Magnetic shield by use of a second magnet - A better way I think.

[Low-Q]

@lumen
In the example with magnet A and B upon eachother, the field from magnet C will be affecting magnet A as well as magnet B. So when you move magnet A to the right, it must fight against magnet C, because magnet C, which wants to go to the right is virtually going to the left when you move magnet A to the right. This energy, in fact a little bit less, is taken back when magnet C is moved to the new center. When you then move magnet A back, the rest of the energy is taken back. So left you have not gained anything.

That is my theory anyway. Because, if magnet C is forced to the left as soon as you move magnet A to the left, there simply must has been spent more energy to move magnet A than it takes to move it without the presence of magnet C.

Vidar

[Low-Q]

I think the "shielded Halbach array" is the closest you would get to creating a monopole effect with minimal field on the sides and the back. it is quite possible that nature itself provides such a Halbach array effect but in what material naturally.

Jerry

With a Halbach array you'll get two poles on one side, so you will allways end up with at least a dipole with both north and south. However, this array is interesting anyway, because you can shape the magnetic field to look like a monopole. But even if it looks like a monopole, it will not be able to push the uniform magnetic field in one direction to achieve force, as you will do with a wire in which a electric current is flowing and creates this circular magnetic field. That wire will move, but not the Halbach array. So back to the drawing board

Vidar

[lumen]

Low-Q

when you move magnet A to the right, it must fight against magnet C, because magnet C, which wants to go to the right is virtually going to the left when you move magnet A to the right.

That is not actually what happens.
It is actually more like this:
Magnet C is moved into the center of what looks to be one magnet, then magnet A is moved expanding the magnet, leaving magnet C off center at a point of higher energy. Magnet C actually helps push magnet A to the new position because it is N to N.  The measured energy used to move magnet A is very close to moving A without C present.
The energy left in magnet C is 15% higher than what it took to move magnet A!

You think you could simulate this on FEMM?

[Low-Q]

Low-Q
That is not actually what happens.
It is actually more like this:
Magnet C is moved into the center of what looks to be one magnet, then magnet A is moved expanding the magnet, leaving magnet C off center at a point of higher energy. Magnet C actually helps push magnet A to the new position because it is N to N.  The measured energy used to move magnet A is very close to moving A without C present.
The energy left in magnet C is 15% higher than what it took to move magnet A!

You think you could simulate this on FEMM?

I have done some simulations in big scale.

Magnet C (N-S) feels a force to the right when it's close to magnet A and B (^S-_N). This force is approx 1300N in my simulation. Magnet A are forced to the left with about 600N - magnet B approx 700N.

Now I slide magnet A to the right so I have two full lengths. Now the force in magnet C is about 580N to the right.

Now I slide magnet C to the right so it fits in the middle if the new A-B positions. The force on magnet C is now 480N to the right.


Did this help you out? Clearly that magnet A must fight against a force in addition to the force from magnet B.

Vidar

[lumen]

Thanks Low-Q for doing a simulation for me.

I was wondering how a simulation would compare to actual data taken along the same paths.
The actual data taken at .05" increments shows moving A with or without C present, to have nearly no difference.

It's interesting how the simulator does not seem to take into account that magnet A's N field is totally consumed into magnet B and should have no effect from magnet C. If magnet C had any connection to magnet A, it could only be to the back side of A and it would be the opposite field and should be pushed the opposite direction.

It seems to be right after both magnets A and B are separated and act as one longer magnet.

Thanks again for the interesting info.