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Aug 30, 2016, 09:46 AM
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Distinguishing ESC failure from motor failure


I had a crash and failed disarm that left one motor spinning on the ground upside down. After finally getting it shut down, that motor now doesn't spin. It tries to spin -- it rotates a few times, stutters, rotates slowly, stutters some more, etc.

I'll pull it all apart tonight to see what's up but I'm wondering if it's possible to tell if it's the ESC or the motor that's bad based on what happened and the behavior.
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Aug 30, 2016, 09:55 AM
Registered User
Quote:
Originally Posted by krachall
I had a crash and failed disarm that left one motor spinning on the ground upside down. After finally getting it shut down, that motor now doesn't spin. It tries to spin -- it rotates a few times, stutters, rotates slowly, stutters some more, etc.

I'll pull it all apart tonight to see what's up but I'm wondering if it's possible to tell if it's the ESC or the motor that's bad based on what happened and the behavior.
I am betting the esc went, haven't ever seen a motor smoke before an esc failure in that situation. Symptoms described sound like esc failure.
Aug 30, 2016, 10:05 AM
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Thread OP
Quote:
Originally Posted by NvS1
I am betting the esc went, haven't ever seen a motor smoke before an esc failure in that situation. Symptoms described sound like esc failure.
That's what I was thinking. I guess that's why people are leery of 4-in-1 ESCs. One failure = four ESCs.
Aug 30, 2016, 10:38 AM
Registered User
Exactly,but they are good for the small ones. Unless it doesnt dis-arm on a crash......
Aug 30, 2016, 05:48 PM
novuh @ propwashed
neonbjb's Avatar
Quote:
Originally Posted by NvS1
I am betting the esc went, haven't ever seen a motor smoke before an esc failure in that situation. Symptoms described sound like esc failure.
Haha I have the opposite experience. I've only killed a couple of ESCs but have done in quite a few motors.

I generally figure it out by the smell test. Separate your motor and ESC and smell each individually, whichever smells stronger is likely the culprit. Only works if you blew some magic smoke though.

If you want to know how to actually tell properly, you'll need to disassemble both components. ESCs generally blow by smoking a component on the PCB. Get a nice bright light and closely examine all of the integrated circuits and capacitors on your ESC. If you find anything that is blackened, broken, or not soldered down you've found your problem.

For motors, you'll need to remove the bell and inspect the windings. The way motors fail is the epoxy on the windings melts, causing them to short together. Look for dark spots on the windings or sections that look melted. These should smell really strongly though so you should be able to find it by that alone. If you don't smell anything I think there is a 90% chance it's an ESC problem.
Aug 30, 2016, 08:30 PM
Registered User
Also look for slipped magnets and or main leads going to the stator cut or ripped out.
Aug 30, 2016, 10:28 PM
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Thread OP
Looks like it was a motor. I had an old ESC and soldered the motor to it. Same behavior. Physically it looks fine but it's definitely not.

Cheaper than a 4-in-1 ESC at least
Aug 31, 2016, 09:08 AM
Team AlienWarpSquad
Use your Ohmmeter and measure resistance bewteen each motor wire. They should all read very low resistance (short).
Then measure from the motor frame to the wires and should read infinite (open).
Aug 31, 2016, 09:09 AM
Registered User
Oh dang, do you have a spare? Was that one of the new red bottoms you just got?
Aug 31, 2016, 09:20 AM
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Quote:
Originally Posted by NvS1
Oh dang, do you have a spare? Was that one of the new red bottoms you just got?
Yup. I think I may have 5 packs flown. As fun and clean and pretty as this build has been, I've had nothing but problems. The disarming issue is VERY strange. I'm not flying it again until I get it figured out.

I also think I burned up a VTX after losing the quad for a good 30 minutes. Video quality is horrible after that and is black-and-white any time the quad isn't directly in line of sight.

Rough start for the Tanto!

Quote:
Originally Posted by waltr
Use your Ohmmeter and measure resistance bewteen each motor wire. They should all read very low resistance (short).
Then measure from the motor frame to the wires and should read infinite (open).
Thanks! I'll put it back together and try that.

I did a continuity test between each of the leads to each other and had continuity between two of them. But I checked some brand new RS2205's I have and they had the same continuity.

Where on the motor frame do you test? With the anodizing or paint or whatever, am I going to be able to check resistance?
Aug 31, 2016, 10:10 AM
Registered User
Quote:
Originally Posted by krachall
Yup. I think I may have 5 packs flown. As fun and clean and pretty as this build has been, I've had nothing but problems. The disarming issue is VERY strange. I'm not flying it again until I get it figured out.

I also think I burned up a VTX after losing the quad for a good 30 minutes. Video quality is horrible after that and is black-and-white any time the quad isn't directly in line of sight.

Rough start for the Tanto!

New antenna matches the rx antenna? both rhcp or lhcp?

I hear you, I spent a lot of time blinging out some of my builds. They look great for a little bit, but after a short while they suffer. Any problems and then you have to deal with removing the the wire wraps and all the other neat stuff. I decided its nice to have one all blinged out but its a bit of a waste of money since it doesnt last and can make repairs take longer.
Aug 31, 2016, 11:50 AM
Team AlienWarpSquad
Quote:
Originally Posted by krachall
I did a continuity test between each of the leads to each other and had continuity between two of them. But I checked some brand new RS2205's I have and they had the same continuity.

Where on the motor frame do you test? With the anodizing or paint or whatever, am I going to be able to check resistance?
If the third motor lead to any of the other two measures as an Open then there is a broken wire in the motor. Commonly this is where the enameled wires from the coils connect to the leads. It is difficult but this can be repaired.

Test by putting both meter leads on the frame to see if the anodizing is conductive or not. If not then many times inside the threaded screw holes are conductive. Or if the meter probes are sharp enough you can push them through the coating to get them to touch the aluminum.
Aug 31, 2016, 01:00 PM
MA, USA
Quote:
Originally Posted by neonbjb
Haha I have the opposite experience. I've only killed a couple of ESCs but have done in quite a few motors.

I generally figure it out by the smell test. Separate your motor and ESC and smell each individually, whichever smells stronger is likely the culprit. Only works if you blew some magic smoke though.

If you want to know how to actually tell properly, you'll need to disassemble both components. ESCs generally blow by smoking a component on the PCB. Get a nice bright light and closely examine all of the integrated circuits and capacitors on your ESC. If you find anything that is blackened, broken, or not soldered down you've found your problem.

For motors, you'll need to remove the bell and inspect the windings. The way motors fail is the epoxy on the windings melts, causing them to short together. Look for dark spots on the windings or sections that look melted. These should smell really strongly though so you should be able to find it by that alone. If you don't smell anything I think there is a 90% chance it's an ESC problem.
Hijacking to ask: crashed and motors were left spinning near idle with broken props (some one blade, some none, right side up, though). When I found the quad after about 10 minutes, the left rear motor smelled like melted plastic. After repairing what was broken, the quad seemed to fly fine on a brief checkout flight. However, when flying the next day, more aggressively, FPV, I would get occasional, brief uncommanded pitch ups. Motor?
Aug 31, 2016, 01:14 PM
Team AlienWarpSquad
Quote:
Originally Posted by mwhidden
Hijacking to ask: crashed and motors were left spinning near idle with broken props (some one blade, some none, right side up, though). When I found the quad after about 10 minutes, the left rear motor smelled like melted plastic. After repairing what was broken, the quad seemed to fly fine on a brief checkout flight. However, when flying the next day, more aggressively, FPV, I would get occasional, brief uncommanded pitch ups. Motor?
Could be either the motor or the ESC or even both.
Only real way to tell is swapping parts.


I haven't post this lately but this is a good thread to do so:

ALWAYS use a Current Limiter when ever connecting a LiPo on the bench for Testing or ESC cal or anytime the Config Gui is opened.
https://www.rcgroups.com/forums/show....php?t=2327875
Aug 31, 2016, 09:52 PM
Registered User
Thread OP
Well I think I found the problem. Looks like one of the three wires completely severed. Doesn't looked burned, could it have just broken or would the failed disarm do that?


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