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Shimano Dynamo Hub

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Shimano Dynamo Hub

Old 01-27-18, 04:53 PM
  #1  
Scratcher33
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Shimano Dynamo Hub

I recently and stupidly decided to overhaul the Shimano Dynamo generator hub on on wife's bike. As soon as I undid the driveside bolt, the part that transmits the power from the hub to the cable came apart. Apparently, there was nothing holding it together other than the bolt. After the overhaul, I put it back together in the same order that it was in originally but now when I plug the lights back in, nothing happens (shocker, I know). Does anyone have knowledge about these? Any resources they could point me towards? I'm not having a lot of luck finding anything on the Internet. It's the dh3n71 model.
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Old 01-27-18, 05:16 PM
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You consulted any of Eugene's Bike Shops Yet?
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Old 01-27-18, 05:18 PM
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No bike shop yet. I'm actually on the other side of the country from Eugene at this point. Just haven't updated my profile.
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Old 01-27-18, 05:48 PM
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Shimano says it cannot be overhauled, but there are videos and step by step guides online that show it can be done. Slowly and carefully.

This guide I like best.

Problem with these dynamo hubs is that the power wire to the external bit is very fragile, and easily breaks off -- especially if you do not know it is there. Still, at least you have a hub that can be saved by using a solder iron. Some hubs have an aluminium electricity wire -- that snaps off even more easily.
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Old 01-27-18, 06:18 PM
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Thanks! That's what happened. The wire snapped and now I need to splice in about a centimeter or so. I've got a soldering iron but not a lot of technical know how with this sort of thing.
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Old 01-27-18, 07:32 PM
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Originally Posted by Scratcher33 View Post
Thanks! That's what happened. The wire snapped and now I need to splice in about a centimeter or so. I've got a soldering iron but not a lot of technical know how with this sort of thing.
The lead wire is a solid strand, so care must be taken not to bend it too frequently. Too late for you I know, but there it is. Soldering in a patch will be tricky. It must be insulated, and small enough to fit in the groove in the axle to permit installation of the cone and washer.
I documented a bearing overhaul of a Shimano dynohub here.

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Old 01-28-18, 01:43 PM
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Lucky, Shimano dynamo hubs are servicable. I think they're the only ones that are. Good luck with the repair!
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Old 01-28-18, 02:20 PM
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Originally Posted by ijsbrand View Post
This guide I like best...

Problem with these dynamo hubs is that the power wire to the external bit is very fragile, and easily breaks off -- especially if you do not know it is there.
That's a very nice series of images! The Shimano hub's output wire configuration is not too dissimilar to the Dahon "Joule" hub (first generation... no pun intended!).

Originally Posted by Scratcher33 View Post
Thanks! That's what happened. The wire snapped and now I need to splice in about a centimeter or so. I've got a soldering iron but not a lot of technical know how with this sort of thing.
I snapped that wire on my first attempt because the part that slips over it *looks* like a nut but is held on by silicone seal.

Originally Posted by Dan Burkhart View Post
The lead wire is a solid strand, so care must be taken not to bend it too frequently. Too late for you I know, but there it is. Soldering in a patch will be tricky. It must be insulated, and small enough to fit in the groove in the axle to permit installation of the cone and washer.
I documented a bearing overhaul of a Shimano dynohub here.
Nice video, as always, Dan! A detailed account of my adventures in dynohub repair land is here: https://hubstripping.wordpress.com/2...le-dynamo-hub/
I realize it's not exactly the same as the Shimano hub, but it's possible that there are enough similarities to be helpful. The images #34 - #40 may help with repairing the wire.

Originally Posted by odiolalluvia View Post
Lucky, Shimano dynamo hubs are servicable. I think they're the only ones that are.
Luckily they're not the only ones! See the link I mentioned. Also, for the record, SON hubs are repairable, and so (I believe) are SP... both may have to be sent back to the factory though.
Hope this helps!
Steve
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Old 01-28-18, 02:58 PM
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oh yeah, user servicable is what i meant. we always have to send in the SON and SP hubs when they need service. Tho one time we just got sent a replacement for the SP and we got to take the broken one apart. It was so much fun. There was so much copper wire inside.
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Old 01-28-18, 03:51 PM
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Thanks for all the help. Definitely seems possible but difficult. I'm hoping I can hunt down some sort of electronics repair shop or something in town where someone might be experienced with fine soldering/insulating. If not, I'll wind up trying my hand at it. Kind of blows my mind that connecting 2 wires can be so difficult in this situation.
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Old 01-28-18, 03:57 PM
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Originally Posted by sweeks View Post
I snapped that wire on my first attempt because the part that slips over it *looks* like a nut but is held on by silicone seal.
How'd you wind up fixing yours?
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Old 01-28-18, 06:12 PM
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Originally Posted by Scratcher33 View Post
How'd you wind up fixing yours?
The images I referenced above show how the repair was made. The repair wire was "magnet" wire, which is insulated with a thin coating of varnish. The easiest way to strip this type of wire is to heat a section of the wire red hot then use a sharp knife to lightly scrape the residue off. Use a little paste flux when soldering; the wires need only be parallel for 2 or 3 mm. This allows the joint to use a short available stub of wire. The joint should if possible be "potted" in epoxy to prevent motion of the wire that might eventually cause it to break.
Steve

EDIT: The magnet wire used in the repair referenced was covered with appropriate lengths of narrow diameter heat-shrink tubing. A heat gun is the best way to shrink this tubing. It's possible to use a match or a butane lighter, but this leaves soot on the tubing.

Last edited by sweeks; 01-28-18 at 10:13 PM.
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