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Luke55
05-13-2012, 12:25 PM
If a horse shoe magnet is broke in two parts . if held perfercly joined. it still have the same power? It goes on a Webster mag

Jaakko Fagerlund
05-13-2012, 11:14 PM
Roughly yes.

J Tiers
05-14-2012, 08:20 AM
But actually no.

The break adds an "air gap" to the magnetic path, in the magnet. While there is a bigger gap elsewhere, this one is actually in the magnet and would be expected to reduce the magnet strength at the other gap a bit.

How much depends on how wide the gap is... how well it can fit back together, and whether the metal is all there or if there are missing pieces that reduce the cross-section.

Old magnets tend to be made of hard steel, which does not deform much, but may splinter, leaving gaps in the break where there isn't any metal.

Could be almost un-noticeable or it could be a 30% drop... all depends.

Jaakko Fagerlund
05-14-2012, 08:58 AM
Exactly, it all depends how good it is once assembled :)

The Artful Bodger
05-14-2012, 04:22 PM
This is on a magneto?

I have never tried this but maybe sticking another, more modern, more powerful magnet across the gap (correctly aligned) would actually increase the magnetism of the old magnet.

Evan
05-14-2012, 05:19 PM
The main problem with a broken magnet is that the shock or other force that caused it to break will partially demagnetize it. Dropping or otherwise shocking a magnet causes the magnetic domains to partially scramble which weakens the field.

Evan
05-14-2012, 05:27 PM
I have never tried this but maybe sticking another, more modern, more powerful magnet across the gap (correctly aligned) would actually increase the magnetism of the old magnet.

There are very large variations in the maximum temperature rating of different magnet materials. Ferrite magnets that are usually used in magnetos have a max working temp of about 300C (572F). Alnico magnets are good to 540C (1000F) but they are easily demagnetized by other magnets. Samarium Cobalt magnets are also good to about 300C but Neodymium magnets of the most common variety are only good to 150C (300F).