FCGear InvoluteRack
|
|
| Menu location |
|---|
| Gear → Involute Rack |
| Workbenches |
| FCGear |
| Default shortcut |
| None |
| Introduced in version |
| v0.16 |
| See also |
| FCGear InvoluteGear |
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
- Switch to the
FCGear Workbench. - 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.
- Press the
- Change the gear parameter to the required conditions (see Properties → Data below).
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
base
- Dataadd_endings (
Bool): If True, then the total length of the rack is teeth * pitch, otherwise the rack starts with a tooth-flank. - Dataheight (
Length): Value of the gear width. - Datamodule (
Length): Module is the ratio of the reference diameter of the gear divided by the number of teeth (see also the information in Notes). - Datateeth (
Integer): Number of teeth. - Datathickness (
Length): Height from the tooth root to the lower side of the rod.
computed
- Datatransverse_pitch (
Length): (read-only) Pitch in the transverse plane (see also the information in Notes).
fillets
- Datahead_fillet (
Float): - Dataroot_fillet (
Float):
helical
- Databeta (
Angle): With the helix angle β a helical gear is created (positive value → rotation direction right, negative value → rotation direction left). - Datadouble_helix (
Bool): True creates a double helix gear (see also the information in Notes) - Dataproperties_from_tool (
Bool): If helix angle β is given and properties_from-tool is enabled, gear parameters are internally recomputed for the rotated gear.
involute
- Datapressure_angle (
Angle): Default is 20° (see also the information in Notes).
precision
- Datasimplified (
Bool): True generates a simplified display (without teeth).
tolerance
- Dataclearance (
Float): Default is 0,25 (see also the information in Notes). - Datahead (
Float): Default is 0,00. This value is used to change the tooth height.
version
- Dataversion (
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")