Assemble a Whitworth Quick Return

You are going to design a 'Whitworth Quick-Return Mechanism'.

Why not start a new mechanism on a new Plane?

See also this link:

A new definition of a Kinematic-Chain:

A kinematic-chain may have:

One, or more, Motion-Parts
One, or more, Dyads

Notice 'or more' in the new definition of a kinematic-chain. This is because it is easy to add Dyads and to add more than one Motion-Part to a kinematic-chain.

A Whitworth Kinematic-Chain:

One Motion-Part
Two dyads

Remember, ALL Dyads have:

Two Parts
Three Joints

Whitworth : Dyads 1 and Dyad 2

Notes about Dyad 1


First, we should look at the Motion-Part and the first Dyad.

A Motion-Part – a CrankRed-14-6
A Dyad

The Dyad is assembled with:

Two Parts: one longRed-14-1b and one shortRed-14-2
Three Joints: a RPR Dyad
otwo Pin-Joints: join the long Part to the Base-PartRed-14-3 (frame); join the short Part to the CrankRed-14-4
oone Slide-JointRed-14-5 to join the long and the short Parts together

Which order do we add the Joints to add a new Dyad?

After you have added the two Parts as 'Free Blue Parts', it is frequently easiest to:

First, add the 'outer' two Joints. They join the two new Parts to two other Parts in the kinematic-chain.
Then, join the two new Parts in the Dyad together – this makes the 'middle' Joint in the Dyad.

Now you do it....Add the first and last joints of the Dyad:

Pin-JointRed-14-3 between the long part and the Base-Part: R – –
Pin-JointRed-14-4 at the end of the Crank: R – R

Join the Parts together.

Slide-JointRed-14-5 to join the two Parts together: RPR

Now - remember about Closures? See Change Closure of a Dyad if the Dyad is in a Closure you do not expect. Keep using the same Change-Closure tool until the Dyad is in the closure you need.

Notes on Dyad 2


The image shows the second Dyad (I have rotated the image  in Dyad 1 by 90º). When the kinematic-chain is solved (kinematically-Defined, and Green), it is simple to add more Dyads, to make a more complex kinematic-chain.

In the image, the second Dyad has:

two more Parts: Red-14-7 and Red-14-8
the Parts are joined to two other Parts
oPartRed-14-1b - which is the Long Part of the first Dyad
oThe Base-Part
the Parts are also joined together.

Now you do it....Add the first and last joints of the Dyad:

Pin-JointRed-14-9 between the long part and one of the new Parts: R –x –x.
Slide-JointRed-14-10a along the Base-Part: R –x–  P.
Pin-JointRed-14-11 joining the two Parts together: R–R–P.

Your challenge is to complete this mechanism. and put each Dyad in the correct 'Closure'.

Why not start a new mechanism on a new Plane?

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