Hub dynamo with clutch for friction-free daylight runnng
Andre Jute
http://store.velo-orange.com/index.php/vo-switchable-dynamo-hub.html
Can't help thinking $130 is not very far off the price of a SON, which
has very low friction.
Posted just for interest. I run my lights day and night, permanently
on. LED lights for practical purposes have infinite life, so there is
no reason not to run them as daylight warning lamps. So, to me, this
Velo Orange initiative looks like an idea whose time has come and gone
with filament and halogen lamps, ta-taa.
DougC
When I desire warning lighting, I prefer to use several Roman Candles
pointing outward and upward in all directions. Some people I meet
disagree, saying that sort of thing is only appropriate for the 4th of
July (US independence day). I say, "get the fuck out of the way, I just
lit another round".
I've noticed that most people's debating skills are very poor. And not
nearly quick enough, too.
------
Seriously though--I would think that if the generator was left open
(that is, nothing using the generator power) the electrical impedance
would drop to basically zero, and there would be no resistance from the
generator at all. ???
Andre Jute
> On 3/21/2011 10:16 PM, Andre Jute wrote:
>
> > Here's a Velo Orange special, a hub dynamo with a clutch.
> >http://store.velo-orange.com/index.php/vo-switchable-dynamo-hub.html
> > Can't help thinking $130 is not very far off the price of a SON, which
> > has very low friction.
>
> (that is, nothing using the generator power) the electrical impedance
> would drop to basically zero, and there would be no resistance from the
> generator at all. ???
I'm not so sure, Doug. Back in the days when Shimano's hub dynamo was
a thing they took over from Sanyo. maybe about 7 years ago (there's
been two or three generations since), tests showed that
a) A SON hub dyno had a lower drag when not under electrical load, as
you expect
and -- wait for it --
b) The Shimano had a higher drag when the lights were off than when
they were on.
I've always felt that the song and dance people made about miniscule
drag differences was just a rationalization by poseurs for buying the
more prestigious SON.
The drag of a working dynohub is probably about the equivalent of a
foot of elevation per mile...
Andre Jute
Visit Jute on Bicycles at
http://www.audio-talk.co.uk/fiultra/BICYCLE%20%26%20CYCLING.html
James
> I've always felt that the song and dance people made about miniscule
> drag differences was just a rationalization by poseurs for buying the
> more prestigious SON.
>
> The drag of a working dynohub is probably about the equivalent of a
> foot of elevation per mile...
I just notice the difference when I flick my Sanyo Dynapower on at 30
km/h. Up to about 40 km/h it doesn't exhibit much drag, yet at 50km/h
and above, the drag becomes much more noticeable. In fact in sprint
training on the road where we might exceed 60 km/h for short periods,
the drag seems to make it very much more difficult than sprinting
without.
What I like is that there is no drag when it is flicked off the wheel,
and it's a simple single bolt to remove the entire dynamo, retaining
the same wheel that I use for training and racing. I can't be
bothered keeping separate wheels for the two activities, and I always
know the condition of my equipment because I ride it regularly and
maintain it likewise.
JS.
Andre Jute
I don't hit 60kph except on the downhills...
The test everyone quotes is this one http://www.myra-simon.com/bike/dynotest.html
which is pretty old. Shimano hub dynamos have been improved with
better bearings since then, so it wouldn't surprise me if the best
Shimanos now beat the SON for drag.
I have no difficulty believing that a hub dynamo will have lower drag
under all conditions than a tyre-driven gennie, though for racing you
probably want to consider the relative weight before the efficiency.
In fact, for racing practice bikes, I like the idea of Reelights,
magnets on the spokes inducing a current in an adjacent lamp on the
for blade, as probably the lightest and most efficient and least drag-
inducing.
Andre Jute
Gotta sleep
Mark J.
>
> When I desire warning lighting, I prefer to use several Roman Candles
> pointing outward and upward in all directions. Some people I meet
> disagree, saying that sort of thing is only appropriate for the 4th of
> July (US independence day). I say, "get the fuck out of the way, I just
> lit another round".
Sprocketman used to advocate using a military flamethrower for bicycle
lighting. But that was over 25 years ago.
> Seriously though--I would think that if the generator was left open
> (that is, nothing using the generator power) the electrical impedance
> would drop to basically zero, and there would be no resistance from the
> generator at all. ???
You'd think, but it's often not the case. A bottle generator not
attached to a light has considerable resistance when spun by hand. My
cheapo hub dynamo has considerable resistance, again when spun by hand.
I've seen credible reports that my model has the same resistance at
speed whether the light is connected or not.
I would add that the "considerable resistance" my hub has is pretty easy
to ignore while cycling. It replaced a bottle dynamo which, because of
the noise it made, was nearly impossible to ignore. I "thought" I
really noticed the drag of the bottle dynamo, but it was possibly just
the noise and a subjective impression.
Mark J.
SMS
> I would add that the "considerable resistance" my hub has is pretty easy
> to ignore while cycling. It replaced a bottle dynamo which, because of
> the noise it made, was nearly impossible to ignore. I "thought" I really
> noticed the drag of the bottle dynamo, but it was possibly just the
> noise and a subjective impression.
Both have considerable drag when operating, but you're correct that the
bottle dynamo gives you audible feedback that the drag is occurring.
Frank Krygowski
> I "thought" I
> really noticed the drag of the bottle dynamo, but it was possibly just
> the noise and a subjective impression.
Noise can have a big psychological effect, much bigger than its actual
physical effect. My one cheap folding bike _seemed_ to become much
easier to pedal after I lubricated all the joints in the joints that
were causing squeaks.
But I had an interesting accidental experience that showed me how low
the drag is from a decent generator - in this case, a Soubitez bottom
bracket generator driving a halogen bulb (with no zener diodes).
I was on a solo tour, cranking along an Indiana four-lane at about 20
mph, for miles and miles. I hit a hard bump, then began hearing some
quiet buzzy noise from the bike, but couldn't identify it. And I
noticed my speed had dropped, a little over one mile per hour. Since
I was miles from nowhere, I was a bit concerned.
Then I realized that my generator had snapped on when I hit the bump.
So at 20mph, it slows me by about 1 to 1.5 mph.
- Frank Krygowski
russell...@yahoo.com
I guess you would have to explain "considerable drag". I have a
Shimano N70 model hub generaotr. Ridden it many thousands of miles,
with the lights on and off. Have never noticed any drag from it.
AMuzi
Had you written "not much drag", I would agree.
Spin that wheel in midair held by the axle some time.
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
Lou Holtman
Andrew in that way you holding the hub at a radius of 4-5-6 mm. Of
course you feel some force. On the wheel radius it's a different story.
It is like the seal drag of sealed bearing. If I switch my lights on and
of I really can't feel the difference with my SON dynamo hub.
Lou
AMuzi
Well it's slight (somewhere in the 120 'off' to 150g/cm 'on'
range according to the only data I have available), but it's
something.
I have 'always on' dynamos on all but one of my bikes.
Whatever the drag is, it beats the hell out of batteries and
switches in my opinion.