Geared-Rocker Part

A Geared-Rocker Part is a kinematically-defined Part.

MechDesigner derives the motion for the Geared-Rocker Part from the:

1.Motion of the DriveR-Part, relative to the Line-of-Centres between the two Gears

The Input Gear is a kinematically-defined Part and also a Rotating-Part.

2.The number-of-teeth on each Gear
3.Mesh of the Gear-Pair: Internal or External Mesh.

You must define the number-of-gear teeth and mesh in the Gear-Pair dialog-box.

tog_minus        Geared-Rocker: Degrees-of-Freedom and Mobility

Gruebler Equation:

F = 3*(N-1) – 2*L- H

F = 3 * (2-1) – 2*1 – 1

F = 3 – 2  –1

F= 0

Degrees-of-Freedom = 0

Parts

N = 2.

There are two parts: the Part we wish to specify as a Geared-Rocker and the kinematically-defined Part to which it is joined.

Lower Pairs (Joints)

L = 1

There is one Pin-Joint.

Higher Pairs (Cams or Gears)

H = 1

There is one Gear-Pair

Therefore, a Gear-Pair and Geared-Rocker does not change the degrees-of-freedom of a kinematic-chain.

It also means you can add as many Gear-Pairs as you want to a kinematic-chain. The number of Degrees-of-Freedom does not change.

tog_minus        The Geared-Rocker in the Kinematics Tree

Geared Rocker in the Kinematics-Tree

A Geared-Rocker is constructed with a:

Part

Part – see Add Part

Dowel

Pin-Joint – see Add Pin-Joint

GearPair

Gear-Pair – see Add Gear-Pair

tog_minus        Preparation of elements before you can add a Gear-Pair

Simple Gear-Pair Preparation

KinChain-GearPairPre1

STEP 1: Add a Rocker:

The Part does not need to be a Rocker.

There must be three elements: Two kinematically-defined Parts, with a Line1s-red2s sketch-element in each, joined with a Pin-Joint3s.

A Rocker joined to a Line in the Base-Part is an example.

Step 1 is complete and the condition is satisfied.

KinChain-GearPairPre2

STEP 2: If necessary, start the Part-Editor to edit the Line and add a dimension4s to the length of the Line

Step 2 is complete

STEP 3: Close the Part-Editor

KinChain-GearPair3

STEP 4: Add a Part5s
STEP 5: Join it with a Pin-Joint6s to the other end of the Line.

Step 5 is complete

It has a Blue Part-Outline.

Now you can use Add Gear-Pair. The Blue Part becomes the Geared-Rocker.

Epicyclic Gear-Pair Preparation

KinChain-GearPairPre1

STEP 1: Join two Points with a Pin-Joint3s, with the Points at the ends of two Lines in kinematically-defined Parts1s-red2s

Each Line sketch-element must be a child to the Parts that are kinematically-defined.

Simple example: a Rocker joined to a Line in the Base-Part.

Step 1 is complete and the condition is satisfied.

KinChain-GearPairPre4

STEP 2: Edit the Line to add a dimension4s to the length of the Line

The CAD-Line in the Rocker has a dimension4s. Therefore, you do not need to add or edit the dimension.

STEP 3: Close the Part-Editor

KinChain-GearPairPre5

STEP 4: Add a Part5s
STEP 5: Join it with a Pin-Joint6s to the other end of the Line.

Step 5 is complete

It has a Blue Part-Outline.

Now you can use Add Gear-Pair. The Blue Part becomes the Geared-Rocker.

Tutorial and Reference Help Files for MechDesigner and MotionDesigner 13.2 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd