ubrayj02

I've got a funky issue with one a bike and I was wondering if anyone on Bike Forums could help me identify the darker colored bottom bracket spindle in the image above.

Both are from Flying Pigeon bicycles, the chrome bottom bracket is from a British/ISO threaded 68mm shell bottom bracket set. The one above it is from a ??? ??? bottom bracket off of a Flying Pigeon of unknown provenance. I know that the mystery BB has a shell that is larger than the 68mm cups I've got on hand.

I want to find out what type of bottom bracket this is - a name, a good guess at its shell size, etc. Unfortunately, the bike is not on the other side of North America and I'm unable to look at it up close and take a pair of Vernier calipers to it.

Any help (or best guesses) would be sincerely appreciated.

T-Mar

It appears to be a Thompson bottom bracket spindle. Thompson were very similar to the one piece Ashtabula crankset, but with cottered cranks. The bottom bracket used over-size, non-threaded cups and the cones threaded onto the spindle to keep everything in place. These bottom brackets are sometimes refered to as Thun. Shell width was typically 65 or 70mm and the cup diameter was 40mm.

ubrayj02

Thanks very much for that! This does indeed look like a Thompson bottom bracket.

There is an exploded diagram of the non-drive side in a great book (that includes instructions on rod brake maintenance as well) called "The bicycle repair book: the new complete manual of bicycle care", By Rob Van der Plas

Now, where in the U.S. am I going to find some replacement parts!? Hah, this will be a laugh.

Thanks again.

T-Mar

Just checked some of my olde books. Apparently these bottom brackets were available in 3 cup sizes: 30mm, 40mm & 45mm.