Cross joints - is there such a thing?

[st00katz]

Hi, I'm new to Fusion 360 and I'm trying to replicate this mechanism for learning purposes. I tried to use two perpendicular slider joints for the cross looking part, but it's not working. One slider at a time works but if both are enabled the mechanism gets stuck. Should I rely on contact sets only? Thanks!

[TheCADWhisperer]

File>Export and then Attach your *.f3d file here.

[st00katz]

Edited my post and attached the file.

[chrisplyler]

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@st00katz wrote:

Should I rely on contact sets only? Thanks!

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No. You should rely on the other Revolve joints, and just use one Contact Set.

[st00katz]

I'm not following you, could you please elaborate?

[TrippyLighting]

Referring to the device shown following the link you need revolute joints to constrain the linkages with the base and arm.

The cylindrical piece at the end of the arm (or the entire arm) and the base need to be part of a contact set, because there is no other way to constrain movement into that "cross" movement.

It might still not work, because it's a fair complex moment pattern and contact sets are respource hungry.

[chrisplyler · Accepted solution]

I obviously didn't get the geometry correct, because my model is not performing correctly with the 1:4 relationship, but is instead crossing the middle of the output wheel and generating a 1:2 relationship. BUT...you can see I've got the revolve joints going on, and the only contact set is the blue arm to the yellow wheel. And the contact set IS working.

https://knowledge.autodesk.com/community/screencast/f2ee8cb2-ae1a-4a68-a115-e2714183c69c

[TheCADWhisperer]

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@st00katz wrote:

Hi, I'm new to Fusion 360 and I'm trying to replicate this mechanism for learning purposes.

Unconstrained sketches. I would not permit a student to enter my Dynamic Simulation class (motion analysis) until they had masted the basics of fully defining a sketch.

[st00katz]

Thanks for pointing that out, I'll look into it.