Convert Cottered crank into One-Piece crank

[c_bishop]

I have a 20" frame I am currently working on which came with a 3 piece cottered crank. I have a really cool solid sprocket (thanks Dingo!) and 1-piece crank I want to get in there, but it just won't fit. Too tight! Has anyone had any luck filing down the insides of the BB shell to expand the bearing holder thingies? I think if I could just make it a bit wider in there I could get it through.

 

[fast eddie]

if it were my bike i would not remove any metal from the bottom bracket - if i am understanding you correctly. in my opinion a 3 peice crank like the one already on your bike is better than a one peice or spingle crank. even though cotter pin are a booger to mess w/ if ya aint the right tool, they're smoother i think. just my 2 cents,
fast eddie outty

 

[shecky]

BB shells for just about any 3 pc crank are simply too small to accommodate a one piece crank. No amount of filing will work. What would be needed is an American BB shell, one wide enough to accommodate one piece cranks.

It may be possible to use a 3 pc BMX crank that accepts chainrings for one piece cranks. These tend to be very durable, showy, and pricey. There may be issues with the threads in the BB shell. Cottered cranks are a remnant to mostly European manufacturing where each country, and sometimes, each manufacturer, used it's own standards.

 

[c_bishop]

Yeah, I've been looking around and found some BMX 3 piece cranks with drive pins that look like they might fit my chainwheel. I think this might be my best best, I'm just being cheap and wanting to use what I have lying around.

 

[GTCOMA]

I don't think what you are trying to do will work. But I did convert/downgrade to a cottered crank from a square press on crank. You just have to replace the center part too and hope the spacing is right.


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