This online article by Carol Raabus was posted in 2009 on the Australian Broadcasting Corporation’s Hobart page. It is about local man Doug Pattison and his re-creation of siege engines. He has built a trebuchet, first used in the twelfth century, and a ballista (a large version of a crossbow), which was first used by the classical Greeks and remained popular until replaced by the trebuchet. Doug sometimes gives public performances of the weapons.
For the story, including a clip of the trebuchet in action, see http://www.abc.net.au/local/videos/2009/04/21/2548797.htm