Step 1.6: Rotate the Part

<< Click to Display Table of Contents >>

Navigation:  Getting Started Tutorials - MechDesigner > Tutorial 1: Add a Part that Rotates - a Crank >

Step 1.6: Rotate the Part

Objective of this Step

We specify the motion for the Part as Constant Angular Velocity - also termed Uniform Rotation Motion.

We learn how to connect wires from output-connectors to input-connectors of FBs (Function-Blocks).

See also: How to Connect Function-Blocks

In MechDesigner, a Motion-Part has its motion defined by the input to a Motion-Dimension FB and the Base-Value parameter defined in its dialog-box.  

A Rocker is the kinematic name in the Kinematics-Tree for a Motion-Part that may rotate continuously or oscillate back and forth.

In a Machine, a Rocker is a nearly always a machine element that 'oscillates back and forth'.

Terminology Reminder:

Motion-Part :

A Part whose motion is precisely specified by a Motion-Dimension FB

kinematically-defined Part :

A part whose state is solved. It has zero degrees of-freedom.

FB :

Abbreviation of Function-Block

Connect a wire :

: ... to drag a wire from the output-connector of a Function-Block to the input-connector of a different Function-Block.

Motion-Values :

Displacement, velocity, and acceleration data that flows instantly from Function-Block to Function-Block

Summary of this Step

1.Review the Kinematic Function-blocks, and the Master-Machine-Angle

2.Add a Linear-Motion FB to the graphic-area.

3.Connect a wire from the output-connector of the Linear-Motion FB to the input-connector of the Motion-Dimension FB.

4.Delete the wire

5.Add, connect, and edit a Gearing FB to rotate the Part in a clockwise direction.

Video of this Step

How to add a Linear-Motion FB and join the FBs with wires'

Kinematic Function-Blocks

Tutorials Steps:

Add a Linear Motion FB; Connect a wire to the Motion Dimension FB


STEP 1: Click Kinematic-FB toolbar > Linear-Motion FB (right of the graphic-area)
- or -
Click Add menu > Add Linear-Motion FB
- or -
Right-click in the graphic-area, and select the Linear-Motion FB icon in the contextual-menu.


STEP 2: Click in the graphic-area.

MechDesigner adds the Linear-Motion FBRed-14-1b to the graphic-area.

Hover+Drag the Linear-Motion FB in the graphic-area to the left of the Motion-Dimension FB.

It is easier to connect the FBs together.


STEP 3: Connect Function-Blocks with wires.

See how: Connect Function-Blocks

The motion-values at the output-connector of the Linear-Motion FB are now also at the input-connector of the Motion-Dimension FB.

The Motion-Dimension = Output from Linear-Motion FB + Base-Value - see Motion-Dimension dialog-box


Cycle the kinematic-chain.

STEP 4: Click Run toolbar > Cycle icon
- or -
Click Run menu > Cycle
- or -
Press ALT+C keys on your keyboard to start and stop the cycle command.

The Crank rotates one time with each Machine Cycle. Watch the red pointer under the Master-Machine-Angle move from 0 to 360 each time the Part rotates one time.

Rotate the Part in a Clockwise direction


As motion-values increase from 0 to 360, the Crank rotates in a counter-clockwise direction. Thus, the positive kinematic direction of an angle is the counter-clockwise direction.

To rotate the Crank in a clockwise direction, we will use a use a Gearing FB (I prefer to use the Gearing FB).

STEP 1: Click Kinematic-FB toolbar > Add Gearing FB

STEP 2: Click in the graphic-area.


STEP 1: Delete the wire between the Linear-Motion FB and the Motion-Dimension FB

To delete a wire:

1.Click the wire in the graphic-area

2.Click your delete on your keyboard, or use the method in the Selection-Window

STEP 2: Connect the Linear-Motion FB to the Gearing FB, and the Gearing FB to the Motion-Dimension FB




Now we can open the Gearing dialog-box

STEP 5: Double-Click the Gearing FB

STEP 6: Edit the Gearing Ratio parameter to -1.

STEP 7: Click OK-tiny-11-15 to close the Gearing Dialog-Box.

STEP 8: Click Run toolbar > Cycle icon
- or -
Run menu > Cycle
- or -
Press the ALT+C key on your keyboard

The Crank now rotates in a Clockwise direction.

Other Notes:

Master Machine Angle (MMA)

Animation Speed

Animation Speed Slider

Animation Speed Slider in the Feedback Area

Edit the Animation-Speed

The Animation-Speed does not change kinematic results.

Drag, to the left or right, with your mouse-pointer above the Animation-Speed Slider scale.

Edit the Simulation-Speed

The Simulation-Speed will change the kinematic results.

Use the Edit menu (or toolbar) > Machine Settings > Machine Speed.