Quote:
Originally Posted by dcb
I would say the default assumption here is that magnet motors are not sustainable as the magnets give up their magnetism for a minuscule amount of rotational energy. They have been around for decades ("Power Wheel" Popular Science, Fall 1980), and trade magnetism for rotational energy. No free lunch. If Bill were not soliciting I wouldn't care.
|
I test my magnets frequently against a magnetometer. To date, in or out of a motor, I've never seen any of the rare-earths lose any of their "pull force".
In another post, you mentioned "keeper" which with a simple flat disc magnet isn't appropriate. A "keeper" according to what I can recall, is a metal bar kept across the poles of antique "horseshoe magnets" most of which were made of magnetized steel, which would lose power over time, to prevent that from happening. The keeper touched both poles. A fridge magnet tends to be hanging on by one pole only, so I don't get how that would apply.
There's a bunch of literature on the rare-earth magnets online at kjmagnetics.com which is where I buy my supplies, and I don't recall anything suggesting that they will drain from use, nor any suggestion that one needs to use a keeper to keep same from happening. I know the things can lose power due to excessive heating, but that's not the same thing.
A lot of information about magnets of one kind doesn't strictly apply to others. For example, the demagnetization of neodymium magnets occurs at arount 175F while samarium magnets hang on through around 570F.
I have to conclude that there is a lot about the things we simply don't know.
Magnetometers are relatively inexpensive, and even more so are the kind I use, made of a transparent plastic tube about a foot long in which resides a pair of opposed short disc magnets mounted in a thinner tube that slides inside the bigger one. That is calibrated by hand using a "Sharpie" marker, and gives only an indication of approximate pull force.
One of the reasons I think that magnetism is a quantum phenomenon is the very fact that it doesn't seem to "drain" in use (with rare earth units). There may be some decay that I've not tested for, but I haven't seen it happen.
You do make me think!!
Cheers, God Bless us and grant us the wisdom to make magnets work for us!
Bill Whedon