Types of Gears

Vocabulary flashcards covering key definitions, types, mechanical characteristics, and visual representations of gears based on the lecture notes.

Gear

A rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque.

Transmission

Two or more gears working in tandem that can produce a mechanical advantage through a gear ratio.

Rack

A non-rotating toothed part that meshes with a gear to produce translation instead of rotation.

Spur Gear

The most common type of gear, characterized by straight teeth and mounted on parallel shafts.

External Spur Gear

A gear with teeth formed on the outer surface of a cylinder or cone, where the larger gear is called the gear and the smaller driving gear is called the pinion.

Internal Spur Gear

A gear with teeth formed on the inner surface of a cylinder or cone, where the larger gear is termed the annular.

Helical Spur Gear

A cylindrical gear with helicoidally shaped teeth that operates with less noise and vibration than spur gears, but produces thrust loads along the gear shaft requiring thrust bearings.

Double Helical Gear

Also known as a herringbone gear, it features two sets of teeth arranged in a V shape (mirror image stacked) to cancel out axial thrust.

Rack and Pinion

A gearing arrangement consisting of a round spur gear (pinion) meshing with a straight-line toothed gear (rack) to transform rotary motion into linear motion and vice versa.

Pin Gearing

A gearing mechanism where the distance from the gear center to the contact point changes as the gears rotate, resulting in a continuously varying gear ratio and output speed.

Bevel Gear

A gear mechanism used to change the direction of shaft rotation, usually mounted on shafts oriented at 90 degrees to each other.

Plain Bevel Gear

The simplest form of bevel gear, resembling a conical spur gear with straight teeth parallel to the generators of the cone.

Crown Gear

A bevel gear whose teeth project at exactly right angles to the plane of the wheel, resembling the points on a crown, typically mating with a wide pinion.

Spiral Bevel Gear

A bevel gear featuring curved helical angle spiral teeth that engage progressively across the tooth face.

Hypoid Gear

A gear system similar to spiral bevel gears used in automobile differentials to transmit torque 90 degrees, distinguished by non-intersecting shaft centerlines.

Hyperboloidal Gear

A gear mechanism formed by two hyperboloids of revolution that transmits motion between two skew axes using straight line cogs.

Worm and Wheel Helical Gears

A drive mechanism consisting of a single-tooth screw-thread gear (worm) that drives an inclined helical gear (worm wheel) in a quiet, non-reversible operation.

Face Gear

A circular disc gear featuring a ring of teeth cut on one side that taper toward the center, usually designed to mate with a spur gear.

Double Enveloping Worm Gear

A worm gear designed with a radially changing pitch diameter to increase the number of teeth in contact and the total shear area.

Non-circular Gear

A specially shaped gear designed for specific functional objectives like ratio variations and axle displacement oscillations rather than uniform torque transmission.

Epicyclic Gears

Also known as planetary gearing, a gear system consisting of one or more outer planet gears revolving around a central sun gear, often enclosed within an outer ring gear (annulus).

Sun and Planet Gears

A gearing configuration used in historical steam engines during the Industrial Revolution to convert reciprocating motion into rotary motion.

Harmonic Drive Gear

A specialized, proprietary gearing mechanism composed of a wave generator, flexspline, and circular spline.

Cage Gear

Also called a lantern gear or lantern pinion, it features cylindrical rods for teeth set parallel to the axle in a circle between two end disks.

Spur Gear Nomenclature

The structural terminology defining gear tooth dimensions and features, including addendum, dedendum, pitch circle, clearance, top land, face width, and circular pitch.