Storing Cookies (See : http://ec.europa.eu/ipg/basics/legal/cookies/index_en.htm ) help us to bring you our services at overunity.com . If you use this website and our services you declare yourself okay with using cookies .More Infos here:
https://overunity.com/5553/privacy-policy/
If you do not agree with storing cookies, please LEAVE this website now. From the 25th of May 2018, every existing user has to accept the GDPR agreement at first login. If a user is unwilling to accept the GDPR, he should email us and request to erase his account. Many thanks for your understanding

User Menu

Custom Search

Author Topic: Magnetic braking of magnets sliding along a sloped aluminum surface  (Read 53491 times)

foxpup

  • Newbie
  • *
  • Posts: 12
We've had a few postings about sliding neo magnets on various aluminum surfaces.  I set up this topic to give that discussion a home.  It really does need its own thread.  Here are 3 youtube videos that are related to the subject

X00000013
May 19, 2009
http://www.youtube.com/watch?v=IqL3Byy9mDA

k4zep
May 19, 2009
http://www.youtube.com/watch?v=bElldY0TKJI

foxxpup
May 19, 2009
http://www.youtube.com/watch?v=edl5PsSyjG0

The idea is that when small neo magnets are caused to slide downhill on aluminum surfaces, they sometimes tumble off if started with one pole up and slide along slowly braking when the other pole is up.  X00000013 and foxxpup's videos demonstrate this effect k4zep's does not.

Please add your comments. :-)

foxpup

  • Newbie
  • *
  • Posts: 12
I was able to verify X00000013's demonstration.  Its a genuine phenomenon.

Personally, I think this phenomenon is a result of non-symetry in the magnetic properties of the neo magnets.   If the magnetic lines in the magnet on one pole were more concentrated than that of the other, the concentrated end might not be able to produce eddy currents in the aluminum as well (or better).   When the aluminum is at a shallow slope like what k4zep did, both ends would produce sliding and braking but as one progressively tries steeper slopes, one end will eventually demonstrate tumbling.  At steeper slopes the other end probably will too.  We need to do more tests.



TinselKoala

  • Hero Member
  • *****
  • Posts: 13958
It's remarkable.
Now I have observed that it is actually the LOWER or leading edge that appears to lift off first and the magnet begins to tumble backwards at least when it first comes off.

The orientation that doesn't come off will lift off at the leading edge too but not as much so it's more stable.

I think this actually indicates that the pole that comes off, is stronger because it gives more levitation from the eddys.

We may be inventing the mag-lev train, or something like that.

TinselKoala

  • Hero Member
  • *****
  • Posts: 13958
@CLaNZeR:

ROTFL there at first when the one just wouldn't go...that was great, I feel a lot better now.

I think it's got to be the protective coating--or, is that perhaps genuine Al-clad, with that protection? The thin layer of pure Al over the alloyed sheet might make a diff.

Regardless, once you get the effect, please look on sideways, and see if you see what I see: the magnets lift off the plate from the lower, leading edge, first.

0c

  • Sr. Member
  • ****
  • Posts: 278
Regardless, once you get the effect, please look on sideways, and see if you see what I see: the magnets lift off the plate from the lower, leading edge, first.

And which end lifts off when the magnet is sliding up the aluminum (or copper)? And does it do it with the same or opposite polarity?

Dave45

  • Guest
 :o 

TinselKoala

  • Hero Member
  • *****
  • Posts: 13958
And which end lifts off when the magnet is sliding up the aluminum (or copper)? And does it do it with the same or opposite polarity?
Don't know but I think that would be a rather interesting experiment. I think it will still be the leading edge but it will be the opposite polarity that jumps off first.
I really dunno, though. It's perplexicating.

ETA someone at lunch today did a BOE calculation and figured that with a little magnet like I used, that small area contains a lot of flux lines  from the magnet but only about 4  lines from the Earth's field, so it's hard to see how the earth's field could be affecting this effect. But wouldn't it be interesting if the southerners got the opposite pole to jump off?

Sean, what's your latitude? If I may be so personal....
 ;)

BEP

  • TPU-Elite
  • Hero Member
  • *******
  • Posts: 1289
Regardless, once you get the effect, please look on sideways, and see if you see what I see: the magnets lift off the plate from the lower, leading edge, first.

 ;D

Kinda like the magnet is hanging ten, isn't it.

The creation of the eddies must be leading with one pole and lagging with the other (go ahead - light the torches and grab the pitch forks).

Now ask yourself does a Foucault current create another Foucault current around it and another around it? Each the reverse of the previous? Since each field is supposed to be the exact amount of force as the source -of the source - of the source - etc. ??
Since the diameter is constantly increasing then the amplitude for each new 'wave' is lower. Much like dropping a pea in a bowl of water.
After all the 'laws' say a current is created that creates a like field when there is relative movement - or does it not?

And what polarity is the magnet being opposed by since N/S are horizontal and the magnet is traveling in a direction 90 deg. to the polar axis?

Then think about a magnet sliding with poles the same axis as the slide path. The third vector direction is determined by the polarity of the leading pole. Now do you wonder why the curve of the path is reversed between S leading or N leading? Simple Right Hand Rule. Right?

This is all fun - being all 'new' and everything. At least watching folks claim each 'new' discovery is fun  ::)

Y'all should be able to come up with some interesting 'scientific method' experiments for such things.

tournamentdan

  • Jr. Member
  • **
  • Posts: 67
It's remarkable.
Now I have observed that it is actually the LOWER or leading edge that appears to lift off first and the magnet begins to tumble backwards at least when it first comes off.

The orientation that doesn't come off will lift off at the leading edge too but not as much so it's more stable.

I think this actually indicates that the pole that comes off, is stronger because it gives more levitation from the eddys.

We may be inventing the mag-lev train, or something like that.
With that being said maybe I was wrong in the other thread. Earlier I said the magnet fell because that pole was weaker, but since the mag starts to flip bottom to up I think it is because the one pole is to strong.
I believe that the eddy currents are the strongest at the bottom of the magnet(in the aluminum), so the repell would be strongest there to. The magnet gains speed and in turn creates eddy strong enough to push the bottom of the mag away which will make the magnetic flux weaker between the mag and aluminum. and by then it starts to tumble down.

EDIT:  I still say that a magnet with more surface area and the same strength that you are using will react normally.

TinselKoala

  • Hero Member
  • *****
  • Posts: 13958
Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #10 on: May 21, 2009, 04:10:25 AM »
;D

Kinda like the magnet is hanging ten, isn't it.

The creation of the eddies must be leading with one pole and lagging with the other (go ahead - light the torches and grab the pitch forks).

Now ask yourself does a Foucault current create another Foucault current around it and another around it? Each the reverse of the previous? Since each field is supposed to be the exact amount of force as the source -of the source - of the source - etc. ??
Since the diameter is constantly increasing then the amplitude for each new 'wave' is lower. Much like dropping a pea in a bowl of water.
After all the 'laws' say a current is created that creates a like field when there is relative movement - or does it not?

And what polarity is the magnet being opposed by since N/S are horizontal and the magnet is traveling in a direction 90 deg. to the polar axis?

Then think about a magnet sliding with poles the same axis as the slide path. The third vector direction is determined by the polarity of the leading pole. Now do you wonder why the curve of the path is reversed between S leading or N leading? Simple Right Hand Rule. Right?

This is all fun - being all 'new' and everything. At least watching folks claim each 'new' discovery is fun  ::)

Y'all should be able to come up with some interesting 'scientific method' experiments for such things.

I can't say whether it's "new" or not, but I was rather amazed that none of the folks I showed it to had seen it before. JK especially. They all thought I was just showing eddy current braking (yawn, what's wrong with TK today, he seems off...) then when I flipped the magnet over it was like 4 bird dogs and a bucket of chicken. They really perked up and started paying attention.


Edit to add, and no matter how much I re read your nice little summary of eddy current effects and the rhrule, I don't see the explanation of why one pole lifts off so much more enthusiastically than the other.

lostcauses10x

  • Full Member
  • ***
  • Posts: 234
Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #11 on: May 21, 2009, 04:24:57 AM »
Ahh questions. are these nickle coated magnets?? If so there will. also be induced currents in that part of the magnet also.  Any one got some plastic coated non niclkle
plated ones??

TinselKoala

  • Hero Member
  • *****
  • Posts: 13958
Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #12 on: May 21, 2009, 04:38:54 AM »
Ahh questions. are these nickle coated magnets?? If so there will. also be induced currents in that part of the magnet also.  Any one got some plastic coated non niclkle
plated ones??

I tried it with my big rectangular ceramics. They do it too, but they are kind of hard to slide stably. But they do it.

And the leading edge thing--I only observed it with a very thin disk --think US Dime --on a big thick Al plate. I can't seem to get it to do it (lift up on the leading edge first) with any of these more cylindrical or square magnets.

TinselKoala

  • Hero Member
  • *****
  • Posts: 13958
Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #13 on: May 21, 2009, 04:41:31 AM »
I mean I get everything BEP says except that part about leading and lagging. I'da thot that at these velocities (that is, non-relativistic ones) the lag would not be noticeable and would have no macroscopic effect.
It almost makes me believe in different pole strengths.

lostcauses10x

  • Full Member
  • ***
  • Posts: 234
Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #14 on: May 21, 2009, 05:17:18 AM »
I mean I get everything BEP says except that part about leading and lagging. I'da thot that at these velocities (that is, non-relativistic ones) the lag would not be noticeable and would have no macroscopic effect.
It almost makes me believe in different pole strengths.
It could be such as one of the poles out is going in on the edges.  Makes for some reasonable explanation. That is if the in and out were real.  Some thing like a cone effect on the intake and out go.

 I will have to agree with the pole variation. Think electron spin and direction of spin in relation to domain and current.