the motor/ESC work together. The Mini2 motors have 12 poles (coils) and 12 associated magnets. The clearance between these is microscopic so it would not take much in there to cause them to stick.

The motors on the Mini2 are "out runners", the rotor/magnets rotate around the outside of the stator (coils).