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SolidWorks Motion Measure Angles Greater Than 180 Degrees.

Patrick James

SolidWorks Motion has a limitation of only allowing angular measurements between -180 and +180 degrees. SolidWorks has a thorough article on this along with a workaround and CAD file for measuring angles larger than 360 degrees.

 

 

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Question:
Is there any workaround to measure angular displacements larger than 360 degrees in a Motion Analysis study?


Answer:
The Angular Displacement plots in Motion Analysis have a measurement range of -180 to +180 degrees. As such, it is not possible to directly measure angular displacements outside of the range of -180 to +180 degrees. As soon as the angles goes over 180°, the displayed result value becomes -179° and not 181°.

As a workaround, you may create a dummy body with low mass density, and create a large ratio gear mate between it and the component you wish to measure the angular displacement for. As the main component rotates, the dummy body will rotate a smaller amount based on the gear ratio used. You can measure the angular displacement of the dummy body, and convert that angle based on the gear ratio to determine the total angular displacement of the main component. 

Depending on how many revolutions of the main component you need to measure, you must adjust the gear ratio accordingly such that the angular displacement of the dummy body does not exceed 180 degrees.

You can find a sample model attached to this solution. Please refer to Motion study 1. It already contains results.
The model is an assembly with a rotating body (rotating component). The rotating body has a rotary motor at 100RPM (equivalent to 600°/s) and since the duration of the simulation is 10, the expected angle of rotation is 6000°. That value is well beyond 180°, and the graph of angular rotation vs time for that body will show many jumps from 180° to -180°. You can see that in "Plot3".
Notice that a dummy body also appears in the model. It is transparent, and the material assign to it is Air so that its mass and inertia is negligible. Notice the Gear Mate defined between them. It as a custom ratio of -100. So for every 100° of rotation of the Rotating component, the dummy component only rotates 1° in the same direction. Consequently, you can view the angular displacement of the Dummy body and see it rotates 60°. See thing, you can immediately understand the Rotating body rotates 100 times more.  Rotating body rotates 60° * 100 = 6000°.

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