Hub Dynamo Lights?

The bike by the firm Giant that I was looking at over the weekend, as an
upgrade for my current cheap-and-cheerful first bike, had front and back
lights that were powered by a hub dynamo.

In Cambridge over the summer on my rented bike, I had experience of a
light powered by rim-dynamo and absolutely _loathed_ it. It was not just
unreliable, only going on when I was pedalling fast and thus failing at
critical intersections whenever I slowed down, but drained so much power
from the bike that I could scarcely manage it on pancake-flat Fenland
terrain. I decided that I would avoid dynamo lights forever and, on
returning, had my home bike fitted with a very expensive and bright
front light powered with a heavy rechargeable battery pack.

But the salesman told me that this power-draining effect of the
rim-dynamo did not apply to dynamos powered from the hub. Can anyone
comment or confirm?

Many thanks
Elisa Francesca Roselli
Ile de France

On Mon, 22 Sep 2003 14:08:34 +0200, Elisa Francesca Roselli
wrote:

The bike by the firm Giant that I was looking at over the weekend, as an
upgrade for my current cheap-and-cheerful first bike, had front and back
lights that were powered by a hub dynamo.

In Cambridge over the summer on my rented bike, I had experience of a
light powered by rim-dynamo and absolutely _loathed_ it. It was not just
unreliable, only going on when I was pedalling fast and thus failing at
critical intersections whenever I slowed down, but drained so much power
from the bike that I could scarcely manage it on pancake-flat Fenland
terrain.

Yes, I remember those. Analytically, I don't think they drain all
that much power in terms of watts. But psychologically they're a drag
(ha!)--that whine as you're tooling down Queens' Road on your way to
the Seeley (OK, *my* way to the Seeley) is pretty frightful.

That said, when they were working, I never lacked lights when I needed
them, which is more than I can say for battery-lights. Unfortunately,
since here in America nobody actually uses their bicycles, there are
no dynamo-driven lights to be found anywhere (except for extremely
cheap dynamo sets--who buys these?--at X*Mart).

-Luigi
contrarian

I decided that I would avoid dynamo lights forever and, on
returning, had my home bike fitted with a very expensive and bright
front light powered with a heavy rechargeable battery pack.

But the salesman told me that this power-draining effect of the
rim-dynamo did not apply to dynamos powered from the hub. Can anyone
comment or confirm?

Many thanks
Elisa Francesca Roselli
Ile de France

"Luigi de Guzman" wrote in message

That said, when they were working, I never lacked lights when I needed
them, which is more than I can say for battery-lights.

Yes, with battery powered lights, you may need to carry a set of spares in
your seat bag.

Unfortunately,
since here in America nobody actually uses their bicycles, there are
no dynamo-driven lights to be found anywhere (except for extremely
cheap dynamo sets--who buys these?--at X*Mart).


When I was a kid in the US, *everybody* had dynamo-powered lights--battery
powered lights were too weak to be really useful. But now, I wouldn't trade
my current battery powered lights for the old 'whine and drag' of the
generator set.

Mark

"Elisa Francesca Roselli"
wrote:

The bike by the firm Giant that I was looking at over the
weekend, as an upgrade for my current cheap-and-cheerful
first bike, had front and back lights that were powered by
a hub dynamo.

[snip]

But the salesman told me that this power-draining effect
of the rim-dynamo did not apply to dynamos powered
from the hub. Can anyone comment or confirm?

I've been running a Shimano NX30 hub dynamo for the last few years. I think
it's excellent.

Hub dynamos are heavier than bottle dynamos, and have a little drag even
with the lights off, but tend to be more reliable (especially in the wet),
more efficient when in use, and aren't sensitive to alignment as rim- or
tyre-driven dynamos tend to be.

I use mine to drive either one or a pair of headlights. I run a separate
LED rear light.

There's a detailed article on dynamos he

http://www.myra-simon.com/bike/dynotest.html

The Shimano Inter-L tested is the old NX10 model, which has been replaced
by the more efficient NX30. Shimano is launching a new 'sports' model in
Germany this autumn, promising further improvements in efficiency.

James Thomson

James Thomson wrote:

Hub dynamos are heavier than bottle dynamos, and have a little drag even
with the lights off, but tend to be more reliable (especially in the wet),
more efficient when in use, and aren't sensitive to alignment as rim- or
tyre-driven dynamos tend to be.

Would you recommend them over a light like the one I have, powered by a
rechargeable battery? Are they more reliable through being always powered, or
less reliable through requiring that you be moving?

Also, if you buy a bike with a hub dynamo and don't like it, can you remove it
or is it a palaver?

There's a detailed article on dynamos he

http://www.myra-simon.com/bike/dynotest.html


Thanks for the link, James. I will study it attentively.

Elisa Francesca Roselli
Ile de France

"Elisa Francesca Roselli"
wrote:

Would you recommend them over a light like the one I have,
powered by a rechargeable battery? Are they more reliable
through being always powered, or less reliable through
requiring that you be moving?

Batteries and dynamos have their own sets of pros and cons, but for a
utility bike I prefer dynamo. You can never forget to recharge a dynamo,
and it remains permanently attached to the bike - an advantage if you stay
out later than expected. There's no risk of batteries running flat during a
long ride. Some dynamo headlamps (Lumotec 'Standlicht' models, for example)
incorporate a capacitor that powers an integrated LED light when the bike
is stationary, and I sometimes carry a separate white LED headlamp as an
emergency light.

Also, if you buy a bike with a hub dynamo and don't
like it, can you remove it or is it a palaver?

You would need a new front hub and spokes. The simplest thing to do would
be to buy a new front wheel and sell your dynamo wheel - which would
probably leave you in profit.

James Thomson

"Elisa Francesca Roselli" wrote in message ...
The bike by the firm Giant that I was looking at over the weekend, as an
upgrade for my current cheap-and-cheerful first bike, had front and back
lights that were powered by a hub dynamo.

In Cambridge over the summer on my rented bike, I had experience of a
light powered by rim-dynamo and absolutely _loathed_ it. It was not just
unreliable, only going on when I was pedalling fast and thus failing at
critical intersections whenever I slowed down, but drained so much power
from the bike that I could scarcely manage it on pancake-flat Fenland
terrain. I decided that I would avoid dynamo lights forever and, on
returning, had my home bike fitted with a very expensive and bright
front light powered with a heavy rechargeable battery pack.

But the salesman told me that this power-draining effect of the
rim-dynamo did not apply to dynamos powered from the hub. Can anyone
comment or confirm?

Dynamo hubs still have an extra load; those 3-6 watts are being
generated from somewhere, no matter where the dynamo is
located.

The bigger problem with dynamo systems is that the dynamo
only generates 3 watts (there is one 6 watt dynamo available).
In the U.S. anyway, a 3 watt lighting system is woefully
inadequate.

The reality is that you can buy a high power rechargeable system
for far far less than a quality dynamo system. A 6 watt dynamo
system will cost well over $300.

Dymotec S12: $247
Headlight: $ 64
Taillight: $ 54

http://www.peterwhitecycles.com/dymotec.asp

I agree that there is a lot to be said for not bothering with
batteries, but this is just too expensive. I can build a high
brightness, rechargeable battery, lighting system for about
$50.

http://nordicgroup.us/s78

Dynamo hubs still have an extra load; those 3-6 watts are being
generated from somewhere, no matter where the dynamo is
located.

Of course, if there's a switch on the light, or you add one in, when the
light isn't on, the drag goes way down.

Peter

Elisa Francesca Roselli wrote in message ...
The bike by the firm Giant that I was looking at over the weekend, as an
upgrade for my current cheap-and-cheerful first bike, had front and back
lights that were powered by a hub dynamo.

In Cambridge over the summer on my rented bike, I had experience of a
light powered by rim-dynamo and absolutely _loathed_ it. It was not just
unreliable, only going on when I was pedalling fast and thus failing at
critical intersections whenever I slowed down, but drained so much power
from the bike that I could scarcely manage it on pancake-flat Fenland
terrain. I decided that I would avoid dynamo lights forever and, on
returning, had my home bike fitted with a very expensive and bright
front light powered with a heavy rechargeable battery pack.

But the salesman told me that this power-draining effect of the
rim-dynamo did not apply to dynamos powered from the hub. Can anyone
comment or confirm?

First, a decent quality rim dynamo, properly set up, should give much
better performance than what you describe. It may be audible when
running, but it shouldn't drain _that_ much power, to "scarcely manage
it on ... flat... terrain."

For comparison: When doing a fast tour a couple years ago, I was doing
roughly 20 mph on long, flat roads, for long distances. At one point,
I accidentally bumped my dynamo and it was on without my knowing it.
At first I was puzzled by the funny noise my bike was making. Then I
noticed my speed had dropped a bit, roughly 1 mph. It took me a
little while to put two and two together and shut the dynamo off, but
it showed me pretty conclusively that my dynamo wasn't slowing me a
_lot_.

It's possible you had an old one whose bearings were very worn, and/or
in dire need of lubrication. It's also possible yours was not
properly aligned with the tire, causing excessive "scrubbing" and
friction. Also, if the spring pressure holding the roller against the
tire is excessive, this can cause more drag.

The first cause seems most likely. The latter two will make some
difference, but they'd have to be extreme, indeed, to make things as
bad as you describe.

Now: I like generators (dynamos) mostly because I find them to be the
most convenient and reliable way of getting decent light. I'll admit,
though, that their installation takes more mechanical (and electrical)
know-how than a simple battery light. The alignment is one aspect of
this. Proper grounding is another, since most still use the frame as
an electrical conductor, rather than the proper double wiring I use.

These aspects should be far easier with a hub dynamo. There's nothing
to align, and they come with proper grounding wires. Furthermore,
they are inherently more efficient, meaning more of your work goes
into producing light, as opposed to friction.

You should probably read the article at
http://www.myra-simon.com/bike/dynotest.html
which compares many different dynamo designs, and puts the energy
losses into proper perspective - at least, on properly installed
dynamos.

BTW, mine is an old Soubitez bottom-bracket (or roller) type dynamo.
It gives good light down to about, oh, 5 miles per hour. Not as
bright as full speed, but then it doesn't need to be as bright as full
speed. Good electrical connections, a good halogen bulb, and a
headlight with good optics are all important.

Once properly set up, you almost never need to think much about your
dynamo. It just keeps on producing light.

- Frank Krygowski

Hub dynamos are heavier than bottle dynamos, and have a little drag even
with the lights off, but tend to be more reliable (especially in the wet),
more efficient when in use, and aren't sensitive to alignment as rim- or
tyre-driven dynamos tend to be.

I use mine to drive either one or a pair of headlights. I run a separate

This congrues with my experience. Three years ago I replaced my
home-maid battery light (outperforming the ones on sale) by a Schmidt
dynohub with 2 headlights. Excellent results. Nightrides are pure
enjoyment now, 70kph in a descent at night is no problem anymore.
Schmidt is a highperformance model, the Shimano a middle-quality
consumer one. The price differs likewise.
Last month, during the long-distance ride Paris-Brest-Paris, there
were lot's of riders using Schmidt hubs, quite some used Shimano hubs.
Those riders relying on battery-powered systems were lot's slower
during the night, except when following Schmidt dynohub equipped
riders.

Ivo