5-7HEAVEN
Well-Known Member
Sounds like you are almost on the same train of thought as me, just a boxcar away. That should work too, I just hate bronze bushings.
If you make external cups for the outer shaft you can use a much larger outer shaft. Then you can use sealed bearings through it for the inner shaft to ride on. Use as much space as you can in the BB and have the bearings outside of it.
Dan, I dislike bushings too!
It took a tremendous amount of time and research to realize that no off the shelf parts exist to spin a larger shaft thru my BS/BSA-type bike frame.
My frame's shell is only 41mm ID.
A standard external BB can only accommodate a custom-made($$)37mm hollow spindle.
There is an external 54mm bearing cup.
However, it accepts a 30mm, not 37mm spindle.
The lack of 52mm bearing availability would prompt you to fabricate custom($$)bearing cups to accept ($$)bearings from factory assembly lines.
The maximum size custom-made($$)spindle to pass thru a 41mm frame is still 37mm.
So the hollow($$) custom-made 37mm spindle won't accept the standard 35mm sealed 1 3/8" bearing INSIDE its core.
Not enough "meat".
Your 37mm ($$) spindle can be designed to accept smaller ID needle bearings to support the 5/8"(16mm) inner shaft,
And THEN! You'll need to find special sprocket adaptors and lock collars to attach to your ($$)37mm hollow main shaft.
And that is why a larger custom($$) shaft is impractical for this project.
Cost of my 1" hollow shaft..10.00
13" long shaft, 3/4" diameter.....$47.00.
Bronze bushings.....$5.00
Used external BB.....$8.00
New 25mm bearings.....$20/pair.
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