TweenPrimary Part is not moving all the other Parts with it. (Model)

[Scottifly]

As others have said, WeldConstraints work just fine.
If I’m working on a Model with many Parts I’ll start with the Anchored Part (I’ll call it Primary from now on), then add the next Part and use the Constraint tools to add a WeldConstraint to the added Part to weld it to the Primary Part.
Now when I need to add another Part to the Model I’ll Ctrl-D duplicate the welded Part. That will duplicate the WeldConstraint as well. You can change the size, shape and other Properties and move it wherever you want on the Model and the WeldConstraint will update the Position.
When you’re done you’ll have all the Unanchored Parts welded to the Primary Part.