I had two motor failures on my backup Mini, both fronts. More detail on that in another topic.

But after ordering two arms with motors, I wanted to disassemble a motor after it was removed from the arm, so I fabricated a very cheap tool to do the job. I cut a 1-1/2" long piece of galvanized steel electrical conduit pipe, which was the perfect size for the motor. It was necessary to cut a slot in one side to accomodate the cable. I do not have a shop press but I was able to easily use an ordinary small drill press. For a press tool, I used an ordinary 1.5" finishing nail with the head and point cut off. It was the prefect size to press out the center pin. Place the motor onto the pipe with the housing end up and push out the armature and axle pin by pressing down about 1/2". If you are using a drill press, do NOT have it running. To reassemble the motor it was much simpler, just push the armature into the housing and press it down with just about any available blunt tool.

Pressing out the pin/armature will deform the housing slightly, but that will return to normal when you press the armature back into the housing.

I was able to clean out the loose iron particles and reassemble the motor. It ran fine for 10 minutes, but I do not trust it to not release more particles, so I installed both new front motors/arms.

What I found inside was a lot of very small pieces of the laminated cores that were jamming the motor, no sand. But that's another topic for now.

Nice Work GaryDoug

Nice tool and good explanation of your work.  Thank you!

Well done.  Always nice to see people making their own tools, when manufactuer's tools are too expensive or not available for purchase.

Nice post McGiver . Lol

Thanks for sharing

djiuser_YOZoFpdlWBla Posted at 9-15 19:19
Nice post McGiver . Lol

I first tried it with just what I had in my pockets, a chapstick, car keys, cough drops, and a "personal protection product". But I couldn't quite succeed ;-)

Hmm, the rotor laminations should be soft iron, and the magnets should be neodymium, there should not be any ferrite in those motors.

Out of interest did you try compressed air to get these out first?

Thanks for sharing

Nice DJI DIY job!

Nice DIY work.

Hi. Thank you for creating this informative post and sharing your personal insight regarding this matter. Just a friendly reminder DJI does not recommend doing any DIY repair. It would be best to let our DJI technician assist you regarding this concern to ensure that all components and features are thoroughly repaired and tested. Thank you.

DAFlys Posted at 9-15 23:55
Out of interest did you try compressed air to get these out first?

I did not on the one motor. Both front motors had this problem. I wanted to disassemble one motor to see what was loose inside. I did use compressed air to remove all the particles (they were magnetically stuck to the magnet) after disassembly. I did use compressed air on the 2nd motor while still intact and both removals were successful. I wanted to make sure of the loose material. If it was sand, the repair could be permanent, but if something else was going on, I was pretty sure it would continue. There were tiny gaps in the laminations at the outer ends, indicating a possible source. Not willing to take a chance for just $60 worth of new DJI parts.

GaryDoug Posted at 9-16 06:57
I did not on the one motor. Both front motors had this problem. I wanted to disassemble one motor to see what was loose inside. I did use compressed air to remove all the particles (they were magnetically stuck to the magnet) after disassembly. I did use compressed air on the 2nd motor while still intact and both removals were successful. I wanted to make sure of the loose material. If it was sand, the repair could be permanent, but if something else was going on, I was pretty sure it would continue. There were tiny gaps in the laminations at the outer ends, indicating a possible source. Not willing to take a chance for just $60 worth of new DJI parts.

Totally agree its not worth the risk for $60.

I just found that you can buy the two front arms/motors for about $50 if you are not in a hurry for shipping: https://usdroneparts.com/product-category/mavic-mini/

Of course, for me that was not an option ;-)

GaryDoug Posted at 9-16 07:45
I just found that you can buy the two front arms/motors for about $50 if you are not in a hurry for shipping: https://usdroneparts.com/product-category/mavic-mini/

Of course, for me that was not an option ;-)

Great job, especially like the idea & use of the custom made/fabricated tools.

Nice fabricating there Doug. Did you find the issue/able to repair to the satisfaction of being able to use the motors, I know your post said you didn't trust them and I don't blame you there.

And yet an even cheaper source for the front arms at $40 a pair: https://www.aliexpress.com/item/ ... .0.0.66d6641djfPTDy

And it's coming from China anyway ;-)

JodyB Posted at 9-16 12:18
Nice fabricating there Doug. Did you find the issue/able to repair to the satisfaction of being able to use the motors, I know your post said you didn't trust them and I don't blame you there.

As I stated above, there were tiny metal particles inside each front motor. I was able to clean them out but do not trust them to not release more particles, and so installed new arms. The repaired motors did run for 10 minutes continuously without a problem. The issue for me is that there was no obvious reason for the loose particles which were definitely ferrous.

GaryDoug Posted at 9-16 14:57
As I stated above, there were tiny metal particles inside each front motor. I was able to clean them out but do not trust them to not release more particles, and so installed new arms. The repaired motors did run for 10 minutes continuously without a problem. The issue for me is that there was no obvious reason for the loose particles which were definitely ferrous.

I wouldnt trust them either, good call!

Could the ferrous particles be accumulated during landings on sand or gravel?

I think I have seen a press made from a coin. From memory two  or three unthreaded holes were drilled in it to mate with existing screw holes in either the motor's rotor or base and a central hole was drilled and tapped so that a screw, of the appropriate size, could be used as the press.

djiuser_vNHka855VU4G Posted at 11-19 11:02
Could the ferrous particles be accumulated during landings on sand or gravel?

Yes it could but non magnetic grit etc. can also jam a motor if gets trapped between the rotor and a motor pole, the clearances are VERY tight. This is one reason people use landing mats or hand launch/catch.