Add a Gear-Pair with Fixed Centres

STEP 1:

Use the Part-Editor to edit a kinematically-defined Part - for example the Base-Part

STEP 3:

Add a dimension to the Line. The exact length of the Line is not important.

STEP 5:

Add two Parts

STEP 6:

Join the Parts with Pin-Joints to the Line

Important Gear-Pair Rule for Pin-Joints and Points on Lines.

Use the Points that are at the end of Line and the Points that are at the end of Lines in Parts.

In this example, because there is only one Line in each Added-Part, we must use the Points at the ends of the CAD-Lines.

STEP 7:

Add a Motion-Dimension FB between Line and the CAD-Line in Part

Part may also be a child to a Dyad, or be Geared Rocker.

Connect wires from other FBs to the Motion-Dimension FB to move Part.

When you do Machine Elements toolbar > Add Gear-Pair, the Command-Manager shows four selection-boxes.

Select these four elements. [Refer to the images above to identify the Elements].

1.	'Green Line' on Gear Part : Part 1 for Gear 1

2.	'Blue Line' on Gear Part 2: Part for Gear 2

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

4.	Centre Distance Dimension: Length Dimension

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

The default Gear-Pair has an:

•	Module that does not change the length you give to the Line-of-Centres much

The Module and the Number-of-Teeth parameters define the length of the Line-of-Centres.

Gear Diameter = Module × Number-of-Teeth

Double-click the edit the Gear-Pair with the Gear-Pair dialog-box.

Edit the Number-of-Teeth and Module parameters.

•	Gear 1 = 60 teeth ;

•	Gear 2 = 2o teeth ;

Length of Line-of-centres = Module × (number-of-teeth Gear 1 + Number-of-Teeth Gear 2) / 2

= 2[module] × ( (60[Gear1 teeth] + 20[Gear 2 teeth] ) / 2) = 80mm

Make Gear 1 'Internal'.

When the Gears have a different number-of-teeth, you can select the 'Internal' Radio button.

The Gear with fewer teeth moves inside the other Gear.

The Gear with more teeth has the Internal teeth form.

In this example:

Length of the Line-of-centres is:

= 2 * ((60 - 20)/2) = 40mm