MechDesigner Reference & User Interface > 2.2 Mechanism-Editor > Mechanisms > Kinematic elements

Ball-Joint

2x Ball-Joints in MechDesigner

Rod-End Bearing

2 x Ball-Joint in
SOLIDWORKS

Terminology:

Ball-Joint :	A Ball-Joint makes a Point in a Connecting-Part coincident with a Point in a different Part. You must add 2 x Ball-Joints to add a Ball-Joint to each end of a Connecting-Part : •1 x Ball-Joint between Points in different Parts that are in the active Mechanism-Editor •1 x Ball-Joint between Points in different Parts that are in different Mechanism-Editors
Spherical-Joint :	The kinematic and equivalent term for a Ball-Joint.
Kinematics-Tree :	Dyads R-S-S, P-S-S - the joints in a dyad use the letter S for a Ball-Joint.
Derived Names:
Connecting-Part :	A Part with a Ball-Joint at its start-Point and at its end-Point.
Part that is Completely-Free :	A Part with 3 degrees-of-freedom (no joints).
Part that is Free :	A Part with 1 or 2 degrees-of-freedom.

Preparation

A typical preparation:

A typical prerpation for Add Ball-Joint

Mechanism A

Usually, Mechanism A is perpendicular(⊥) to Mechanism B

•Part is kinematically-defined - in the image, Part is Pink

Mechanism B - the active Mechanism-Editor

Three Parts:

1 x Part is usually the Base-Part - it is kinematically-defined.

2 × Parts are not kinematically-defined.

•Part is a Part that is free. It has a Pin-Joint to join it to the Base-Part.

•Part is a Part that is Completely Free. It does not have any joints before you do Add Ball-Joint.

Notes:

The Mechanism-Editors cannot be parallel to each other. They are usually perpendicular(⊥) to each other.

As you add the Part that is Completely-Free, try to estimate its length. If it is too short or too long, the Ball-Joints cannot join the Completely Free Part to Part and Part - you do not get the expected result.

Add Ball-Joint × two(2)

Do Add Ball-Joint two(2) times. One time to each end of the Completely Free Part.

STEP 1: Start the Add Ball-Joint command

Mechanism menu > Add Ball-Joint

Kinematic elements toolbar > Add Ball-Joint

STEP 2: Add Ball-Joint #1

Mechanism-Editor B is active.

1.Click Point at the end of the Part that is Completely-Free

2.Click Point at the end of the Part that is Free.

If you cannot select the Points to add a Ball-Joint, disable the Auto-Update tool, and try again.

After you do Add Ball-Joint #1 you can see the Ball-Joint symbol.

However, Points do not snap together. You must do Add Ball-Joint #2.

STEP 3: Add Ball-Joint #2

1.Click Point at the other end of the Part that is Completely-Free

2.Click Point - the Pink Point - at the end of the Part that is kinematically-defined in Mechanism-Editor(A)

Result - Graphics-Area

The Ball-Joints snap to the Points in Mechanisms A and B.

The Parts that were Completely-Free and Free are now kinematically-defined Red-14-5

If the arrangement of the Parts that were Completely-Free and Free is not correct, then see Change-Dyad Closure

RESULT - Kinematics-Tree

In the Kinematics-Tree,

There is a new Dyad - the R-S-S dyad.

The three Joints in the Dyad are:

•Pin-Joint is the R joint - R is for Revolute-Joint

•Ball-Joints are the S Joints - S is for Spherical-Joint

Connecting-Part: Edit Length, Rod Diameter, Ball-Diameter

Notes:

•You cannot add Solids to Connecting-Parts.

To edit the Length of the Connecting-Part

1.Mechanism-Editor: Double-click the symbol for the Connecting-Part

It is now open in the Part-Editor.

2.Part-Editor: Edit the Length dimension of the Connecting-Part

3.Exit the Part-Editor

To edit the Symbolic Radius of the Connecting-Part

1.Mechanism-Editor: Double-click the symbol for the Connecting-Part

It is now open in the Part-Editor.

2.Part-Editor: Add a Line or Circle

3.Part-Editor: Add a dimension to the Line or Circle

4.Exit the Part-Editor

The dimension of the Line or Circle is the Radius of the Connecting-Part.

To edit the symbolic diameter of the Ball-Joint - see Ball-Joint dialog

Notes:

In the Part-Editor, when the view is not the Front View, the CAD-Line, Axes, sketch-elements and dimensions may show in unusual places! If you cannot add or edit a dimension: do View toolbar > Front Plane (F3)

To see the symbol of the Ball-Joint: enable Visibility toolbar > Show Solids in Mechanisms