Tutorial 2A: Four-Part kinematic-chains

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Tutorial 2A: Four-Part kinematic-chains

Four-bar Kinematic-Chains

Four-Part Kinematic-chains - which you may call a four-bar mechanism, four-bar linkage, or even four-bar -

They are the basis of the most frequently used mechanism in packaging machines.

This tutorial uses Pin-Joint and Slide-Joint elements. We combine the joints in different ways to configure the mechanism in different ways.

Objective of this Tutorial

To build kinematic-chains that have a total of four Parts and four Joints.

To learn about Dyads.


Try to add Parts that are approximately equal in length to the Parts that are in the tutorial images. If necessary, edit the length of a Part - see Step 1.7: Edit the Length of the Crank.

Terminology: Reminder from Tutorial 1

Plane :

the flat surface to which we add a new Mechanism-Editor. The Front-View of each Mechanism-Editor is perpendicular to its XY-Plane - NOT relative to the Global XYZ axes

Mechanism-Editor :

the workspace that includes the Mechanism-Plane , the graphic-area, the contextual -toolbars, and the Mechanism-Editor name-tab.

Part :

an element that becomes the moving, or fixed, rigid-bodies in the machine.

Part-Outline :

the symbol for a Part. We click the Part-Outline to  select the Part.

Joint :

general term for an element that constrains the relative movement between two Parts.

Pin-Joint :

a joint that constrains two Points to move together, with one Point in two different Parts.

Kinematic-Chain :

two or more Parts joined together with one or more Joints.

Kinematically-Defined :

Part or Kinematic-Chain that moves in a manner as specified by at least one Motion-Part. Parts that are kinematically-defined have Green Part-Outlines.

When a Part has a:

Green Part-Outline: the Part is a kinematically-defined Part. We also call it a Solved Part.

Blue Part-Outline: the Part is not a kinematically-defined Part. We also call it an Unsolved Part

Our target is to make all Part-Outlines Green, ALWAYS.

Motion-Part :

a Part, that is kinematically-defined, whose motion is precisely specified with a Motion-Dimension FB

Function-Block :

a tool to plan motions for Motion-Parts. It provides motion-values at its output-connector.

Motion-Dimension FB :

a Function-Block(FB) that identifies a Motion-Part.

Linear-Motion FB :

a Function-Block(FB) whose output follows the Master-Machine-Angle. The default output increases from 0 to 360 as the MMA increases from 0 to 360. You can edit the starting value, to be different to the MMA.

Gearing FB :

a Function-Block(FB) with which you can apply parameters to the motion-values at its input, in the form of a linear equation, to give different motion-values at its output.

Master-Machine-Angle :

the clock that, when you cycle the machine, moves at a constant rate from 0 to 360, again and again.

The position of each kinematically-defined Part is a function of Master-Machine-Angle.

Rocker :

a Motion-Part that rotates with a specific motion relative to a different Part.

Crank :

a Motion-Part that rotates continuously with a uniform rotary motion.

Terminology: Tutorial 2

Slide-Joint :

a Kinematic-Joint that constrains Line is one Part to be collinear with a Line in a different Parts.

Slider :

a Motion-Part that slides with a specific motion relative to a different Part. It may index progressively, slide continuously (as a 'conveyor'), or reciprocate back-and-forth.

Dyad :

a Dyad is a kinematic construction of:

2 Parts, and

3 Joints

Dyad Closure :

a different way to assemble the same Dyad.

Motion FB :

a Function-Block(FB) that is a link to a Motion in MotionDesigner

Crank-Rocker :

a kinematic-chain with one Motion-Part (the Crank) and one Dyad that has three Pin-Joints, and the output oscillates (rocks) back-and-forth.

Crank-Slider :

a kinematic-chain with one Motion-Part (the Crank) and one Dyad that has two Pin-Joints and one Slide-Joint, and the output reciprocates (slides) back and forth.

GST-Icon-AddMechanismEdit Kinematic-Chains

Step 2.1: A Crank-Rocker

Step 2.1A- The Concept of Dyads

Step 2.2: Add a Motion FB

Step 2.3: A Crank-Slider

Step 2.4: Change the Closure of the R-R-P Dyad

Step 2.5: A Slider-Crank

Step 2.6: A Scotch-Yoke

Step 2.7: Assemble your own Whitworth Quick Return Mechanism

Step 2.8: How to Model Pin-in-Slot Mechanisms

Step 2.9: How to Model a Pin in a Curved Slot