Question about interacting magnet fields 2

[13th]

Im an amatuer designer/inventor and have a question about the nature of magnets. I am currently working on a machine which may incorporate magnets into the design...

OK... i hope this makes sense.

Represented bellow are 3 disc magnets in a tube. Magnet 1 (|1NS|) and magnet 3 (|3SN|) are static. magnt 2 (|2SN|) is attached to magnet 3 via magnet attraction. S & N represent the polarity of the magnets (south and north respectively).


|1NS|.......|2SN|.|3SN|

A force is applied to magnet 2, breaking the connection between 3 & 2.
and propeling it towards 1.

<-----
|1NS|.|2SN|.......|3SN|

When this force has stopped, magnet 1 repels magnet 2 in the direction
of magnet 3 and is then reattached to magnet 3.
----->
1NS|.......|2SN|.|3SN|

In my machine, doing this !consistantly! for periods of time at rates of up to 20 times a second are essential to the function.

Question1 will the interacting magnetic fields gradualy decrease the strength of the magnets?

Question2 are there any undesired effects of moving a magnet in this manner back and forth

Thankyou for your time.

 

[13th]

http://www.eng-tips.com/viewthread.cfm?qid=185401&page=7

The above page answers question 1, i beleive.

Consistancy is the key, though... can my above operation move at the same speed given the same force applied each time?

 

[IRstuff]

The slamming of magnets together can potentially cause some demagnetization

TTFN

FAQ731-376

 

[electricpete]

"Question2 are there any undesired effects of moving a magnet in this manner back and forth"

Hard to say what's an undesired effect is without knowing what the heck the machine is.

You will be creating a time-varying magnetic field. This can induce currents in thick metal or metallic loops. It may also disrupt electronics.

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[13th]

Thank you electric pete and IRstuff for you reply.

I have now incorporated a mechanical stop into the design so that the magnets never actually touch also practical as i have chosen Neodymium magnets which are quite brittle. Would this stop any demagnetising from them slamming together?


"You will be creating a time-varying magnetic field. This can induce currents in thick metal or metallic loops. It may also disrupt electronics."

Ok... i had a gut feeling about this so the electronics are located as far away from the magnetic mechanism as possible... my device is mobile so out of curiosity is there a possibility of harnessing the electric currentfrom the time-varying magnetic field to charge a battery?

The rest of my device is constructed from brass and aluminium, strong magnets should have no effect on these materials, right?

Thanks for your time and knowledge

 

[MJR2]

The time-varying magnetic field creating currents is another way to say you may have eddy current heating. This is particularly noticeable in brass and aluminum. If the magnets are moving in relation to the metal they may heat the metal.

You can nicely demonstrate this to yourself by dropping a magnet down the inside of a piece of copper water pipe. It will slow noticeably.

You could possibly harness the electricity but it will take you more energy to get it than you make.

Mike

 

[13th]

Thank you MRJ2...

so the heat generated from eddy currents could effect the strenght of magnetism possibly causing a loss in consistancy of the operation?

The force that moves magnet 2 is pressurised air, so the air flow may offset any heating of brass and alluminium. The other option would be to not use brass and aluminium and use a strong plastic composite instead... but this could cause components to wear out quicker.

I had it pointed out to me that wrapping a copper coil around the tube which encases the magnets could be used to create an electrical charge which could be harnessed to charge a battery... is this so? and is it worthwhile?

 

[MJR2]

Heat will reduce the magnetic field produced.

...wrapping a copper coil ...

Yes it could produce a current. Worthwhile is up to you and the application.

A flashlight is made that is charged in this manner.

Mike

 

[13th]

Excellent,

Thank you everyone for your help, i'm very grateful, with the advice given i've made several design changes and saved myself a lot of head-aches.

 

[cwbiii]

Your machine uses pressurized air to run it. Energy had to be put in to pressurize that air. Trying to charge a battery from the magnets motion will also take energy from the system which would require more pressure to run it at the same speed. You can do what you want as long as you realize that you need that source of pressurized air to run your machine off of.

Chuck