Rough Motor - gritty, armature contact, bearing

[dougcjohn]

Noticed when purchased, the Rt Ft Motor felt a little rough compared to the other 3 motors.
Having many sUAV's... some have tension or very minor roughness that smooths up with initial flights.

I've flown probably 20 batteries and the Rt Ft Motor now feels more rough. Power Off, Actually feel it snag & hang at times contacting something. Other times if manually worked for a bit it just feels gritty. Can power it up both on bench (no Props) or fly it without issues so far. But it's not a smooth motor, and I'm feeling this may effect flight control or fail.

Originally thought maybe it felt worse because grass or dirt got into motor from low flights... but the other 3 have remained silky smooth.

I've created a DJI Service Ticket. I have the 2 Yr Refresh Care, so that's a challenge to get service ticket on a "Non-Rapid Replacement" path to a normal Service repair... I'm thinking warranty repair.

Has this been a noticed issue with other Owners?

 

[Terry 63]

Check to see if that motor runs hotter than rest. Be careful though as motors get quite hot if you are flying at high speeds. To me it sounds like a bad bearing. it will likely continue getting worse until it either seizes or gets so lose the motor itself is damaged. If you have access to compressed air you could take off the propeller and try to blow any foreign matter out of the motor. You said you noticed it when purchased. Did you notice it before any flights. If so it would be a manufacturing defect.
I think you are on the right path in sending it back to DJI for service or replacement.

 

[dougcjohn]

@Terry 63 , we're on same track. I've already taken prop mount off, and motor screws to lift motor up off base. Blew compressed air but didn't see any debris within motor.

I did fly it last night after take down and examination... motors were close to same, I'd say problem motor may have been a bit warmer but didn't IR Temp check either.

I'd agree, my 1st assumption was bearing or misaligned Stator around rotor (maybe loose). I lean a little to the slightly loose Stator because it feels like something snags and catches... then with CCW & CW turns it changes to a grind feeling. If you finger spin it, then retest it again feels like rotor is contacting stator again.

My memory does recall an "out of box check over"... and I'm fairly certain the 1 motor felt a bit tighter... which isn't uncommon on small motors in mass-production. More tighter in spindle bearing tension, but didn't detect roughness or gritty... that developed after several flights.

Got ticket done, DJI has sent their UPS shipping label and Case number. I have to say, with DJI's new revamped service process... I've had great experience with repairs: XT2, Lightbridge Air Unit, multiple cameras, A3 Pro IMU, etc. They've got a nice format now and I appreciate the UPS shipping To & From Service.

 

[rktman]

in my not insignificant experience with such things (mostly not these tiny motors, but the design principles are the same) I'd put money on 99% a faulty bearing, not easily fixable, gotta replace the motor.

 

[dougcjohn]

in my not insignificant experience with such things (mostly not these tiny motors, but the design principles are the same) I'd put money on 99% a faulty bearing, not easily fixable, gotta replace the motor.

Could be, highly possibe although tiny bearings tend to have more close together "hits" that the spacing of the armature & sator. This one I could feel a hit every few (8-12) degrees turned and often could feel a positive contact. I couldn't see any contact when atrempting to examine... but vision wasn't optimal.

Not seeing the motor out & more closely, I'm guessing on bearing size too. It'll be determined soon, I'm curious.

It was sent into DJI for warranty repair. Oddly I haven't received any update yet, unlike past repair tickets... received an acknowledgment of receipt in 2-3 days post ship. If it was a possible component issue, they may be routing it to other team than normal repair service. Should hear something this week. I have 2yr Care Refresh, and not wanting to use 1 of 3 on this repair, since it wasn't crash related.

I did pick up a 2nd FPV Kit at BestBuy to use... had intentions to return (no restock fees in my State, and have 45 days as a ElitePlus), but I may decide to retain. I noticed on hot humid days, the little craft gets pretty warm after sequentially running 3-4 batteries. If in middle of playing, might be beneficial to swap crafts allowing one to cool.

 

[rktman]

Did that with the Mini 2... backed into a tree, wild loss of control, all on video UNTIL the gimbal tore off.

Found replacement aircraft only, new, got one and kept the otherwise completely flyable damaged aircraft for parts.

 

[dougcjohn]

Did that with the Mini 2... backed into a tree, wild loss of control, all on video UNTIL the gimbal tore off.

Found replacement aircraft only, new, got one and kept the otherwise completely flyable damaged aircraft for parts.

Did what? Damaged a motor? This one didn't have any crash... gritty out of box and increased.
Glad ya got new Mini replacement too and now spare parts!

 

[rktman]

Sorry for my brief comment... "that" being picked up a replacement, so have two.

 

[dougcjohn]

Update on DJI Repair, I received an email indicating repair was warranty (repair/replace) and it will be sent back in 2-3 days. They indicated $64 for warranty repair... didn't indicate what that all covered.

Was a bit longer than previous repair tickets, but I continue to be impressed with DJI repair process, shipping, etc.

 

[dougcjohn]

Received the FPV on Thursday, 7/22.
All Motors feel the same, although all motors have a little more tension / resistance than other DJI FPV units... but that may be new vs broken-in.

It does appear that they replaced the whole craft, not 1 motor while under warranty, Care Refresh not accessed. I sent it out with Green canopy, came back with smoked canopy and Green & SD card wrapped up separately.

Whole process took about 3 weeks.