Hacker News Reader

Comment by wodenokoto | Hacker News Reader

I was surprised to read that the magnets weaken over time. I honestly thought permanent where really permanent, but according to a google search:

> 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.[1]

So while they apparently do degrade, it still makes me wonder what these people are doing to markedly reduce the power of their magnets considerably over just a few year.

[1] K&J Magnetics - FAQ https://www.kjmagnetics.com/faq.asp

View on HN

Makes sense when you think about it. The property of magnetism is caused by the alignment of the atoms in the material. Surely this ordering is as subject to entropy as all other order.

But the speed at which people are reporting their magnets losing strength makes me think they're either using low-quality magnets, or their brains getting used to the sensations and tuning them out. I think if mammals had an evolutionary purpose for sensing magnetic fields, they'd already have methods for doing so. From recollection I think dolphins have this trait and use it to navigate.

>, or their brains getting used to the sensations and tuning them out.

or nerve damage from having a magnet just under the surface, several of the people here said it hurt to bump them

I would have thought this too, but most of them are reporting that they can no longer hold paper clips or other small metal objects. It has to be either quality issues, or some third cause.

The problem with Neodymium magnets is that they are notoriously fragile and can chip easily or even explode after being kicked (and the tiny parts would rearrange in unpredictable ways around your nerves and capillars). You don't want such thing happening inside your flesh probably

https://www.youtube.com/watch?v=Vt8NOdINJ1s

From what I read it could be the buildup of scar tissue around the magnet. I can't find the source, sry.

As a parallel question: does that mean that permanent magnet motors degrade their performance over time ?

To a negligible amount in my experience. Many electrical motors have an official shelf-life of around 10 years, due to other factors. If the magnet is treated correctly, it wouldn't loose much strength, maybe 1-2%.

Some magnets lose strength from concussions and higher temperatures. A very strong magnetic field can also damage the magnet. That said, motors with permanent magnets have quite good performance properties and are pretty energy efficient.

And if your magnet fails, you can always revitalize it with an external magnetic field.

Probably exposing them to strong magnetic fields.

Reply on news.ycombinator.com