Magnetic braking of magnets sliding along a sloped aluminum surface

[TinselKoala]

http://www.youtube.com/watch?v=bas00qdj6Xc

[RunningBare]

Nice demonstration, also shows the magnets dragging edge keeping it stable.

http://www.youtube.com/watch?v=bas00qdj6Xc

[lostcauses10x]

TK nice vidio.

[TinselKoala]

Hey all,

I've been following this "from the shadows" since the X0 post in the Mylow HJ replication thread as I've always been fascinated by this behavior (mag in a copper tube) since I first saw it when Dennis Lee (?) showed it in one of his Tube vids (not the best source, I know. But it is demonstrated plenty of other times by others w/ less of an agenda).

The question I have (and will test shortly using an aluminum level. Thanks foxx!) is what happens when you roll a longer axially magnetized cylinder mag down the slope.

If there is a difference in field strength of the polarities and the eddy currents produced by them, wouldn't the rolling cylinder mag consistently roll towards one side of the aluminum slope? If you rotate the mag 180 degrees will it then consistently roll off the opposite edge?

I think I saw TK say something about using "more" cylindrical mags (longer?), but I ASSUME that it is 1 polarity down, and 1 polarity up as that's what shows this effect so well.
I was just wondering if TK had rolled any of those cylinders laying down with both polarities in contact with the aluminum stock?

I found the 4' al level and tried rolling a 1/4" W X 1/2" L N42 neo that had 1 end "sharpied" black to differentiate the 2.
It's not a good test IMHO because of the variance in thickness of the al (very thin on the sides, very thick in the middle), but it did show some interesting effects when rolling the neo down the length.

I need better control materials for the al slope (i.e. consistent thickness of al, true measurement of slope angle, etc.) to really have any data that matters, but I did notice some peculiar behavior as it was rolling down.

No matter how carefully I placed it, it would not roll longer than 1' without rolling off the level. Sometimes when rolling a polarity would seem to hit the thick middle of the levels I-beam like structure and the mag would swing vertical to the floor and then off the level.

As I said, nothing conclusive to my tests and they were hardly done in a controlled method, but it's acting wacky enough for me to start looking around for al bar stock.

@ TK, lumen, X0, etc.

If this experiment is something you haven't tried yet (unless you know of the reason for this effect and choose not to [re]validate it) , please give it a whirl.


I just think that if one polarity is stronger, the mag should roll off the bar to one side consistently. This has NOT been my experience with it yet, but my al stock is hardly of uniform thickness.

Another "wild hair" (or is it hare?) thought:

If there would be, for lack of a better term, magnetic "turbulence" from having both polarities in contact with the same al stock, could someone use a long cylinder mag and roll it down 2 al lengths sitting side by side with side rails on the outer edges to see if the cylinder has one side that falls through the center gap between the 2 "rails" every time?

I'll try to locate some al that fits the criteria above to set up a test.

Just some thoughts gents.

It was one of the first things I tried, actually. There are too many variables, or were when I tried it, for me to say one way or the other. I too thot that the cylinder would curve if the pole strengths or even the field geometry was different. But the silly cylinders try to go either way, and I think I need more expensive apparatus to do it properly. Like a brick to prop the slide on. But the rolling cylinders definitely do slow down compared to a non-magnet of same mass and geometry.

[Yucca]

@TK,
nice vid, you mentioned above that earth flux is pretty negligible compared to the mag flux. Do you think this ratio of flux strengths is in the same ballpark to the ratio of observed forces (braking force/seperation force)?

wow. our resident 'experts' are rehashing old news...

posted sept. 04, 2007
http://www.youtube.com/watch?v=iABmUEH5s0k

Errm... The quoted vid does not demonstrate the asymetric behaviour being discussed?
edit: woops, AbbaRue already said this.