help with schmidt hub lighting options

I have a friend who is about to embark on a schmidt hub adventure. I am acting as a psuedo-technical
liaison... But I know nothing about these hubs or dynohub lighting in general...

but here is a small list of criteria... He does not necessarily care about a standlight He would
like the smallest front light that he could mount down low on a fork leg. He would love to have two
bulbs for symmetry I know that you can have a 'secondary' light with a schmidt hub (higher velocity
and the total 6V) but is it possible to run two lesser bulbs in series?

It seems like most dyno-driven lights have 6V / 2.4W halogen bulbs in them Is it possible to have
two 1.2W (or1.5W) bulbs in series? Do 1.2W bulbs exist?

I've seen all the lighting options on peter white and sheldon's site... but they seem big and
clunky... does anyone have comments on this light: Hella Micro-FF DYNAMO HEAD LAMP

thank you all in advance

geoff

 

if it is a 6V system and you want to bulbs in series, you want two 3V bulbs(each 1.2 watts) or you
could run two 6Vbulbs in parallel(each 1.2 watts) don't know if you can get either bulb sorry, but
parallel is that way to go you can switch then on/off separately in parallel if one bulb blows the
other one will still work in series if one blows you lose them both

pretty sure this is right and am sure someone will yell at me if it isn't

 

"stu" <[email protected]> wrote in message news:<[email protected]>...
> if it is a 6V system and you want to bulbs in series, you want two 3V bulbs(each 1.2 watts) or you
> could run two 6Vbulbs in parallel(each 1.2 watts) don't know if you can get either bulb sorry, but
> parallel is that way to go you can switch then on/off separately in parallel if one bulb blows the
> other one will still work in series if one blows you lose them both
>
> pretty sure this is right and am sure someone will yell at me if it isn't

Right in theory, but wrong in practice.

The Schmidt Dynohub (as well as its cheaper "cousin" the Shimano Nexus) delivers voltage that
increases with speed. At 10 km/h, you get 6 V, and at 20 km/h you get 12 V, and so on... Bottle
generators have similar patterns, BTW.

If you plug your own headlight directly into the hub, you will have to ride very slowly or you will
burn lights in a jiffy. That's why the Lumotec and Bisi headlights have a voltage-limiting diode..
If you want symmetry, you will have to design your own electronic limiting device or you will have
to find some way to install both bulbs (6 W 1,2 W in parallel) _after_ the diode.

BTW, on Peter White's site http://www.peterwhitecycles.com , you'll find a lot of theoretical info
on these headlights.

Regarding performance, installing the headlight heside the wheel (somewhere along the fork) shows
lots of shade from the tire, and if you ride in rain, snow or mud, it will get dirty very quickly. I
would suggest you install the headlight on the fork crown. Best compromise, very good results, still
allows for handlebar bag, unless the rider is only 5' tall.

 

the hella lights are designed with voltage limiting diodes...

i did not think about how the lighting would be hampered by the wheels... thank you for that
information.

geoff

"Michel Gagnon" <[email protected]> wrote in message
news:[email protected]...
> "stu" <[email protected]> wrote in message
news:<[email protected]>...
> > if it is a 6V system and you want to bulbs in series, you want two 3V bulbs(each 1.2 watts) or
> > you could run two 6Vbulbs in parallel(each 1.2 watts) don't know if you can get either bulb
> > sorry, but parallel is that way to
go
> > you can switch then on/off separately in parallel if one bulb blows the other one will still
> > work in series if one blows you lose them both
> >
> > pretty sure this is right and am sure someone will yell at me if it
isn't
>
>
>
> Right in theory, but wrong in practice.
>
> The Schmidt Dynohub (as well as its cheaper "cousin" the Shimano Nexus) delivers voltage that
> increases with speed. At 10 km/h, you get 6 V, and at 20 km/h you get 12 V, and so on... Bottle
> generators have similar patterns, BTW.
>
> If you plug your own headlight directly into the hub, you will have to ride very slowly or you
> will burn lights in a jiffy. That's why the Lumotec and Bisi headlights have a voltage-limiting
> diode.. If you want symmetry, you will have to design your own electronic limiting device or you
> will have to find some way to install both bulbs (6 W 1,2 W in parallel) _after_ the diode.
>
> BTW, on Peter White's site http://www.peterwhitecycles.com , you'll find a lot of theoretical info
> on these headlights.
>
>
> Regarding performance, installing the headlight heside the wheel (somewhere along the fork) shows
> lots of shade from the tire, and if you ride in rain, snow or mud, it will get dirty very quickly.
> I would suggest you install the headlight on the fork crown. Best compromise, very good results,
> still allows for handlebar bag, unless the rider is only 5' tall.

 

Michel Gagnon wrote:
>
> "stu" <[email protected]> wrote in message news:<[email protected]>...
> > if it is a 6V system and you want to bulbs in series, you want two 3V bulbs(each 1.2 watts) or
> > you could run two 6Vbulbs in parallel(each 1.2 watts) don't know if you can get either bulb
> > sorry, but parallel is that way to go you can switch then on/off separately in parallel if one
> > bulb blows the other one will still work in series if one blows you lose them both
> >
> > pretty sure this is right and am sure someone will yell at me if it isn't
>
> Right in theory, but wrong in practice.
>
> The Schmidt Dynohub (as well as its cheaper "cousin" the Shimano Nexus) delivers voltage that
> increases with speed. At 10 km/h, you get 6 V, and at 20 km/h you get 12 V, and so on... Bottle
> generators have similar patterns, BTW.

This doesn't tell the story very well.

First, voltage generally rises with speed, but it's not a linear function. Decent generators are
designed to self-regulate. The voltage tops out at about six volts for all but a few (rare) 12
volt models...

... ASSUMING you've got the standard bulbs fitted! That would be a 2.4 watt headlight and a 0.6 watt
taillight, or just a 3 watt headlight.

Nearly all bike generators actually attempt to supply a constant current of 0.5 amp. If you put in a
bulb with higher resistance, the voltage output rises to the amount necessary to pass the 0.5 amp.
Obviously, if you have no bulb attached, the voltage will get quite high (and will be pretty much
linear with speed). But this has little to do with actually powering a headlight.

>
> If you plug your own headlight directly into the hub, you will have to ride very slowly or you
> will burn lights in a jiffy. That's why the Lumotec and Bisi headlights have a
> voltage-limiting diode..

Such diodes aren't always necessary. Again, most generators self-regulate pretty well, based on the
inductance of the coils. The diodes help somewhat, but they're not always necessary.

> If you want symmetry, you will have to design your own electronic limiting device or you will have
> to find some way to install both bulbs (6 W 1,2 W in parallel) _after_ the diode.

If you want symmetry, you can install two ordinary generator lights in series, with
suitable switches.

Putting lights in parallel reduces the resistance the generator sees. This will cause the generator
to put out less voltage. It probably won't regulate itself as well, either.

I've got two headlights mounted in series, with a switch to short out the second one, thus taking it
out of the circuit. My generator (an old Soubitez) drives one light up to about 14 mph. At that
speed, I can open the second one's switch, putting that lamp in series with the first. The generator
responds by raising the voltage to about 12 volts, and I've got two lights. Total output is about
six watts, which is _way_ plenty for me.

If the first lamp did blow out, I could short across its terminals and use just the second light.
But generators are soft-start by nature. My bulbs seem to last forever.

>
> BTW, on Peter White's site http://www.peterwhitecycles.com , you'll find a lot of theoretical info
> on these headlights.
>
> Regarding performance, installing the headlight heside the wheel (somewhere along the fork) shows
> lots of shade from the tire, and if you ride in rain, snow or mud, it will get dirty very quickly.
> I would suggest you install the headlight on the fork crown. Best compromise, very good results,
> still allows for handlebar bag, unless the rider is only 5' tall.

My handlebar bag is pretty huge. It would block any lamp mounted at the head tube. I made a
lightweight rack to hold the two headlights out ahead of the front of the bag, just above the front
tip of the front fender. I've tried several different mounting points, and this is by far my
favorite. It does away with that problem of wheel shadow - which was a real annoyance, once.

--
Frank Krygowski [email protected]

 

In article <[email protected]>, [email protected] says...
> Michel Gagnon wrote:
> >
> > "stu" <[email protected]> wrote in message news:<[email protected]>...

> > Regarding performance, installing the headlight heside the wheel (somewhere along the fork)
> > shows lots of shade from the tire, and if you ride in rain, snow or mud, it will get dirty very
> > quickly. I would suggest you install the headlight on the fork crown. Best compromise, very good
> > results, still allows for handlebar bag, unless the rider is only 5' tall.
>
> My handlebar bag is pretty huge. It would block any lamp mounted at the head tube. I made a
> lightweight rack to hold the two headlights out ahead of the front of the bag, just above the
> front tip of the front fender. I've tried several different mounting points, and this is by far my
> favorite. It does away with that problem of wheel shadow - which was a real annoyance, once.

Not everyone has a front rack, but if you do, ahead of the front rack is a great place for a
headlight, especially if you ever ride in rain or fog. It gets the light ahead of the wheel, so no
shadow problems, and it also gets the light far enough forward that even in the fog, there isn't
much glare up from the light into your eyes.

--
[email protected] is Joshua Putnam <http://www.phred.org/~josh/> Books for Bicycle Mechanics and
Tinkerers: <http://www.phred.org/~josh/bike/bikebooks.html

 

Tue, 22 Apr 2003 22:47:27 -0400, Frank Krygowski:

>
>If you want symmetry, you can install two ordinary generator lights in series, with suitable
>switches.

If the original author wants to use 2 Hella Micro-FF it is easy to build a small toggle switch into
each housing. One switch should allow to open the whole circuit, the other switch should allow to
"bridge" the second headlamp for low speed use (in the 5...15 km/h range you will get more light
with only one headlamp). Both headlamps should be equipped with 6V-3W bulbs.

>Putting lights in parallel reduces the resistance the generator sees. This will cause the generator
>to put out less voltage.

Yes. Two 6V-3W bulbs with about 12 Ohms resistance in parallel means only 3 to 3.5 Volts on
both bulbs.

> It probably won't regulate itself as well, either.

It will regulate itself perfectly to its maximum current of 550-570mA - but the won't mean you will
have light ;-)

>If the first lamp did blow out, I could short across its terminals and use just the second light.

The build in supressor diodes in generator headlamps take care, that a blown bulb wont let you ride
in the dark, because the current can still flow via the "diode" (more or less two anti-serial diodes
in one housing). But: Heat sinking is not perfect - so you better change the blown bulb soon or care
for better than original heat sinking.

> But generators are soft-start by nature. My bulbs seem to last forever.

Nominal livitime for those 3W or 2.4W bulbs is 100 hours, but 50-80 is more realistic in my
experience.

>My handlebar bag is pretty huge. It would block any lamp mounted at the head tube. I made a
>lightweight rack to hold the two headlights out ahead of the front of the bag, just above the front
>tip of the front fender. I've tried several different mounting points, and this is by far my
>favorite. It does away with that problem of wheel shadow - which was a real annoyance, once.

A good alternative on a bike with cantilever sockets is to use a strong "brake booster" to mount the
headlamps side-by-side.

geoff raynak wrote:
>>>
>>>I've seen all the lighting options on peter white and sheldon's site... but they seem big and
>>>clunky...

Bigger is better ;-) Small optics are more effected by tolerances in production of the reflector or
the bulb. A bulb with a tiny mispositioned filament will result in an ugly chaotic light
distribution in a Micro-FF while you dont notice much difference when using a big reflector (like
the BISY FL or older Union headlamps). Bigger (especially "deaper") reflectors also catch more of
the light form the bulb and direct it to the road. But
- the Micro FF is not bad when used with matched bulbs.

Happy tinkering! Andreas

 

geoff raynak wrote:

> He would like the smallest front light that he could mount down low on a fork leg.

Low mounting distorts the patch of light. I experienced this with Schmidt's own BisyFL lamp, mounted
on a Zinkens Dynashoe LT (left side of front wheel, about the height of cantilever brakes):
adjustment gets tricky in order to have the best far/near-illumination ratio. Moved the lamp back to
the fork crown. Sh. Brown has a 'new' bike on his pages, with a Lumotech mounted about the height of
the lowrider-hole in the fork. Seems to work for him.

> He would love to have two bulbs for symmetry

I don't quite see the point in this. I have ridden above setup for about two years, and the shadow
of the wheel did not bother me. With a good lamp with an appropriately focused beam, the wheel's
shadow angles away at 45 to 60 degrees.

> I know that you can have a 'secondary' light with a schmidt hub (higher velocity and the total 6V)
> but is it possible to run two lesser bulbs in series?

What most people do (and is described on Schmidt's homepage) is add a second fully-powered lamp. The
SON can drive that lamp from 18-20kph on. If your friend wants even more light, tell him to use
6V/3W bulbs (HPR64) in both lamps and a battery powered LED taillight.

Patrick

 

Joshua Putnam <[email protected]> wrote:
>Not everyone has a front rack, but if you do, ahead of the front rack is a great place for a
>headlight, especially if you ever ride in rain or fog. It gets the light ahead of the wheel, so no
>shadow problems, and it also gets the light far enough forward that even in the fog, there isn't
>much glare up from the light into your eyes.

Coming home in the fog last night, I was very annoyed by the 3 bars of light coming up from my
(handlebar-mounted) Cateye LED headlight - luckily, the fork crown mounted Bisy didn't give me any
trouble. The batteries were flat in my battery halogen bulb headlight, but I imagine it would have
had equally odd effects. Focussing is the answer...
--
David Damerell <[email protected]> flcl?

 

On Tue, 22 Apr 2003 22:47:27 -0400, Frank Krygowski wrote:

>> Regarding performance, installing the headlight heside the wheel (somewhere along the fork) shows
>> lots of shade from the tire, and if you ride in rain, snow or mud, it will get dirty very
>> quickly. I would suggest you install the headlight on the fork crown. Best compromise, very good
>> results, still allows for handlebar bag, unless the rider is only 5' tall.
>
> My handlebar bag is pretty huge. It would block any lamp mounted at the head tube. I made a
> lightweight rack to hold the two headlights out ahead of the front of the bag, just above the
> front tip of the front fender. I've tried several different mounting points, and this is by far my
> favorite. It does away with that problem of wheel shadow - which was a real annoyance, once.

I've got the headlamp on one of my bikes mounted on the left fork blade just below the fork crown,
using one of Peter White's Cronometro NOBs. No problems with shadows from wheel, tire or fender.
Another possibility with a real heritage behind it is the small French rack, typically made to
support a front handlebar bag, as often seen on bikes made for randonneuring, such as Alex Singers
and Rene Herses. Typically, those racks have a light fitted right to the front of the rack. The lamp
is positioned almost exactly where Frank has his lights mounted.