magnetic flux shielding idea

[rrintoul]

I was trying some experiments that showed promise for shielding.  I figured it was just a mechanical problem.  When I saw that simple pieces of steel (like a bread knife) would shield a rare-earth magnet I started trying to find a way to move the shield over the magnet as closely as possible without touching it ( using bearings of some kind ).  The closest I got was a chunk of steel attached to an old hard drive spindle.  When the shield got close to the magnet it shot above it and wanted to stay there.  So I attached an elastic band to resist this.  I found I could get very close to equilibrium, i.e. it took very little force to move the shield into place and back (exposing the magnet).  I'm almost convinced this could lead to a shield that takes less energy than the attraction of the magnet it shields.  It takes a lot of time experimenting though.

[gyulasun]

Hi rrintoul,

Your solution sounds interesting. Could you share some more details?  i.e.  what distance is the shield able to cover?  how does the surface area of the shield compares to that of the magnet?  what size has got the magnet, is it also from a harddrive?  etc.

If you could make a photo from your setup it would be the best but of course only if you wish to do so.

Thanks
Gyula

[rrintoul]

Thanks Gyula,

The shield naturally wants to cover the entire magnet.  The elastic band is tensioned enough that it tries to resist this attraction and uncover the magnet.  The magnet was from a package of rare-earth magnets from Lee Valley Tools.  It was the 3/4 inch circular magnet.  I don't have the pieces assembled anymore after my move to New Zealand, but here is a crude picture.

Regards,
Reade

[rrintoul]

I think that some kind of rolling bearings to either side of the magnet so the shield slides just over but not touching would resist the attractive forces better.  I think that would scale better and allow for a very strong magnet.  I just couldn't find parts to do that.

[rrintoul]

The shield itself was just some bracket I found that was less than 2mm thick.  From what I read the larger / longer the shield is in relation to the magnet, the better it disperses the magnetic forces.