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

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On Sun, 31 Jul 2022 00:53:48 -0000 (UTC), bob prohaska
<bp@www.zefox.net> wrote:

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

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.
--
Cheers,

John B.

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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.

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On Sun, 31 Jul 2022 00:53:48 -0000 (UTC), bob prohaska
<bp@www.zefox.net> wrote:

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.

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

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John B. <slocombjb@gmail.com> wrote:

On Sun, 31 Jul 2022 00:53:48 -0000 (UTC), bob prohaska
<bp@www.zefox.net> wrote:

Does anybody have a good way to grab and remove magnetic
debris with the consistency of flour to fine sand? I've

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.

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

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On Sun, 31 Jul 2022 15:16:25 -0000 (UTC)
bob prohaska <bp@www.zefox.net> wrote:

<snip>

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.

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:

https://www.google.com/search?q=cleaning+speaker+magnets

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

https://www.amazon.com/18354-Seal-Removable-Caulk-10-1-Ounce/dp/B001QFZS6E/

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 :(

--
Leon Fisk
Grand Rapids MI

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On 7/30/2022 5:53 PM, bob prohaska wrote:

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

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.

--
This email has been checked for viruses by AVG.
https://www.avg.com

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

bob prohaska <bp@www.zefox.net> wrote:

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

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

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Cydrome Leader <presence@mungepanix.com> wrote:

bob prohaska <bp@www.zefox.net> wrote:

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.

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

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

Thanks for writing,

bob prohaska

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