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FCGear TimingGear

From FreeCAD Documentation

FCGear TimingGear

Menu location
Gear → Timing Gear
Workbenches
Gear
Default shortcut
None
Introduced in version
v0.16
See also
FCGear TimingGearT

Description[edit | edit source]

The FCGear TimingGear command creates a timing gear.

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.

Above: Timing gear

Usage[edit | edit source]

  1. Switch to the Gear Workbench.
  2. There are several ways to invoke the command:
    • Press the Timing Gear button in the toolbar.
    • Select the Gear → Timing Gear option from the menu.
  3. Change the gear parameter to the required conditions (see Properties).

Properties[edit | edit source]

See also: Property View.

An FCGear TimingGear object is derived from a Part Feature object and inherits all its properties. It also has the following additional properties:

Data[edit | edit source]

base

  • Dataheight (Length): Default is 5 mm. Value of the gear width.
  • Datanum_teeth (Integer): Default is 15. Number of teeth.
  • Datatype (Enumeration): Default is gt2. Type of timing gear – profile pitch for timing belts (see Notes).

computed

  • Datah (Length): (read-only) Radial height of teeth.
  • Dataoffset (Length): (read-only) X-Offset of second arc mid-point.
  • Datapitch (Length): (read-only) Pitch of gear.
  • Datar0 (Length): (read-only) Radius of first arc.
  • Datar1 (Length): (read-only) Radius of second arc.
  • Datars (Length): (read-only) Radius of third arc.
  • Datau (Length): (read-only) Radial difference between pitch … diameter and head of gear.

version

  • Dataversion (String):

Notes[edit | edit source]

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

Useful formulas[edit | edit source]

Symbol Term Formula
p Pitch p=πm
d Pitch Diameter d=zm
da Addendum Diameter da=d+2m
For given pitch diameters (d):
l Belt Length l=2a+π(d1+d2)2+(d1d2)24a
a Axle Base a=l4π8(d1+d2)+(l4π8(d1+d2))218(d1d2)2
For given pitch (p) and numbers of teeth (z):
l Belt Length l=2a+p2(z1+z2)+p2π2(z1z2)24a
a Axle Base a=l4p8(z1+z2)+14(lp2(z1+z2))22p2π2(z1z2)2

Scripting[edit | edit source]

Use the power of Python to automate your gear modeling:

import FreeCAD as App
import FreeCADGui as Gui
import freecad.gears.commands
gear = freecad.gears.commands.CreateTimingGear.create()
gear.num_teeth = 12
gear.height = 5
gear.type = "gt5"
App.ActiveDocument.recompute()
Gui.SendMsgToActiveView("ViewFit")