noun
the central gear in an epicyclic train
• Hypernyms: ↑gear, ↑gear wheel, ↑geared wheel, ↑cogwheel
• Part Holonyms: ↑epicyclic train, ↑epicyclic gear train
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noun : the gear wheel on the central axis in a sun-and-planet motion — see sun-and-planet motion illustration
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Mach.
(in an epicyclic train) the central gear around which the planet gears revolve. Also called sun wheel.
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sun gear,
the central gear around which the planetary gears revolve: »
For reverse…the front clutch is released and the rear clutch engaged so that the large sun gear is now connected to the turbine (Jud Purvis).
Useful english dictionary. 2012.