German magnet motor

[gregs78cam]

Is this thread dead already?   The underlying problem with this design is that your magents situated around this drum are arranged with like poles forced towards each other.  This will, unavoidably, over time kill these magnets.  Sorry, just the facts man.

[TinselKoala]

Looks like some people think otherwise:
"22. Will my neodymium magnets lose strength over time?
Very little. Neodymium magnets are the strongest and most permanent magnets known to man. If they are not overheated or physically damaged, neodymium magnets will lose less than 1% of their strength over 10 years - not enough for you to notice unless you have very sensitive measuring equipment. They won't even lose their strength if they are held in repelling or attracting positions with other magnets over long periods of time.

23. Will neodymium magnets lose strength if they are held in repelling or attracting positions for a long time?
In most applications, the answer is simply "no". If the magnets will be exposed to higher temperatures while in repelling applications, the answer is "possibly". The exact answer is a bit too complicated for a FAQ answer, and requires specifics about the application."

From the FAQs at a leading manufacturer of magnets:
http://www.kjmagnetics.com/faq.asp#time

Of course I suppose they could be wrong.

I wonder who I should believe?

Force-distance relation and properties of repelling Sm-Co5 magnets in orthodontic clinical use: an experimental model
Lars Bondemark 1 Jüri Kurol 1
  1 Department of Orthodontics, Institute for Postgraduate Dental Education, Jönköping, Sweden
Correspondence to  J. Kurol, Department of Orthodontics, Institute for Postgraduale Dental Education, Järnvägsgatan 9, S-553 15 Jänköping, Sweden
Copyright Munksgaard 1992
KEYWORDS
dental alloys • magnetics • orthodontic appliances • stress, mechanical
ABSTRACT

In recent years, magnets and magnetic forces have been suggested as an alternative to traditional orthodontic devices such as elastics, springs and wires. The purpose of this study was to analyze the reliability and the Output of forces for prefabricated orthodontic repelling Sm-Co5 magnets and the force conditions for the magnets after 5 months of maximal loading. The test-machine consisted of a jig where the tested pair of repelling magnets was mounted close to the clinical situation. With a cylindrical strain gauge transducer, a micrometer screw, a bridge-amplifier, and a Mingograph jet recorder, force-distance diagrams were constructed. The force-distance diagrams showed that the forceâ€"distance curve was hyperbolic and that the mean force when the magnetic pole faces were almost in contact with each other was 214. 9 g, SD 13. 42 g. The Variation of magnetic force between different Sm-Co5 magnets was 6â€"9%. The difference in force before and after 5 months of maximal loading of the magnets was not significant. The test results indicate that with proper handling of the forces according to the new force diagrams, the system is reliable for orthodontic use.

[gregs78cam]

hhmmm.  OK.  All that I know is that I arranged some around a wooden cylinder and the ones that I had pressed into it had noticably less force after about a month than those I hadn't.

[nightlife]

gregs78cam, that is interesting. I wonder if the wood absorbed some of the energy or if some else close by did.

[Charlie_V]

@gregs78cam

Firstly, were you using rare earth magnets purchased from a reputable source?  Secondly, did you actually measure the magnetic field with a Gauss meter or were you going on "the feel" of the magnets?  There has been many times when months later, the magnets I had seemed to feel less strong.  But after measuring them, the flux was exactly the same.  The difference was I had started working with bigger magnets and the ones I used before did seem weak but their strength hadn't changed, only my reference point.  I think it was probably all in your head man.