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Old September 14th 17, 08:26 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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Posts: 10,538
Default Is there an updated Dynotest somewhere?

On 9/14/2017 1:46 AM, bob prohaska wrote:
Sepp Ruf wrote:

For Rob who might experience mental drag uphill from just having to see a
big, heavy, non-laminated hub slowly revolving in the front wheel, the
smallish Shimano DH-T780-1N, 1.5W 250mA class, might suffice[1] once he
grows sick of the Soubitez. Best price I see is 96 euros a pair from CNC
Hamburg on ebay, no overseas shipping available, though.
http://www.ebay.com/itm/253093811841

[1]
DRL does not require more than 100 lumens if you get the optics right.


It's a bit puzzling how folks seem to excuse poor design in dynamo hubs
when they're considerably more fanatic about optimizing every other part
of a bicycle.

In particular, the 3 watt standard is utterly archaic. Folks now are
starting to use dynamos to power electronics, and I suspect most would
opt for more than 3 watt lights if useful designs were available.


Well, dynamos are not limited to 3 Watts. As James and others have
discussed, they'll put out more power if presented with bigger loads,
i.e. more resistance. They're essentially constant current devices. I
used to occasionally drive two halogen headlamps from my Soubitez roller
dynamo. Others do it with hub dynos. (It doesn't work well with a bottle
dyno, though, because the smaller drive roller is more prone to slipping.)

Second, despite the current fashion for mega-lumen lights, I've seen no
evidence that road cyclists need them, and I've seen the disadvantages.
IME, a good B&M LED headlight lights up a stop sign nearly 1/4 mile way.
It also illuminates the road very well; and with ever-improving LEDs,
the current models are probably better than the ones I own.

And it's a little ironic that the mega-lumen fans choose to ignore poor
optical design in their headlights, leading to inferior illumination
while blinding others. I think that's a bigger problem than a few
percent less theoretical efficiency in the dynamo.

Finally, there are devices which will power a phone or a GPS unit from a
hub dyno. Personally, I'd prefer to limit people from (say) playing
their stereo speakers while they ride!
At this rate I won't "get sick" of the Soubitez, I'll wear it out.


I've got two that are working very well. They're decades old. One was a
gift, from a friend who ripped out its output wire. A little solder
fixed that.

--
- Frank Krygowski
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