Option 2: Orbiting Centre Gear-Pairs

Arrangement 1: Orbit a gear around the outside of a gear

Arrangement 2: Orbit gear around the inside of a gear.

Preparation for Option 2

Elements to select to add an Epicyclic Gear

STEP 1: Edit a kinematically-defined PartRed-14-3
STEP 2: Add a LineRed-14-1b
STEP 3: Close the Part-Editor
STEP 4: Add two Parts Red-14-3Red-14-2
STEP 5: Join PartRed-14-3 to LineRed-14-1b with a Pin-JointRed-14-5
STEP 6: Join the PartRed-14-2 to the other end of PartRed-14-3 with a Pin-JointRed-14-6

In this configuration, you MUST use the Points that are at the end of the CAD-Lines in the Parts.

STEP 7: Add a Motion-Dimension FB between the LineRed-14-1b and the CAD-LineRed-14-3

Note: The CAD-LineRed-14-3 along the centre of a Part has a dimension.

Use Add Gear-Pair


Click Machine-elements toolbar > Add Gear-Pair


Add Gear-Pair opens in the Command-Manager.

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

1.The Green Line on Gear Part 1 Red-14-1b
2.The Blue Line' on Gear Part 2 Red-14-2
3.The Green Line between the Gear centres Red-14-3
4.The Dimension of the Cad-Line that joins the Gear centres Red-14-7

In the Command-Manager we use the terms:

Green Line is usually the CAD-Line in a kinematically-defined Part.
Blue Line is usually the CAD-Line in Free Part

Video - Add Orbiting Gear-Pair


Tutorial 14:

Add Gear-Pair - Orbiting


Edit Number-of-Teeth, Module and Mesh


Default Gear-Pair: Orbiting Gear rotates around the outside of a Sun Gear

In the default, the two Gears have:

an external tooth form.
the same number-of-teeth
module that will minimize a change of length to the Line-of-centres.

The module and the number-of-teeth on each Gear give the length of the Line-of-centresRed-14-3.


Edit the Number-of-Teeth and Module

Gear 1 = 60 Red-14-1b
Gear 2 = 20 Red-14-2
Module = 2

Gear Diameter = Module * number-of-teeth

Length of Line-of-centres = Module * ((Number-of-Teeth Gear 1 + Number-of-Teeth Gear 2) / 2).

= 2 * ((60 + 20)/2) = 80mm


Make the Orbiting Gear rotate around the inside of a Ring Gear

When the Gears have a different number-of-teeth, it is possible to make one of the gears internal.

Gear 2 moves inside Gear 1.

Length of the Line-of-centres is now:

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

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