About to modifie objects with hinges, strange simulation...

[tonn]

Hello everybody and merry christmas.
I am learning sk.phy.
I'm some little confused because if I move, rotate or scale objects that has hinges, when I do the simulation everything is wrong. It's like something has been lost.
I have a car with 4 simple cilinder with a hinge (a simple wheel). After some modifications, (for example incline the car rotating it ), I discover that the gizmo showed when use the joint connector is in another place other than where it should be. (and the simulation does not work, my car does not roll, just across the floor...)
What can I do? Start again?

Now,(some minutes after posting) I dont now what happen but everything is ok. Any idea ? Any advice ?

Another time... This time I have problems.
Now using some tutorials (for example windmill.skp) to experience some, if I explode the group helix-hinge, the gizmos showed are strange... And the helix go down, across the soil ....

Any idea ? Any advice ?

Thanks

[Physicsguy1]

Joints are pretty finicky - As far as I know we've been trying to get rid of these for a long time. You can't copy them, you can't hookup two objects to a controlled joint, nor can you explode them. When you are dealing with joints, don't do anything to them and chances are everything will work.

I suggest starting from the beginning, or putting new joints in.

-Chris

[Jibe1982]

I'm having the same problems, SP seems to behave very randomly by linking itself two objects or unlinking them.

[Mr.K.1]

Sometimes it is best to start over, delete/replace a joint or explode/remake the group that is causing problems.

Moving and rotating shouldn't be an issue at all, unless you moved joint off center in wheels or anything.
Scaling can go nuts tho, my advice is to scale only internal groups/geometry and not the external groups, or if you already scaled try exloping/remaking the group to reset it (this is also very important with static-mesh as it doesn't like scale).

Also it's always best to upload the problematic model so we can see what is going on.