On 9/9/2017 4:24 AM, Sepp Ruf wrote:
bob prohaska wrote:
Many years ago a fairly quantitative report on the performance of
bicycle lighting dynamos was published on the Web. The link is
http://www.myra-simon.com/bike/dynotest.html

Most of the brands named are long gone. Is there a more modern
report of similar quality to be found? I've looked and found nothing
remotely quantitative, just a lot of exuberant descriptions. There
seem to be a considerable number of new (mostly hub) dynamos, hopefully
somebody has measured what they can do.

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/


Some things that have changed since the dynotest age:

- bottle dynamo market has mostly bifurcated into "cheap replacement" and
"pointless hipster specialty" items
https://fahrradzukunft.de/18/labortest-felgenlaeuferdynamos/

- more (bottle) dynamos feature inbuilt hard voltage limitation, potentially
limiting light output

- new, low-power "1.5W" generator category, marketed at dragophobes


subjective advice:
Shimano generators have improved. For their 3 Watt hubs, stay away from
anything even more basic than their, from old to new, DH-3N30, DH-3N31,
DH-C3000 hub lines.

Get (import) an identical pair of low-to midrange Shimano hubs, and in case
of failure, beat SON's (or Taiwan's) service turnaround time hands-down by
locally rebuilding the wheel.


Good info from Sep Ruff (and I wish I read Deutsch).

But Bob, can I ask what your objectives are? I ask because some of this
may not matter much any more. Seems to me there was a time when it made
sense to worry about which dynamos might put out a little more power, or
which had a little less drag. But with modern LED dynamo lights from
Busch & Muller, there is plenty of light available right where you need
it; and almost any dyno can supply the power. You'll never notice the
differences in drag between the various hub dynos.

I agree that the Shimano DH-3N30 works perfectly well. The two bikes I
ride most often at night have hub dynos. But on a couple bikes that I
ride only occasionally at night, I've got old bottle dynamos or roller
dynamos. They work very well and have the benefit of zero drag when off.
Yet those bikes have good lights available whenever needed, with no
battery worries.

And a bottle or (if you're really lucky) a roller dynamo can be had for
free these days. It's a benefit of being out of fashion. Their main
disadvantage is trickier installation, requiring understanding their
wiring and perhaps fabricating a bracket. But I can handle that.


--
- Frank Krygowski