Fixed Pulleys Centres: Pulleys become driven by a Belt
This design arrangement is a little more unusual than the Belt driven by a Pulley.
Physically, the Belt is wrapped around freely rotating Pulleys. The Belt is driven by a motion-values at the input-connector to the Motion-Path FB.
Free Running Pulleys that are driven by a Belt
Preparation:
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| STEP 1: | Edit the Base-Part |
| STEP 2: | Add a sketch-loop - with lines and arcs only - to represent the Path of the Belt |
Either Hover+Drag or merge the Points at the end of each Line and Arc to give a .
| STEP 3: | Add a dimension to each Arc |
The radius of the Arc is not important. MechDesigner adds a Pulley with an integer number-of-teeth with a Pulley that has a radius that is near to the starting dimension.
| STEP 4: | Close the Part-Editor |
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The Command-Manager has one selection-box:
Click a sketch-element in the sketch-loop.
Click  in the Command-Manager.
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A Motion-Point shows at the start-Point of the sketch-element you select in the sketch-loop. It is inside the Point-Symbol
| STEP 6: | Add a Linear-Motion FB |
Connect the Linear-Motion FB to the Motion-Path FB with a wire.
Motion-values of 0 - 360 [at the output of the Linear-Motion FB] move the Motion-Point the total length of the sketch-loop.
You can use motion-values from any Function-Block, E.g.: Motion FB of course.
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| STEP 7: | Add Parts : one part for each Pulley / Arc |
The length of each Part is not important.
| STEP 8: | Add a Pin-Joint between the start-Point of each Part and the centre-Point of each Arc |
The Pin-Joint will be at the centre of the Pulley.
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'Add Pulley' command
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Do to add each Pulley.
Click Add Pulley in the:
- or -
Add Pulley opens in the Command-Manager.
Select the four element in the graphic-area.
Note:
See Preparation, above, to identify the four elements.
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Click the Pin-Joint
Click the Motion-Path FB
The Part-Editor opens to show the sketch-loop
Click the radius Dimension of an Arc sketch-element
The Part-Editor closes.
Click the Part, with a Pin-Joint at the centre-Point of the Arc.
Click to close the Command-Manager
Do again, to add a Pulley at the other Arc.
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Notes:
| • | The Pulleys are 'Driven-Pulleys'. |
This means their angular-velocity is given by the linear-speed of the Motion-Point along the sketch-loop (Belt) and the radius of the Pulley.
| • | When you add a Pulley, the radius of the Arc changes so that there are an integer number-of-teeth on the Pulley. |
| • | The Parts are horizontal when the is zero. |
| • | Driven Pulleys are Purple |
| • | Edit the number-of-teeth with the Edit Pulley dialog. |
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