Why add a Pulley?

The motion of a Pulley is related to the motion of a Belt.

Either the 'Pulley moves the Belt' or the 'Belt moves the Pulley'.

There is a maximum of one 'Pulley that to drive a Belt'.

You can add any number of 'Pulleys that are driven y a Belt'.

Use the Pulley dialog-box to edit the Pulley parameters.

Two Pulleys and 'Kinematic Properties'.

After 'Add-Pulley', a rotating-part becomes a Pulley.

The Pulley is a:

DriveR-Pulley: Add a Pulley to a Green rotating Part. MechDesigner calculates the Linear Velocity of the Belt from the Angular Velocity of the Pulley.

or a:

DriveN-Pulley: Add a Pulley to a Blue rotating Part. MechDesigner calculates the Angular Velocity of the Pulley from the Linear Velocity of the Belt.

Add Pulley


Mechanism Local Toolbar : Add Pulley icon


Mechanism Menu Toolbar > Add Pulley

Edit with...

Pulley dialog-box


What for:

To add a DriveR-Pulley or a DriveN-Pulley.

Elements that you need before you can use this command.:

A sketch-path with Arcs and Lines. You must add dimension to the Arcs. The sketch-path represents the path of the Belt.
A Motion-Path FB linked to the sketch-path. This gives a Motion-Point on the sketch-path.
A Part, that is joined with a Pin-Joint to the centre-Point of each Arc, for each Pulley in the sketch-path.

The first Pulley becomes either a DriveR Pulley or a DriveN Pulley. The second, and more, Pulleys must be DriveN.

Note: The sketch-path of a Belt may be closed or open. It is usually closed.

PREPARATION - edit a Part to add a sketch which is the path for the Belt.



Edit the Base-Part, or an Added-Part. Add a sketch-path to represent the path of the Belt.

The sketch-path must be made with Lines and Arcs. You can make the sketch-path a sketch-loop.

Each Arc1s-red must have a dimension4s

When the Arc is intended for a DriveR-Pulley - the Pulley drives the Belt

DriveR-Pulley with sketch-loop in Base-Part

1.Add a Line2s, or CAD-Line
2.Merge the start-Point of the Line with the centre-Point3s of the Arc1s-red that becomes the centre of the DriveR-Pulley.


DriveR-Pulley with sketch-loop in Added-Part

1.Add a new Line9s or CAD-Line
2.Make the new Line9s co-linear with the CAD-Line along the centre of the Part.
3.Merge the start-Point of the new Line with the centre-Point of the Arc.

Do NOT use the start-Point of the CAD-Line given with the Added-Part.

When the Arc is intended for a DriveN-Pulley - the Belt drives the Pulley


You do not need to add a Line from the centre-Point of the Arc when the Pulley will be driven by the Belt.



Click Add a Motion-Path FB7s .
Click a sketch-path that is the path of the Belt. A Motion-Point8s will move with the Belt.

Note: The default direction for a Motion-Point is counter-clockwise along the sketch-path. The initial position of the Motion-Point is at the most clockwise point of the sketch-element you select.

When the Arc is intended for a DriveR-Pulley - the Pulley drives the Belt

The DriveR-Pulley gives the velocity to the Motion-Point(s) along the sketch-loop.

A Rocker5s[or other kinematically-defined Part], that has a Pin-Joint6s at the centre of an Arc(1s-red in sketch above)


When the Arc is intended for a DriveN-Pulley - the Belt drives the Pulley

DriveN-Pulleys rotate with a peripheral speed given by the Belt.

Elements in the Mechanism-Editor

A Free-Part5s that has a Pin-Joint6s at the centre of an Arc1s-red


What to do:

If the Belt will have more than one Pulley, AND one of the Pulleys is kinematically defined [Green], the add the Pulley to this Part before you add the Pulleys to other rotating Parts at other arcs in the sketch-path.

Click Add Pulley in the Mechanism menu or the Mechanism Local-Toolbar

1.Click the Pin-Joint6s at the centre of the Rotating-Part*5s and Arc1s-red
2.Click the Motion-Path FB7s that gives the Motion-Point8s that moves along the Arc
3.Click the dimension4s given to the radius of the Arc when the Part-Editor opens
4.Click the Rotating-Part*5s joined with the Pin-Joint6s at the centre of the Arc1s-red
5.Click OK in the Command-Manager

* Rocker for a DriveR-Pulley, Free-Part for DriveN-Pulleys, or the Base-Part if the Pulley is fixed to the Frame.




Adds a Pulley schematic to the graphic-area.
The Radius of the Arc ÷ Pulley Pitch Circle Diameter changes to give an integer number-of-teeth.
The Radius of the Arc becomes 'Read-Only' in the Part-Editor.
Use the Pulley dialog-box to edit the number-of-teeth.
If you add a Pulley to a Free-Part, it becomes a kinematically-defined Part, a Pulley-Rocker.


How to...

Full Video of Add Pulley and Belt

Add sketch-elements, Add Rocker, Add Motion-Path FB, Add a Pulley, Add DriveN-Pulley.


Physical Design Parameters

We do not use a database to make sure the Belt Tooth-Pitch, Belt-Length, Minimum number of Pulley-Teeth are available in sales literature. You must enter these values.

Length of the Belt

Usually, you want the belt to have an integer number-of-teeth. To edit he length of the belt to give a specified 'Belt Length' edit the Motion Path FB. In it, you can give a 'target belt length' and select a dimension in the sketch-loop to be a driven dimension to make the total length of the sketch-loop/belt give an integer number-of-teeth.

Minimum Number-of-Teeth on a Pulley

You must make sure the Number-of-Teeth parameter in each Pulley > minimum practical number-of-teeth. Typically, it is 10 teeth.


MechDesigner adds a DriveR-Pulley or a DriveN-Pulley




The Kinematics-Tree adds a Pulley-Rocker for each DriveN-Pulley you add to the model.
The Red Belt - in the icon - identifies that the Belt drives the Pulley.


This is a kinematically-defined Part (a Rocker or one of two Parts with a Pin-Joint in a Dyad)

See Also:Pulley dialog-box

Help Files for MechDesigner and MotionDesigner 11.1 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd