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Question: Can Shimano a dynamo be oriented the 'wrong way'

Posted: 7 Aug 2008, 12:15pm
by natmat
Hello,

Does anyone know much about Shimano's excellent DH-3N70 Ultegra dynamo hub? If so then please read on, you may be able to help me...

The instructions say it must be mounted so it rotates in the correct direction. I'm wondering whether it would be wise to mount the other was round. "Why such madness?", I hear you say, well...

I'm thinking of buying a Cotic Roadrat and the Roadhog forks have disk mounts on their leading-edge, so the disc itself would have to be mounted on the right hand (off-) side (looking forward) of the wheel. This would mean the dynamo hub would rotate in the 'wrong' way the vast majority of its life.

I'm thinking that this would be VERY bad to do, but does anyone know otherwise?

Over to you,
Nathan.

Posted: 7 Aug 2008, 12:44pm
by cranky
I know nothing about the 3N70 but .... some newer Schmidt hubs will dismantle themselves when run in reverse. I don't think there's any electrical reason why a hub should be run 'one way only' so I'd guess the 3N70 may just decide to dismantle itself too :!:

Posted: 7 Aug 2008, 8:26pm
by andrew_s
The electrical contacts must be on the right when the wheel is in the bike.

If the wheel is used with the contacts on the left, the central part of the hub will unscrew itself, and likely snap the electrical connection between the hub innards and the contacts.
It's for the same reason as LH thread BB fixed cups and LH threads on left pedals.
The newer Schmidt hubs are the same, but the old ones with the black centre are pressed together rather than screwed, and can be used either way round. I don't think you'd be able to find a disk version even if they were made.

To run the hub the wrong way round, you'd probably have to key the threaded section to stop it undoing - something like drill a small hole and jam a peg in it.
Schmidt may give advice for their hub - eg how deep you can drill without wrecking the weather sealing.