FCGear TimingGear

From FreeCAD Documentation
Jump to navigation Jump to search
Other languages:
English • ‎français • ‎italiano

FCGear TimingGear.svg FCGear TimingGear

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


The purpose of timing gears is to allow the camshaft and crankshaft to turn the timing chain. The crankshaft turns to move pistons up and down inside the cylinders. The camshaft turns to allow intake and exhaust valves on the cylinders to open and close. These components are important for proper engine timing.

Timing gears are connected to a timing belt or timing chain.

Timing-Gear example.png

Above: Timing gear


  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.


  • Datah: Radial height of teeth (not changeable, is calculated automatically).
  • Dataoffset: X-Offset of second arc mid-point (not changeable, is calculated automatically).
  • Datapitch: Pitch of gear (not changeable, is calculated automatically).
  • Datar0: Radius of first arc (not changeable, is calculated automatically).
  • Datar1: Radius of second arc (not changeable, is calculated automatically).
  • Datars: Radius of third arc (not changeable, is calculated automatically).
  • Datau: Radial difference between pitch … diameter and head of gear (not changeable, is calculated automatically).


  • Dataheight: Default is 5,00 mm. Value of the gear width.
  • Datateeth: Default is 20. Number of teeth.
  • Datatype: Default is gt2. Type of timing gear – profile pitch for timing belts (see also the information in Notes).


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


  • type: The pitch of the timing belts (distance from tooth centre to tooth centre of consecutive teeth) is specified in types. GT2 has a pitch of 2 mm, GT3 of 3 mm, GT5 of 5 mm etc..


Limitation are not known yet.

Useful formulas

  • addendum diameter = pitch diameter + 2 * module
  • belt length = 2 * axle base + belt tooth pitch : 2 * (teeth 1 + 2) + belt tooth pitch² : 4 * pi² * axle base * (teeth 1 - 2)²
  • axle base = belt length : 4 - belt tooth pitch : 8 * (teeth 1+2) + ¼ * sqrt [belt length - ½ * belt tooth pitch * (teeth 1+2)² - 2 * belt tooth pitch² * (teeth 1+2)² : pi²]