The Steorn Permanent Magnet Motor Replication Project: It's FLUX time.

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Clockwise rotation



gotta go mulch leaves --- later...

[smarthousesys]

I really wonder if you can use a lema in any scheme that has magnets on the rotor. Basically the shielding takes effect blocks off the magnets in the lema and then the rotor magnets are simply attracted to the shielding and you are back where you started- sticky point.

[thevorlon]

I urge all of you to read the following statements from Sean McCarthy on the Steorn forum. It directly relates to the LEMA.

It seems to me that he is trying to say that you could not get more energy out of a PMM using the LEMA than you would put in moving the shield back and fourth. Apparently, the repulsive magnet would come into play and cause a problem if I am understanding this correctly. 

Hi Folks,

I know that a lot of people have been asking if LEMA part of our OU technology and if not what is it and why did we design it?

The answer is no, it is not part of the OU technology. As previously stated we have developed several anti-counterfeit technologies in the past, these technologies where developed for a client FraudHalt (you can see a quick overview of the technologies at http://www.fraudhalt.com/demos/)

As you can see both of these technologies have a very heavy optics involvement. Anyone who works with optics will know that you typically build prototypes on an optical bench.

So? Well optical benches use magnetic clamps - these type of clamp are turned on and off by moving a shield in front of the clamping magnet. LEMA was a concept to help reduce the force that the person using the clamp has to apply in the camping/unclamping of these types of devices.

Thanks,

Sean


Hi bobcat,

Lets take an objective view of LEMA. It is in essence designed to reduce the force required to actuate a magnetic field (as noted above). However it is interesting to take an energy view of what is happening.

Assume the LEMA unit is standing upright. If you remove the top magnet and move the shield up and down (excluding friction) you will get a net zero energy balance. Why? Because the energy you put into moving the shield up will be regained when the shield is pulled back into its original position. Adding the second magnet does not change the net zero energy sum, just the level of forces (and hence energy) involved.

So in a friction free world you have the ability to create a machine with a LEMA type device that gives you a fluctuating magnetic field for no energy. So if LEMA can be used to develop an OU device then you need to be able to harness this field without substantially changing the net energy profile of LEMA.

Thanks,

Sean


Hi bobcat,

The key issue is what is the energy equation when you switch the shield in the presence of another magnetic field? The best thing to do would be to test this
(a force meter would be required). I think that you will find that the net energy equation for such a system will sum to zero.

Thanks,

Sean

[gyulasun]

I really wonder if you can use a lema in any scheme that has magnets on the rotor. Basically the shielding takes effect blocks off the magnets in the lema and then the rotor magnets are simply attracted to the shielding and you are back where you started- sticky point.

Hi,

Basically you are right BUT by carefully selecting the thickness of the shield, the distances between the shield and both the rotor / stator magnets you can get a setup where the following should happen: as the rotor magnet approaches the shield there will be a small attraction force between them (the thickness of the shield can be a bit higher at the entering side than at the leaving side for instance this is one trick) and the attraction force diminishes to nearly neutral when the rotor magnet is facing the still just covered stator magnet.

I included my drawing on how I think to use the LEMA concept in a permanent magnet motor.
I prefer using longer magnets of either cylindrical or rectangular shape (the length is chosen to minimize the effect of the opposite poles).
The position of the arms operating the shields is shown just before the moment the shields are about to move: the upper shield will be shifted to the left, the lower shield will be shifted to the right when the arms are activated by the rotor.  Several refinements are still needed.  AND much experimenting with the thickness/shape of the shield is also needed.
I will try to build such a setup I drew in the next couple of weeks as my free time lets it.

Comments are welcome.

Regards
Gyula
     

[pinestone]

[\quote] Gyulasun       ...Hence why for the need of 4 magnets?   Possibly I am missing something here, could you explain?[/quote]

Thanks for pointing that out.

OK I'll elaborate a bit:

You can use the magnets in what ever configuration you require.
I don't know how your motor is built. I was just trying to show a method of 'kicking past' the 'sticky spot' where opposing polarities meet.

If you need an N pulse, then the flywheel magnet should be north polarity at the point at which it passes the pickup coil. If you need a S pulse, just flip it around.

You may need to reverse the polarity on the diode, too for your individual application.

It wasn't ment to be an exact diagram, but only a mechanical/electrical concept drawing.

I haven't had the time to read the entire thread, but I did notice you folks talking about getting 'stuck'.

∞