Just checked my motors speed...

[NRJ]

I'm sorry. I thought that your issue was with the slowest motor. The blue line is the fastest motor. That is also one of the most heaviest loaded. That could mean a bearing in it's very earliest stages. It could also be something about the prop, since you mostly notice it when flying. For some reason the ESC want's to spin the prop faster than the others, which would suggest some prop abnormality. What do you hear with no props?

If you move the props around, does it follow the prop? What about trying a new prop?

The other thing to consider, is that is the motor going fastest. It will probably sound different for that reason.

Well when I am flying, I can't tell where the sound is coming from. So, that is when I brought it home and got the dat file and all that stuff. I also then used the stethoscope to listen to all the motors. I do not have the props on when I hear the noise with the stethoscope. That is when I found the Left Back motor to sound way different than the other three. The other three all sound smooth and fine. The Left Back motor sound I'll have to say, rough like something is hitting or rubbing continuously. When I am outdoors flying, I can't tell where the sound is coming from and it is hard to tell the speed too. I did put a tachometer on my props at home, and the readings with props on are shown below. I also checked the balancing of the props which are not nicked or damaged or tweaked in any way and are balanced both on the horizontal and vertical axis accurately.

Thanks again.

 

[Dounin Front]

Well when I am flying, I can't tell where the sound is coming from. So, that is when I brought it home and got the dat file and all that stuff. I also then used the stethoscope to listen to all the motors. I do not have the props on when I hear the noise with the stethoscope. That is when I found the Left Back motor to sound way different than the other three. The other three all sound smooth and fine. The Left Back motor sound I'll have to say, rough like something is hitting or rubbing continuously. When I am outdoors flying, I can't tell where the sound is coming from and it is hard to tell the speed too. I did put a tachometer on my props at home, and the readings with props on are shown below. I also checked the balancing of the props which are not nicked or damaged or tweaked in any way and are balanced both on the horizontal and vertical axis accurately.

View attachment 64858
Thanks again.

Please! Replace the LB motor and see if things are restored to normal. Then you can properly dissect the old motor and hopefully see where the problem was.
I hope you're not just messing with us. I think anyone on this forum would have merely replaced the motor that you described as feeling and sounding odd.
Worst case is it won't cure the problem and you will have another piece of test equipment (the new motor).

 

[With The Birds]

I dont know if you have digital scales handy (would be a nice compliment to the taco, stethoscope and the IR theometer and probably other diagnostic tools you have amassed by now). I would have done this for you however mine wont power up for some reason. Determine the load present at the end of each boom. This will demonstrate the potential thrust contribution of each motor and prop to heep the AC in a stable hover having regard to the weight distribution.

You shouldnt expect the motors to run at equal speeds under any flight condition. The weight distribution inbalance should give you a better read on what any vatiations you might expect. Load and RPM wont correlate to a simple ratio though. Motor and prop efficiency will vary with RPM.

Your seemingly significant speed variations tested on the ground, to the extent they correlate to those measured in flight (particularly in a hover) may well be expected also. We know the flight controller logs rpm and other motor performance paramaters, it would seem perfectly logical to apply the known thrust differentials to the ESC control logic to keep the propulsion outputs balanced.

 

[NRJ]

I have listed my plans in several completions to this post a couple of times. Continue testing the noise until the thermometer comes in and I can then test the motors heat. Then I will probably replace the noisy motor. You want me to go and do it. But each time I say what I am going to do, another new person such as yourselves come in and offers me new methods, procedures or something altogether new. I listen and I am the one learning here. As stated before, I appreciate everyone's help. I'm just waiting for my thermometer to come in to complete my process.

As it turns out, all of you are right and it is near impossible to pin down any one noise, anomaly, or most issues if it doesn't stick right out in front of you. So, I too am through with this post. I have learned much. I will fix my drone with much more knowledge than I once had. Good day and happy flying.

 

[N017RW]

You could have tested post-fight motor temps days ago with some of the best tools on the planet... Your fingers.
DJI does not intend consumers to acquire a plethora of 'test' equipment to maintain and fly their toy flying camera.

 

[Dounin Front]

I have listed my plans in several completions to this post a couple of times. Continue testing the noise until the thermometer comes in and I can then test the motors heat. Then I will probably replace the noisy motor. You want me to go and do it. But each time I say what I am going to do, another new person such as yourselves come in and offers me new methods, procedures or something altogether new. I listen and I am the one learning here. As stated before, I appreciate everyone's help. I'm just waiting for my thermometer to come in to complete my process.

As it turns out, all of you are right and it is near impossible to pin down any one noise, anomaly, or most issues if it doesn't stick right out in front of you. So, I too am through with this post. I have learned much. I will fix my drone with much more knowledge than I once had. Good day and happy flying.

Thanks, but please at least post the final result. All that participated in your post/thread will automatically be notified so we can see the outcome.
Believe me, we are curious what you find. All the best.

 

[NRJ]

Thanks, but please at least post the final result. All that participated in your post/thread will automatically be notified so we can see the outcome.
Believe me, we are curious what you find. All the best.

Yes I will for sure. You all have contributed greatly to my knowledge. I also enjoyed talking with everyone too. This is a great forum and I have found it very helpful now and in the past. I'll post my results when completed. Thanks.

 

[NRJ]

You could have tested post-fight motor temps days ago with some of the best tools on the planet... Your fingers.
DJI does not intend consumers to acquire a plethora of 'test' equipment to maintain and fly their toy flying camera.

Doesn't matter what DJI wants, it's what I want. I'm a gadget guy too and I love the new digital tool conveniences. So when I find out I can get one for $3.99 or for $15.95, I may choose to do it if it will benefit me. Better than a blister if it really is hot. Lol. Take care NO17RW.

 

[N017RW]

All I'm saying is you could have answers already or you were really interested.

 

[David_Cambridge]

My 2 cents (remember them) is that these drones are complex enough, and the systems immature enough that explorations like this are not wasted time.

You can easily solve the immediate problem by swapping out the motor, but using the tools at hand, and thinking hard about the problem will take you a long way to fully mastering the drone. The Wright brothers spent in the neighborhood of 10 years studying birds and flying kites before their successes at Kitty Hawk.

 

[NRJ]

My 2 cents (remember them) is that these drones are complex enough, and the systems immature enough that explorations like this are not wasted time.

You can easily solve the immediate problem by swapping out the motor, but using the tools at hand, and thinking hard about the problem will take you a long way to fully mastering the drone. The Wright brothers spent in the neighborhood of 10 years studying birds and flying kites before their successes at Kitty Hawk.

Thank you. Very well said.

 

[Teejay41]

Here's one, on eBay UK. Liqoo Digital LCD Non-Contact Infrared Thermometer Laser IR Point -50 to 380℃ Doubtless eBay.com has them too.

I've had one similar to this for several years and use it for loads of things. It's always proved reliable and consistent.

Tony.

 

[NRJ]

Okay, I have the final results from my analysis, research, findings, and repairs. I put it all together in Microsoft One Note and published it in two parts to Adobe as pdf files. They are entitled; Bad Motor Rising Phase 1 9-20-2016, and Bad Motor Rising Phase 1b 9-20-2016. They are attached for your review and comments. Thanks.

 

[Dounin Front]

Okay, I have the final results from my analysis, research, findings, and repairs. I put it all together in Microsoft One Note and published it in two parts to Adobe as pdf files. They are entitled; Bad Motor Rising Phase 1 9-20-2016, and Bad Motor Rising Phase 1b 9-20-2016. They are attached for your review and comments. Thanks.

Thanks for posting your results and I'm glad you had a good outcome to your issue.
You asked a question about the correlation between motor speed and temperature.
"As you can see from this graph, the Left Back Motor (noisy) is hotter than all the rest by at least 6 degrees. Six degrees doesn't seem that much until you compare that with the previous speed/load graph above, where the speed is disproportionately slower. So, it is working less but creating more heat. For what reason?"
Don't you think the higher hovering temperature of the LB motor is a result of the lower speed of the motor, thus providing less cooling from the LB prop? It looks like the props do a good job of keeping the motors cool. That might be a very good reason not to let a drone idle for extended periods with the props off to drain the battery. The props cool the motors very efficiently, as their speed increases.
Since the load was quite a bit lower on LB and underperforming, I wonder if there was an open in a winding. Is that a possibility?

 

[NRJ]

Thanks for posting your results and I'm glad you had a good outcome to your issue.
You asked a question about the correlation between motor speed and temperature.
"As you can see from this graph, the Left Back Motor (noisy) is hotter than all the rest by at least 6 degrees. Six degrees doesn't seem that much until you compare that with the previous speed/load graph above, where the speed is disproportionately slower. So, it is working less but creating more heat. For what reason?"
Don't you think the higher hovering temperature of the LB motor is a result of the lower speed of the motor, thus providing less cooling from the LB prop? It looks like the props do a good job of keeping the motors cool. That might be a very good reason not to let a drone idle for extended periods with the props off to drain the battery. The props cool the motors very efficiently, as their speed increases.
Since the load was quite a bit lower on LB and underperforming, I wonder if there was an open in a winding. Is that a possibility?

That's a good observance that the slower rpm's was not cooling as it should be due to the slower prop rotations. I would agree. Concerning the "open in a winding" would certainly be a possibility. I haven't disassembled the old motor because I don't have the right equipment. I saw on a YouTube video that they took apart the older phantom motors using a press, but this motor seems to be different. Not sure how to take it apart or with what equipment. Any idea's? Thanks.

 

[David_Cambridge]

Very good analysis. Thanks for sharing it.

 

[NRJ]

Very good analysis. Thanks for sharing it.

Thank you and you're welcome. It was quite a long thread and there were many people involved which helped me greatly. It's the least I can do to let everyone know how it turned out. And a nice turn out indeed. Thanks again David.

 

[flyNfrank]

@NRJ, did you ever get the thermometer?

 

[NRJ]

I sure did. That is what proved the result of the motor replacement. Once the motor was changed out, it helped firm up the result that the motor was bad. The test results after showed that the speed and temperatures all were operating within acceptable limits within each other. In other words, all motors were running within the same range and all within 64 rpm of each other at hover. The temperatures (as David_Cambridge) alerted me to is that the motors motors are cooled by the propellers. So, the temperatures are also within good range of each other once again too. You may have missed my final analysis. I entitled it, "Bad Motor Rising" phase 1 and phase 1b. Both are in pdf for your review. It is thread #93. My bird is flying great now. Thanks for asking.

 

[flyNfrank]

I sure did. That is what proved the result of the motor replacement. Once the motor was changed out, it helped firm up the result that the motor was bad. The test results after showed that the speed and temperatures all were operating within acceptable limits within each other. In other words, all motors were running within the same range and all within 64 rpm of each other at hover. The temperatures (as David_Cambridge) alerted me to is that the motors motors are cooled by the propellers. So, the temperatures are also within good range of each other once again too. You may have missed my final analysis. I entitled it, "Bad Motor Rising" phase 1 and phase 1b. Both are in pdf for your review. It is thread #93. My bird is flying great now. Thanks for asking.

So you are saying the old motor temps and speed were good? I will go look at post #93 to see what I can make from it.