﻿ Getting Started Tutorials - MechDesigner > Tutorial 2A: Four-bar Kinematic-Chains > Step 2.6: Reconfigure to a 4-bar Scotch-Yoke

# Step 2.6: Reconfigure to a 4-bar Scotch-Yoke

Here, we change the kinematic-chain to a Scotch-Yoke. The purpose of this tutorial is to practice how to delete and add different joints.

This tutorial also helps you to add a Sliding-Joint that is not along the CAD-Line (the center-line of an Added-Part), but along a Line you add to a Part with the Part-Editor

 To assemble simple, four-bar kinematic-chains, We need: •One Motion-Part : A Motion-Dimension FB identifies the Part that is the Motion-Part. A Motion-Part is a Rocker or a Slider. •One Dyad : All Dyads ALWAYS has:oTwo PartsoThree Joints

### What is a Scotch-Yoke?

Below, there are two typical images of a Scotch-Yoke as they are often found in many kinematics books.

The Motion-Part is a:

Crank – colored Black.

Three Joints: a horizontal Slide-Joint, a vertical Slide-Joint, a Pin-Joint in the Slot

Two Parts: one horizontal sliding-part – colored Red – and the other Part is... where?

Where is the second Part in the Dyad?

In the image above, the second Part of the Dyad does not seem to exist.

The image to the left shows the other Part in the Dyad. It is a:

Vertical sliding-part – it is 'sliding-block' - colored Green.

The kinematic-chains in the images to the left are kinematically identical, but they are slightly different physical designs of a scotch yoke.

One top image shows a pin that is in a slot. The bottom image shows a pin that is in a sliding-block, and the sliding-block is in a slot.

Kinematically they are the same, and you must model them in MechDesigner in the same way.

 Can you guess the kinematic tree?

### The Kinematics Tree

 The Rocker has three elements: a.Pin-Joint b.Partc.Mot-Dim Rocker – a Motion-Dimension FB for a RockerThe RP-P Dyad has five elements, as do ALL Dyads. d.Pin-Joint1 e.Part3f.Slide-Joint2g.Part2h.Slide-Joint