Permanent magnets & maximum force

[Thrice]

What's the theoretical maximum force? At a certain distance & per kg, i guess. How would you go about calculating this?

 

[Jack111]

Very difficult to calculate without some microscopic details of the system.

If you had a hysteresis curve for the material you could calculate the field strength nearby the magnet roughly, but it'd still be geometry dependent and probably not that accuracte to the real system.

 

[Thrice]

But is there an upper limit for all materials? I was under the impression there's a limit to how strong (per unit mass or something) permanent magnets can get. I'll try track down the link.

 

[Thrice]

Theoretical analyses show that, if required by the application, Inductrack systems can be designed to levitate more than 40 metric tons per square meter of Halbach array, with up to 50-to-1 ratio of levitated weight of a train car to magnet weight. These levitation forces are close to the theoretical maximum that can be exerted by permanent magnets. Actual values achieved in a test run at GA are about 30 metric tons per square meter, in close agreement with the theoretically predicted levitation force for the configuration that was tested.

Source: http://www.llnl.gov/str/November03/Post.html