Planetary Gear System
A planetary transmission system (or Epicyclic system as it is also known), consists normally of a centrally pivoted sun gear, a ring gear and several planet gears which rotate between these. This assembly concept explains the term planetary transmission, as the planet gears rotate around the sun gear as in the astronomical sense the planets rotate around our sun.
The advantage of a planetary transmission is determined by load distribution over multiple planet gears. It is thereby possible to transfer high torques utilizing a compact design.
Gear assembly 1 and gear assembly 2 of the Rohloff SPEEDHUB 500/14 have two selectable sun gears. The first gear step of the stepped planet gears engages with sun gear #1. The second gear step engages with sun gear #2. With sun gear 1 or 2 coupled to the axle,or the coupling of sun gear 1 with the ring gear, three ratio variations are achievable with each gear assembly.