You will edit the Crank-Slider to be an Offset Crank-Slider.

You will explore the Kinematics-Tree and the elements in the :

•Rocker (Motion-Part)

•R-R-P dyad

You will use the Kinematic elements toolbar > Change Dyad Closure command to see:

•4 × Closures with the R-R-P dyad

You will understand why and when:

•Dyad-closures can solve

•Dyad-closures cannot solve

Machine-Cycle :

The MMA changes by 360.

Motion-Part :

A Part whose position we control with a Motion-Dimension FB.

Rocker :

A Motion-Part whose angle we control with a Motion-Dimension FB.

Crank :

A Rocker whose angle changes with a uniform angular velocity.

Rotating-Part :

A Part that you join with a Pin-Joint to a different Part.

Sliding-Part :

A Part that you join with a Slide-Joint to a different Part.

Dyad :

A dyad is a kinematic construction of:

•2 Parts, and

•3 Joints

Dyad Closure :

A different way to assemble the two Parts in a dyad.

Crank-Slider Mechanism:

A kinematic-chain that has continuously-rotating Rocker (Crank) and a dyad that has two Pin-Joints and one Slide-Joint. The output is the sliding-Part that reciprocates back and forth.

Offset Crank-Slider Mechanism :

A Crank-Slider Mechanism in which the Pin-Joint (x-R-x) of the R-R-P dyad is offset from the Slide-Joint (x-x-P)

Unrestricted Dyad Closure :

The dyad can solve throughout the machine-cycle.

Restricted Dyad Closure :

The dyad cannot solve for a period within a machine-cycle.

Broken dyad :

The dyad cannot solve now at this machine-angle.

There are two videos. They show the dyad-closures when they are broken and not broken

As you look at these videos, identify the Motion-Part. The Motion-Part ALWAYS moves with the motion-values that are at the input-connector of the Motion-Dimension FB.

The videos show: Unrestricted and Restricted Dyad Closure and Invalid Closures of the R-R-P dyad.

Video 1: CRANK + R-R-P dyad - 4 VALID Closures

R-R-P dyad : 4 Valid Closures

Video 2: CRANK + R-R-P dyad - 2 VALID & 2 INVALID Closures

R-R-R dyad - 2 Valid Closures and 2 Invalid Closures

Expand the Kinematics-Tree

STEP 1: Edit the sliding-Part

The sliding-Part opens in the Part-Editor

STEP 2: Add  Geometry - a short Line

STEP 3: Add Constraints

You are now in the Part-Editor.

STEP 4: Delete the Pin-Joint

The two Parts are again not kinematically-defined, or not solved.

If you cannot click the Pin-Joint only, then, as described in detail in Step 2.3:

•use the Selection-Window to delete the Pin-Joint

or

•delete the Pin-Joint from the Assembly-Tree

STEP 5: Move the sliding-Part; Add the Pin-Joint again.

The R-R-P dyad is again complete.

The three Joints in the dyad are:

Revolute - Pin-Joint

Revolute - Pin-Joint

Prismatic - Slide-Joint

Now we use the term Offset Crank-Slider.

Is this the dyad-closure you want?

Save your Mechanism : CTRL+S

Four Valid Closures

In the image you can see:

1 x Arc with a center at the Pin-Joint (R-x-x)

2 x Lines that are parallel to the Slide-Joint (x-x-P)

In the image you can see that the Arc and Lines intersect in four places.

4 x indicate where the Arc and Lines intersect.

These are the positions of the Pin-Joint in the four dyad-closures.

Two Valid Closures and two Invalid Closures

In the image you can see

1 x Arc with a center at the Pin-Joint (R-x-x)

2 x Lines that are parallel to the Slide-Joint (x-x-P)

In the image you can see that the Arc intersects one of the Lines.

2 x indicate where the Arc and Line intersects.

These are the positions of the Pin-Joint in the two VALID dyad-closures.

STEP 1: Start the Change Dyad Closure command

The Command-Manager starts.

It has one selection-box.

You must select a Part from the dyad

STEP 2: Click a Part-Outline

STEP 3: Complete the Command a Part-Outline

STEP 4: Repeat the Commands

The images show the four different closures of the Offset R-R-P Closures.