Motor Stuttering

[Gray Harlequin]

Hi all. I have been having an issue with my motor stuttering. It stutters at low throttle and continues up to full throttle. If I rev the throttle quickly from the off position I can get it to spin normally sometimes, but will begin stuttering again at low throttle. After researching, it seems the likely cause is bad connection on either the motor or ESC. I tried experimenting using 2 identical motors and 2 different speed controllers. Here are the results:

ESC A + Motor A = stuttering
ESC A + Motor B = works
ESC B + Motor A = works
ESC B + Motor B = works

This makes no sense to me. If it's a bad ESC, why does it work with an identical motor? If it's the motor, why does it work with a different ESC? I have checked all the wire connections and have tried changing every setting on the ESC (start force, timing, etc.). Does anyone have any other ideas on what the problem could be or how to resolve this?

 

[Merv]

... any other ideas on what the problem could be or how to resolve this?

Typically, stuttering is caused by a broken connection. In that case, motor doesn’t spin, it just stutters. You still could ha a bad connection, one that is working most of the time. Try gently tugging on each of the connecters and wires. If you have a bad connections, it will come off.

It could also be a timing issue. If the connections are sound, try changing the timing on the ESC.

 

[Gray Harlequin]

Typically, stuttering is caused by a broken connection. In that case, motor doesn’t spin, it just stutters. You still could ha a bad connection, one that is working most of the time. Try gently tugging on each of the connecters and wires. If you have a bad connections, it will come off.

It could also be a timing issue. If the connections are sound, try changing the timing on the ESC.

A broken connection was my first thought as well as it acts as if one phase wasn't working. That's why I am confused as to why the motor works on another ESC and the ESC works well with an different motor of the same type. I re-checked all the connections and they are sound. I tried all 5 timings on the ESC with no changes.

I then went through all 13 "start force" settings and hit upon one that worked (sort of). A start force of "0.125" had the motor spin up without stuttering (0.75 is default). I have no idea why that exact setting is the only one that works as 0.094 and 0.188 had the stuttering issues. I had thought that it was fixed, but if I moved the throttle too rapidly, it would start stuttering, then after a couple of seconds would kick in with an awful screeching sound and then ran normally. I tried all of the timing settings again and also tried a higher PWM frequency. Neither fixed this issue.

My current theory is that there is some subtle damage or short in the windings that will not allow it to run unless it is in a very narrow range of parameters. The reason why it may work with the other ESC is because that one has an "Automatic" timing mode that compensates for it somehow. I would need someone much smarter in this stuff than me to know if that explanation makes sense.

 

[quorneng]

Grey Harlequin
Your logic testing would suggest there is a problem with Motor A.
What sort of connectors are you using between the motor and ESC?
Could it be that one Motor A connector is suspect when on ESC A but works fine on ESC B?
Compared to the running voltage the 'sensing' voltage that the ESC uses to set the next pulse is tiny so is sensitive to any form of 'poor' connection.
Unless you are into motor rewinding I fear it will just have to be replaced.
I have a couple of small practically brand new motors in this condition now clearly labelled 'scrap' just in case I do decide to learn how rewind them.

 

[Merv]

...The reason why it may work with the other ESC is because that one has an "Automatic" timing mode that compensates for it somehow...

I don't have an answer. If It works on the other ESC, I'd let well enough alone. If it aint broke don't fix it.

 

[Gray Harlequin]

I have a couple of small practically brand new motors in this condition now clearly labelled 'scrap' just in case I do decide to learn how rewind them.

If It works on the other ESC, I'd let well enough alone. If it aint broke don't fix it.

Unfortunately, I think this particular motor will remain on the shelf for now. At least it gives me a reason to research brushless motors and ESCs more in-depth. Although it does seem to work with the second ESC, I don't trust it. Thanks for everyone's help.