﻿ Three Shafts, Two Belts, Four-Pulley, with two pulleys on One Shaft

# Three Shafts, Two Belts, Four-Pulley, with two pulleys on One Shaft

### Fixed Pulley Centres : Two or more Pulley Sets

Use Two Belts to:

 • Give a larger speed reduction
 • Reduce total belt span
 • Wrap the belt more around the DriveR-Pulley.

The image to the left shows

 • Three shafts
 • Two belts
 • Two Pulleys on one shaft.

### PREPARATION IN THE Part-Editor

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

The start-Point of the Line MUST be merged with the centre-Point of the Arc.
[It is easier to Add the Arc, then Drag the Line from the centre of the Arc].

 STEP 4: Dimension each Arc

The exact radius of the Arc is not important.  Edit the Pulley later to enter the number-of-teeth.

See Edit Pulley dialog-box

 STEP 5: Close the Part-Editor

### PREPARATION IN Mechanism-Editor

 STEP 6: Add a Motion-Path FB

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 Part for each Arc
 STEP 8: Add a Pin-Joint between a Point in each Part and the centre-Point of an Arc.
 STEP 9: Add a Motion-Dimension FB to the Part at the Arc you wish to be the Drive Pulley.

There should be one Rocker that identifies the axis that will be the Drive Pulley.

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

There should be one Rotating-Part for each Pulley you will add.

The length of the Parts are not important.

#### Use Add Pulley

Click Add Pulley in the Function-Block Toolbar

Add Pulley opens in the Command-Manager. You must use Add Pulley for each Pulley.

Select these four elements for each Pulley. We add a Pulley to the left Arc first.

Refer to the images above to identify the Elements. Select, from top to bottom.

 1 The Pin-Joint
 2 The Motion-Path FB

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

 3 The Dimension of the Arc sketch-element

The Part-Editor closes

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

MechDesigner adds the Pulley.

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

Notes:

 • A Drive Pulley is given to the Pulley on the same axis as the Rocker.
 • The Linear Speed of the Belt = Radius of Drive Pulley *Angular Speed of Drive Pulley
 • The angular speed of the Rocker gives the linear speed to the belt.
 • This then gives the angular speed to the other Rotating Parts, and the Driven Pulley

#### PREPARATION IN Part-Editor

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

You must merge the centre-Point of the Arc for the second belt, with the centre-Point of the Arc for the first Belt.

[Add the Arc first, then use Merge-Point tool in the Part Local Toolbar].

 STEP 3: You MUST dimension each Arc

The exact radius of the Arc is not important. You can edit the number-of-teeth on Pulley later.

See Pulley dialog-box

 STEP 4: Close the Part-Editor

#### PREPARATION IN Mechanism-Editor

 STEP 5: Add a Motion-Path FB

Click a sketch-element in the sketch-loop that represents the path of the second belt

Step 5 is complete

The Motion-Point shows at the start-Point of the sketch-element you click.

### Use Add Pulley

 STEP 6: Add a Pulley

Make the selections for the Command-Manager:

 a. Select the Pin-Joint at the centre of the Part Pulley
 b. Select the Motion-Path FB
 c. Select the Radius dimension of the Arc (the Part-Editor opens to select the Radius of the Arc)
 d. Select the Part

Click OK in the Command-Manager.

The Pulley shows in the graphic-area.

Note: You do not need to add a rotating-Part for the second belt, with a different Pin-Joint. We 're-use' these elements.

 STEP 7: Add a different Pulley at the other end of the sketch-loop

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