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DH-3N20 bearing adjustment



 
 
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  #1  
Old August 18th 18, 12:25 AM posted to rec.bicycles.tech
bob prohaska
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Posts: 48
Default DH-3N20 bearing adjustment

What's the conventional wisdom for setting preload on
Shimano hub dynamo bearings?

On a normal hub I'd adjust the cone finger tight and
set the locknut without moving the cone. The dh-3n20
hub is quite a bit more limber owing to the diaphragm
like ends.

If more preload is needed, how much?

Thanks for reading,

bob prohaska



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  #2  
Old August 19th 18, 03:27 AM posted to rec.bicycles.tech
Steve Weeks
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Posts: 5
Default DH-3N20 bearing adjustment

On Friday, August 17, 2018 at 6:25:19 PM UTC-5, bob prohaska wrote:
What's the conventional wisdom for setting preload on
Shimano hub dynamo bearings?

On a normal hub I'd adjust the cone finger tight and
set the locknut without moving the cone. The dh-3n20
hub is quite a bit more limber owing to the diaphragm
like ends.

If more preload is needed, how much?

Thanks for reading,

bob prohaska


This video may be helpful: https://www.youtube.com/watch?v=oXptXRqxj9c
AFAIK, in general cup/cone bearings are meant to be adjusted for very slight (if any) preload, but certainly no slack.

If I'm right, the cup/cone bearing is on the non-output side, with a cartridge bearing on the output side. It's probably harder to get the bearing adjustment right on a dynohub because of the interaction between the magnets and the poles of the stator, which give the hub bearings a sort of "notchy" feel.

For comparison, replacement of the cartridge bearings in another dynohub (Dahon "Joule") is described he https://hubstripping.wordpress.com/2...comment-105597
Steve
  #3  
Old August 19th 18, 05:14 AM posted to rec.bicycles.tech
bob prohaska
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Posts: 48
Default DH-3N20 bearing adjustment

Steve Weeks wrote:

This video may be helpful: https://www.youtube.com/watch?v=oXptXRqxj9c


The narrator simply says, at 13:06, "It's standard cup and cone". The
bearing is standard, but the shell looks a great deal more limber than
a normal slender hub shell.

Experimenting with the adjustment, I stayed with the "finger tight, hold
the cone and set the lock" habit. That preloads the bearing by the axial
clearance of the cone on the threads. The shell has considerably more give
and might warrant more preload than a conventional hub.

There's no cartridge bearing on either side, per the video.

Good video, by the way.

bob prohaska

  #4  
Old August 19th 18, 05:32 PM posted to rec.bicycles.tech
AMuzi
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Posts: 9,765
Default DH-3N20 bearing adjustment

On 8/18/2018 11:14 PM, bob prohaska wrote:
Steve Weeks wrote:

This video may be helpful: https://www.youtube.com/watch?v=oXptXRqxj9c


The narrator simply says, at 13:06, "It's standard cup and cone". The
bearing is standard, but the shell looks a great deal more limber than
a normal slender hub shell.

Experimenting with the adjustment, I stayed with the "finger tight, hold
the cone and set the lock" habit. That preloads the bearing by the axial
clearance of the cone on the threads. The shell has considerably more give
and might warrant more preload than a conventional hub.

There's no cartridge bearing on either side, per the video.

Good video, by the way.


I think your hubshell comments are a red herring to bearing
adjustments. Ignore your theory it's not a factor.

Where you're uncertain about proper bearing adjustment, for
example on a dynamo where the field always feels 'rough',
lock one side as usual but mount that locknut in a vise.
Adjust the other side and check with one hand on the axle,
the other at the rim. Adjust until play is removed.

The principle here is that sideplay causes uneven and more
rapid wear, there being only one ball on each side in
contact at any one time. With proper full contact, wear is
optimized. Overtightening introduces a higher load on the
contact points and should be avoided. For a QR axle, check
adjustment in the bike with QR closed.



--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971


  #5  
Old August 20th 18, 02:46 AM posted to rec.bicycles.tech
bob prohaska
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Posts: 48
Default DH-3N20 bearing adjustment

AMuzi wrote:

I think your hubshell comments are a red herring to bearing
adjustments. Ignore your theory it's not a factor.

Fair enough. The shell stiffness is the key to the question.

Thanks for posting,

bob prohaska



 




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