To go mountain biking at night, you need a really bright light or three to keep the trail lit up. When the idea for this light was conceived, you could expect to pay ~$1/lumen for mountain biking lights. Because 400+ lumens is the minimum for a safe ride, commercial lights were way out of our budget. So we built our own.

The resulting light has two settings, 420 lumens for 6 hours, and about 1100 lumens for 2 hours. The whole project cost about $60, so our price per lumen was way better than the commercial option.

The CREE leds we bought had about ~130 lumens/watt, and lenses that interface directly with a board of three. They came on a circular board that was the exact size of the inside of a copper reducer from Home Depot. This is gave us a housing and a way to dissapate heat at the same time. The LED's were about ~20, and represented a third of the cost of the project.

The LED driver circuit came from Instructables, and cost about $1 to build.

We used Eneloop rechargable batteries because they hold a charge for a long time, and can be used for other things when not riding. This was half of the cost of the project.

The LED mounting board was attached with thermal greaseto the back of a 1/2" end cap that had been ground flat.

This reducer made up the front of the light, and the LED sat inside the big side. The tabs that prevent tubes from going through had to be ground out, because the tube that made up the back of the light extended further than usual into the head.

The un-notched end of tube goes through the back of the head, and the cap goes over it on the inside of the head. The LED board is mounted to the cap, and the hole drilled in the cap allows the wires to escape. The little piece with three notches will get pressed into the head to hold everything in place. The notches are bent down to hold the lens tight against the LED board.

And, after a couple of years of abuse, its still shining bright