Add a Gear-Pair with Fixed-Centres

2.	Part-Editor : Geometry toolbar > Add Line | Drag to add the Line

3.	Part-Editor: Geometry toolbar > Add Dimension | Add the dimension to the Line.

The exact length of the Line is not important.

1.	Mechanism-Editor: Kinematic-elements toolbar > Add Part | Drag to add a Part

2.	Mechanism-Editor: Kinematic-elements toolbar > Add Pin-Joint | Join the CAD-Line of Part with Pin-Joint to the end of Line

Part must be a kinematically-defined. It is not important how it becomes kinematically defined. To add a Motion-Dimension FB is one example.

a.

Pin-Joint

b.	Line (STEP 1)

c.	CAD-Line in Part (STEP2)

1.	Mechanism-Editor: Kinematic-elements toolbar > Add Part | Drag to add a Part

2.	Mechanism-Editor: Kinematic-elements toolbar > Add Pin-Joint | Join the CAD-Line in Part with Pin-Joint to the other end of Line

Click Machine-elements toolbar > Add Gear-Pair

The Command-Manager has four selection-boxes.

Select the elements in the graphic-area (see images above to identify the four elements) :

1.	Green Line (in Part )

2.	Blue Line (in Part )

3.	Green Line that joins Gear Centres: Line will be the 'Line-of-centres'.

4.	Centre Distance Dimension: Length Dimension of Line

Click to complete the command

MechDesigner adds the Gear-Pair.

In the default case: it has an External Mesh, and the two gears have the same number-of-teeth.

The default Gear-Pair parameters

•	Number-of-Teeth - Teeth on Driving Gear = Teeth on Driven Gear

The Length-dimension of Line is now driven by the Number of Teeth and Module parameters. You cannot edit its dimension in the Part-Editor.

Open the Gear-Pair dialog-box to edit the Gear-Pair parameters. E.g: double-click a gear, or see How to open a dialog-box.

Mesh: External

Gear Pair dialog-box > Define tab > Gear Mesh & Number-of-Teeth > Mesh : External

•	Number of Teeth, z1 (Driving-Gear) : 60

•	Number of Teeth, z2 (Driven Gear) : 20

Gear Pair dialog-box > Parameters tab > Gear Tooth Parameters: >

Length of Line (External Mesh)= 2(module) × (60(# Teeth ) + 20(# Teeth)) / 2) = 80mm

Mesh: Internal.

Gear Pair dialog-box > Define tab > Gear Mesh & Number-of-Teeth > > Mesh : Internal

The Gear with fewer teeth moves inside the other Gear. An internal mesh is not possible when the Gears have equal number-of-teeth.

When the Gears have an internal mesh, we subtract the number of teeth to find the length of the Line of Centres.

Length of Line (Internal Mesh)= 2(module) × (60(# Teeth ) - 20(# Teeth)) / 2) = 40mm