Step 16.2: Motion-Path FB, Ram-R

<< Click to Display Table of Contents >>

Navigation:  Getting Started Tutorials - MechDesigner > Tutorial 16: Motion-Path FB and Blend-Curves >

Step 16.2: Motion-Path FB, Ram-R

Motion-Path: Ram-R and Ram-P

We can use the Motion-Path FB to build two new pseudo-dyads:

•Ram-R

•Ram-P

An application of the Ram-R dyad is to model an engine valve and cam where we want to control the distance between the center of the rotating cam and the center of the roller on the rocker.

Another application is to control the motion of a linear actuator that drives a scissor lift.

Kinematics of a Ram-R

GST-16-2-MD-RamR-F

Ram-R

The Ram-R is a similar to an R-R-R dyad. In the Ram-R dyad, one of the Parts extends.

The Ram-R uses the Motion-Path FB to add a Motion-Point to a sketch-element ( in the image, the CAD-Line) in one Part.

We join the other Part to the Motion-Point with a Pin-Joint.

We add a motion to the input of the Motion-Path FB to control the motion of the Motion-Point.

The Red Arrow is the path of the Motion-Point along the CAD-Line of one of the Parts.

tog_minus        How to add a Ram-R

GST-16-2-MD-RamR-A

STEP 1: Add two Parts and join with Pin-Joints to a Line in the Base-Part.

1.Edit the Base-Part | Add Line, Add Dimension 100mm, Add Horizontal Constraint

2.Close the Part-Editor

3.Add two Parts

4.Edit the length of the Parts =100mm

5.Add Pin-Joints between the start-Points of each Part and the end-Points of Line
Motion-Path FB

Motion-Path FB

STEP 2: Add a Motion-Path FB

1.Click Kinematics-FB Toolbar > Add Motion-Path FB

Add the Motion-Path FB to a CAD-Line (a sketch-path)

2.Click the CAD-LineRed-14-1 along the center of the Part

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

The default position of the Motion-PointRed-14-2 is at the start-Point of the sketch-element you select (in this case the CAD-Line), and coincident with the Pin-Joint on the left.
Motion-Path dialog-box

Motion-Path dialog-box

STEP 3: Edit the start Position of the Motion-Point.

There are two Parts that you have joined to the Base-Part with Pin-Joints. You will add one more Pin-Joint (See STEP 4) to give three(3) points of a triangular shape. Motion values at the input to a Motion-Path FB will control the length of one of the sides of the triangle before we add the final Pin-Joint.

1.Edit the Motion-Path FB

In the Point Parameters separator

2.Edit Linear OffsetRed-14-5 = 40mm

3.Close the dialog

The Motion-PointRed-14-3 is now 40mm from the start-Point of the CAD-Line.
GST-16-2-MD-RamR-D
GST-16-2-MD-RamR-E

STEP 4: Add Pin-Joint

1.Click Kinematic-elements toolbar > Add Pin-Joint

2.Click the end-PointRed-14-4 of the Cad-Line and then the Motion-PointRed-14-3 that is at 30mm along the CAD-Line

The Pin-JointRed-14-5 joins the two Parts. The Ram-R dyad is now defined.

The Parts are kinematically-defined, with Green Part-Outlines.

You may need to change the closure of the Ram-R dyad.

STEP 5: Change Dyad Closure

1.Kinematics toolbar > Change-Dyad-Closure

2.Click one of the two Parts.

3.Click OK-tiny-13-17 in the Command-Manager to complete the command.

STEP 6: Add a Linear Motion FB and a Motion FB

STEP 7: Edit the Data Type at the output from the Motion FB

When you connect a Motion FB to a Motion-Path FB, you MUST edit the Output Data-Type to Linear or Rotary (the Data-Type should NOT be Motion).

1.Edit the Motion FB to open the Motion FB dialog

In the Motion FB dialog:

2.Enable LinearRed-14-4 as the Output Data-Type

Close the dialog.

STEP 8: Edit the Motion in MotionDesigner

The maximum displacement is 50mm.

STEP 9: Connect the Linear-Motion FB to the Motion-FB to the Motion-Path FB

GST-16-2-GA-CamMotion

Add a 2D-Cam

GST-16-2-GA-CamProfile

Note: This cam is not going to be useful for an engine.

STEP 1: Add the Cam Roller

1.Edit PartRed-14-9 Add Circle, Add Dimension, Add Coincident Constraint  

Constrain the circle to the end-Point of the CAD-Line

2.Do Solid menu > Add Profile

3.Click the circleRed-14-11
GST-16-2-GA-RamR-09

 

STEP 2: Add the Cam-Part

1.Add a PartRed-14-12 and join it with a Pin-Joint at the left of the Line in the Base-Part*.

2.Add Motion-Dimension FB - so that PartRed-14-12 is a Motion-Part (Rocker).

3.Connect a Linear-Motion FB to the input of the Motion-Dimension FB.

4.Edit the Motion-Dimension FB > Base-value = 0.

PartRed-14-12 is the horizontal Cam-Part.

* The Select-Elements dialog opens. CTRL + CLICK the start-Point of the PartRed-14-12 and the start-Point of the Line in the Base-Part.
GST-16-2-GA-RamR-11

STEP 3: Add the 2D-Cam

1.Do Machine elements > Add 2D-Cam

2.Click the new PartRed-14-12 as the Cam-Part.

3.Click the ProfileRed-14-11 as the Follower-Profile

The 2D-Cam is now in the graphic-area.

 
GST-16-2-GA-RamR-12

Kinematics-Tree

We call this kinematic-chain the Ram-R dyad

Kinematic-Chain #1 : The R-R-R is the Ram-R dyad - normally, this would be a structure. But a motion controls the length of one of the Parts in the dyad.

Kinematic-Chain #2 :The Rocker represents the Cam-Shaft.