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Handle Geometry In Exercise 5.2.2 - Creating Mate Connectors Changes CoM

JoeORourkeJoeORourke Member Posts: 3
Hey Everyone!

I redid this exercise but I am running into the same issue. I'm initially trying to follow the directions verbatim in order to better understand how OnShape works and handles. The issue I am running into is with the way the arm loads the angle of geometry in Slide (Step) 12 eventually translates into an "incorrect" center of mass measurement for the end of the exercise. Setting the limits for the first Revolute handle restricts this even more (the degrees seem to be off by maybe about 50 degrees). This means I can't fully close the handle into the "tucked" position.

I am wondering if there is a specific tool/step I am overlooking that wasn't explained or if anyone has noticed this as well.

The answer is probably to obviously just manually rotate the handle or change the limit restrictions, however, since there is a measurable portion at the end, I assume there must be a correct orientation to set in order to get the correct result.

I hope that makes sense. Here is a link to the document to view, maybe someone will spot something.
https://cad.onshape.com/documents/6df77812f77b0bb1fc477e28/w/9a6bc93a2386a3253cfb00f4/e/08c37b784d83ca1fa9c09814

Best,
Joe

Answers

  • mahirmahir Member, Developers Posts: 867 ✭✭✭✭
    It looks like you've placed some unnecessary limits on Revolute1. The arm should be in this position for a correct mass measurement. Since you're free dragging the handle, the measured CG won't be exactly what the quiz says, but it should be close.


  • KatieHuffmanKatieHuffman Member, Onshape Employees, Developers Posts: 75
    @joe_o_rourke the reason why you are not getting the correct answer is because in your exercise, you had the X-Y alignment between the Mate connectors for the Revolute mate between the arm and base different than the example. You can think of this as the "zero" position where the limits are set from. Your zero position was different then the example, hence the discrepancies in the center of mass answers. This is unclear in the exercise, and I have updated it. Please check slide 14 in the exercise again, and thanks for the catch!
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