Mechanism | Add Ball-Joint

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Mechanism | Add Ball-Joint

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)

See also: Ball-Joint dialog-box, Connecting Part Length and Diameter.

See also Ball-Joint configurations

Add Ball-Joint

Add Ball-Joint icon

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:
MD-GA-AddBallJoint-Prep1

Mechanism-Editor A

Usually, it is perpendicular(⊥) to the active Mechanism-Editor (b)

•Part Red-14-3 in a kinematically-defined Chain(in GREY)

Mechanism-Editor B - the active Mechanism-Editor

•two(2) PartsRed-14-4Red-14-5 that are not kinematically-defined

A typical arrangement has:

•Part Red-14-4 : a Free-Part that is a Sliding-Part (with a Slide-Joint) or, a Rotating-Part (with a Pin-Joint)

•Part Red-14-5 : 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 Red-14-4 and Part Red-14-3 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 PartRed-14-4 and PartRed-14-3, 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.

MD-GA-AddBallJoint-Prep2

STEP 1: Add Ball-Joint #1

1.Make Mechanism-Editor B active.

2.Click PointRed-14-1b in the Completely-Free Part

3.Click PointRed-14-2 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 PointRed-14-1b and PointRed-14-2

MD-GA-AddBallJoint-Prep3

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

However, the PointsRed-14-1bRed-14-2 do not snap together.

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

 
MD-GA-AddBallJoint-Prep4

STEP 2: Add Ball-Joint #2

1.Click PointRed-14-3 at the other end of the Completely-Free Part

2.Click PointRed-14-4 - the Grey Point - in the kinematically-defined Part that is in Mechanism-Editor(A)

 
MD-GA-AddBallJoint-Prep5

Result - expected

The Ball-JointsRed-14-6Red-14-7 snap to the Points in Mechanism(A) and (B).

The Completely-Free Part and the Free Part are kinematically-definedRed-14-8

 
MD-KT-AddBallJoint

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-JointsRed-14-6Red-14-7 are the S Joints in the S-S-R and the S-S-P Dyad.

A Connecting PartRed-14-5 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 - see Ball-Joint dialog-box
MD-GA-BallJoint-EditConnectingPart

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.
MD-GA-BallJoint-EditConnectingPart-Dim

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

See Ball-Joint dialog-box.

 
MD-GA-BallJoint-EditConnectingPart-Show