Bicycle Maintenance 

I was searching for an in-person bicycle maintenance class, and the closest one I found was in Bethlehem, PA, at CAT.
CAT is a non-profit organization dedicated to supporting bicycling, pedestrians, and public transportation in the Lehigh Valley. 

The class was four hours long and taught by an amazing man named Scott, a mechanical engineer with experience working in power plants. This was an introductory class, so we covered threads, fasteners, bike parts, lubricants, and performed a full tune-up. We worked on wheels, bearings, cleaning the chain and cassette, brake adjustments, and derailleur adjustments.

The most interesting part for me was learning about the derailleur. The derailleur, a key component in bicycle maintenance, has evolved significantly over the past century. Early systems, such as those designed by French inventor Paul de Vivie in the early 1900s, required riders to shift gears manually by moving the chain. Innovations accelerated after World War II, with companies like Campagnolo introducing spring-loaded parallelogram designs that became the standard for modern bikes. Today, derailleurs are made with advanced materials, feature indexed shifting, and even incorporate wireless or electronic systems, ensuring precise and reliable gear changes for all cycling disciplines. 

The parallelogram mechanism is a crucial part of modern derailleur design. It consists of interconnected links that form a parallelogram shape, allowing the derailleur to move the chain laterally across the sprockets while maintaining consistent alignment. This design provides smooth and precise gear changes, as the chain path stays predictable and controlled, even under load. This innovation, introduced in the mid-20th century, is what makes modern derailleurs so efficient and reliable.