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Author Topic: Magnetic braking of magnets sliding along a sloped aluminum surface  (Read 53486 times)

BEP

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #30 on: May 21, 2009, 11:59:43 AM »
then when I flipped the magnet over it was like 4 bird dogs and a bucket of chicken.

Yea, I had several so-called 'educated' folks declare I was using fishing line during my demonstration. Oops, I think that was before mono filament line ( just kidding  ;)
It was when I was just a kid, in my thirties.

Quote
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.

Really? I thought I did offer 'my' explanation. The lead is about 30 deg. and the lag around 90, if I remember correctly. I liken it to the center of gravity shifting position on an unbalanced wheel as RPM changes. In effect, the moving magnet is trying to align itself with the field it is creating. This happens with either polarity but one polarity presses the leading edge against the track surface, slowing the decent, lessening the whole effect. The other polarity causes the leading edge to lift allowing for a speed increase which aids the effect.
 
Ever wonder why the one pole down makes it look like the magnet is almost glued to the metal while moving? I don't think it is because of the 'like' pole being created under it or because of the 'like' pole being created before it.

« Last Edit: May 21, 2009, 01:28:26 PM by BEP »

0c

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #31 on: May 21, 2009, 04:05:23 PM »
Yea, I had several so-called 'educated' folks declare I was using fishing line during my demonstration. Oops, I think that was before mono filament line ( just kidding  ;)
It was when I was just a kid, in my thirties.

Are you aware of any books, papers, or websites that discuss this behavior?

Quote from: BEP
Really? I thought I did offer 'my' explanation. The lead is about 30 deg. and the lag around 90, if I remember correctly. I liken it to the center of gravity shifting position on an unbalanced wheel as RPM changes. In effect, the moving magnet is trying to align itself with the field it is creating. This happens with either polarity but one polarity presses the leading edge against the track surface, slowing the decent, lessening the whole effect. The other polarity causes the leading edge to lift allowing for a speed increase which aids the effect.

At the moment, I think this is the most rational explanation we have. But I still have some questions:

1) As TK mentioned, these speeds are far from relativistic. Why would the oppositional field created by the eddy current lead or lag the magnet?

2) Why would polarity make a difference (unless there is some external influence)?

Still wondering what TK's upsliding experiment will show us.

jibbguy

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #32 on: May 21, 2009, 04:06:01 PM »
Just a thought: Has anyone tried this again with the plate turned 90 degrees to the original orientation; which could indicate if the "crystalline-like" structure of the alum plate's "grain" had any influence on the drag effect?

0c

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #33 on: May 21, 2009, 04:11:25 PM »
If I may point you to OC's idea that led to the whipmag, this is also a theory based on flipping the magnets at the correct moment to overcome the sticky spot, we got some odd results from replication but no free runner, the interesting part was certainly the stator and rotor magnets spinning in opposite directions.

(even more interesting was stator and rotor spinning the same direction)

Yeah, I been thinkin about this. I wonder if this type of effect could be used to "flip" a magnet over into an alternate orientation?

0c

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #34 on: May 21, 2009, 04:15:40 PM »
Set the magnet to slide down. If flux is flowing into the Al. from the pole facing it, then dragged through the Al. due to the magnet in motion,being bent  upward/dragged/held back from where it came, the exit point of the aluminum would be higher in the aluminum, above the magnet, thus a change in the path of flux from the norm.
But, if flowing out from the outer pole of the magnet, the one thats not facing the Al., then the flux direction is not influenced by the Al. drag before entering the Al. So the  point of entering and exiting will be in different from each other.

Are you trying to say that Lenz law is viscous? That there's a delay? Or that the oppositional field is actually created before the magnet arrives?

foxpup

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #35 on: May 21, 2009, 04:21:57 PM »
Hi all,

I've done another experiment involving the same high strength cylindrical magnet on aluminum.  Its crude but I think demonstrates my point about the behavior of these magnets.

http://www.youtube.com/watch?v=aYcAt--xJcw&feature=channel_page

I really do think this is the result of nonsymetry in the way the magnets are magnetized and nothing fancier than that.
(my own humble opinion)

What's weird is that weeks ago this magnet just showed up in my possession, stuck to the front of my filing cabinet.

Enjoy!

lostcauses10x

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #36 on: May 21, 2009, 06:30:13 PM »
hmm this actually could be dependent on the direction of the magnet poles.
 Think of the direction of induced current, and the current dispersal. If such is directed at the surface of the plate, the pattern of current flow will change at the surface.
 Think of skin effect of current flow in a wire. 

One direction of polarity it goes at the surface, the other direction it goes from the surface.

wattsup

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #37 on: May 21, 2009, 07:25:48 PM »
Here is my explanation as to why the magnet slides slower on one pole then the other based on Lumens video. (Allready posted here)
http://www.youtube.com/watch?v=a0YCTwWvykw

I am sure it has to do with the way the magnetic fields exit the magnet and re-enters the magnet. It is not magnetic attraction but simply the direction in which the magnetic field tear through the mass of the AL as it falls.
http://www.overunity.com/index.php?topic=7039.msg179592#msg179592

exxcomm0n

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #38 on: May 21, 2009, 07:28:00 PM »
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.

;)

Yucca

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #39 on: May 21, 2009, 09:10:54 PM »
@all

I tried a good sized neo disc sliding down aluminium ladder surface inclined just off vertical.

Video, about 2 mins long:
http://www.youtube.com/watch?v=A458J8dttu4

Definitely noticed that north side facing alu will always hug the surface. But when south side faces alu it drops away from the surface, it seems to drop away when the magnet reaches it´s terminal velocity which is quite slow due to the lenz braking.

I think there must be a repulsive force that fights gravity and lifts the mag away from the alu surface because the surface was not vertical and gravity wants to keep in on the surface.

If this effect could be seperated somehow from the lenz braking then perhaps it could be used for some gain?

I would like to see this experiment done in the southern hemisphere, so any Aussies or Kiwis etc. try it and tell.

NOTE:
I made sure to lift a non sticky plastic stick off the front magnet face to release it, using fingers or supporting underneath the bottom edge can cause the magnet to be influenced by mr hand. But trapping the magnet against the alu by using a stick and then pulling the stick away will not influence its horizontal position as much.

EDIT:
My young daughter, asked "why" it does this? After the vid I tried to explain but couldn´t stop her calling "why", I think my last answer was "because one sides different"
« Last Edit: May 22, 2009, 02:56:20 AM by Yucca »


RunningBare

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #41 on: May 22, 2009, 12:40:59 AM »
Nice demonstration, also shows the magnets dragging edge keeping it stable.

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

lostcauses10x

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #42 on: May 22, 2009, 01:36:03 AM »
TK nice vidio.

TinselKoala

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #43 on: May 22, 2009, 01:50:51 AM »
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

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #44 on: May 22, 2009, 02:17:32 AM »
@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.