Definition

1. Noun:
   • A gear in an epicyclic system: An "epicyclic gear" is a specific type of gear, specifically the outer gear in an epicyclic train. It rotates around a central gear (the sun gear) while also having its own axis of rotation. This arrangement is fundamental to creating different gear ratios in a compact space, commonly found in automatic transmissions and differentials.

Usage Examples

• Noun:
  • The mechanic replaced the damaged epicyclic gear in the car's automatic transmission.
  • In this planetary gearset model, the epicyclic gear is also called the ring gear because it encircles the other gears.
  • The design uses an epicyclic gear to achieve a high reduction ratio without increasing the size of the assembly.

Advanced Usage

• Technical Context: The term is almost exclusively used in mechanical and automotive engineering contexts to describe a component within a planetary gear system. Its function is defined by its relationship to the "sun gear" and "planet gears."
• "Epicyclic gear train": This is the full system in which the epicyclic gear operates. It consists of the central sun gear, one or more planet gears (which mesh with both the sun and the outer gear), and the outer epicyclic/ring gear, all held within a carrier.

Variants and Related Words

• Ring gear: A common synonym for "epicyclic gear," describing its physical shape as a ring with internal teeth.
• Annulus gear: Another technical synonym for the outer gear in an epicyclic system.
• Planetary gearset: The complete assembly that includes the epicyclic gear, sun gear, and planet gears.
• Epicyclic train: Another term for the entire gear system.

Synonyms

• Ring gear
• Annulus gear
• Outer gear (in the specific context of an epicyclic system)

Related Phrases

• Epicyclic gearing: Refers to the general principle or technology of using gears in an epicyclic (planetary) arrangement.
• Epicyclic transmission: A transmission system that utilizes epicyclic gearsets to change speed and torque.

Noun

1. an outer gear that revolves about a central sun gear of an epicyclic train