Lights chronically disappear from my bike, so I thought I would create an affordable, magnetically mounted bike light that I can quickly detach from my bike when locking it up. The lights are cheap enough that I don't care too much if I forget to remove them and they get stolen, but because they are so easy to attach, I am more likely to remove them and slip them into my pocket. They are also cheap enough that I can make lots of them and leave them scattered in various bags and on various bikes.

I started with a blue light for a headlight, although this could easily be done with a red rear light.

Of course, this only works with steel bikes, so if you have a carbon, aluminum, or titanium frame, this won't work particularly well.

Step 1: Ingredients

Required Items:

Cheap clip on running lights (I purchased these)
Very strong magnets (I tore them out of some old hard drives)
5-minute 2-part epoxy
Mixing sticks and surface

Step 2: Disassembly and Construction

Disassembly

Remove the clip from the back of the light by sliding out the pin that holds it in place. The pin can be pushed out with anything pointy, including a straightened paperclip, fork tine, or exacto knife blade point. Once the pin is out, the clip should just fall off. There is also a spring that has to be removed, which is substantially easier with a pair of pliers.

Construction

Open the epoxy and squeeze a healthy sized blob onto your mixing surface. Promptly mix together well with the mixing sticks. Transfer the epoxy to the back of the light and carefully lower the magnet into place. Do not get epoxy on the recessed screw heads, otherwise you won't be able to change the battery. Let cure.

Step 3: Completion

Once cured, mount the light on your bike and ride safely off into the night.

I clipped this light to the front of my bike and rode all over town without it shifting around or falling off. The magnet seems sufficient to hold it firmly in place.