I have a Old Austrian sears frame that I found being thrown out and made into a fixed gear. I've had it for a few months and it would always make a odd noise coming from the bottom bracket. I never got to opening it up until it died on me and seized up a few months ago. I've opened it up today and it seems one of the bearing cages got ruined. I do not know what style of bottom bracket this is though and what I can replace it with. It seems to be a combination of cottered and American one piece. Does anyone know what kind of crank this is or what I can replace or repair it with?

Looks like a Thompson/Thun unit. If the cones are in decent shape, just clean it up and use new balls. If you're in the mood to replace it, there are conversion units to allow you to use square-taper cotterless cranks.

This is a great example of an old idea (the axle fixed to the RH arm) that has come back into popular use and claimed to be better then some other old design (3 piece cranks). Andy.

[MENTION=20548]JohnDThompson[/MENTION] I'd rather replace it to a square taper if possible. Do you know of any of these conversion units?

It seems that it must have came loose and one of the bearing cages got mashed up as chunks of metal came out when I took this apart. Some were stuck between the cone and the bb shell, only one bearing cage came out on the drive side.

The loss of the cages is meaningless. If the races are OK, rebuild with loose balls of the same size.

Switching to Sq. taper means buying an adapter (if you can find one), new BB, and new cranks. It would lose any character of being what it is, and odds are a suitable frame with OK BB and cranks would cost less anyway.

Your call, and hopefully JT can point you to a source if you want to go the new cranks route.

There are thousands of those conversion parts out there. Just google american to european bottom bracket adapter. Of course, you will also need a bottom bracket and crankset.

Here's an example:

Robot Check

This bb shell doesn't appear to be as big as a American ashtabula crankset

Well, they're available in Europe, anyway:



Home / Bicycle Parts City Bike / Bottom Bracket / Bottom Bracket Complete / Thun Bottom Bracket Cotterless 127/40mm Thompson Press-Fit

Yea A Swedish/Austrian way of making a Utilitarian bike at low cost , domestically.

IF you really want to go square taper - NOTE, I would not - you are going to need some tools, the first of which is a caliper - I use a Harbor Freight digital caliper, often on sale for about $10- - to measure what you have.

Confirm that the cups are not threaded into the BB shell - early '80's bikes with 3 piece style cranks and Shimano's FFS have cups that are threaded into a standard 68mm x 1.375" BB shell. If they are threaded the threads will be visible inside the cups. Your pictures are not high enough resolution for me to see.

If the cups are not threaded, knock the cups out of the frame. Confirm that the ID of the BB shell is around 1.324", in which case you are almost home, because you can use a Sunlite Repair BB like this one: Sunlite Bottom Bracket Set 68 x 127.5 Sqar Thrdls F/Repair
You need to choose your crankset, then choose the BB with a compatible axle length.

If the ID of the BB shell is less than 1.324" and the wall thickness is sufficient, you could have the house reamed out. If it is less than 1.375 (and probably 1.380"), you can probably use the Sunlite BB.

If the OP's bottom bracket is a Thun/Thompson, the ID of the shell is likely 40mm (1.575"), and the cartridge you suggest will be too small to seat in the shell.

So where would you get cotter pins for a rig like this?? Do they still make them?

Whenever I've needed them - not that often - I've had zero trouble buying them from whatever slightly grimy looking bike (repair) shop that was within easy reach along my commute.