To rotate, or not to rotate, that is the question!

[cedricmartin]

Imagine if you will, two blocks that have curved surfaces of the same radius; one concave, the other convex. The intent is for these two surfaces to be in contact and to slide radially, around the center of the radius.

Question: does this sliding motion become Revolute, Cylindrical, Slider, or Planar? Also, when establishing a joint between these two blocks, how do I choose the center of rotation, etc., for the action that I am trying to achieve.

Once again, any help would be appreciated.

Cedric.

[HughesTooling]

Have you tried a Ball Joint. Picking the spherical surface will create a joint at the center of the sphere.

[SaeedHamza]

Hi,

Check this screencast please

https://knowledge.autodesk.com/community/screencast/b87464c6-3ecd-49e4-abda-fa5765be3007

Regards, Saeed

[Anonymous]

I'm assuming the two surfaces are cylindrical, rather than spherical.  You're not really clear....  Anyway, if that is true, then you can use either a cylindrical or revolute joint, depending on what you want to accomplish.  If you want the two surfaces to slide on each other, then they MUST be concentric, and the rotation axis MUST be their common center axis.

Regards,

Ray L.

[cedricmartin]

You are right on the ball with your answer and I know how the two components should behave, but I am having trouble establishing the rotational axis.

This is a screen shot of the two components in question. Assume that the component on the right is fixed and the component on the left is intended to be adjustable. The two curved surfaces are both 4.00" radius so, as you state, the axis of rotation will be 4.00" in from the curved mating surfaces. However, I am having trouble establishing that point as the rotational axis.

As you can see, the component on the left has two slots and the component on the right has two tapped holes. Cap screws will hold these two components together, while allowing a few degrees of radial movement either side of the centerline of the curved surfaces. 

I want to join these two components, which are part of a larger assembly, so that I can animate the finished product to show the degree of adjustment.

Hope this clarifies the situation and, again, I would appreciate your help.

Regards,

Cedric.

[mroek · Accepted solution]

@cedricmartin: You want a revolute joint here, not a cylindrical. When creating the joint, you should be able to establish the correct axis of rotation if you first select the ungrounded (left) component by first hovering over the curved surface, then pressing and holding the CTRL key to allow you to select the center point for that surface (provided it is circular, and not created by a spline or something). Then do the same for the grounded component, making sure to select it's center point by hovering over the surface and pressing CTRL to lock the inference.

I attached a really simple model where I did just this, not sure if it helps, though.

[cedricmartin]

Sorry I didn't get back to you sooner, but I just wanted to thank you for your help. With your help, I got it done!

Now, I just have to try doing the same thing during animation. Wish me luck!

[mroek]

Good to hear! But you should't really mark your own answer as the accepted solution (unless it really was).  🙂

[HughesTooling]

Not sure if @cedricmartin knows how to change the accepted answer so I've changed it.

There's a bit of info on marking accepted answers here.

Mark