The Israel Technion is running the TechnoBrain contest to build the largest yoyo in the world. It involves a 30 meter crane, a 20 meter rope and some of Israel’s most inventive engineering students. Update! The winner was Eyal Moshe Cohen – a mechanical engineering student and (wait for it) an ex Paratrooper.
http://www.israel21c.org/news/technion-goes-yo-yo/
http://www.jpost.com/Sci-Tech/Article.aspx?id=225197