cleaning permanent magnets

I finally got the Shimano dynamo hub apart and sure enough, a magnet was loose, apparently lifted by rust forming between magnet and iron field ring.

It isn't hard to sand the rust off the magnet and field piece but it's quite hard to remove the resulting magnetic particles from the assembly. Just a few bits of debris left behind will keep the magnet from settling into place and thus give clearance problems.

Does anybody have a good way to grab and remove magnetic debris with the consistency of flour to fine sand? I've tried masking tape, but it's slow and won't reach into recessed spaces. Thanks for reading,

bob prohaska

Reply to
bob prohaska
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One thing that I do is use compressed air to blow it off. The really small particles don't blow off, but they can be herded to an edge for picking off.

Reply to
Bob Engelhardt

Post the above to rec.bicycles.tech and you'll get more answers then you can imagine, but pay attention to any response from an Andrew Muzi, who has been in the business for years and years.

Reply to
John B.

The old-time method was to coat the article to be cleaned with collodion, allow it to dry, then peel the collodion film off by hand. This is still used to clean optical surfaces such as front-surface aluminum mirrors.

Collodion is a strippable coating, and other strippable-coating kinds may be suitable for cleaning magnets.

Joe Gwinn

Reply to
Joe Gwinn

I read rec.bicycles.tech routinely and will try that next. I was hopeful that folks who do metalworking might have some experience cleaning permanent magnet field assemblies after machining.

Use of dynamo hubs is rare among cyclists. One other community that could offer insights would be the folks who use electric RC models. Alas, the newsgroups I can find on eternal-september don't have an electric-power subgroup. General web searches aren't much help without very well-chosen keywords, which I have so far failed to guess.

Thanks for writing,

bob prohaska

Reply to
bob prohaska
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Had this problem with big magnets on sirens back in the day. More of a rust problem on them though. Sometimes you could get lucky if they weren't too bad. Blow with shop air and masking tape folded with sticky side out over something like feeler gauge material...

I get a few hits searching on this with:

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I like Joe's suggestion :) I've used this temporary caulk around the window AC unit before:

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It pulled off well in the fall when removing the unit for winter. Doesn't keep well, use it up shortly after opening it because it will spoil before needing it again next year :(

Reply to
Leon Fisk

Just a wild idea. Cover it in RTV silicone, give it a day or two to cure. Peal it off.

Never tried it. Just popped up in my head right now.

Reply to
Bob La Londe

try soft glue that doesn't stick to metal, like the white elmers. Blu-tack sometimes works for debris on magnets too.

Reply to
Cydrome Leader

Dammit! didn't think of that, and I have some on the shelf 8-( Next time it's apart....

Thanks for writing,

bob prohaska

Reply to
bob prohaska

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