Generic system to mount those old style 2xAAA battery bicycle lights to your bike, in a way that you can easily put it on and off by the power of magnets :)

You need:

• Magnets: diameter: 8mm, height: 4mm. For each set (1x male and 1x female) you need 4 magnets.
• To mount you either need:
  • M3 bolts and square nuts. Normal nuts are probably also fine, but make it a bit less easy to install.
  • Tie wraps, at most 3,75mm wide.
• Optionally some rubber (the blue stuff in my pictures)

The magnets are embedded in the print, meaning you should pause the printer (preferable automatic) on the right layer to put in the magnets. It can be a bit tricky to get both magnets in without them flying towards each other. I applied a bit of glue stick glue in the hole to make them stick a bit. It was enough to keep them there during the next layers.

Important: Choose the right orentation when you put in the magnets. I chose to match the orientation of the two magnets in the same part. It keeps everything simpler.

The lights get glued to part A. I used epoxy glue. Make sure to sand it well before gluing. Some of these lights have a easily removable mount, leaving a flat surface. For others you need to brake it loose and sand it a bit flat.

Some holes in part B are covered with a 0.25mm layer, in order to make sure the bridging goes right. Otherwise it would be printing a circle mid air. Afterwards you need to drill the thin layer away with a 3.2 or 3.5mm drill

As a bonus you can now put your lights on your fridge!

Designed using FreeCad. File is included.