Preventive Motor Maintenance

[captain-marvel]

Curious what type of life people are seeing from their motors?

I am wondering if there should be a scheduled maintenance \ replacement period for the motors. It seems to me those are the items most likely to go bad mid flight, and are also rather easy to swap.

Thoughts?

Currently my drone only has about 6 hours worth of flights.

 

[Meta4]

Brushless motors are extremely low maintenance and are likely to outlast most of the Phantoms they are mounted on.

 

[captain-marvel]

Brushless motors are extremely low maintenance and are likely to outlast most of the Phantoms they are mounted on.

Right, which is why its hard to determine if the motor is to blame for some of the crashes you see, or if its faulty wiring feeding the motor.

 

[nickyb]

You can buy motor dust caps from eBay, I guess these would help when the P3 is not in use and would help keep any largish pieces of grit from the armature. I think also, the occasional spray with compressed air, like from cleaning a keyboard would not hurt. Just my 2p worth.

 

[StratocasterDave]

For what it's worth, I heard on the Ask Drone U podcast the other day that you can expect 1600 hours. I believe DJI says 250 hours (which seems low to me).

 

[captain-marvel]

For what it's worth, I heard on the Ask Drone U podcast the other day that you can expect 1600 hours. I believe DJI says 250 hours (which seems low to me).

Very interesting! Thanks

 

[N017RW]

Definitely hundreds of hours based mostly on bearing quality.

I have a CP-heli with 650+ hours on the outrunner and no maintenance.

 

[TX-Xced]

As a preventive measure I replaced the #4 motor at 10.1 hours.

I replaced it because while hand rotating the motor I could feel a distinctive difference from motors 1,2,&3. I understand on a brushless motor "feeling" the actual difference in the field magnetism doesn't mean a bad motor, but I could also hear that it had a different tonal pitch than the other. To further justify replacing the motor - I secured the P3 to the deck ran one prop on each motor at a time just above idle - when I got to the #4 motor it had noticeable vibration (props are balanced) to it.

So based on the above I decided to replace it - for $20 it was/is cheap insurance.
I also drilled small holes in the center of each arm so I could add a drop of fine machine oil occasionally to the bottom bearing. I know oiling bearings on brushless motors is a subjective subject - but for me I feel better doing so. FYI the arms are reinforced on the inside with Bondic.
Conclusion: After replacing the motor the sound went a way and the P3 holds position better - position hold was never a real problem but its just locked in that much more now.

I did tear down the original motor to see if I could find the cause of the vibration. After pressing our the shaft checking it for trueness then reassembling it along with oiling the bearings it seems to run fine on the bench now.

So I bet the issue was with the bearing(s) like others have said I assume any motor failure will be related to the bearings.

One thing that did surprise me was the small gauge of the wire on the motors.

 

[ianwood]

The only preventative maintenance needed is exactly as @TX-Xced did. You check them every once in a while and replace them as needed. You can opt to replace the bearings but the motors are so cheap, there's really no point.

To check them, turn them before flight. Make sure they turn smoothly and evenly. If any one is different than the others, take note. After flight, carefully check how hot they are. If one is different than the others, take note.

Also, if a motor takes an impact from a crash, the life of the bearing can be significantly shortened.

 

[yorlik]

Aging and difference in speed are TOTALLY UNRELATED!

All motors are in closed loop control and must Go right speed or your drone will not fly.

Just watch them. They will do fine for 5-10 years of use. If they have an issue, you will hear it.

Just fly.

 

[With The Birds]

I bought myself an inexpensive contactless tachometer and I check RPM on all 4 props on a periodic schedule. Should a motor begin to age, you'llll notice a difference in RPM compared to the 3 others...Time to replace!
Neiko 20713A Digital Tachometer, Non-Contact Laser Photo 99, 999 Rpm Accuracy: Amazon.ca: Tools & Home Improvement

Once a year I add a very tiny drop of high speed bearing oil to the top bearing of each motor. As far as the bottom bearings. they are more trouble to reach but I hope some of the top oil finds its way down. Must be carefull...very tiny drop using smallest seringe I can find

Sorry if my English is a bit crapy...French being my first language and typing my very last one...LOL

Happy Flying!

The tachometer is unlikely to be helpful in this application. The motors will run at whatever speed is commanded by the flight controller absent a severe mechanical issue (ie failed bearing that allowed the rotor magnets to hit the stator poles) or an open circuit in the windings. The later failure mode would trigger an ESC error. You will have noticed that the speed of the motors varies while idling on the ground so variations are normal. Oiling is probably not recommended with shielded bearings, some may find its way into the bearing but the excess oil will trap attract grit and other foreign matter that finds its way into the motor.

 

[N017RW]

Post-flight motor temps as compared to each other is the easiest way to monitor health.

These temps vary with ambient conditions and flight profile.

Nominal temps are not spec-ed so there is no way to say what is normal.

They should never be too hot to touch so no need for exotic tools when fingers will do just fine.