What is the cycle drivetrain?

The cycling drivetrain is what makes a cycle a cycle. It is a geometrical combination of pedals, cranksets, cassettes, chains and wheels. Drivetrains are nothing unique to cycling. You use one whenever you are driving your car.

What is the role of the drivetrain?

The immediate drivetrain responsibility is to transform pedaling into forward force.  This can be viewed from two perspectives: Force Transfer and Power Transfer. In the first we will see that rear tire force is dependent on gearing and always a fraction of the pedal force. In the latter, we will see that Pedaling Power is transformed with the exception of a small amount of friction losses into rear tire power.

Drivetrain Force and Power Transfer

The drivetrain actually does two interrelated things:

• Transform pedal force into rear tire force.
• Transform pedaling power into rear tire power.

You might be getting lost as to why we are talking about forces and power in the context of the drivetrain. First, the drivetrain calculations involve both. The first part follows the force transformations from the pedal to the rear wheel and in doing so helps us to understanding the underlying drivetrain dynamics.

Once we have the forces, we can then compute the pedaling power which is what the cyclist is exerting, and then compare it against what the forward power requirements are to complete a given riding scenario in a given time.

Next Topic:   Drivetrain Force Transfer