Getting Started Tutorials - MechDesigner > Tutorial 10: Model Mechanical Devices

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

2.PPR or RPP dyad

The video is of 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.

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

STEP 1.Add the Motion-Part – a Crank

1.Edit the Base-Part : Geometry toolbar > Add Line : Drag to add the Line Add Horizontal Constraints, Add Dimensions, Close the Part-Editor

2.Mechanism-Editor: Click Kinematic elements- > Add Part : drag to add the new Part.

3.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.

4.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 in Command-Manager

5.Mechanism-Editor: Click Kinematic FB toolbar > Add Linear-Motion FB: and click the Graphic-area. Joint the FBs with a wire. You have a Crank

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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.Mechanism-Editor: Click Kinematic elements- > Add Part : Add a Part

2.Mechanism-Editor: Click Kinematic elements- > Add Pin-Joint: Click the start-Point of Part , click the end-Point of the Line in the Base-Part.

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Dyad: Part-1 and Joint-1

1.Mechanism-Editor: Click Kinematic elements- > Add Part : Add a Part

2.Mechanism-Editor: Click Kinematic elements- > Add Slide-Joint

a.Click the CAD-Line in the Part

b.Click the CAD-Line along the Crank

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Preparation for the middle Joint - Joint 2

1.Edit Part: Geometry toolbar > Add Line : Drag to add a Line, Vertical Constraints, Add Dimensions

2.Close the Part-Editor

Note: The +X-axis is the direction you drag to the add the Line. - from its start-Point to its end-Point.

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Dyad: Joint 2

1.Mechanism-Editor: Click Kinematic elements- > Add Slide-Joint

a.Click Line in Part

b.Click CAD-Line in Part

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Result:

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.

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The Kinematics-Tree

One kinematic-chain with a Motion-Part - Rocker (Crank) - and an 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 kinematic-chain.

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Step 10.3: The Oldham Coupling

Step 10.3: The Oldham Coupling

The Oldham Coupling