Change Dyad Closure

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Change Dyad Closure

Change Dyad Closure / Change Configuration Assembly of a Dyad

Terminology

Dyad :

 

A dyad is an assembly of two Parts and three joints.

Each Joint can be a Slide-Joint, a Pin-Joint, or a Ball-Joint.

- One joint joins the two Parts together

- The other two joints join the two Parts to two other Parts that are kinematically-defined.

The two Parts in a dyad are kinematically-defined.

Assur Groups :

A different name for a dyad.

Dyad Closures :

The different ways you can assemble the two Parts of a dyad

“Configuration of the Dyad's Assembly” is a different way to express “Dyad Closure”.

Types of Dyad :

Planar Dyads: R-R-R, R-R-P, R-P-R*, R-P-P, P-R-P

Spatial Dyads: S-S-R, S-S-P

R :

Revolute Joint = Pin-Joint

P :

Prismatic Joint = Slide-Joint

S :

Spherical Joint = Ball-Joint

*

This dyad does not correctly change its closure if the Pin-Joint(R) are offset from the Slide-Joint and along the y-axis of each Part in the dyad.

See more: Dyads

Change Dyad Closure

RRR Dyad - Closure 1

RRR Dyad
Closure 1

Command-Manager: Change Dyad Closure

Command-Manager: Change Dyad Closure

RRR Dyad - Closure 2

RRR Dyad
Closure 2

STEP 1: Start the Change Dyad Closure command

Change Dyad Closure icon

1.Mechanism menu > Change Dyad Closure

OR

1.Kinematic elements toolbar > Change-Dyad Closure

The Command-Manager indicates you must select a Part in the Dyad.

STEP 2: Select one Part in the Dyad

2.Click the Part-Outline of a Part in the Dyad whose assembly-configuration (Dyad-Closure) you want to change.

STEP 3: Complete the Command

3.Click OK-tiny-11-15 in the Command-Manager

The configuration of the assembly (Dyad Closure) should now be different.

<<< compare the bottom image with the top image.

STEP 4: Do again, if needed

4.If necessary, do 1 to 3 again and again to find the configuration of the assembly you want to apply to your design.

Top-Tip:

When there are many dyads in the model, it is sometime difficult to see which dyad whose closure you need or want to change.

1.Kinematics-Tree: Click to expand each Kinematic-Chain in the Kinematics-Tree

2.Kinematics-Tree: Click each dyad

The color of the five elements in the dyad (2 Parts + 3 Joints) change to the Selected Color (usually red) in the graphics-area.

Assembly-Configurations of the R-R-P Dyad

The joints in the R-R-P Dyad are: Revolute – Revolute – Prismatic.

In MechDesigner, the joints are: Pin-Joint – Pin-Joint Slide-Joint.

There are 4 possible assembly configurations (Dyad Closures) for this dyad.

The image below shows an Offset-Slider-Crank mechanism.

4 x Assembly Configurations of an Offset-Crank-Slider

4 x Assembly Configurations of an Offset-Crank-Slider

PartRed-14-1b is the Crank - to illustrate the 4 dyad closures. The Crank is not in the Dyad.

Dyad: The Parts in the R-R-P dyad are Parts Red-14-2 and Red-14-3.

To imagine the four assembly-configurations, we imagine we have not yet added the Pin-Joint (R2) between PartRed-14-2 and PartRed-14-3.

PartRed-14-2 : can rotate around the Pin-Joint, R1, at the end of the Crank.

Therefore, Pin-Joint R2 can ONLY be on the red circle at the end of PartRed-14-2.

PartRed-14-3 : can only slide along the Slide-Joint, P1, along LineRed-14-4.

Important: The Point in PartRed-14-3 for Pin-Joint (R2) is offset from the Slide-Joint and not on the Slide-Joint.

Therefore, Pin-Joint R2 can ONLY be on one of the red lines that are offset from the Slide-Joint.

The red circle intersects the red lines at 4 places.

Therefore, the Pin-Joint R2 can be at 4 places.

Therefore, the Offset Slider-Crank and the R-R-P dyad has 4 possible assembly configurations (Dyad Closures).