Fixed Pulleys Centres: Pulleys become driven by a Belt

This design arrangement is a little more unusual than the Belt driven by a Pulley.

Physically, the Belt is wrapped around freely rotating Pulleys. The Belt is driven by a motion-values at the input-connector to the Motion-Path FB.

Free Running Pulleys that are driven by a Belt



STEP 1: Edit the Base-Part
STEP 2: Add a sketch-loop - with lines and arcs only - to represent the Path of the Belt

Either Hover+Drag or merge the Points at the end of each Line and Arc to give a sketch-loop.

STEP 3: Add a dimension to each Arc1s-red

The radius of the Arc is not important. MechDesigner adds a Pulley with an integer number-of-teeth with a Pulley that has a radius that is near to the starting dimension.

STEP 4: Close the Part-Editor


STEP 5: Click Kinematic-FB toolbar > Add Motion-Path FB

The Command-Manager has one selection-box:

Click a sketch-element in the sketch-loop.

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


A Motion-Point2s shows at the start-Point of the sketch-element you select in the sketch-loop. It is inside the Point-Symbol

STEP 6: Add a Linear-Motion FB

Connect the Linear-Motion FB to the Motion-Path FB with a wire.

Motion-values of 0 - 360 [at the output of the Linear-Motion FB] move the Motion-Point the total length of the sketch-loop.

You can use motion-values from any Function-Block, E.g.: Motion FB of course.



STEP 7: Add Parts3s : one part for each Pulley / Arc

The length of each Part is not important.

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

The Pin-Joint will be at the centre of the Pulley.

'Add Pulley' command


Do Kinematic-elements > Add Pulley to add each Pulley.

Click Add Pulley in the:

Mechanism menu

- or -

Kinematic-elements toolbar

Add Pulley opens in the Command-Manager.

Select the four element in the graphic-area.


See Preparation, above, to identify the four elements.




1s-red Click the Pin-Joint

2s Click the Motion-Path FB

The Part-Editor opens to show the sketch-loop

3s Click the radius Dimension of an Arc sketch-element

The Part-Editor closes.

4s Click the Part, with a Pin-Joint1s-red at the centre-Point of the Arc.

Click OK-tiny-11-15 to close the Command-Manager

Do Add Pulley again, to add a Pulley at the other Arc.




The Pulleys are 'Driven-Pulleys'.

This means their angular-velocity is given by the linear-speed of the Motion-Point along the sketch-loop (Belt) and the radius of the Pulley.

When you add a Pulley, the radius of the Arc changes so that there are an integer number-of-teeth on the Pulley.
The Parts are horizontal when the MMA is zero.
Driven Pulleys are Purple
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