Hello
the trick of all that is this 💭
Put the joint orange(servo)to the piece orange
then Group the Joint orange(servo) to the piece orange
Only now use the "Joint Connector" from Servo orange to the "Parent" white!!!

"Parent" white is previously made like this
Put the joint violet(Hinge)to the piece violet(horizontal cylinder)
then Group the Joint violet(Hinge) to the piece violet(horizontal cylinder)
Only now use the "Joint Connector" violet Hinge to the "Parent" white (vertical pieces grouped)!!!
(Input Name in Controller for initialize it)

Rule is "put the joint to something"(not with the "connector"), "group the joint with the something", then "joint connector" the joint to a parent
Have fun Sketchy Physics 😉concepta.jpg

roboticArmTest2.skp

11s.jpg

Nice work and thanks for adding the images 🤓

Ahhh, okay, thanks. I was just messing around with sketchy physics when i made this model and wasn't really paying attention to dimensions, thanks!

Don't know who made this model,found it on Warehuse.

http://i12.tinypic.com/6o0ycso.jpg