Pinion
[Image:Annular (PSF).svg|thumb|right|Pinion and annular gear]
A pinion is a round gear—usually the smaller of two meshed gears—used in several applications, including drivetrain and rack and pinion systems.
Applications
Drivetrain
Drivetrains usually feature a gear known as the pinion, which may vary in different systems, including- the typically smaller gear in a gear drive train. In many cases, such as remote controlled toys, the pinion is also the drive gear for a reduction in speed, since electric motors operate at higher speed and lower torque than desirable at the wheels. However the reverse is true in watches, where gear trains commence with a high-torque, low-speed spring and terminate in the fast-and-weak escapement.
- the smaller gear that drives in a 90-degree angle towards a crown gear in a differential drive.
- the small front sprocket on a chain driven motorcycle.
- the clutch bell gear when paired with a centrifugal clutch, in radio-controlled cars with an engine.
Rack and pinion
[Image:Rack and pinion animation.gif|thumb|right|Rack and pinion animation]In rack and pinion systems, the pinion is the round gear that engages and moves along the linear rack.