Gear

Introduction
This page is intended to differentiate some kind of gears by their (hopefully) correct names. There will be not much information about the design in detail; there are enough proper descriptions in the wiki pages and elsewhere in the www.

Gear
A Gear is a toothed wheel that can be paired with other gears, racks, chains, or belts to form a gear train (which is usually called a gear as well).

Native speakers, feel invited to add local synonyms, or spelling variations

Bevel gear
A bevel gear meshes with another bevel gear to connect two angled rotation axes.



The FCGear BevelGear tool creates a basic bevel gear, a solid object that needs to be trimmed to shape in following steps.



Cage gear
See lantern gear.

Chain wheel
The driving gear (attached to the crank arms) of a bicycle drivetrain is usually called a chain wheel. See cog wheel and sprocket.

Cog
The driven gear (attached to the rear wheel) of a bicycle drivetrain is usually called a cog. See cog wheel and sprocket.

Cog wheel
A cog wheel, or cogged wheel, is an assembly of a hub(?) and several inserted teeth, the actual cogs.



Early wooden cog wheels were used to drive lantern gears. See gear trains. The cogs could have other angles than 90° relative to the axis to build angled gear trains:



Cog wheels have been replaced with single body gears that are called sprockets if they mesh with cylindrical teeth such as the rollers of a (roller) chain, or ladder-like roller racks.
 * In case of a bicycle's drivetrain the driven sprocket is called cog and the driving one is called chain wheel.
 * In connection with rack railways the gears were still called cog wheels or pinions.

Crown gear
A crown gear is similar to a larger bevel gear, but meshes with spur gears instead of another bevel gear. See Crown gear and spur gear.



FreeCAD provides a tools to model crown gears:
 * [[Image:FCGear_CrownGear.svg|24px|link=FCGear_CrownGear]] FCGear CrownGear: Creates a crown gear.

Double helical gear
A double helical gear has two symmetric rows of helical teeth that have an angle other than 90° to the axis of rotation. Double helical gears mesh with other double helical gears, double helical racks, or internal double helical gears.

FreeCAD provides two tools to model double helical gears:
 * [[Image:FCGear_InvoluteGear.svg|24px|link=FCGear_InvoluteGear]] FCGear InvoluteGear: Creates an involute spur gear by default.
 * [[Image:FCGear_CycloidGear.svg|24px|link=FCGear_CycloidGear]] FCGear CycloidGear: Creates a cycloid spur gear by default.

Helical gear
A helical gear has helical teeth that have an angle other than 90° to the axis of rotation. Helical gears mesh with other helical gears, helical racks, or internal helical gears. See Skew gears.

FreeCAD provides two tools to model helical gears:
 * [[Image:FCGear_InvoluteGear.svg|24px|link=FCGear_InvoluteGear]] FCGear InvoluteGear: Creates an involute spur gear by default.
 * [[Image:FCGear_CycloidGear.svg|24px|link=FCGear_CycloidGear]] FCGear CycloidGear: Creates a cycloid spur gear by default.

Internal gear
The FCGear InternalInvoluteGear tool creates an internal involute gear.

Lantern gear
A lantern gear is an assembly of a front plate(?) and a back plate(?) and several bolts called rollers connecting both plates.

This kind of gear looks similar to an ancient lantern or a bird cage, that's why it's called lantern gear or cage gear.



Early wooden lantern wheels were driven by cog wheels. See cog wheel gear trains.

Pinion
Pinions are sprockets that are paired with racks.

Sprocket
A sprocket is a gear meshing with roller racks, roller chains, or timing belts, but not with another sprocket.

FreeCAD provides three tools to model sprockets:
 * [[Image:FCGear_TimingGear.svg|24px|link=FCGear_TimingGear]] FCGear TimingGear: Sprockets for timing belts (timing pulleys, toothed pulleys), creates a solid object.
 * [[Image:FCGear_LanternGear.svg|24px|link=FCGear_LanternGear]] FCGear LanternGear: Sprockets for chains or racks (chain wheels, cogs, pinions), creates a solid object.
 * [[Image:PartDesign_Sprocket.svg|24px]] PartDesign Sprocket: Sprockets for bike chains (chain wheels, cogs), creates just an outline.

Spur gear
A spur gear has straight teeth that are aligned parallel to the axis of rotation. Spur gears mesh with other spur gears, racks, or internal gears.

FreeCAD provides two tools to model spur gears:
 * [[Image:FCGear_InvoluteGear.svg|24px|link=FCGear_InvoluteGear]] FCGear InvoluteGear: Creates an involute spur gear by default.
 * [[Image:FCGear_CycloidGear.svg|24px|link=FCGear_CycloidGear]] FCGear CycloidGear: Creates a cycloid spur gear by default.

Timing pulley
Timing (belt) pulleys or or toothed pulleys are sprockets to use with timing belts.

Worm gear
The FCGear WormGear tool creates a WormGear.

Racks
A Rack is like a gear segment having an infinite radius.

Involute rack
FreeCAD provides a tool to model involute racks for spur gearing, helical gearing, and double helical gearing:
 * [[Image:FCGear_InvoluteRack.svg|24px|link=FCGear_InvoluteRack]] FCGear InvoluteRack: Creates an involute rack for spur gearing by default.

Cycloid rack
FreeCAD provides a tool to model cycloid racks for spur gearing, helical gearing, and double helical gearing:
 * [[Image:FCGear_CycloidRack.svg|24px|link=FCGear_CycloidRack]] FCGear CycloidRack: Creates a cycloid rack for spur gearing by default.

Cog wheel and lantern gear




Cog wheel and roller rack
See Rack and pinion.