Orbiting Pulley centres

OrbitingPulleys

Orbiting Pulley Centres

There is one fixed Pulley, joined to the Base-Part.

The belt path is on a rotating Part. The Orbiting Pulleys rotate with rotating Part around the centre of one fixed Pulley on a rotating Part.

Each Part can be:

DriveR Pulley
The DriveR Pulley is kinematically-defined with a motion before you use Add Pulley.
The DriveR Pulley rotates to move the Belt.

Linear Motion of Belt = Drive Pulley Radius x Drive Pulley Angular Motion

DriveN Pulley
The DriveN Pulley becomes kinematically-defined by Add Pulley.
The Belt moves to rotate the DriveN Pulley.

Angular Motion of Pulley = Linear Motion of Belt / Pulley Radius.

tog_minus        Preparation

MD-17-20

STEP 1: Edit the Base-Part
STEP 2: Add a Line
STEP 3: Make it Horizontal
STEP 4: Close the Part-Editor

Step 4 is complete

MD-17-21

STEP 5: Add a Part

This Part will be the rotating frame for the Orbiting Pulley.

MD-17-22

STEP 6: Edit the new Part
STEP 7: Add an two Arcs and two Lines to give the Path of the Belt
STEP 8: Add a Line, drag from the Centre of the Arc near the Part Axes
STEP 9: Add a dimension to each Arc3s

Step 9 is complete

Note that the centre of the Arc is not at the Origin of the Part.

A Drive Pulley has one important rule -

'You must merge the centre-Point of the Arc and the start-Point of the Line'

However, a rule that you might not know is:

'You cannot merge the centre-Point of the Arc with the start-Point of the CAD-Line along the centre of the Part'.

This means you cannot use the CAD-Line for the centre-Point of the Arc.

This is why we added a new Line to merge the centre-Point of the Arc with it.  This is the only reason.

STEP 10: Close the Part-Editor

MD-17-23

STEP 11: Add a Pin-Joint1s-red between the Line in the Part and the Line in the Base-Part

Note: the Pin-Joint does not use the Point at the Origin of the CAD-Line.

 

MD-17-24

STEP 12: Add a Motion-Dimension FB and Linear Motion FB

Use the Pin-Joint, the Line in the Base-Part and the Line in the Part for the

 

STEP 13: Add a Motion-Path FB2s

Select the sketch-loop around the Crank.

MD-17-26

STEP 14: Tidy up the Line in the Part!

Now, we can :

make the start-Point of the Line coincident with the Origin of the CAD-Line - add coincident constraints between the point and the X-axis and Y-axis of the CAD-Line
make the end-Point of the Line coincident with the ray of the CAD Line

tog_minus        Use Add Pulley

Add-Pulley-icon

Click Add Pulley in the Function-Block Toolbar

MD-17-25

Add Pulley opens in the Command-Manager.

Refer to the images above to identify the four Elements you must select to add a Pulley. From top to bottom:

1.Click the Pin-Joint1s-red
2.Click the Motion-Path FB2s

The Part-Editor opens. It shows the sketch-loop to which you have added the Motion-Path FB

3.Click the Dimension3s of the Arc sketch-element

The Part-Editor closes

4.Click the Base-Part4s.
Select the Base-Part because the Pulley is fixed to the Base-Part.

MechDesigner adds the Pulley. It is Cyan colour. This identifies it is a 'Drive' pulley.

MD-17-27

You must use 'Add Pulley' for each shaft centre where you want to add a Pulley.

STEP 1: Add a Part with a Pin-Joint to the centre-Point of the Arc at the other end of the sketch-loop.

Do not add a Motion-Dimension to the Part - leave it as a Free-Part with a Blue Part-Outline.

STEP 2: Add Pulley again

This time the Pulley has a Magenta colour. This means it is a 'DriveN' pulley.

 

Help Files for MechDesigner and MotionDesigner 11.1 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd