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Author Topic: Magnetic braking of magnets sliding along a sloped aluminum surface  (Read 53502 times)

RunningBare

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #75 on: May 23, 2009, 06:15:57 PM »
Keep in mind you have to consider the area/volume of the metals, I would doubt very much that a small piece glued to the magnet would have any effect.

Just a weird thought:

Attach an aluminum disc to the bottom of the magnet and slide it down the aluminum ramp.

The aluminum disc will remain static WRT the magnet. The magnet will induce Foucault (eddy) currents and an oppositional magnetic field in the ramp. The moving oppositional field in the ramp will induce secondary eddies and more oppositional magnetic forces into the aluminum disc.

... or maybe not.

jimcreeper

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #76 on: May 24, 2009, 06:54:36 PM »
It is my opinion that the magnets flip over, instead of sliding down, because the south side of the magnet is attracted to the alum more. It cant get a good grip and tumbles the rest of the way.

May be more going on its hard to tell. The north side seems to attract to the alum only very little.

There appears to be either a difference in the north and south magnet fields, or different elements constructs create different magnet field interaction, or both.

lostcauses10x

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #77 on: May 24, 2009, 07:22:16 PM »
0c one of them things in the whipmag no one seem to have observed is the use of inductors that seems (with what I had to measure with ) no major reaction to the slowing of the moving rotor. Just one of them observations. Hmm,,,,
I see a copper plate in the times to come for me.

TinselKoala

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #78 on: May 24, 2009, 07:56:50 PM »
0c one of them things in the whipmag no one seem to have observed is the use of inductors that seems (with what I had to measure with ) no major reaction to the slowing of the moving rotor. Just one of them observations. Hmm,,,,
I see a copper plate in the times to come for me.

CLaNZeR, IIRC actually did do rundown comparisons with the MKJDs of several different materials (different alum. alloys, I think) and found that they do slow the AGW rotating stator enough to stabilize it, and the different alloys behave slightly differently in this regard. I don't know if that's significant at all but I thot I'd mention it.

lostcauses10x

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #79 on: May 24, 2009, 08:16:41 PM »
TK I saw some of that. yet in my not so accurate rundown times, I saw no real variation of the rotor with only them MKJD.  Were as I can account for the induction action of such (rotor magnet layout, I expected more drag). I could not measure such.
Any practical application of such, Hmm who knows. May try a coil, or coils and drive the rotor and see what happens.

CLaNZeR, IIRC actually did do rundown comparisons with the MKJDs of several different materials (different alum. alloys, I think) and found that they do slow the AGW rotating stator enough to stabilize it, and the different alloys behave slightly differently in this regard. I don't know if that's significant at all but I thot I'd mention it.

0c

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #80 on: May 24, 2009, 08:51:50 PM »
Summary of what we know so far, please correct me if I make any errors here:

1) The magnetic repulsion from eddy currents appears to affect the leading edge of the sliding magnet differently than the trailing edge, lifing the leading edge away from the conductive material. At the extreme, the leading edge  will "flip" away and the magnet will fall.

2) There seems to be a difference between north and south pole response, similar to what might be expected if one pole was stronger than the other. At steep angles, the magnet may "pop" off the conductive ramp when one pole is in  contact, but will slide smoothly when the opposite pole is facing the ramp.

3) There appears to be a "cling", or attraction, on the trailing edge of the sliding magnet. It is apparent even when the conductive material (aluminum or copper) is slightly past vertical.

4) Diamagnetic (copper) and paramagnetic (aluminum) materials show no difference with respect to magnet polarity. There may be a difference in the magnitude of the effect.

5) Orientation with respect to the earth's magnetic field does not seem to make any difference. The effect is identical in the northern and southern hemispheres.


NOTE: Since editing capabilites are limited in this forum, if you want to correct or add to any of these statements, please copy, edit, and post the changes in a new post. Hopefully, the latest copy will always contain the most current and accurate information.

lostcauses10x

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #81 on: May 24, 2009, 08:56:12 PM »
good summery oc

lumen

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #82 on: May 25, 2009, 05:05:33 AM »
Wow, I've been away for a week and just read this entire thread.
I like TK's video showing the effect even past vertical into a negative angle.
I believe the only way TK's magnet can hang on to a negative is because of the ring magnet he is using.

The center hole must allow some additional gripping affect from the opposite polarity to grab onto the opposite field induced in the aluminum.

That is interesting!

lumen

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #83 on: May 25, 2009, 06:36:48 PM »
I'm starting to believe the trick with magnets is not using iron, but a non magnetic metal.



lumen

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #85 on: May 29, 2009, 05:01:00 PM »
@TK
I like the disk rotation test. Is that something going on that makes the magnets spin or maybe the string wound up more in one direction than the other?

It looks like when the S pole is first in the approaching disk direction, the N pole does not want to be inline with the plate where the S pole has been. Is this just the way it looks or is something going on there?



TinselKoala

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #86 on: May 29, 2009, 05:13:53 PM »
@TK
I like the disk rotation test. Is that something going on that makes the magnets spin or maybe the string wound up more in one direction than the other?

It looks like when the S pole is first in the approaching disk direction, the N pole does not want to be inline with the plate where the S pole has been. Is this just the way it looks or is something going on there?

I think this is a good experiment but in this video there are some obvious problems. Still, I think the result that one pole rides lower is a good one.
I need to make an arrangement where both poles see the same velocity of the moving conductor beneath them. Maybe a repeat of the "dangerous high-speed eddy current levitation" setup of Bill Beatty might work. Or I can put more hooks in my ceiling and compare the opposite region of the disk, which should reverse the velocity asymmetry beneath the poles of the magnet stack.

I tried to get the doubled fishing line untwisted, and when the magnet stack agrees with the compass I believe it is untwisted. If it is twisted it makes a bit of torque that swings the stack off North one way or the other.

In Scott's video he doesn't give credit to Lumen but I pointed out in the comments to that vid that Lumen (and X0000013) first pointed out the effect to me.

lostcauses10x

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #87 on: May 29, 2009, 05:44:38 PM »
TK I see a hinged or gimbal holder for such tests.  Not going to be an easy thing on a driven plate.

 The other method I see with such is a very long plate on a liner slide as a driven plate.

lumen

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #88 on: May 29, 2009, 06:14:51 PM »
A rotating beer keg?

This sounds like a fun experiment. The keg needs to be empty!

lostcauses10x

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Re: Magnetic braking of magnets sliding along a sloped aluminum surface
« Reply #89 on: May 29, 2009, 06:29:09 PM »
The keg needs to be empty!
LOL I will help with that, the emptying part that is..

A rotating beer keg?

This sounds like a fun experiment. The keg needs to be empty!