Most torque converters have a stall speed around 2000 - 2500 RPM. Which also happens to be the RPM range that your vehicle normally runs at cruising speed. At a lower speed you would be simply running a viscous coupling between the engine and transmission.
Then, thereâs the obvious choice: A dynamo attached to one of the bike wheels. (These devices in general are called generators, but when attached to a bike, a generator is traditionally referred to as a dynamo.
Derailleur gears. Derailleur gears are a variable-ratio transmission system commonly used on bicycles, consisting of a chain, multiple sprockets of different sizes, and a mechanism to move the chain from one sprocket to another.