Magnet life under a load

[AB Hammer]

I have read and heard that magnets last 500 years. This would be great if it would be under a load.
But my question is why so many magnet motors fail even after they seem to work. I am 48 years old and have seen many magnet test and even motors at school as I was growing up. Some motors that where hooked up to a gernerator and only last about a month or so before they end up disasembling them. In my mind it tells me that a magnet under a load depolarize after a bit. This is why I havn't done much with magnets.

Can anybody tell me where to find life expectentcies under a load for a magnet?

[ken_nyus]

Some things I have read...

Modern "super" magnets are different from older permanent magnet technologies. I think there is a "knee" above which a magnet can be de-magnetized, when in repulsion, but as long as you work below this knee, you are safe.

Just what I have gathered from the web.

[tinu]

But my question is why so many magnet motors fail even after they seem to work. I am 48 years old and have seen many magnet test and even motors at school as I was growing up. Some motors...

Please show me a single working magnet motor.
Please, please! I?m dead serious and not joking at all.
I?ve never seen one in my whole life and my training as well as my related experience (what a waste of time!) deny them.
Show me at least one clearly working for 5+ minutes and I?ll be more than grateful. What the heck, I?ll be even ready to re-write some of the science!

Again, I am very serious in my kind request and I suppose a lot of other members here would like to see it too.

Many thanks in advance,
Tinu

[Nastrand2000]

@ Tinu,
I believe he is speaking about conventional magnet motors ( coils and wires and such) that run a generator.
Jason

[hansvonlieven]

G'day Hammer and all,

I have handled many motors in my life that used permanent magnets, some of them have been running since the 1940's and 1950's without apparent diminishing of the magnetic field.

The one thing though that will knock the magnetism out of ANY magnet is heat. Some magnetic materials are more heat tolerant than others but all suffer from that flaw. The motors you describe sound to me like motors that ran too hot for what they were designed to do, usually due to overload or poor ventilation.

Hans von Lieven