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

# Before and After: Graphic-Area & Kinematics-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

 •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.

 •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.

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

Kinematics-Tree

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

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