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Is there an updated Dynotest somewhere?
On 9/10/2017 7:55 PM, James wrote:
On 10/09/17 15:24, bob prohaska wrote: Sepp Ruf wrote: As the more recent tests were mostly conducted "by SON's Andreas Oehler or one of his buddies," they have not met r.b.t's stringent anti-corruption criteria: https://www.cyclingabout.com/dynamo-hub-drag-lab-testing/ (is a translation of https://fahrradzukunft.de/14/neue-nabendynamos-im-test/ That article actually comes somewhat close to what I was looking for. The real disappointment is the photo: It shows a (very expensive) Schmidt hub containing a clawpole armature. That is somewhat borne out in the efficiency. It's only around 50%. Seems to me Schmidt has considerable room for improvement. Even the cheapest electric machines use laminated armatures. If that represents the state of the hub dynamo art it's in a bad way. They're obviously aware of eddy current losses (note the notch in the visible pole piece) but the losses extend to the entire volume of magnetic material. It's as if they're unaware of the skin effect. For the moment I think I'll try to revive my old Soubitez roller dynamo and hope somebody gets past the 19th century. Notice the laminated magnetic material in the SP dynamo hub. https://janheine.files.wordpress.com/2012/09/pv8.jpg But it doesn't seem like it affected the efficiency very much. I think we're chasing diminishing returns. The major point of the article at https://www.cyclingabout.com/dynamo-...g-lab-testing/ is that the drag is not much to worry about. -- - Frank Krygowski |
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