Add a Gear-Pair with an Orbiting center

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Add a Gear-Pair with an Orbiting center

B: Orbiting Center Gear-Pairs

Arrangement 1: Orbit a gear around the outside of a fixed-gear - External Mesh.

Arrangement 2: Orbit gear around the inside of a fixed-gear - Internal Mesh.

Preparation for Orbiting Gear-Pair


1.Edit a kinematically-defined PartRed-14-3

2.Add a LineRed-14-1b

3.Close the Part-Editor

4.Add two Parts Red-14-3Red-14-2

5.Join PartRed-14-3 to LineRed-14-1b with a Pin-JointRed-14-5

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-14-4

Note: The CAD-LineRed-14-4 along the center of a Part has a dimension.

Add Gear-Pair


Click Machine-elements toolbar > Add Gear-Pair


Add Gear-Pair opens in the Command-Manager.

Select these four(4) elements. Refer to the images above to identify the Elements.

1.Click the Green Line Red-14-1b

2.Click the Blue Line Red-14-7

3.Click the Green Line between the Gear centers Red-14-4

The Part-Editor opens automatically.

4.Click the Dimension of the Cad-Line that joins the Gear centers Red-14-7

Click OK-tiny-11-15 in the Command Manager to Add the Gear-Pair.


In the Command-Manager we use the terms:

Green Line for -usually - the CAD-Line in a kinematically-defined Part.

Blue Line for - usually - the CAD-Line in a free Part

After you add the Gear-Pair - the free Part becomes a kinematically-defined 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

The default Gear-Pair has:

an External Mesh form, equal number-of-teeth

a module that minimizes a change to the length of the Line that is the Line-of-centers.

Length of the Line-of-Centers

= Module × ( (Number-of-Teeth Gear 1 + Number-of-Teeth Gear 2) ÷ 2).


Edit the Number-of-Teeth and Module:

Gear 1 = 60

Gear 2 = 20

Module = 2

Length of Line-of-Centers

= Module × ((Number-of-Teeth Gear 1 + Number-of-Teeth Gear 2) / 2)

= 2 × ((60 + 20)÷2) = 80mm


Edit the Mesh - Orbiting Gear rotates inside the Stationary Gear.

Internal Mesh

When the Gears have a different number-of-teeth, it is possible to move the smaller gear to the inside of the larger gear.

Length of the Line-of-Centers with an Internal Mesh is:

= 2 × ((60 – 20)÷2) = 40mm