Abstract: A sequential planetary stack transmission system is provided. The system includes a stack of planetary gear sets, each gear set including a sun gear engageable with a rotatable central shaft, and freely rotatable concentrically about the central input or output shaft when not engaged with the central shaft. A plurality of planet gears engage with the sun gear, and a ring gear engages with the planet gears. The ring gears form a ring gear barrel rotatable as a unit concentrically with respect to the central shaft. A shifting assembly within the hollow central shaft engages sequentially with the sun gears to provide a desired gear ratio. The planetary stack assembly and the shifting assembly are disposed within a case. The system is suitable for a variety of applications, and is particularly suitable for bicycles.

Abstract: A sequential planetary stack transmission system is provided. The system includes a stack of planetary gear sets, each gear set including a sun gear engageable with a rotatable central shaft, and freely rotatable concentrically about the central input or output shaft when not engaged with the central shaft. A plurality of planet gears engage with the sun gear, and a ring gear engages with the planet gears. The ring gears form a ring gear barrel rotatable as a unit concentrically with respect to the central shaft. A shifting assembly within the hollow central shaft engages sequentially with the sun gears to provide a desired gear ratio. The planetary stack assembly and the shifting assembly are disposed within a case. The system is suitable for a variety of applications, and is particularly suitable for bicycles.