Step 10.3: The Oldham Coupling

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Step 10.3: The Oldham Coupling

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 Dyad

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.

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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 : 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 OK-tiny-11-15 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 CrankRed-14-1b

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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 PartRed-14-2 : Add a Part

2.Mechanism-Editor: Click Kinematic elements- > Add Pin-JointRed-14-3: Click the start-Point of PartRed-14-2 , 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 PartRed-14-4 : Add a Part

2.Mechanism-Editor: Click Kinematic elements- > Add Slide-JointRed-14-5

a.Click the CAD-Line in the PartRed-14-4

b.Click the CAD-Line along the Crank

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Preparation for the middle Joint - Joint 2

1.Edit PartRed-14-4: Geometry toolbar > Add LineRed-14-6 : 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-JointRed-14-5

a.Click LineRed-14-6 in PartRed-14-4

b.Click CAD-LineRed-14-7 in PartRed-14-2

 

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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 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.