Magnetic Shielding

[gaby de wilde]

the trick of shielding is in closing the magnetic loop with it. If done well only one kind of flux propagates beyond it. Either north or south but never both. It should be simple to build a spinning device. It wont have much power but it can be made to work. For real power you would need to switch the flux in big cores rather then thin sheets.

One step at a time :-)

Then there is a way of placing the shield on the domain wall. Thats also " shielding" but quite different.

[Charlie_V]

The problem with shielding is that the shield will mimic the same magnetic field as the magnet (with reversed poles of course).  I tried to use shielding to weaken, periodically, the magnetic field coming from a permanent magnet and going into a coil.  The flux from the shield was such that it matched with the flux generated from the coil.  So in the end, it was the same as just moving the permanent magnet back and forth - the counter torque was not reduced at all with the shielding.  I abandoned this idea. 

It is true however, you want to make the shield as thick as possible.  You don't need mu-metal.  Steel plumbing pipe found at any hardware store (or Lowes) is about 3/16 to 1/4 inch thick and makes a great shield - and is really cheap.  Mu-metal is just too expensive and you need so many layers.  Low carbon steels also work better because they have higher saturation than normal steels.

But like I said earlier, shielding does not work - atleast what I've tried, and I tried many many arrangements.  You want to destroy the back EMF's affect on the prime mover and I'm fairly certain that shielding is not the way to do that.

[gyulasun]

Have anyone ever studied the effects of lenses on the magnetic field

Hi Superhero,

No it never occured to me...  you mean optical lenses, right?  If you do, is there any hint that made you ask this question? Perhaps you tested it?

Gyula

[raburgeson]

The best solution would be to figure out what is acually happening in the center of a simple bar magnet. Is it a depletion zone, the action of a vortex, or what. If we can move the null point inside the magnet to one end it should make the flux almost non exist on that end. I know what he is up to and I won't really tell. The simple explanation is he hit the perfect number of rotating magnets around a rotating magnetic armature with the right number of poles and, knows the proper gearing for the outside ring of rotating magnets and wants to build a motor.

[mscoffman]

Have anyone ever studied the effects of lenses on the magnetic field

Magnetic fields do not "project" out of an object like a ray. They come out of it. A line of magnetic flux exists at each point
around a loop. It's kind of a touchy feely way of making sure that anything crossing the magnetic field line gets
integrated into the loop as a whole. So while one can redirect magnetic flux around a gap you can not project it
across a gap, focusing and insulation are generally therefore not available to static magnetic field.

:S:MarkSCoffman