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

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

Scotch-Yoke: the RPP Dyad

In this step, you will change the kinematic-chain to a Scotch-Yoke.

You will add a Slide-Joint that is not along the default CAD-Line that is from the start-Point to the end-Point of all added Parts.

In this step, we dd a new Line to the Part, and then use it for the Slide-Joint.


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 Parts

oThree 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.

Scotch-Yoke Mechanism - False!

The Motion-Part is a:

Crank – colored Black.

A Dyad uses:

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.

Scotch-Yoke - Kinematic-chain

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.



Tutorial 2; Step 2.6

Edit model to design a simple Scotch-Yoke mechanism


Step by Step

tog_minus Change the Kinematic-chain from a Slider-Crank to a Scotch-Yoke

The Kinematics Tree


The Rocker has three elements:



c.Mot-Dim Rocker – a Motion-Dimension FB for a Rocker

The RP-P Dyad has five elements, as do ALL Dyads.