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aus+uk / uk.d-i-y / Re: Sturmey Archer DynoHub Magnet

SubjectAuthor
* Sturmey Archer DynoHub Magnetthescullster
+- Re: Sturmey Archer DynoHub MagnetTim+
`* Re: Sturmey Archer DynoHub MagnetTheo
 `- Re: Sturmey Archer DynoHub Magnetthescullster

1
Sturmey Archer DynoHub Magnet

<t39194$cut$1@dont-email.me>

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From: Phi...@nospam.com (thescullster)
Newsgroups: uk.d-i-y
Subject: Sturmey Archer DynoHub Magnet
Date: Thu, 14 Apr 2022 12:41:23 +0100
Organization: A noiseless patient Spider
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 by: thescullster - Thu, 14 Apr 2022 11:41 UTC

Hi All

I took the back wheel off my "vintage town bike" last weekend and opened
a right can of worms......

The problem was I couldn't install the wheel such that the centre of the
hub remained static with the wheel spindle and the outer hub rotated
with the wheel. The inner and outer were very difficult to rotate
separately (that's without any spindle nuts/washers tightened).
Prior to this I had been riding the bike occasionally without any issues.

So I extracted the complete dyno hub inner and outer to discover that
the whole thing is full of crud and needs a serious clean.

The problem (or point of interest) is that a warning stamped on the hub
states that the inner and outer parts of the hub must not be separated
without a keeper. It appears that the centre of the assembly is a kind
of layered steel plate construction.
Will the magnetic effect be lost if the complete assembly is dumped in a
meths bath or similar?

Thanks

Phil

Re: Sturmey Archer DynoHub Magnet

<1454296834.671630057.359257.tim.downie-gmail.com@news.individual.net>

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From: tim.dow...@gmail.com (Tim+)
Newsgroups: uk.d-i-y
Subject: Re: Sturmey Archer DynoHub Magnet
Date: 14 Apr 2022 11:57:11 GMT
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 by: Tim+ - Thu, 14 Apr 2022 11:57 UTC

thescullster <Phil@nospam.com> wrote:
> Hi All
>
> I took the back wheel off my "vintage town bike" last weekend and opened
> a right can of worms......
>
> The problem was I couldn't install the wheel such that the centre of the
> hub remained static with the wheel spindle and the outer hub rotated
> with the wheel. The inner and outer were very difficult to rotate
> separately (that's without any spindle nuts/washers tightened).
> Prior to this I had been riding the bike occasionally without any issues.
>
> So I extracted the complete dyno hub inner and outer to discover that
> the whole thing is full of crud and needs a serious clean.
>
> The problem (or point of interest) is that a warning stamped on the hub
> states that the inner and outer parts of the hub must not be separated
> without a keeper. It appears that the centre of the assembly is a kind
> of layered steel plate construction.
> Will the magnetic effect be lost if the complete assembly is dumped in a
> meths bath or similar?
>
>
> Thanks
>
> Phil
>

You’ll probably find chapter and verse on dynohubs here.

https://www.sheldonbrown.com/dynohubs.html

(You are correct about the perils of opening them).

Tim

--
Please don't feed the trolls

Re: Sturmey Archer DynoHub Magnet

<QJg*smGLy@news.chiark.greenend.org.uk>

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From: theom+n...@chiark.greenend.org.uk (Theo)
Newsgroups: uk.d-i-y
Subject: Re: Sturmey Archer DynoHub Magnet
Date: 14 Apr 2022 12:58:02 +0100 (BST)
Organization: University of Cambridge, England
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Originator: theom@chiark.greenend.org.uk ([212.13.197.229])
 by: Theo - Thu, 14 Apr 2022 11:58 UTC

thescullster <Phil@nospam.com> wrote:
> Will the magnetic effect be lost if the complete assembly is dumped in a
> meths bath or similar?

"5. Unless it is essential to do so, the armature and magnet should never be
separated. If they are to be separated, a keeper ring is absolutely
necessary, because the magnet will lose some of its magnetism unless there
is always iron inside it. Even a moment's separation will cause loss of
magnetism, and a spanner placed across the magnet is useless as a substitute
for a keeper ring."

https://www.sheldonbrown.com/dynohubs.html
and plenty more info around:
https://minisystem.blogspot.com/2011/12/sturmey-archer-gh6-dynohub-magnetic.html
https://blog.andrew-lohmann.me.uk/2019/07/bicycle-hub-dynamo-maintenance-project.html
(elsewhere suggests using a scrap armature as a keeper - if you have another
hub, of course)

Theo

Re: Sturmey Archer DynoHub Magnet

<t3p9l3$1o5$1@dont-email.me>

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From: Phi...@nospam.com (thescullster)
Newsgroups: uk.d-i-y
Subject: Re: Sturmey Archer DynoHub Magnet
Date: Wed, 20 Apr 2022 16:42:26 +0100
Organization: A noiseless patient Spider
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 by: thescullster - Wed, 20 Apr 2022 15:42 UTC

On 14/04/2022 12:58, Theo wrote:
> thescullster <Phil@nospam.com> wrote:
>> Will the magnetic effect be lost if the complete assembly is dumped in a
>> meths bath or similar?
>
> "5. Unless it is essential to do so, the armature and magnet should never be
> separated. If they are to be separated, a keeper ring is absolutely
> necessary, because the magnet will lose some of its magnetism unless there
> is always iron inside it. Even a moment's separation will cause loss of
> magnetism, and a spanner placed across the magnet is useless as a substitute
> for a keeper ring."
>
> https://www.sheldonbrown.com/dynohubs.html
> and plenty more info around:
> https://minisystem.blogspot.com/2011/12/sturmey-archer-gh6-dynohub-magnetic.html
> https://blog.andrew-lohmann.me.uk/2019/07/bicycle-hub-dynamo-maintenance-project.html
> (elsewhere suggests using a scrap armature as a keeper - if you have another
> hub, of course)
>
> Theo

Thanks to both Tim and Theo

Referring to your links I managed to strip (a bit), clean and
reconstruct the dynohub bit.
I took a risk and pushed the iron core about 1/3 of the way out of the
magnet in each direction so I could attack it with a toothbrush.
A meter on the contacts after completion was showing a healthy AC
voltage approaching 12v with a hand spin.

Don't feel the need or inclination to dismantle the gear hub :)

Phil

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