Multiple-Pulleys driven by one Pulley

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Multiple-Pulleys driven by one Pulley

Fixed-Center Pulleys

We will add a Multi-Pulley and Belt system.

We can define the motion of ZERO or ONE Pulley. In this model we will define the motion of ONE Pulley. THe motion of the others are found from the velocity of the Belt.

We will edit the Number of Teeth on each Pulley

We will edit the Length of the Belt with Controlling Dimension, using the Target Belt Length parameter.



STEP 1: Add a closed sketch-chain (sketch-loop) to represent the Path of the Belt

a)Edit the Base-Part

b)Part-Editor: Add a sketch-loop with more than two Arcs

c)Part-Editor: You MUST add a dimension to each Arc. The exact radius of the Arc is not important.

The Belt will be Driven by a Driving-Pulley, which will be a Rocker

d)Part-Editor: Add a Line Red-14-1b - its start-Point is merged or coincident with the center-point of an Arc.

e)Close the Part-Editor


STEP 2: Add Motion-Path FBRed-14-2  

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

The Motion-PointRed-14-3 shows at the start-Point of the sketch-element you select in the sketch-loop.


STEP 3: Add a Rotating-Part for each Pulley.

Add one rotating-Part with its Pin-Joint at the centre of each Pulley.

The length of each Part is not important.


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

A maximum of one kinematically-defined PartRed-14-4 can be a Driving-Pulley.

Do Add Pulley


Add menu > Mechanism sub-menu > Add Pulley

Machine-elements toolbar > Add Pulley


The Add Pulley dialog starts in the Command-Manager.

Do Add Pulley to the kinematically-defined Part first.

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

1.The Pin-Joint

2.The Motion-Path FB

The Part-Editor opens with sketch-path to which you add the Motion-Path FB

3.The radius Dimension of the Arc

The Part-Editor closes

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

5.Click  in the Command-Manager.


The Pulley should now be in the model.

Do Add Pulley × five(5) to add a total of five Pulleys.

Notes: Default colors of the Pulleys:

Driving-Pulleys are Lilac

Driven-Pulley are Magenta

Use Edit Pulley dialog box


Edit the Number-of-Teeth on a Pulley.

1.Open the Pulley dialog-box

Double-click a Pulley in the graphic-area

- or -

See How to open a dialog-box


In the Pulley dialog-box

2.Edit the Number-of-Teeth

Repeat 1 and 2 for each Pulley.


3.Edit the Motion-Dimension FB to 0º .

When the Driving-Pulley is at 0º, the other Pulleys will also be at 0º.

Edit the Length of the Belt

Belts have an integer number-of-teeth. Also, belt manufacturers have preferred lengths of belts. We use the Motion-Path dialog-box to enter a Target Path Length

The Target Belt Length tool moves a Pulley, or a controlling-dimension, to edit the length of the belt.

Thus, we need a dimension in the sketch-path that will change the length of the belt. We will edit the length of the Belt to a length that is exactly divisible by Tooth-Pitch to give an integer number of teeth on the Belt.


In the design to the left, we will make the Tensioning Pulley the pulley at the top the sketch-path.

Therefore, we will select this dimension highlighted in RED. (102.2)

This dimension is called the Controlling Dimension.

The Motion-Path dialog-box will change the Controlling-Dimension as we edit the Target Path Length


STEP 1: Edit the Motion Path FB to edit the Length of the Belt.

1.Double-click the Motion-Path FB  to open its dialog-box dialog box (or see How to open a dialog-box)

2.Motion-Path dialog-box > Length Control tab > Control-Length of Path  > Belt Tooth Pitch =10 (mm)

You will see the Actual Path Length is not equal to Tooth-Pitch × Integer Number-of-teeth

3.Click the Controlling Dimension box

The Part-Editor opens to edit the Part in which the belt is defined by the sketch-path.

4.Click the dimension you want to use to change the length Belt - see above

The Part-Editor closes

The dimension value shows in the Controlling Dimension box

The default Target Path Length = Actual Path Length

The Maximum and Minimum Dimension Values are Soft-Limits to the Controlling-Dimension.

You can edit the Maximum and Minimum Values if you need to edit the Controlling Dimension by more.

6.Edit the Target Path Length SLOWLY with the Spin-Box tool to increase or decrease the Actual Belt Length.

If the Actual Path Length does not change, you probably to Increase the Control-Dimension Min

Then edit Target Path Length again.

If needed, you can select a different dimension to adjust.

1.Click the Clear Controlling Dimension button, immediately below Path Length using Dimension