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FCGear_InvoluteRack.md

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  • GuiCommand: Name: FCGear InvoluteRack MenuLocation: Gear -> Involute Rack Workbenches: FCGear_Workbench Shortcut: None Version: v0.16 SeeAlso: FCGear_InvoluteGear

FCGear InvoluteRack

Description

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

Usage

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

Properties

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

Data

{{Properties_Title|base}}

  • add_endings|Bool: If {{True}} (default), then the total length of the rack is teeth * pitch. If {{False}}, then the rack starts with a tooth-flank.

  • height|Length: Default is {{Value|5 mm}}. Value of the gear width.

  • module|Length: Default is {{Value|1 mm}}. Module is the ratio of the reference diameter of the gear divided by the number of teeth (see Notes).

  • teeth|Integer: Default is {{Value|15}}. Number of teeth.

  • thickness|Length: Default is {{Value|5}}. Height from the tooth root to the lower side of the rod.

{{Properties_Title|computed}}

  • transverse_pitch|Length: (read-only) Pitch in the transverse plane (see Notes).

{{Properties_Title|fillets}}

  • head_fillet|Float: Default is {{Value|0 mm}}.

  • root_fillet|Float: Default is {{Value|0 mm}}.

{{Properties_Title|helical}}

  • beta|Angle: Default is {{Value|0 °}}. With the helix angle β a helical gear is created -- positive value → rotation direction right, negative value → rotation direction left.

  • double_helix|Bool: Default is {{False}}, {{True}} creates a double helix gear (see Notes).

  • properties_from_tool|Bool: Default is {{False}}. If {{True}} and beta is not zero, gear parameters are recomputed internally for the rotated gear.

{{Properties_Title|involute}}

  • pressure_angle|Angle: Default is {{Value|20 °}} (see Notes).

{{Properties_Title|precision}}

  • simplified|Bool: Default is {{False}}, {{True}} generates a simplified display (without teeth).

{{Properties_Title|tolerance}}

  • clearance|Float: Default is {{Value|0.25}} (see Notes).

  • head|Float: Default is {{Value|0}}. This value is used to change the tooth height.

{{Properties_Title|version}}

  • version|String:

Notes

  • 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.

Useful formulas

See FCGear InvoluteGear.

Scripting

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")

⏵ documentation index > Addons > FCGear > [External Command Reference](Category_External Command Reference.md) > FCGear InvoluteRack