Fixed Pulley Centers: Belt becomes driven by a DriveR Pulley

This design arrangement is very common : there is one Driven Pulley.

The belt becomes driven by the Driven-Pulley. The other Pulleys become driven, via the Belt.

Preparation: Sketch-Loop and the Pulleys


STEP 1: Edit the Base-Part
STEP 2: Add a sketch-loop to represent the Path of the Belt

In this example, the sketch-loop has two Arcs and two Lines.

STEP 3: Add a Line 1sg and merge the start-Point with centre-point of the Arc.

It is easier to Add the Arc, then Hover+Drag the Line to merge it with the centre of the Arc.

STEP 4: You MUST dimension each Arc1s-red

The exact radius of the Arc is not important. MechDesigner uses the dimension to add a Pulley with an integer number-of-teeth and near to the radius. (you can edit the number-of-teeth later).

STEP 5: Close the Part-Editor


STEP 6: Add a Motion-Path FB2s

Select the sketch-loop that represents the path of the belt.

The Motion-Point shows at the start-Point of the sketch-element you select in the sketch-loop.


STEP 7: Add one Part3s for each Arc

The length of the Parts is not important.

STEP 8: Add a Pin-Joint4s between a Point in each Part and the centre-Point of an Arc.

Usually, use the origin of each Part for the Pin-Joint.

STEP 9: Add a Motion-Dimension FB5s to the Part you wish to be the Drive Pulley.

There should be one kinematically-defined Part5s that identifies the axis that will be the Drive Pulley. In this case, it is a Rocker.

[Not shown in the image: You can add a Linear-Motion FB to the Motion-Dimension FB]

Use Add Pulley


You must use Add Pulley for each Pulley.

Click Add Pulley

Add menu > Mechanism sub-menu > Add Pulley

- or -

Kinematic-elements toolbar > Add Pulley


Add Pulley opens in the Command-Manager.

Click, in the graphic-area, the four elements from top to bottom.

See 'Preparation' images to identify the elements: 1s-red2s3s4s:

1s-red The Pin-Joint

2s The Motion-Path FB

The Part-Editor opens to show the sketch-loop to which you added the Motion-Path FB.

3s The Dimension of the Arc sketch-element

The Part-Editor closes.

4s The Part joined with a Pin-Joint at the centre of the Arc.

Click 'OK' to complete the command.


MechDesigner adds the Pulley.

Do Add Pulley again, to add a Pulley to the right-hand Arc and Part.


A Drive-Pulley is given to the Pulley on the same axis as the kinematically-driven Part (the Rocker, in this case).
Belt Speed = Radius of Drive-Pulley * Angular-Velocity of the Drive-Pulley
The Belt-Speed gives the angular-velocity of the Driven-Pulleys
The Drive Pulley can transmit a Torque and tension to the Belt
Drive Pulleys are Cyan
You can edit the number-of-teeth with the Edit Pulley dialog.

Tutorial and Reference Help Files for MechDesigner and MotionDesigner 13.2 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd