Is a hub dynamo sufficient?

"Timothy Murphy" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I have an ancient Rudge with a hub dynamo,
and I'm wondering if this is sufficient to lighting,
or is it now considered that one should use battery-powered lights?

The modern dynohubs are usually 2.4 or 3.0 W. They are quite sufficient for
commuting under normal conditions. The old one you have is, or rather was,
1.8 W when new. Since the magnetic field of the magnet in the hub becomes
weaker with decades, your hub is perhaps not good for real use anymore.
Halogen bulbs make the dynohub light much brighter, but still they require
voltage of about 4.5 - 6.5 V, which your Rudge dyno won't be able to
provide.

Cheers,

T.

Timothy Murphy said:

I have an ancient Rudge with a hub dynamo,
and I'm wondering if this is sufficient to lighting,
or is it now considered that one should use battery-powered lights?

While it's entirely possible the hub you have is not really good enough
by current standards, a modern dynohub generally /is/ good enough and
has many advantages over battery lamps. What they're not really cut out
for is use at high speed on unlit roads and especially for high speed on
unlit tracks, or for serious sports machinery where a bespoke Go Faster
Hub would be more in keeping, especially during daylight hours. For a
general purpose bike a good dynohub is IMHO a great asset and my
preferred lighting option.

The Schmidt SON is generally reckoned to be the cat's pyjamas of the
dynohub world, but the recent Shimano units are quite a bit cheaper and
don't lag too far behind. Partner with good lamps designed for use with
dynohubs, like B&M or SON, and I think you'll probably be impressed with
how good it all works. Standlights (which keep running for a couple of
minutes after you stop) are nice.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

And your old dynohub will cause noiceable drag evn when it is off.OK
for popping to the shop and back , but like always having a headwind on
a commute.
TerryJ

I have 2.4 watt halogen bulb in a B&M Lumitec front lamp which is wired
in parallel with a rear LED - both powered by my Schmidt dynamo hub.

The front lamp is very bright, and good on unlit roads. However, I have
noticed that the older version - a round shape, which my cycling buddy
has got, appears to be brighter than the oval shape which I have got.
The bulb is the same, so it must be the optics of the lense and
reflector of the round lamp that are better. Halogen bulbs do develop a
tint over time which can make them appear dimmer though.

in message <[email hidden]>, Timothy Murphy

(') said:

I have an ancient Rudge with a hub dynamo,
and I'm wondering if this is sufficient to lighting,
or is it now considered that one should use battery-powered lights?

In my opinion dynamos are on the whole better than battery powered;
they're there when you need them, and (provided you carry spare bulbs if
needed) won't let you down. Dynamo lights are very widely used in
Germany, and I think may even be a legal requirement there - and the
Germans are no slouches when it comes to either technology or road
safety.

Quoted message said:

If I do use the hub dynamo,
can I get extra bright bulbs nowadays?

At various prices. You can get various different replacement filament
lamp units, or you can go the whole hog and get the Solidlights 1203d,
which while very expensive should give masses of light.

<URL:http://www.solidlights.co.uk/products/1203d.php>

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
;; Our modern industrial economy takes a mountain covered with trees,
;; lakes, running streams and transforms it into a mountain of junk,
;; garbage, slime pits, and debris. -- Edward Abbey

Simon Brooke said:

in message <[email hidden]>, Timothy Murphy

(') said:

I have an ancient Rudge with a hub dynamo,

[...]

Quoted message said:

Quoted message said:

If I do use the hub dynamo,
can I get extra bright bulbs nowadays?

At various prices. You can get various different replacement filament
lamp units, or you can go the whole hog and get the Solidlights 1203d,
which while very expensive should give masses of light.
<URL:http://www.solidlights.co.uk/products/1203d.php>

An "ancient Rudge" probably has a Sturmey Archer Dynohub, which I doubt
will run the 1203d, certainly not at full power. So the "whole hog"
would include a new hub dynamo as well.

A new bottle dynamo would be cheaper than a new hub dynamo, and more
powerful than the old one, but doesn't have the same "always there,
never slips" quality a hub dynamo does.

You can get a replacement halogen bulb to suit the SA Dynohub, which will
be more efficient than the original (and will also be more efficient
_with the Dynohub_ than a bulb for a standard new dynamo).
http://www.reflectalite.com/lightmodel.html GH107/GH105

(A standard dynamo bulb is 0.5A 6V 3W, or 0.4A 2.4W with a 0.1A 0.6W tail
in parallel. The Dynohub one is 0.3A 5V 1.5W, which looks like half the
power. But if you run the standard new bulb off an old Dynohub, it will
still only put the same current though it that it would through the correct
bulb, so will use about the same power but at a lower efficiency.)

In theory a 1W Luxeon LED and rectifier would be a good match to a Dynohub,
and should be more efficient than the halogen, especially at lower speeds.
(The Solidlight uses two 3W Luxeons, which have a higher drive current, and
also has some fairly sophisticated electronics.)

If you do keep the old dynamo try disconnecting it to see if the drag
is less than just switching off.If it is then fix a proper switch in
the circuit for this purpose.I used to pull the wires off to switch the
light off for this reason.Used like that it is a good reliable legal
light.
terryj