Getting Started Tutorials - MechDesigner > Tutorial 14: Gear-Pairs / Rack-Pinions > Before and After: Graphic-Area & Kinematic-Tree

Before and After: Graphic-Area and Kinematics-Tree

Summary

Add Gear-Pair removes one degree-of-freedom from a rotating-Part.

Before you do Add Gear-Pair

•A rotating Green Part

•A freely, rotating Blue Part

•A Green Line that joins, with Pin-Joints at its start-Point and its end-Point, the Green Part and the Blue Part

After you do Add Gear-Pair

•One Green Part that is the Driving Gear

•One Green Part that is the Driven Gear - this is the Geared-Rocker in the Kinematics-Tree.

•One Green Part that joins the two Gears.

Before and after Add Gear-Pair - Details

Basic Preparation for Add Gear-Pair

Before Add Gear-Pair.

•Three (3) Parts:

otwo(2) (moving or stationary) kinematically-defined Parts (Green Part-Outline)

oone(1) Part is not kinematically-defined (Blue Part-Outline).

•Three(3) Lines: a Line in each Part

•Two(2) Pin-Joints: one Pin-Joint at the each end of Line to join its start-Point and end-Point to two Lines

•One(1) dimension: Line must have a dimension to specify its length. Use the Part-Editor to add a dimension to specify its length.

GST-T14-0-B

After Add Gear-Pair

•Part becomes a kinematically-defined Part ( its Part-Outline changes from Blue to Green)

•Part is the Geared-Rocker in the Kinematics-Tree.

•The motion of Part is defined by the motion of Part and the gear-parameters that you define with the Gear-Pair dialog

•The Pin-Joints are the rotational-centers of the gears.

•Line joins the two gear centers and is called the Line-of-centers.

Notes

Part may be stationary, or move relative to the Base-Part.

Lines can be CAD-Lines

Kinematics Trees: GEARED-ROCKER- before and after Add Gear-Pair

Kinematics-Tree
BEFORE Add Gear-Pair

Kinematics-Tree before Add Gear-Pair

The Kinematic-Chain has two assemblies

Solved : Rocker

•Any rotating-Part that is kinematically-defined before you do Add Gear-Pair.

It is important to know that this Part may be moving or stationary, a Motion-Part, or

Unsolved

•A Part that is NOT kinematically-defined before Add Gear-Pair.

•A Pin-Joint.

Kinematics-Tree
AFTER Add Gear-Pair

Kinematics-Tree after Add Gear-Pair

The Kinematic-Chain now has two Solved Kinematic-Sub-Assemblies:

Rocker - a kinematically-defined rotating-Part .

•Any rotating-Part that is kinematically-defined before you do Add Gear-Pair.

Geared-Rocker - a kinematically defined rotating-Part.

•Pin-Joint

•Part

•Gear-Pair element

The motion of a GEARED-ROCKER is a defined by the motion of Rocker and parameters defined in the Gear-Pair dialog.

Basic Gear-Pair Arrangements

Use Add Gear-Pair for different gear arrangements.

A)Two gears, with fixed centers

B)One gear orbits around a gear with a fixed center.

Use the same command for each gear arrangement.

Gear-Mesh: Videos Examples

We can use the Gear-Pair dialog to get these different gear-arrangements.

Gear-Pair: Fixed centers

Mesh: External		Mesh: Internal
Step Down: # Teeth Gear 1 < Gear 2	Step Up: # Teeth Gear 1 > Gear 2	Step Up: # Teeth Gear 1 > Gear2	Step Down: # Teeth Gear 1 < Gear2

Click to play each video

Gear-Pairs: Orbiting centers

Mesh: External		Mesh: Internal
# Teeth: Gear 1 < Gear 2	# Teeth: Gear 1 > Gear 2	# Teeth: Gear 1 > Gear2	# Teeth: Gear 1 < Gear2
			Fixed Gear is smaller and internal to Orbiting Gear

Before and After: Graphic-Area & Kinematics-Tree