Grinding Servo :(

[fuzzball27]

Well, the subject is pretty much self explanatory: I have a servo motor that is making a grinding noise. Interestingly though, it only begins to make the grinding sound after running about 30+ seconds. I e-mailed LEGO (that did a whole lot of good ) and I called LEGO (they wanted me to mail it to their tech guy )
I knew I should have gone here for help in the first place, but I thought I might get a motor out of the deal -guess not. Any help? I don't think its a goner, it just sounds like something is loose. I tried to get into one of my other motors before, but I was unable to get it open because of the axle/pin connectors...how do I get it open?

Thanks

[mightor]

Don't open it, just mail it back to Lego and you'll get a new one. They'll be happy to replace it.

- Xander

[rghansen]

Well, the subject is pretty much self explanatory: I have a servo motor that is making a grinding noise. Interestingly though, it only begins to make the grinding sound after running about 30+ seconds.

Are you sure it's not a software problem? I would think that a defective servo would start grinding as soon as it started to move and not after 30 seconds. Can you describe the error in greater detail. What was the servo doing during the first 30 seconds? Other than the grinding noise, did it seem to work OK? Does the grinding noise stop after a while? Does it only occur during a certain range of servo motion? Does the servo work OK with other programs? Have you tried replacing the servo with another one?

From what I've heard, these servos are supposed to be very robust. And from my experience, software errors are much more common than hardware errors.

[fuzzball27]

It is not a software error, I know because I switched the motor and it sounded fine. Also, I know it is not robot design (i.e.. a tire rubbing something) because I did testing with just the motor by itself. When I first run the motor, it sounds and acts fine, but gradually a grinding noise starts and it builds in volume until it is very loud and noticeable. Sometimes it sounds slightly like a chomping noise almost as if one part of a slow moving gear is off center. I'm not sure if it affects performance because I did not want to put stress on the motor while it was giving me trouble. It does not stop grinding after time.

[doc222]

Test the motor by hand turn it slowy about 5 turns. feel for a bumping or clicking or a rough spot. If found sounds like a gear is chipped or broke it should be very predictable( at the same point per 5 revolutions. If it happens at odd turns meaning not predictable it may some thing got in it like sand. Taking it apart may void the warranty.

Not knowing what it was used for in the past or when it "broke" makes it hard to tell what it may be, IE was it stalled, was it used in sand off road etc?

In my bot that i am working on right now I have many times overrotated a articulation. The new joints are so strong now they dont click so these can stop a motor dead and hold it under full power until thermal switches it off or I cancel the program. have done this to many times to count, never broke a motor to date.

Best of luck, let us know the outcome.


Doc

[fuzzball27]

5+ rotations and no oddities. As I said before, it only starts to make the noise after some time of operating. I have never used my robot near any dirt or sand or eve outside as far as I know. I think I might need to just take mightor's advice, unless of course someone know the solution.

[doc222]

sounds lke it may be the motor its self , perhaps a brush is wearing off. This is what kiils most Lego motors in the end there are two brushes thatare no more than a flat metal parts that wears against the armature. When they start to go the sound rough. How old is your servo?

Doc

[fuzzball27]

I have five servos, three I got two or three years ago, and two I got just over a year ago. I don't know if it is older or newer, but no other motors are giving me similar trouble. I think that I'll just send it in if it is a brush.

[doc222]

i wish I would have dated mine too. I have about 12 and have no idea what ones are the older or newer. I have a few that are more noisy for sure. The one good thing though for a servo they are rather inexpensive at 18$ compared to say a stepper motor. Next batch of motors when I get some I will date them. I know mine are all over 3 years old. I would send it off to Lego they most times just replace it.

Doc