An assembly file (*.iam) is only a list of hyperlinks to part files (*.ipt) and a record of assembly constraints.
Attach the part (*.ipt) files here.
I don't think that video shows relative motion, but you will use Rotational/Translation constraint (perhaps with a couple of tricks).
Please mark this response as "Accept as Solution" if it answers your question.
-----------------------------------------------------------------------------------------
Autodesk Inventor 2013 Certified Professional
Autodesk AutoCAD 2013 Certified Professional
Certified SolidWorks Professional
Inventor Professional 2013 SP 1.1 Edu 64-bit
GeForce GTX 560M i7-2670QM @ 2.2GHz 8GB RAM
http://home.pct.edu/~jmather/content/DSG322/inventor_surface_tutorials.htm
http://www.autodesk.com/edcommunity
Still waiting for -Draft option on any Rib feature.
