How to add a 'Fixed Gear-Pair...



STEP 1: Use the Part-Editor to edit a kinematically-defined Part - for example the Base-Part3s
STEP 2: Add a Line
STEP 3: Add a dimension7s to the Line. The exact length of the Line is not important.
STEP 4: Close the Part-Editor
STEP 5: Add two Parts1s-red2s
STEP 6: Join the Parts with Pin-Joints5s6s to the Line3s

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

Use the Points that are at the end of Line3s and the Points that are at the end of Lines in Parts1s-red2s.

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 Line3s and the CAD-Line in Part1s-red

Part1s-red may also be a child to a Dyad, or be Geared Rocker.

Connect wires from other FBs to the Motion-Dimension FB to move Part1s-red.


Add Gear-Pair


STEP 8: Click Machine-elements toolbar > Add Gear-Pair


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'1s-red on Gear Part : Part 1 for Gear 1
2.'Blue Line'2s on Gear Part 2: Part for Gear 2
3.'Green Line'3s that joins Gear Centres: Line will be the 'Line-of-centres'.
4.Centre Distance Dimension7s: 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.

In the Command-Manager we use the terms:

'Green Line', which relates to a Line in a kinematically-defined Part
'Blue Line', which relates to a Line in the Part that is not kinematically-defined

The 'Green Line' and the 'Blue Line' are often CAD-Lines. All Parts become kinematically-defined after you add the Gear-Pair.

Video - Add Standard Gear-Pair


Tutorial 14:

Add Gear-Pair - Standard


Basic Settings: Number-of-Teeth, Module and Mesh


The default Gear-Pair has an:

External tooth form
Equal Number-of-Teeth
Module that does not change the length you give to the Line-of-Centres3s 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 1s-red;
Gear 2 = 2o teeth 2s;
Module = 2

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

Tutorial and Reference Help Files for MechDesigner and MotionDesigner 13.2 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd