Though hardly a classic, there is one thing that I found thought provoking while disassembling this bicycle, and that is the mysterious bottom bracket. It’s a proprietary unit, I think, with standard BSA right hand threads on the non-drive left side cup, but the drive side is an extended cylinder that mates with the left cup to form a sealed unit that can be disassembled, complete with standard 1/4″ plain ball bearings and a cottered crank axle. The whole setup is wedged into a threadless oversized bottom bracket shell by tightening the assembly, fitting the wedged lock ring, first matching a keyway in the shell to a notch cast on the large cup, much the same way as some old seatpost pins and quill stem pinch-bolts slot in to stop them rotating. Rubber seals on the axle holes help stop outside entry of water and grit. Perhaps modern sealed BBs have evolved from this idea ?
Why make such a big deal about an old non-standard BB ? Well, this is an old bike blog, so you won’t be seeing octalinks, hollowtech IIs, BB30, BB90, or that sort of newer thing, but this one made me take notice because the bearings and surfaces inside were in truly excellent condition considering the bike’s age and assumed usage. This is because the rust, grit and water build-up inside the frame remains outside the casing as you can see from the corroded exterior. Often this accumulated gritty gunk finds its way into the bearings and a completely new BB is required, but not here !
As well as that, they are user serviceable unlike the modern sealed bearing square taper replacement BBs that are long term throwaways. And they need to be in this case because if this fixed cup had worn out 30 years later it would be very difficult to replace, perhaps then making the bike useless ! What else would one fit – with no threads ? Of course, that’s true only because this system didn’t become a standard arrangement…
I am going to experiment with converting it to a square taper axle, as I have said before I’m not a fan of cotter pins unless on a ‘valuable classic’ and even then that’s only for originality… if that works the bike can be modernised with a lighter chainset, with the hope that this bracket will stay put.