Thompson Bottom Bracket
A while ago, I bought an old (1960's?) three speed for dirt cheap and converted it to a fixie. I love it. I've gotten everything on the bike exactly how I want it, except for one thing... The Thompson bottom bracket. I have to re-adjust it all the time, and I'm not sure if I can ever get a different chainwheel or cranks. (The chainwheel is permanantly attatched to the crank, which is permanantly attatched to the axle and the fixed cup.)
I understand these things are pretty rare, as a search on Google turned up only a few relevant websites which just said, "this is what a Thompson bottom bracket is, it's pretty rare."
I guess my question is this - is it possible to convert this type of bottom bracket to conventional cup and cone or cartridge? If not, is there any way I could get different cranks or a different chainwheel? Anywhere I could find parts for Thompson bottom brackets?
Thanks so much in advance for your help.
Can you completely remove the current crank and bottom bracket? If you can, take the frame to a bike shop and have them check if the bb shell has any of the current standard threading and is a standard width. If it's English threading and 68 mm wide or Italian threading and 70 mm wide you are good to go with any type modern bb and crank.
If the frame is an old Raleigh and has their not-quite-English threading (same diameter, 26tpi instead of 24tpi) you may be able to find suitable cups as NOS in an older bike shop or on-line.