Yet another, free, all magnetic idea.

[Low-Q]

I found something interesting with the shielding.

Take a piece of metal that is highly attracted to a magnet and attach the magnet's south pole to the metal (front side).  Now, place another magnet on the same side of the metal (front side) at the opposite end, with it's south pole attached to the metal.  With this arrangement, when you take a third magnet and come in on the back side of the metal, you will feel a repelling force as you approach the metal with one of it's poles.  If you continue, then it will attract to the metal and overcome the repelling force. Also, another piece of metal will stick to the backside of the metal.  So, with this arrangement, the shielding spread the magnetic field over a greater area on the back side of the metal, but didn't eliminate it (sticky spot is weaker, but covers a larger area).

Now flip one magnet over (where it's north pole is attached to the metal), but keep it on the same side of the metal as the other magnet.  With this arrangement,  you will feel no repelling force as you approach the backside of the metal with either pole, and it will be immediately attracted to the metal. Also, another piece of metal will not stick to the backside of the metal.  So, with this arrangement, the shielding eliminated the magnetic field on the backside of the metal (no sticky spot).

This works the other way around also, with the metal sandwiched between the magnets.  Another piece of metal won't stick to either side of the sandwiched metal.  This gives me a few ideas for a magnet motor.

Tell me how or if we can use this to our benefit with the shielding of the ring magnet's sticky spot.

Drawings?

[gravityblock]

Instead of drawings, I uploaded two small videos to youtube, 

http://www.youtube.com/watch?v=_81SxByRNR8 and
http://www.youtube.com/watch?v=aJFgMB5ezsE


The videos are grainy and a little dark, but you should be able to see what I'm talking about in regards to the shielding being able to eliminate the sticky spot if properly done.  If the videos are unclear or you still don't know what I'm talking about, please let me know, and I will upload a better video.

[broli]

GB, let me tell you what I think of your experiment.

First of all it shows that instead of using a PM magnet a ferromagnetic material might be better. Second of all. It brings up kind of a brain dilemma to me. I don't know exactly how to communicate it over. If you consider the ferromagnetic change I just made and relook at the two ring magnets pancaked together including the shielding tubing on the inside you'll see that your experiment is very similar. But instead you just used one magnet and also shielded its back.

I know this is a bit confusing, my communication is a bit off at this late hour. But the main thing that you pointed out here is using ferromagnetic material instead of a PM.

[Low-Q]

Instead of drawings, I uploaded two small videos to youtube, 

http://www.youtube.com/watch?v=_81SxByRNR8 and
http://www.youtube.com/watch?v=aJFgMB5ezsE


The videos are grainy and a little dark, but you should be able to see what I'm talking about in regards to the shielding being able to eliminate the sticky spot if properly done.  If the videos are unclear or you still don't know what I'm talking about, please let me know, and I will upload a better video.

In the first video:
Starts with both magnets with same pole towards the metal piece. Field will exit the metal piece somewhere in the middle of its surface and go towards the other pole on the magnets. This piece will therfor attract the screwdriver.
Ends with turning one magnet. About all fields are going parallell to the metal piece and directly to the other magnet. There is allmost no external field that attracts the screw driver.

Second video:
It starts with both magnets facing the metal piece with the same pole. The field will follow the piece and exit at the end/edge of it where the screwdriver is attracted. The field goes back to both magnets opposite pole. It ends with turning one magnet so the magnetic field will cross right over to the other magnet, and no magnetic field will exist in the end/edge of the metal piece.

Vidar

[gravityblock]

This allows both the rail magnet and ring magnet to be shielded without the rail magnet's shield to stick to the ring magnet's shield, which is a force keeping the rail magnet from escaping the shield of the ring magnet.

If the rail magnet is not shielded, then it will attract to the shielding of the ring magnet and keep it from escaping.  The rail magnet and the ring magnet must both be shielded properly so they won't stick to each other.

Think of the screwdriver as being a shield.  The screwdriver doesn't attract to the magnet's shield in the videos, but I can't keep the rail magnet's shield from attracting to the ring magnet's shield.   

Since the shielding don't stick together in the video, then the shielding shouldn't stick to each other with the rail and ring magnet, but it does. 

I'm going to try the nails for the shielding instead of the batteries, so I can have a uniform thickness of shielding for both the rail and ring magnets.