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The Lost Magnetic Property (1930-1950 Pole Piece)
forest:
Can't be mu metal.It should not be attracted to magnet.For me it looks like something with high permeability but which forbid closing of field lines around it. Is there a possibility that the effect lies in shape not much in alloy composition ?!
G_Motion:
Oldspeaker.pdf shows it's shape. I don't think the alloy was highly permeable but it must have been significantly greater than the permeability of air for the speaker to work. Orthodox magnetic theory says magnetizability equals permeability times a constant, yet a sample of permalloy claimed to be a hundred times more permeable than cold rolled steel has half CRS's attraction. It makes no sense to me.
Hope:
Babbit like that used in model T motors as bearing material, perhaps or even more feasible is bismuth. With a PMH we have magnetized ordinary aluminum, paper, string, wood, etc. PMH= permanent magnetic holder. We simply place the item to be magnetized between the magnet and the bar that is normally used to cover the magnet between uses.
onthecuttingedge2005:
Hi G-Motion.
do you remember what the speaker came out of? some old cars made in that era may still hold them installed, most old car collectors have the old speakers rebuilt to work again.
maybe this direction will give you better luck in finding one, maybe in an old wrecking yard with that vintage of car models still present.
good luck.
Jerry 8)
G_Motion:
Car radios weren't common then and the piece I had didn't come from one. I don't think it came from a floor model, they usually had large speakers with electro magnets, so it must have come from a desk top model.
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