After half a dozen iterations, this was the first reasonably working, acceptable feeling, and good-sounding ratchet mechanism.

allows clockwise rotation blocks counterclockwise rotation

design features:

• allows for a large inner bore (e.g. rotary encoder shaft or 5.2mm screwdriver bit)
• printable with 0.4mm nozzle
• 2cm diameter
• no assembly required. Print in place.

To get a full ratchet: mirror the assembly and add a mechanism/part that pushes one of the springs out. In neutral both leavers are engaged and the ratchet is completely locked.

Btw. Good luck copying it without going through half a dozen of iterations. Going from it barely works to this isn’t easy. For my part: Version 5 was working and close to the final design. It took another 10 rounds to get it usable and from there some more to fine-tune it.