Cylindrical Joint problem

[lemelman]

I thought I had got the hang of joints, but I've come to a full stop.

I created a cylindrical joint between a slip-tee and a pipe. When I animate the joint, it works as expected, but when I try to move the tee along the pipe it behaves like a rigid joint. The screencast illustrates my problem. 

What have I done wrong please?

[chrisplyler · Accepted solution]

You have got to Ground at least one of the Components so it cannot move. Then Joints that are in some way, either directly or indirectly, assemble to that Grounded Component will operate properly.

[lemelman]

This is very mysterious The whole assembly was built up from one, grounded, pipe. As shown in the attached screenshot. How it became ungrounded is a mystery - I certainly didn't do it on purpose. But it works now.

Thankyou for your assistance.

[chrisplyler]

I think you know enough by now. I'm not sure why, when you tried to drag the fitting and the whole assembly moved instead, your brain didn't instantly think, "My first step should be to check whether an appropriate component is grounded or not."

[lemelman]

Although I didn't mention it in my initial post, I did try grounding the "Undercarraige bot" component, but it had no effect. Because of that, it never occurred to me that the very first grounded component had somehow become ungrounded. Why would it? Come to that, why did grounding the Undercarraige bot component not do the job?

[chrisplyler]

I don't know which of the many components visible is the Undercarriage bot. I have to assume, if it being Grounded did not keep those Components that are Jointed either directly or indirectly to your sliding fitting, then it itself is not at least indirectly attached to that fitting through successive Joints.

I see that the entire bit that moved together in your video is Jointed together, but that nowhere does any of it have a Joint to any of the other stuff above it.