Knowra Epicyclic gearing Epicyclic gearing Epicyclic gearing is a gear arrangement in which one or more gears orbit a central gear as a carrier rotates. Its compact layout can provide multiple speed and torque ratios.
Planetary gear train : A gear train with a central sun gear, orbiting planet gears, and a carrier, often enclosed by a ring gear. This common epicyclic layout shows how the central gear, orbiting gears, and carrier interact.
Automatic transmission : A vehicle transmission that selects gear ratios automatically as driving conditions change. Planetary gear sets provide its compact selectable ratios through controlled clutches and brakes.
Parallel-axis gear train : A gear train whose gear axes remain fixed relative to the supporting frame. Unlike epicyclic gearing, its gears do not orbit as their support rotates.
Gear ratio : The relationship between the rotational speeds or tooth counts of meshing gears. Epicyclic trains combine ordinary gear ratios with the carrier’s motion.
Sun gear : The central gear in a planetary gear train, meshing with surrounding planet gears. Its rotation helps determine the train’s output when the carrier or ring is held or driven.
Bicycle hub gear : A bicycle gear system enclosed in the rear hub, using internal mechanisms to change the wheel’s drive ratio. Many hub gears use planetary trains to shift without exposed derailleur gears.
Compound gear train : A gear train with at least one shaft carrying two or more rigidly connected gears. It can achieve large ratios, but its axes remain fixed rather than traveling on a carrier.
Angular velocity : The rate at which an object’s angular position changes over time. Each gear member has an angular velocity, and the carrier makes those velocities interdependent.
Planet gear : A gear that meshes with a central sun gear and usually a surrounding ring gear while mounted on a carrier. Its spin and orbit combine because its axle moves with the carrier.
Wind turbine gearbox : A gearbox that raises a wind turbine rotor’s slow rotational speed for a generator. Epicyclic stages can deliver high speed increases in a compact, load-sharing package.
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