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.