Square taper BB for cottered crank convert
 

Hi, I'm converting two bikes from cottered crank to Square taper.
First bike is an old German "MARS Markenrad", second is a "prophete Clipper".

They both have threadless BB shells with press in cups.
Where can I find a threadless BB? I have converted one using a threadless BB by german BB manufacturer "F.A.G.". It was a real cowboy job as the two parts of the BB do not srew together, they are both pressed into the shell. In my case I have no press, so I used the traditional Hammer and two by four method. I don't want to repeat this, so I'm looking for a better BB. The original press in cups for the cottered crankset appear to have an outer diameter of 40mm, which is bigger than most square taper BBs. Whenever I go on the internet to find a new BB i can only find info on the shell width, spindle length and maybe the thread pitch, not the cup outer diameter. Am I missing somthing here? Are my measuring calipers broken? Does this 40mm size exist?

Thanks
Colin

Velo Orange sells a threadless square taper bb that a lot of people have good luck with. Google their website and you'll see it.

I offer a suggestion, if you can find a sealed bearing with the OD of your hub shell's ID,

and an ID of the bearing of 17mm, then A Phil Wood spindle may be pressed in.
you would need a spacer between the bearings, to keep them separated.

a common BB is about 35~36mm, a machine shop could turn and thread
some rings to make the metal required to reduce the BB Shell
to make current parts fit..
Ask some frame builders .. they may prefer to braze in metal,
that will require a repaint of the burned paint areas, of course.

It really depends on how much funds you want to pour into this,
it could easily run into several hundred. [ Dollars GBP Euros, etc]

+1, .. Velo Orange in Maryland, has a BB for Stripped threads,
But I cannot say they will work
when there is a extra 5 mm ID to fill.
the mounting may lack purchase to hold onto.