Originally Posted by krazygluon
I'm starting to think of the world of lighting and figure I should get some front lights on my bike. I was wondering if anyone knows how possible it would be to use a dynamo hub to power either an LED or HID system. I'm imagining the HID is probably out of the question (not a consistent enough source of voltage to keep the ballast/spark gap happy)
Thanks in advance for any advice (or whacks on the skull if this is just a stupid idea
)
Most dynamo hubs are designed to provide a fairly constant 1/2 amp of current at around 6 volts, to power a 3 watt halogen bulb. Not the most impressive output figure, but the better lights have carefully shaped lenses & reflectors to put a tightly focussed beam of light right where an on road cyclist needs it. These lights are not especially effective for mountain biking, though. As you said, the output may not be consistent enough for a HID light.
There is at least one LED headlight on the market that is designed to work with a dynamo hub, it's significantly more expensive than a halogen headlight from the same maker.
I'm commuting with a Shimano DH-3N71 hub generator and a Busch & Mueller Lumotec headlight, with a battery powered taillight. It's made my ride home at night very pleasant. I also brought this set up on my tour around Tuscany last May, I was glad to have it when I was cycling to the airport to go home before sunrise, and when I was cycling through a couple of long tunnels in the mountains. If I get into randonnee / Audax style riding like I'm thinking of, a Schmidt dynamo hub and 2 halogen headlights would be a nice way to go, although it wouldn't be cheap.
For more about dynamo hubs and the lights to go with them, visit:
http://www.peterwhitecycles.com.