Professional Repair and
Shop Operation Class

Thursday, December 1, 2005

Drivetrain

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Anna
Another day, another new instructor. Anna had worked as a frame builder for Seven Cycles and I recall as a bicycle messenger in New York. She was a knowledgeable and entertaining instructor. We learned more about various drivetrain components. One of the important things I learned during the week was how to make the various measurements necessary to be able to properly replace worn components on customer bikes. While I've learned from our mechanics in the shop, it was good to delve more deeply into the topics and to use the Sutherland’s Handbook to locate the proper parts based on the measurements.

We learned about bolt circle diameter (for chainrings), chain widths, chain installation, over locknut dimension, and freewheels and freehubs. Not all new material for me, but it was an opportunity delve into the subjects more deeply. It was also a chance to finally memorize the gear inches equation: (Front chainring teeth/Rear cassette teeth) * Rear wheel diameter.

During the open lab session I removed the Bike Friday bottom bracket, with some guidance from John. Mine was an older sealed cartridge that was slightly different than the ones we had removed in class. I planned to order a new, upgraded replacement to install the following week. I decided not to tackle the task of removing the sealed wheel bearings, although I should have, given the assistance that was available.

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