Bike tail light adapter for Cat Eye B-1 rear reflector bracket

The Cat Eye B-1 rear reflector bracket attaches to the frame cross brace right behind the saddle post. It is considered a "vintage" part, and can easily be found on eBay. It is used to mount the Cat Eye RR-290 reflector, which is still sold by Cat Eye – although the bracket is no longer sold.

This adapter lets you mount a saddle-post taillight on the reflector bracket.

I made this because I wanted to mount a taillight on my old Nashbar road bike, but I have a tool bag occupying the position under the saddle, so I couldn't put a tail light there.

The adapter prints as a vertical cylinder but the slot that surrounds the bracket is angled at 73°, which is the typical angle of a bicycle saddle post. The adapter is screwed in place with the original self-tapping screw from the reflector.

Printing

The only critical setting is the number of perimeters. Use 4 perimeters to cover the bite of the self-tapping screw threads.

Assembly

1. Slide the adapter onto the bracket, so that the slope of the adapter would be parallel to the saddle post.
2. The screw is inserted from the forward-facing side of the adapter, opposite the rear side where the taillight would go.
3. You need to exert a lot of pressure on the screwdriver to get the threads started.
4. Don't over-tighten. The screw does not need to be tight, just snug. Its only purpose is to lock the adapter in place to prevent it from slipping off.