Minimotor: Loose magnets

[Helgeo]

My wifes mini-motor started making strange noises yesterday. I have now taken the motor apart and found that one of the magnets was broken, it is missing a corner. And all the magnets are loose! I assume they should be glued into the iron rotor?

Will the performance be much affected by one of the magnets missing a piece? About 3-4% of this magnet is missing.

Any advice for gluing the magnets back in?
I plan to use epoxy. How important is it to have the magnets 100% evenly spaced? I think that will be difficult unless I find something to shim between the magnets as I glue.

Helge

[Cornelius]

3-4% of one magnet missing - I don't think you'll notice any difference.

You should try to get the spacing as precise as possible, or uneven performance and possibly excess noise will be the result. I don't know what the spacing should be, but you can probably guess by looking at it; use matches as spacers, or cardboard if there's little space.

It's very important not to remove any magnets and mix them before you glue them back; the have to be in the right order! (North/South poles in the right order.) Glue one by one. And BE CAREFUL! I'm guessing it's Neo magnets, and they are rather powerful buggers; they'll nip your skin easily if they come together, and can splinter if they're hit hard... (By getting attracted to each others for example...)

But let others here tell you if they're really glued or not; I think they should be, but i've never opened any of those motors... Made some windgenerators with neomagnets though, and one doesn't want any loose magnets there...

[Helgeo]

Cornelius, Thanks for your advice.

Epoxied magnets back in. Spaced them with 1 layer of standard copy paper, perfect fit. And the motor works like a dream again :-)

For those who want to know: The mini motor has 20 magnets.

[Cornelius]

Good to hear!

You didn't happen to take some pictures of the opened motor? (We're always curious of what's inside things... )

[Helgeo]

Sorry, no pictures. I always forget. Too busy fixing the problem.
If I have to open it again I will take pictures.

But I can share the procedure for taking the motor apart:
1. remove the lid on the wire side.
2. remove the nut on the other side
3. push the axle with entire motor out of the hub
4. Remove planet gear assembly, make sure not to loose the washer on the outside of this assembly
5. Remove circlip next to the small gear on the motor
6. Remove 3 screws holding small gear and pull out gear. If stuck the screws just removed can be entered in the threaded holes in the assembly to pull it out.
7. Remove the key that keeps the small gear from rotating.
8. Remove the next circlip.
9. Give the axle a gentle tap with a hammer and the motor will come apart

Reverse above procedure for assembly.

When taken apart you will see that there are two ball bearings inside the motor in addition to the two in the hub. Might be an idea to check these for wear.

Helge

[Sundsvall]

Thank you for your description, Helge. I'm always forgetting the camera myself.

Peter