Hub Dynamo's

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Hub Dynamo's

Postby timbo » Tue Jul 31, 2007 12:59 pm

Does anyone have experience using hub dynamo's for lighting the night road instead of the usual battery lights. I'm interested to know how much drag (friction?) is applied by the dynamo when being used, and does the drag disappear when the light is turned off? I know its an expensive option to add to a current bike, but is standard on bikes such as the Vivente World Randonneur as mentioned on Honestpuck's tourer/commuter post.
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by BNA » Tue Jul 31, 2007 1:14 pm

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Postby Kalgrm » Tue Jul 31, 2007 1:14 pm

Removing the drag would involve separating the magnet from the coil, so I doubt the drag disappears after the light is turned off.

Something I'd like to investigate is a dynamo charger for batteries. That way you can turn on the dynamo going down hills to charge up a battery during the day and then have a battery powered LED for night riding.

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Graeme
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Postby Bnej » Tue Jul 31, 2007 2:54 pm

From what I have heard, if the light is not drawing current then drag is minimal. Don't know how it works exactly.

The drag will be 3W + a bit of inefficiency. This is likely to be noticeable only if you are doing very little work, pedalling an extra 3W of effort isn't much.

Haven't actually used one, but that's what I've heard.
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