Hi, I'm new- to bikes (mostly) and this forum.
I recently came across a Follis frame (French build, little to no information available) and I'm stripping it, repainting it, and converting it to a fixed a gear for commuting. I would like to replace the crank system and bottom bracket with new parts (the old crank system is a bit rusted and banged up, and one of the cotter pins was rusted out and broke during the uninstallation).
I'm not sure how to measure what size bottom bracket I need, and I'm not sure that the ones I'm looking at will be compatible with the crank set I'm looking at. Also (this is probably a dumb question) but does the fixed right cup stay on during the installation of of a new bottom bracket?
These are the parts that I'm looking at: