FCGear CycloideGear

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FCGear CycloideGear.svg FCGear CycloideGear

Menu location
FCGear → Create a Cycloide gear
Default shortcut
Introduced in version
See also
FCGear InvoluteGear


Cycloidal gears are very sensitive to an inaccurate adjustment of the centre distance, which then leads to a change in the transmission ratio. For these reasons, cycloidal gears are hardly found in mechanical engineering but are only used in special cases such as in the watch industry, for roots type blowers or for the drive of gear racks.

Cycloid-Gear example 1.png

From left to right: Spur gearing, helical gearing, double helical gearing


  1. Switch to the FCGear workbench icon.svg FCGear Workbench.
  2. Invoke the command several way:
  3. Change the gear parameter to the required conditions (see Properties → Data below).




  • DataPlacement: Placement is the location and orientation of an object in space.
  • DataLabel: User name of the object in the Tree view.


  • Datainner_diameter: Default is 5,00. Rolling circle of hypocycloid (see also the information in Notes).
  • Dataouter_diameter: Default is 5,00. Rolling circle of epicycloid (see also the information in Notes).


  • Databackslash: Default is 0,00. Backlash, also called lash or play, is the distance between the teeths at a gear pair.
  • Databeta: With the helix angle β a helical gear is created (positive value → rotation direction right, negative value → rotation direction left).
  • Dataclearance: Default is 0,25 (see also the information in Notes).
  • Datadouble_helix: True creates a double helix gear (see also the information in Notes)
  • Dataheight: Value of the gear width.
  • Datamodule: Module is the ratio of the reference diameter of the gear divided by the number of teeth (see also the information in Notes).
  • Datanumpoints: Default is 15, change of the involute profile. Changing the value can lead to unexpected results.
  • Datateeth: Number of teeth.


The parameter descriptions of the View tab will be found in Property editor, further below at Example of the properties of a PartDesign object.


  • Cycloidal gears must always be specially matched to each other and can generally not be exchanged at will!
  • In a gear pair, both gears have the same values for inner_diameter and outer_diameter. See also the information in Properties cycloid parameter view below.
  • clearance: At a gear pair, clearance is the distance between the tooth tip of the first gear and the tooth root of the second gear.
  • double_helix: To use the double helical gearing the helix angle β (beta) for the helical gearing must first be entered.
  • module: Using ISO (International Organization for Standardization) guidelines, Module size is designated as the unit representing gear tooth-sizes. Module (m): m = 1 (p = 3.1416), m = 2 (p = 6.2832), m = 4 (p = 12.566). If you multiply Module by Pi, you can obtain Pitch (p). Pitch is the distance between corresponding points on adjacent teeth.


Limitation are not known yet.

Useful formulas

For more information see FCGear InvoluteGear.svg Involute gear.

Properties cycloid parameter view

CycloidGear inner-outer-diameter 2.svg