The green component in question is identified as a type of ratchet mechanism, specifically a ratcheting freewheel mechanism. It allows gears to turn freely in one direction while engaging in the opposite direction. The design is based on the deflection of the ratchet rather than a traditional pivoting arm-and-spring style. There are options for plastic freewheels available commercially, or they can be custom fabricated. The specific design details of the component remain uncertain.