three-speed gear

n.

三速链轮；三连齿轮；

Three-speed gear shifting box for power-driven tools
An approach for the kinematic design of three-speed gear mechanisms for electric bicycles
The Systematic Design of Automatic Three-speed Gear Hub for Bicycles
The fly with the three-speed gear shift
Three-speed gear shifting box for power-driven tools
The Design of Three-speed Front Internal Gear Hub for A Bicycle
A BELT PAPER KYMOGRAPH WITH A THREE SPEED GEAR SHIFT
Study Of Three Speed Gear Box
The Relative Speed Gear Instantaneous Center Theorem of Three-Gear Mechanisma and Its Application
Change-speed gear, especially for bicycles