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# high static magnet force

## high static magnet force

(OP)
Hello,
My company has been building a breakaway device for years now with a pair of magnets firmly mounted to the device.  The mating piece is a piece of mild steel.  They have the magnets oriented in opposite poles; they (I believe erroneously) call it a Halbach array.  There's a steel backing piece to transfer the magnetic flux from one magnet to the other.

During my playing w/ magnets, when all magnets are oriented parallel, the force to pry off the steel puck is about the same as when they are oriented opposites.  Now, I must note that it is MUCH easier to get the bloody magnets to orient NSNSNS than NNNNNN.  Even stuck to a thick pc of steel, they want to flip flop.

Since the permeability of the N52 magnets is about the same as air, the magnetic circuit that I draw has the same amount of resistors and the same amount of motors regardless of orientation.

My question,
If I had a mild steel rod say 1.25" OD w/ a 1" ID counterbore 3/8" deep.  Say the end is ¼" thick. (the whole thing kinda looks like a socket w/o the hole in the middle)
Then I stick a single cylinder magnet (say 3/8"dia, 3/8" tall) in the base of this.  Same height as the counterbore.  When I stuck this to a steel plate, the circuit that I draw shows much less resistance...wouldn't this mean higher force than simply sticking the magnet to it?

This implies that we could get the same amount of force using less \$ N52.

I understand that if the ID of the steel counterbore were reduced to near the same size as the dia of the magnet, then it would 'short-circuit' and all the flux could easily travel from the front of the magnet to the rear and it wouldn't need to stick to the mating pc of steel.

Am I hallucinating here?  Some of the guys I work w/ have been doing magnets at MIT and I don't want to step on any toes, but it seems like it would work.

I suppose the obvious solution is to go play on the lathe ... In the time it took to write this...

Jason
"Major consumer electronics manufacturer" Mechanical Engineer.

### RE: high static magnet force

Could you provide a sketch of your setup? You should also clearly indicate the magnetization orientation of the magnet.
As far as I can understand your description (magnet in the bore), it is obvious that you get a higher force if you correctly close the magnetic circuit with a magnetic conductor like mild steel.

prex
http://www.xcalcs.com : Online engineering calculations
http://www.megamag.it : Magnetic brakes and launchers for fun rides

### RE: high static magnet force

The static attractive force is always highest if the magnet is "Keepered."  The magnetic flux needs to go from a North Pole to a South Pole through the Keepering Iron.

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