Kinematics of an PRP Dyad

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Kinematics of an PRP Dyad

PRP Dyad

Dyads do not change the number of Degrees-of-Freedom of a kinematic-chain. If the kinematic-chain has Green Part-Outlines before you add the Dyad, it should have Green Part-Outlines after


To show you how to add this Dyad, we have two design cases.

In Case 1, we join the two Parts in the Dyad to the Base-Part and the Rocker

In Case 2, we join the two Parts in the Dyad to the Base-Part and the Slider

There are two Slide-Joints and one Pin-Joint in the PRP Dyad, and two Parts.

I follow a consistent three-step procedure:

General Three-Step Procedure to add a Dyad

STEP 1: Add the two Parts

STEP 2: Add the two 'outer' Joints: Join each Part to two separate Kinematically Defined Parts

STEP 3: Add the 'inner' Joint: Join the two Parts together

Warning

Note: Occasionally, a Dyad does not operate correctly. The Pin-Joints 'break' when you cycle the machine, even though you cannot see why they break.

It is possible that MechDesigner has assembled the Dyad in a Closure where the Parts cannot reach the Joints - even though to you, they should assemble. To correct the problem, you may need to change the Dyad closure until the assembly operates as you expect it to.

CASE 1:
Rocker and Base-Part

CASE 2:
Slider and Base-Part

Examples

 

'Expand' then 'Play'

 

 

'Expand' then 'Play'

 

Videos

PRPRocker1

PRPSlider1

Preparation:

Two Kinematically Defined Parts:

Case 1: Part 1:Base-Part, Part 2:Rocker

Case 2: Part 1:Base-Part, Part 2:Slider

Note:  LineRed-14-1b added to the Slider. The Slide-Joint of the Dyad cannot be parallel to the Slide-Joint for the Slider.

PRPRocker2

PRPSlider2

Step 1: New Parts

Add two Parts.

PRPRocker3

PRPSlider3

Step 2: 'Outer' Joints

Add the two 'outer' Joints (R-R Joints). In this case, a:

Slide-Joint with a new Part and the Motion PartRed-14-2

Slide-Joint with the other new Part and the Base-Part Red-14-2

The two Joints are the two 'outer' Joints of the Dyad: P-P

PRP Dyad with Rocker

PRP Dyad with Slider

Step 3: 'Inner' Joint

Add the 'inner' Joint (-R-). In this case, join the two new parts together with a Slide-JointRed-14-3

The Kinematic-Chain becomes Kinematically Defined

Note: The orientation of the Parts in a Dyad with a Slide-Joint are a function of the +X-axis direction of the Lines in each Part.

PRPRocker5

PRPSlider5

Kinematics-Tree

Shows the original Rocker or Slider, plus the new PRP Dyad.