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Old 09-14-2009, 02:08 PM
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Retmachinist Retmachinist is offline
Motorized Bicycle Elite Member
Join Date: Oct 2008
Location: Urbandale Ia
Posts: 637
Default Re: How do I change one piece crank to 3 piece crank?

Just today I had the same problem, needed to change an old one piece crank to a wider 3 piece crank that will clear the motor on a West Coast Chopper Bike.
I took a long bottom bracket shaft from the loose ball set up and machined it for 5/8" I.D. sealed bearings. They are pretty tough so I had to use Ceramic tooling.
Then I removed the bearing cups for the original bearings and machined bearing caps from 6061 aluminum to support the sealed bearings. Worked out pretty slick.

Attached Images
File Type: jpg Bottom Bracket Conversion 001.JPG (606.7 KB, 546 views)
File Type: jpg Bottom Bracket Conversion 008.JPG (627.9 KB, 538 views)
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