Originally Posted by
steelbikeguy
If the reflector and bulb holder can be removed from the lamp assembly in a non-destructive fashion, I think your method is optimal. Do you just use RTV, or some other non-permanent adhesive, to mount the optics and 'tronics of the donor light? How much can be done to get the heat moved to the light's housing? That seems to be one of the problems that will unique to each light.
My little Jos light has the reflector attached to the lens, leaving a hole in the reflector that is just large enough to admit the bulb. The bulb itself mounts in a little threaded holder that inserts into the reflector assembly...
My general idea is to make an aluminum part that would fit in place of the bulb holder and would act as a mounting platform for two small LEDs wired in series. The LEDs would be aimed sideways into the reflector. The aluminum piece would serve to conduct the LEDs' heat out to the reflector and then to the light's housing. The aluminum piece would also act as the ground connection, since the reflector served as the return path for the incandescent bulb.
I expect to have the rectifier diodes mounted behind the reflector.
This is very much just in the conceptual stage right now. The goal is to be very minimal but still draw 3 watts from the dynamo.
Like some of my other electronics projects, it will end up being primarily a mechanical project. My hope is that a hacksaw and file will sufficient <fingers crossed>
Steve in Peoria
Most people have not had good luck using existing mirrors and optics designed for incandescent bulbs for LED upgrades. The directional nature of most LEDS does not work well with the old fashioned concave reflectors. As for retrofitting the B&M guts, the challenge was less in mounting (Goop brand adhesive is great!) and more in creating an effective head sink as you mentioned. the B&M reflector has a built-in slot designed to hold the surface-mount LED and heatsink. I was able to use a piece of brass bar stock that fit the slot perfectly. I bent the bar stock to fit inside the Luxor housing, and covered some of the bar stock with shrink tubing and used it to affix the main board from the B&M. This photo pretty much sums it up. You can see the backside of the reflector glued to the original reflector bezel. No original parts were destroyed in the retrofitting process.
