﻿ MechDesigner Reference & User Interface > 2.2 Mechanism-Editor: > Kinematic elements > Add Ball-Joint

You must do Add Ball-Joint two(2) times, to add a Ball-Joint to each end of one Part. The Part with a Ball-Joint at each end has the derived name of Connecting-Part.

One Ball-Joint joins the Connecting-Part to a Part in the active Mechanism-Editor.

And one Ball-Joint joins the connecting Part to a Part in a different Mechanism-Editor.

Terminology:

 Ball-Joint : A Ball-Joint makes a Point in one Part to be coincident with a Point in a different Part. Connecting Part : A Part with a Ball-Joint at its start-Point and at its end-Point Completely-Free Part : A Part with 3 degrees-of-freedom Free Part : A Part with 1 degree-of-freedom

#### Preparation

A typical preparation:

Mechanism-Editor A

 Usually, it is perpendicular(⊥) to the active Mechanism-Editor (b) •Part in a kinematically-defined Chain(in GREY)

Mechanism-Editor B - the active Mechanism-Editor

 •two(2) Parts that are not kinematically-defined A typical arrangement has: •Part : a Free-Part that is a Sliding-Part (with a Slide-Joint) or, a Rotating-Part (with a Pin-Joint) •Part : a Completely Free Part (no joints)

Notes:

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

The Completely-Free Part joins to Part and Part to give the two(2) S joints in the S-S-R or S-S-P dyad. S is for Spherical-Joint

Try to estimate the length of the Completely-Free Part.

If the Completely Free Part is too short or too long, so that the Ball-Joints at each end cannot possible join with Part and Part, you will not get the expected result.

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

 1.Make Mechanism-Editor B active. 2.Click Point in the Completely-Free Part 3.Click Point in the Free Part If you cannot select the two(2) Points to add a Ball-Joint: 1.Toggle-Off the Auto-Update tool before you select Point and Point

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

However, the Points do not snap together.

They do snap together after you do Add Ball-Joint #2

 1.Click Point at the other end of the Completely-Free Part 2.Click Point - the Grey Point - in the kinematically-defined Part that is in Mechanism-Editor(A)

Result - expected

 The Ball-Joints snap to the Points in Mechanism(A) and (B). The Completely-Free Part and the Free Part are kinematically-defined

Note: If the arrangement of the two Connecting-Part and the Part that was the Free-Part is not correct, then see Change-Dyad Closure

Kinematics Tree

In the Kinematics-Tree,

The Ball-Joints are the S Joints in the R-S-S Dyad (also P-S-S Dyad)

The letter S represents a Spherical-Joint.

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

 Notes: •You cannot add Solids to Connecting-Parts. •To edit the the symbolic diameter of the Ball-Joint - Edit the Length of the Connecting-Part Edit the Connecting-Part in the Part-Editor: 1.Mechanism-Editor: Double-click the symbol for the Connecting-Part 2.Part-Editor: Edit the Length dimension of the Connecting-Part 3.Exit the Part-Editor Edit the Symbolic Radius of the Connecting-Part Edit the Connecting-Part in the Part-Editor: 1.Mechanism-Editor: Double-click the symbol for the Connecting-Part 2.Part-Editor: Add a Line or Circle 3.Part-Editor: Add a dimension to the Line or Circle 4.Exit the Part-Editor Notes: When you edit dimensions in a Part and 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, then do View | Front Plane. Use Visibility toolbar > Show Solids in Mechanisms