I have a 3d assistive device offered by a textbook.As shown in this model, handle bar is mounted to the plate at the pivot pin of the plate and linked to the middle pin of the kicking rod. The kicking rod is inserted into the two lower brackets mounted on the plate. I set up the gravity and defined a contact joint. When i run simulation, i expect to see that the handle bar move forward and kicking rod move backward due to gravity. But, unfortunately, all the plate, handle and kicking rod fell down directly due to the gravity as if there no restriction at all. I really appreciate your help.