×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

passive magnetic bearings

passive magnetic bearings

passive magnetic bearings

(OP)
Are there any manufacturers out there making passive magnetic bearings?  My application is small, about 3-10 mm spindle.

RE: passive magnetic bearings

Hello,

That is a rather small diameter for a magnetic bearing. Especially a passive one.

You cannot have an entirely passive all-magnetic bearing. There is some sort of a principle (different names are being used) that says that an all magnetic bearing does not work. So, you either need a mechanical support somewhere. Usually a point contact at the end of the shaft or a "self-generating" eddy current stabilizing bearing. Or an active magnetic bearing.

But, as said, the diameters are small. Is there room for larger bearings? What speed range is your application? Ever considered air?

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: passive magnetic bearings

You are probably thinking about Earnshaw's theorem.

I don't think it applies.  For one thing you have spinning shaft which is not a static condition and the relative motion can be used to induce currents.  For another thing, there are a number of tricks that can be used to get around it.  Strange things happen when you use a superconductor.

http://www.google.com/search?hl=en&q=passive+magnetic+bearing

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

RE: passive magnetic bearings

The spinning can also create gyroscopic forces which can be stabilizing

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

RE: passive magnetic bearings

Pete,

I wouldn't call a superconducting device "passive". You have to keep it cold, and for that you need energy.

And, no, magnetic bearings do not work with at least one support. That can be a self-generated current in a coil, but then again, it is getting active - in a way - although with no electronics. That is the "self-generating" eddy current stabilizing bearing that I was referring to in my post.

Tests with that kind of bearings show that they get quite hot. And that's no wonder.

Do you have hands-on experience with this bearing type? At what speeds? My experience is not so positive. There was a Canadian company that had some co-operation with SKF some years ago. Have been using air instead. But even air is getting quite "hard" when speed gets high. Good for low speeds, though.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources