Awesome little magnets which happen to be about the same size as LEGO studs.
About this creation
These 1/8" Rare Earth (neodymium-iron-boron) magnets are $1.98 for a pack of two at any RadioShack. The field is a little narrow, but very strong up close. I say get as many as you can.
A few possible installations. Very useful, but these parts cannot be reused. With the white brick, I also applied some Krazy glue from the other end of the bolt-hole. This is because getting the magnet into a bolt-hole often deforms the hole to the point that the magnet falls out. This has very rarely been a problem when installing the magnets to the bottom of a part (such as a brick or plate).
In these photos, two white bricks modified like the one in the first photo are used to suspend a loaded battery box.
And now, a few experiments. The one advantage that Lego magnets have over these is their ability to align themselves for the right polarity. So I set out to build a grappler that would do the same thing. First - the grappler has to be strong enough to separate the magnets once they're joined. Second - it has to rotate easily so the field can align. Third - the magnets should be close together, to form a single field which is more likely to rotate into position. So basically we need two magnets, opposite poles facing outward, straddling a loose fulcrum. In these photos, most of the magnets are color-coded in orange and green to represent opposite poles.
I tried to do a horseshoe arrangement first. And ran into the first problem - you can't mount the grappler using a bolt which is parallel to the field of the gripping magnet, like you do with an M-Tron magnet. Here's why:
So I tried arrangements which would put two magnets back-to-back, with the fulcrum perpendicular to the field. Solutions:
As you can see in the last photo, the fulcrum is provided by a 2x2 plate with a half-bolt on top. The issue with the arrangement that uses the 1x1 socketed brick is that the magnets don't quite clear the plate. This can be solved by putting extra 1x1 plates between the magnets and the brick, but that spreads the field out and weakens the structure.
Finally I thought of something else. At first I didn't think I could do a 'horseshoe' arrangement, since a single set of magnets is strong enough to separate a bolt. Then I noticed a few parts lying in front of me, tried something new, and voila!. This grappler is the best I've come up with. It uses two magnets, rotating laterally. It can be used to grip a single load magnet, or two. It works because the slotted red Technic bricks maintain a far stronger grip on the axle than any other part the same size. And like a bolt, the gray studded axle doesn't protrude past the magnets.
The construction of the grappler:
And just for fun, magnetic shock absorbers!
D_Y_A_M_I - I can't remove the magnets from any of these parts without cutting them open.
Tim_Tsai - I'm seeing the same ads. Unfortunately that site doesn't seem to be entirely up and running.