The magic ratio worked well for 3 races. Even starting with new hardware, by race #4 the chain started falling off . The magic ratio is supposed to let you run a single speed on a bike with vertical dropouts and no tensioning device. It works. Briefly. Here’s my temporary solution for last weekends race:
While it worked OK, it’s ugly, really ugly. I don’t do ugly, it must go.
Zero magic and 100% purty!