The Oldham Coupling

The 'Oldham Coupling' transmits power between shafts that are parallel and offset from each other.

A 'floating' disc, in the middle of the coupling, has a raised rib on each face. Each rib is perpendicular(⊥) to each other. The raised ribs engage with slots in flanges on the input and output shafts.

The Oldham Coupling is a kinematically-defined chain that is built with a:

1.Motion-Part, and

The video shows an 'Oldham Coupling'.

'Input': The Input Crank – the Motion-Part

'Output': The Output Crank – rotates at the same constant speed.

'Middle Disk': This transmits power/torque from the Input to the Output Crank.


A kinematic-chain has a Motion-Part. as an input.

STEP 1.Add the Motion-Part – a CrankRed-14-1b
1.Edit the Base-Part :
2.Part-Editor: Geometry toolbar > Add Line : Drag to add the Line , Add Horizontal Constraints, Add Dimensions, Close the Part-Editor:
3.Mechanism-Editor: Click Kinematic elements- > Add Part : drag to add the new Part.
4.Mechanism-Editor: Click Kinematic elements- > Add Pin-Joint: Click the start-Point of the new Part and the start-Point of the Line in the Base-Part.
5.Mechanism-Editor: Click Kinematic FB toolbar > Add Motion-Dimension FB: Click the Pin-Joint the Line in Base-Part; the CAD-Line in Part. and OK-tiny-11-15 in Command-Manager
6.Mechanism-Editor: Click Kinematic FB toolbar > Add Linear-Motion FB: and click the Graphic-area. Joint the FBs with a wire. You have a CrankRed-14-1b


We now want to add a Dyad. Dyads ALWAYS have two Parts and three Joints. Never forget this!

STEP 2.Add the Dyad

Dyad: Part-2 and Joint-3

The output of the Oldham Coupling rotates.

1.Add a Part
2.Join it with a Pin-Joint to the Point at the end-Point of the Line in the Base-Part.


Dyad: Part-1 and Joint-1

1.Add a Part
2.Add a Slide-Joint between the CAD-Line in the Motion-Part (Crank) and the CAD-Line along the new Part.


Dyad: Joint 3 ...Preparation

1.Edit Part-1 - it has a Slide-Joint along the Motion-Part (Crank)
2.Add a Line that is perpendicular(⊥) to the CAD-Line*
3.Close the Part-Editor

Note: The +X-axis is the direction you drag to the add the Line.


Dyad: Joint 3

1.Add a Slide-Joint between the Part 1 and Part 2

To add the Slide-Joint:

a.Click the CAD-LineRed-14-1b in Part-2
b.Click the LineRed-14-2 we added to Part-1


The Oldham Coupling is Complete.

You can add Extrusions to the Parts to show the coupling as a Solid model.


Note: Part-1 (the Output-Part) may be 180º to the direction it is in this image. The direction of the +X-axis of the Output-Part is the same direction Line (start-Point to the end-Point) you add to make the Slide-Joint.

The +X-axis of a Line is the same as the direction you drag your mouse-pointer to add the Line.


The Kinematics-Tree shows the Motion-Part - Rocker (Crank) and the new R-R-P Dyad.

Note: this is the same Dyad as the Scotch Yoke!

Oldham Coupling, you connect the R Joint to the Base-Part and the P-P Joints are internal to the kinematic-chain.

Scotch-Yoke, you connect the P Joint to the Base-Part, and the R-P Joints are internal to the mechanism.

Tutorials and Reference Help Files for MechDesigner and MotionDesigner 14.2 + © Machine, Cam, Mechanism, and Motion Design Software by PSMotion Ltd