Add a Gear-Pair

We will add a Gear-Pair with an orbiting gear.

(See Tutorial 14 for more information on Gear-Pairs)

btn_delkeywordPreparation 2A: Add an Eccentric Gear-Pair


The Internal Gear will be fixed to the Base-Part. The External Gear will orbit the inside of it. The External Gear, that is inside the Internal Gear, has 1/3 the number-of-teeth.

STEP 1: Add a Rotating Part - see Tutorial 1 for a complete list of instruction. This is a Summary:
1.Add a Line to the Base-Part.
2.Add a Part to the Mechanism-Editor
3.Add a Pin-Joint between the Part and the Point at the left of the Line added to the Base-Part
4.Add a Motion-Dimension FB to identify the Part as a Rocker
5.Add a Linear-Motion FB
6.Connect the Linear-Motion FB to the Motion-Dimension FB


STEP 2: Add a Epicyclic Gear-Pair
1.Add a Part
2.Add Pin-Joint between the end-Point of the Rocker and the start-Point of the new Part

We are now ready to add a Gear-Pair




STEP 3: Add a Gear-Pair


1.Click Machine element toolbar > Add Gear-Pair

The four elements to add this Gear-Pair are:

Red-14-1b The Horizontal Line in the Green Base-Part

Red-14-2 The CAD-Line in the Blue Added-Part

Red-14-3 The CAD-Line in a Green Part that connects the Base-Part to the Added-Part

Red-14-4 The length dimension of the CAD-LineRed-14-3

Note: The Part-Editor will open automatically for you to select the length dimensionRed-14-4 of the Line.


To close the Command-Manager you can:

1.Right-click in the graphic-area (a shortcut)

- or -

2.Click OK-tiny-11-15  in the Command-Manager

MechDesigner draws the Gear-Pair with an

External mesh
Equal Number of Teeth (z1 & z2)
A typical module (m)

Note: for information only. Pitch Diameter (D)  = m.z1  and m.z2 (5.20=100mm) | Circular Pitch (Pc) = m. π = D.π  ∕  N

Use Edit menu> Application-Settings > Graphic tab > Display Colours  > Gear-Pair and change the colour to give a good contrast with Background colour.


STEP 4: Edit the Gear-Pair
1.Double-Click the Gear-Pair in the graphic-area (or see How to open a dialog-box)

The Gear-Pair dialog-box opens. Edit the Gear-Pair as follows:

Define tab : Gear Mesh and Teeth > Gear 1: 60 Teeth | Gear 2: 20 Teeth | Internal Mesh (radio-button)
Parameters tab > Gear Tooth Parameters > Module = 5
2.Click OK-tiny-11-15  to close the Gear-Pair dialog-box.
3.Cycle the model (ALT+C) to see that the Large Gear is stationary, and the Small Gear rolls around the inside of the Large Gear.


STEP 5: Edit the Part with the small gear with 20 teeth to add a new Line

We want the length of the new Line to equal the radius of the small Gear. The Pitch Diameter (D) = m × z1  and 5 × 20 =100mm

1.Part-Editor: Add Line : Drag to add a Line
2.Part-Editor: Geometric Constraint > Coincident Constraint | Click the start-Point of the Line and the start-Point of the CAD-Line
3.Part-Editor: Geometric Constraint> Add Equal | Click the new Line and the original CAD-Line
4.Part-Editor: Add Horizontal : click the new Line
5.Exit the Part-Editor


STEP 6: Add a Trace-Point to the end-Point of the new Line.
1.Click Kinematic-elements toolbar : Add Trace-Point
2.Click the end-PointRed-14-1b of the new Line
3.Click OK-tiny-11-15 in the Command-Manager
- or -

MechDesigner shows the Trace-Point.


If you cycle the machine (ALT+C as the Shortcut) you will see the Point at the end of the Line move along the Trace-Point.

Tutorials and Reference Help Files for MechDesigner and MotionDesigner 14.2 + © Machine, Cam, Mechanism, and Motion Design Software by PSMotion Ltd