Homemade Generator Taillight

Several months ago, I built my own generator taillight. I wanted something very bright but that won't blind riders close behind me. One of my pet peeves is randonneurs who mount bright taillight pointing upward as if they're signaling UFOs.

My taillight is made from a red CREE LED emitter and a fan-beam lens. the lens is oriented to give a wide beam from side to side, but very narrow in the vertical direction. the intent is to help keep the light from blinding other riders close behind me.

To house the emitter, I used a 1 inch copper pipe cap and cut it down to the length of the emitter and lens holder. The LED came mounted to a "star" plate with solder pads for the power wires. I mounted the star to the bottom of the pipe cap by tapping two holes in the cap and screwing the star down with some thermal grease for heatsinking.

The lens holder wasn't made specifically for this LED so I had to cut way at parts of it to fit. I then used silicone adhesive to hold it in place inside the pipe cap. The power wires come in through a small hole in the back that is sealed with more silicone.

Here you can see the finished light with the lens attached. The domed shape of the lens and the internal ridges give it the desired beam pattern. The light is ready for mounting on the bike.

I didn't make a mounting adapter for the light. Instead, I used a padded adele clamp (basically a large P-clamp) that was attached to a Cateye taillight clamp sized to fit the bike's chainstay. the wires are zip tied to the frame and run up to an LED headlight that provides a rectified current from the dynohub to the taillight.

Here's another shot of the mounted light.

So, how bright is the light? Very, very bright. Other riders have told me that they can see the light a long way off even in full sun. The LED puts very little extra load on the generator and I have it, and the twin LED headlights operating day or night. By the way, the generator light is brighter than the Planet Bike SuperFlash on the right chainstay that I keep for backup.