Re: Rear dynohub
- From: Günther Schwarz <strap@xxxxxx>
- Date: Fri, 29 Jun 2007 20:37:33 +0200
Günther Schwarz wrote:
Colin wrote:
In article <13379126.NeFPhzC8cK@xxxxxxxxxxxxxxxxxx>, strap@xxxxxx
says...
But this time the event
started in the evening, and while the fancy new dynohub in the rear
wheel together with my DIY headlight turned out to be extremely
useful
<snip>
Out of interest ( and I suspect there could be a good deal of
interest from Trike riders looking for decent dynamo lighting), what
was the the make / model of the dynohub, and how did you feel it
performed?
Shimano FH-C811 [1]. I mentioned this hub already in a posting to urc
some weeks ago. It performs nicely together with my home built front
light (just a rectifier made of four Schottky diodes and two Cree XR-E
LEDs in a series arrangement) and a standard "Toplight Flat" by bumm
in the rear. Don't even think about driving a standard halogen light
with this dynohub. It is simply not strong enough. But as the new
XR-Es outperform halogen lamps in the ratio of luminous flux and
electrical power consumption by a factor three to four the hub is
useful together with the highly efficient light. It might work
together with the DLumotec or other commercial LED front lights. But I
did not test this. I will send the wheel to a well known private lab
in Hamburg soon. So please be patient, there will be some data
available in the near future. Until then the only thing I can say is
that I was pleased on how well the combination works.
And here we go:
<http://www.enhydralutris.de/Fahrrad/Beleuchtung/node79.html>
I have to admit that even with some knowledge of German this page is
somehow more suitable for the expert reader. To convert frequency to
speed:
v = 2 f / N * 3.6 * C km/h,
where f is the electrical frequency, N the number of poles (22 for this
hub), and C the wheel circumference.
If I read correctly the hub behaves much like a typical dynohub with the
exception of showing a typical current of 0.3A instead of 0.5A.
Efficiency is above 50% while I can't get directly information about
power consumption with the circuit open or shorted. As usual with
dynohubs in pratice I can't tell from the drag if the light is on or
off. In my setup (homemade LED light and small 406 wheel) output is
sufficient from approx. 6km/h on which is sufficient for my local
hills.
Some additional data:
appr. 750g without quick release
6 bolt disc attachment IS2000
135mm, 52mm (35 + 32.5 + 19.5 + 48), 2x 74.4mm
Shimano spec. 55.65mm with 7mm dish
Shimano 4.1V, 1.12W at 110 RPM 15 Ohm
Günther
.
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