|FCGear → Create an Involute rack|
|Introduced in version|
Gear racks are used to convert a rotary motion into a linear motion or vice versa. The following examples show the different applications:
- A rack with gear on at a retaining weir.
- Various rack systems of rack-and-pinion railways.
- Rack and pinion steering in a vehicle.
- Rack and pinion winch as mechanical hoist (e.g. car jack).
- Pneumatic rack and pinion drives used to control valves in pipeline transport.
From left to right: Spur gearing, helical gearing, double helical gearing
- Switch to the FCGear Workbench.
- Invoke the command several way:
- Press the Create an Involute rack button in the tool bar.
- Using the Gear Menu → Involute rack.
- 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.
- Datatransverse_pitch: Pitch in the transverse plane – not changeable, is calculated automatically (see also the information in Notes).
- Dataadd_endings: If True, than the total length of the rack is teeth * pitch, otherwise the rack starts with a tooth-flank.
- 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)
- Datahead: Default is 0,00. This value is used to change the tooth height.
- 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).
- Dataproperties_from_tool: If helix angle β is given and properties_from-tool is enabled, gear parameters are internally recomputed for the rotated gear.
- Datasimplified: True generates a simplified display (without teeth).
- Datateeth: Number of teeth
- Datathickness: Height from the tooth root to the lower side of the rod.
- Datapressure_parameter: Default is 20 (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.
- transverse_pitch: The value is the result of multiplication of module * pi. This means for the standard involute rack of FCGear: 15 (teeth) * 3,14 (transverse_pitch) is 47.12 mm. See also module further 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. The result of the multiplication is displayed in transverse_pitch
- pressure_parameter: Only change the parameter, if sufficient knowledge of the gear geometry is available.
For more information see Involute gear.
Use the power of python to automate your gear modeling:
import FreeCAD as App import freecad.gears.commands gear = freecad.gears.commands.CreateInvoluteRack.create() gear.teeth = 20 gear.beta = 20 gear.height = 10 gear.double_helix = True App.ActiveDocument.recompute() Gui.SendMsgToActiveView("ViewFit")