Getting Started Tutorials - MechDesigner > Tutorial 14: Gear-Pairs / Rack-Pinions > B: Orbiting Gear Centers

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.

Epicyclic Gear-Pair - Prepare

Three Lines in three Parts

STEP 1: Three Lines in Three Parts

1.Edit a kinematically-defined Part (usually the Base-Part) with the Part-Editor.

2.Add a Line ; and add Constraints and Dimensions, as needed.

3.Close the Part-Editor

4.Add two Parts

5.Join the start-Point of Line in Part to the start-Point of Line with a Pin-Joint

6.Join the start-Point of Line in Part to the end-Point of Line in Part with a Pin-Joint

All Lines and or CAD-Lines

Dimension to Line for Gear-Centers

STEP 1: Add a Dimension

Edit Part in the Part-Editor

You can see that there is a Dimension along the CAD-Line - Line - in Part

Exit the Part-Editor

Model is prepared for Epicyclic Gears

STEP 3: Add a Motion-Dimension FB other FBs

1.Kinematic FB toolbar > Add a Motion-Dimension FB

Click Pin-Joint

Click Line

2.Click in the Command-Manager.

3.Kinematic FB toolbar > Add a Motion-Dimension FB

Add Gear-Pair

Command-Manager for Add Gear-Pair

STEP 1: Start the Add Gear-Pair command

1.Expand the Machine-elements toolbar

2.Click Add Gear-Pair

The Command-Manager has four selection-boxes.

STEP 2: Select the four elements

See images above for element numbers

1.Green Line on Gear 1: Line - it is in a Part that is kinematically-defined

2.Blue Line on Gear 2: Line in Part that is NOT kinematically-defined

3.Green Line Joining Gears: Line in Part that is kinematically-defined - that will join to the Gear centers

The Part-Editor opens to edit Part

4.Center Distance Dimension: Length Dimension of Line

STEP 3: Complete the command

1.Click to complete the command

Epicyclic-Gears

The default Gear-Pair has an External Mesh, and the gears have equal number-of-teeth.

In the Command-Manager we use the terms:

Green Line for a Line in a Part that is kinematically-defined.

Blue Line for a Line in a Part that is NOT kinematically-defined.

Videos

Video - Prepare for Epicyclic Gear-Pair

Video - Add Epicyclic Gear-Pair

Edit Epicyclic Gear-Pair

Edit Number-of-Teeth, Module and Mesh

GST-T14-B1-A

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

The default Gear-Pair has:

•an External Mesh form, and the number-of-teeth on each gear are equal.

•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).

GST-T14-B1-B

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

GST-T14-B1-C

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

Gear-Pair with an Orbiting Center