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

# Mechanism | Add Ball-Joint

#### What is a Ball-Joint?

A Ball-Joint makes a Point in one Part to be coincident with a Point in a different Part. The Parts con rotate about three orthogonal axes.

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

One of the two(2) Ball-Joints joins the Connecting-Part to a Part that is in the active Mechanism-Editor. The other Ball-Joint joins the connecting Part to a Part in a different Mechanism-Editor.

Terminology:

 Connecting Part : : a Part with a Ball-Joint at its start-Point and end-Point Completely-Free Part : : a Part with 3 degrees-of-freedom (0 Joints, on the Mechanism-Plane) Free Part : : a Part with 1 degree-of-freedom (1 Joint, on the Mechanism-Plane)

 Kinematic Elements Toolbar : Add Ball-Joint icon Menu : Add menu > Mechanism sub-menu > Add Ball-Joint Dialog-Box : Ball-Joint dialog-box You must know : How to add Mechanism-Editors to different Planes. The difference between a Free-Part and a Completely Free Part.

### 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.

### Add Ball-Joint (two(2) TIMES)

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

STEP 1: Add Ball-Joint #1

 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

STEP 2: 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

Notes:

You cannot add Solids to Connecting-Parts.

You can edit the:

The length of the Connecting-Part.

The symbolic diameter of the Connecting-Part between the Ball-Joints.

The symbolic diameter of the Ball-Joints.

In the Kinematics-Tree, each Ball-Joint is represented by the letter S, which is for Spherical-Joint.

The Ball-Joints are the S Joints in the S-S-R and the S-S-P Dyad.

A Connecting Part is a Part with two(2) Ball-Joints.

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

 1.Edit the Connecting-Part to edit its length and to add a dimension for the diameter of Rod. 2.Edit the Ball-Joint to edit the diameter of the ball-symbol. To edit the Ball-Diameter of the Ball-Joints - Edit the Length of the Connecting-Part and its symbolic diameter MechDesigner uses the first dimension you add to the Part in the Part-Editor as the symbolic radius for the Connecting-Part. To add and edit a Dimension, you must edit the Connecting-Part 1.Double-click the symbol for the Connecting-Part MechDesigner opens the Connecting-Part in the Part-Editor. 2.Add a Line or Circle 3.Add a dimension to the Line or Circle Note: 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 click View | Front Plane. 4.Edit the Dimension with the dimension tool 5.Edit the Length of the Connecting-Part to 100mm, in the usual way. 6.Close the Part-Editor Use Visibility toolbar > Show Solids in Mechanisms Edit the Length of the Connecting-Part and its symbolic diameter