﻿ Getting Started Tutorials - MechDesigner > Tutorial 15: Patterns - Indexing-Chain example > Step 15.4: Add a Chain-Link and Drive Pulleys

# Step 15.4: Add a Chain-Link and Driving-Pulleys

### A Chain-Link

A Chain-Link rotates as it moves around each Pulley. Currently, we do not have a Part that rotates.

We can add a rotating-Part that makes a kinematic-link between the two Slider Sets.

The Chain-Link is represented by one of the two Parts in an R-P-R Dyad.

As always, a Dyad has two Parts and three Joints.

Add a new Part - add a Pin-Joint (R--). Join it to a Point on Y-Slider of Slider-Set 1

Add a new Part - add a Pin-Joint (--R). Join a Point on Y-Slider of Slider-Set 2

Add a Slide-Joint (-P-) - between the CAD-Lines in each of the two new Parts

The two Parts and three Joints make the R-P-R Dyad.

### The Pulleys

We add a rotating-Part at each end of the Chain to represent the Pulleys

They must rotate (12÷5) times each time the Chain cycles one time.

#### Add an RPR Dyad to the Slider Sets

Remember, Dyads always have two Parts and three Joints.

Add an R-P-R Dyad between Slider-Set 1 and Slider-Set 2

This dyad is: R(Pin-Joint) - P(Slide-Joint) - R(Pin-Joint)

Top-Tip: Temporarily hide the Motion-Dimension FBs.

STEP 1: Add two Parts and R Joints

 1.Add a Part (Part 1) 2.Rename the Part as Tool-Part. 3.Add a Pin-Joint between the Part and the start-Point of Y-Slider1 4.Add a Part (Part 2) 5.Add a Pin-Joint between the Part and the start-Point of Y-Slider2

The two Pin-Joints are the Revolute joints in the RPR dyad.

STEP 1: Add a Slide-Joint to join the Part 1 and Part 2

 1.Add a Slide-Joint between the CAD-Line in Part 1 (Tool-Part) and the CAD-Line in Part 2

The Slide-Joint completes the RPR Dyad.

The Part-Outlines of the Part 1 and Part 2 become Green.

When you cycle the machine, you will see the RPR Dyad move with the Slider-Sets.

STEP 2: Add a Measurement FB between the Pin-Joints

 1.Kinematic FB toolbar > Add Measurement FB 2.Click the Point at the Pin-Joint at R-P-R 3.Click the Point at the Pin-Joint at R-P-R 4.Click the graphic-area to place

As you cycle the model you will see the length variation between the Pin-Joints is from 100mm to 93.55mm.

#### Add the Pulleys

STEP 1: Add rotating-Parts for the Pulleys

 1.Edit the Base-Part: Add Line: Add Coincident Constraint between start-Point and the center-Point of the Arc 2.Exit the Part-Editor 3.Mechanism-Editor : Add Pin-Joint , click the start-Point of each Part and the center-Point of each Arcs.

STEP 2: Rotate the Pulleys at the correct Speed

The Chain - with 12 links - makes one full belt-length in each machine-cycle. Each Pulley has 5 Teeth for Chain-Links.

We can use the Gearing FB to change the rotational speed of the Pulleys.  The ratio  is #12/5 × Pulley Rotations per 1 Belt Path of 12 Links

 1.Add a Motion-Dimension FB to each rotating-Part 2.Add a Gearing FB 3.Edit the Gearing FB : Enter Gearing Ratio = 12/5 (2.4) 4.Add a Linear-Motion FB 5.Add wires between the Function-Blocks in usual way.