Getting Started Tutorials - MechDesigner > Tutorial 17: Belts and Pulleys > Step 17.2: Option 1 - Fixed Pulley Centers

Control the Length of the Belt with a Dimension.

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

The Target Belt Length tool controls a dimension, which we name the 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 length of the Controlling-Dimension changes as we edit the Target Path Length

The Controlling Dimension can only be Point to Point or Length of a Line.

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 dialog (or see How to open a dialog)

2.Motion-Path dialog > 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 Start Length-Control button

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 is in the Controlling Dimension box.

The default Target Path Length = Actual Path Length

The Control-Dimension Min and Control-Dimension Max are Soft-Limits to the Controlling-Dimension.

You can edit the Controlling Dimension Maximum /Minimum if required..

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

Troubleshooting.

If the Actual Path Length does not change,

6.Increase the Control-Dimension Min until it is near to the actual Control-Dimension in the sketch.

7.Then edit Target Path Length again.