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Author Topic: Magnetic Shielding  (Read 30097 times)

mbell

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Re: Magnetic Shielding
« Reply #15 on: November 04, 2006, 11:44:34 PM »
I have a ton of hard drives laying around some old some new. Where i get this is from the end of the read write heads. There are two shields and the magnets are glued to the shields. The magnet will stick to the shield but will block any magnatism beyond that. It is hard to get the magnet away from the shield (because of the glue) and the magnets are very powerfull for their size. I am going to try this motor as I think it can be done useing the shields from the hard drive. http://www.fdp.nu/otherwheels/bartosz.asp?URL=bartosz.asp If you attach the shields to both magnets like it shows in the picture you should not get any attraction or repulsion until just before the magnets come face to face. The shields are in the new hard drives 3.5 inch and the are at the back end of the read write heads. They are like a half circle and the magnets are glued to them. The magnets are very easy to break so you have to be carefull if you want to save the magnets. I can post pictures of this if you need me to.

I think also if you use the hard drive as the turntable could you also get power out of the motor? This is what I am going to try as I think if you use the shields out of the hard drives and attach as shown in the picture it should work. (maybe) lol...

I hope this helps
Thanks
Mike
« Last Edit: November 05, 2006, 02:46:14 AM by mbell »

Paul-R

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Re: Magnetic Shielding
« Reply #16 on: November 05, 2006, 04:11:08 PM »
There is a concept of "shadowing" as distinct from "shielding" as discussed on:
http://tech.groups.yahoo.com/group/minatowheel/
Also, google for "parallel path" and check out "changing fields" on
http:www.fdp.nu
mu-metal has a reputation for shielding, although fields have a
way of leaking around the job.
Paul.

gaby de wilde

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Re: Magnetic Shielding
« Reply #17 on: November 28, 2007, 03:00:40 AM »
The easiest way is to look at simple wheel designs such as this that show shielding

http://www.fdp.nu/otherwheels/bartosz.asp?URL=bartosz.asp

Not saying it will work, but the logic is there.

Could you give us an example of where exactly on a magnetic motor would you be placing this insulating material? Where exactly is the spot that you are trying to insulate?

I look forward to hearing your results.

here is an idea using a shield I just drew up, the goal is to keep the shield in the exact center.
(http://img.go-here.nl/shielded-pistons.gif)

If this would run down one could wrap a coil around the shield and pulse that. With all the exotic shielding material you have I think this kind of contraption looks most interesting?

:-)

rrintoul

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Re: Magnetic Shielding
« Reply #18 on: November 28, 2007, 04:18:36 AM »
...
Also I would be interested in knowing how easy the material can be pulled away from a magnet when sliding it rather than pulling?
Also if you form a air gap between this material and the magnet, does it still shield?
...

Sean, this notion of sliding the shield rather than pulling directly away reminded me of an experiment I did.  The shield was as close to touching the magnet as possible, and it was very attracted to the neo.  When the shield covered the neo though, it almost perfectly turned it off.  You could put iron bolts right against the shield and there was very little noticeable attraction, even though the distance was only a few mm.  I found by using a strong elastic band to counter the shield's desire to cover the neo, I could create a close-to-equilibrium that made it quite easy to slide the shield on and off.  Here's a crude picture:

(http://www.overunity.com/index.php?action=dlattach;topic=171.0;attach=6347)

Reade

stardelta

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Re: Magnetic Shielding
« Reply #19 on: December 29, 2007, 01:17:07 PM »
Found this clip ..someone playing around with robbed hard drive mags and some type of shielding strip from a DC motor....

http://www.youtube.com/watch?v=yf2oybnz-vQ

gaby de wilde

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Re: Magnetic Shielding
« Reply #20 on: January 15, 2008, 08:49:25 PM »
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

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Re: Magnetic Shielding
« Reply #21 on: January 31, 2008, 05:29:45 PM »
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

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Re: Magnetic Shielding
« Reply #22 on: March 18, 2014, 10:39:14 PM »
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

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Re: Magnetic Shielding
« Reply #23 on: August 25, 2014, 08:25:11 PM »
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

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Re: Magnetic Shielding
« Reply #24 on: August 26, 2014, 11:30:27 PM »
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

sulo-wilen

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Re: Magnetic Shielding
« Reply #25 on: August 28, 2014, 09:35:13 PM »
As I am not really aware of this: just a silly question: as far as I understand that physical shape of magnet does not affect much about the shape of the magnetic field? else than smaller=weaker?


Just thinking about the directing of field. or perhaps using other magnets ot compromise it..  but I think that if this would be so easy this problem would be solved already..


On other hand I think that some magnetic motors should use some kind of cam drive mecanism to have "timing" on the attracting magnet.. and a decent flywheel.

raburgeson

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Re: Magnetic Shielding
« Reply #26 on: August 30, 2014, 10:52:44 AM »
Geometric shapes have a lot to do with it. Johnson's magnetic motor, is one example. I had a magnet from GE, it misteriously disappeared after it had been posted in here in the past. It had a Angle about 45 degrees on one end. I had a picture of it here long ago, maybe it can be dug up? All the magnets I had are gone. It might be here somewhere but, I have given up looking.

teslaedison

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Re: Magnetic Shielding
« Reply #27 on: September 16, 2014, 02:10:04 AM »
the perfect shielding are magnets that repels each other as in North to North and South to South as cushioning's to each other without any metal to metal frictions either !!!  I am putting two diagrams to show you this
Thomas C.

teslaedison

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Re: Magnetic Shielding
« Reply #28 on: September 17, 2014, 06:01:26 PM »
here is a link to help with pyrolytic graphite shields or repels magnetic fields too
http://en.wikipedia.org/wiki/Pyrolytic_carbon


http://en.wikipedia.org/wiki/Diamagnetism


I hope this helps you guys out
Tom




teslaedison

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Re: Magnetic Shielding
« Reply #29 on: November 02, 2014, 06:52:50 PM »
The best known magnetic shielding is magnets themselves with North repels North and South repels South right Hint Hint !!!
Thomas