Originally Posted by
agmetal
I was researching some of this stuff a while ago (LED conversions of vintage lights for use with vintage DynoHubs, that is), because I also have a 1930s-40s 8-volt DynoHub that I want to use with a bike of the same age. What I learned then is that most LED bulbs don't tend to work very well with parabolic reflectors. I did find some that were sort of a "tree" or cube of LEDs, though, so that they would at least theoretically work better with that type of reflector....but then there's the question of getting it to work with the 8-volt hub.
the mis-match between the LED's radiation pattern and that of the incandescent is definitely an issue. You'd get better results by aiming the LED rearwards at the reflector than aiming it forward, where only a small percentage of the light will strike the reflector.
The Reflectalite uses a 'side emitting" optic, which aims most light to the sides. This does use some of the reflector, which forms the light into a beam. I used an early Luxeon 5 watt LED with the reflector from a Union headlight back when the Schmidt hub dynamo first came out. It was an improvement over the incandescent dynamo lights of the era! However, using a more modern LED with a good molded "TIR" optic produces much better results.
The other issue with installing a proper 3 watt LED is providing cooling for the LED. In a perfect world, you would provide some aluminum to conduct the heat from the LED to an external heatsink. Adding an external heatsink to a vintage or retro headlight is often not an option. A second option would be to conduct the heat from the LED to the steel housing of the light. It's not optimal, but might be good enough.
The Reflectalite avoids this issue by only using about 1 watt of power. With a 3 watt dynamo, that would be a waste. With a Dynohub that is also trying to power a taillight, it might be perfect.
Steve in Peoria