Eletric motor break-in?

[Charles Hofacker]

I just received an electric motor from Brodak and when I turn it by hand it "catches" or "sticks" at multiple positions of rotation. This feels like a pure mechanical "jam" and not a magnetic force of some kind. Is this normal? Does the motor need to "broken in"? Or, should I return it to Brodak?

[jfv]

What size motor is it?  I've had some issues with the bearings on the Arrowind 2826.  The 2820's run smooth as silk.

[Tim Wescott]

'Lectric motors don't run with the kind of fine tolerance that IC engines do.  If it's really mechanical and not magnetic then the motor is defective and should be returned.

Some of the motors I've handled have had pretty strong magnetic detents, though.  If you've only handled something like eFlight motors before then one of the really stiff ones might seem broken.  I'm a determined motor-fondler, and I fly with a bunch of RC guys who show up with all sorts of different stuff at the field, so I know whereof I speak.

It's hard to describe (assuming you're not sure), but if it's mechanical it should have more of a "grinding" quality to it, and it won't necessarily line up with the magnets.

[John Cralley]

What Tim says. I have motors that feel like they go bump-ity-bump when I rotate them and they work fine! Mind you they don't make any noise when rotated and they tend to have their own build in brake when I fly.  

[Charles Hofacker]

'Lectric motors don't run with the kind of fine tolerance that IC engines do.  If it's really mechanical and not magnetic then the motor is defective and should be returned.

Some of the motors I've handled have had pretty strong magnetic detents, though.  If you've only handled something like eFlight motors before then one of the really stiff ones might seem broken.  I'm a determined motor-fondler, and I fly with a bunch of RC guys who show up with all sorts of different stuff at the field, so I know whereof I speak.

It's hard to describe (assuming you're not sure), but if it's mechanical it should have more of a "grinding" quality to it, and it won't necessarily line up with the magnets.

Thanks for the info... I'm going to return it for exchange. It is definitely a mechanical "catch" or "jam" not a "bumpity bump" magnetic feel. It will jam solidly with no further rotation possible until it is "backed off" a bit then continue turning. Brodak has always been really good correcting things even when it was my mistake and not theirs like ordering the wrong part.

[John Cralley]

Yep send it back -- may have debris, magnet loose, bad bearings or what have you!

[Tim Wescott]

Thanks for the info... I'm going to return it for exchange. It is definitely a mechanical "catch" or "jam" not a "bumpity bump" magnetic feel. It will jam solidly with no further rotation possible until it is "backed off" a bit then continue turning. Brodak has always been really good correcting things even when it was my mistake and not theirs like ordering the wrong part.

I believe that the highly technical, engineering term for your motor's condition is "broken".  By all means you should send it back for replacement.

[Dennis Adamisin]

I just wrote Charles directly but will share the essential bits here.  There is a 99.9% chance that what he is experiencing is a M3 x 6mm flathead motor mount screw that got loose from the accessory bag and magnetically sucked into the motor through a cooling opening.  Durned unfortunate but it happens.  Takes a minute or two to find & retrieve it using tweezers, forceps, needle nose pliers or similar. Pretty unlikely that is lodged into a place where it cannot easily be retrieved or where it can damage anything.  Of course Brodak will stand behind it.

The motors I build with usually have the cooling openings taped over, its AMAZING what those neo-magnets can suck off a workbench! 

[John Cralley]

I just wrote Charles directly but will share the essential bits here.  There is a 99.9% chance that what he is experiencing is a M3 x 6mm flathead motor mount screw that got loose from the accessory bag and magnetically sucked into the motor through a cooling opening.  Durned unfortunate but it happens.  Takes a minute or two to find & retrieve it using tweezers, forceps, needle nose pliers or similar. Pretty unlikely that is lodged into a place where it cannot easily be retrieved or where it can damage anything.  Of course Brodak will stand behind it.

The motors I build with usually have the cooling openings taped over, its AMAZING what those neo-magnets can suck off a workbench! 

Sounds like a good guess Denny! What l called debris. 

[Charles Hofacker]

I just wrote Charles directly but will share the essential bits here.  There is a 99.9% chance that what he is experiencing is a M3 x 6mm flathead motor mount screw that got loose from the accessory bag and magnetically sucked into the motor through a cooling opening.  Durned unfortunate but it happens.  Takes a minute or two to find & retrieve it using tweezers, forceps, needle nose pliers or similar. Pretty unlikely that is lodged into a place where it cannot easily be retrieved or where it can damage anything.  Of course Brodak will stand behind it.

The motors I build with usually have the cooling openings taped over, its AMAZING what those neo-magnets can suck off a workbench! 

Sure enough! There was a small machine screw inside the motor. I had to push it around a bit with a dental pick to get it in a position to extract it with tweezers. It was lodged under the area where the power leads enter the frame in a spot that was not easy to see. It's gone now and I'm a Happy Camper!

[Crist Rigotti]

Dennis is da man!   

[Target]

Nice catch, Dennis!!
Probably not your first rodeo, eh?

Now that is what I would call a happy ending for everyone.
I'm tucking that one into my bag o' tricks.

I'm glad that the original poster shared.

R,
Chris

[Tim Wescott]

Sure enough! There was a small machine screw inside the motor.

I want to apologize to you and to Dennis -- I had considered this as a possibility, but thought "Nah, not with a brand new motor", and didn't "waste time" in my response.

I'd like to say "lesson learned" but I do this all the time, and "lesson learned, again" just doesn't have the same ring.