The Main Gun
In regard to the main gun (thanix cannon), take a look at this link-
http://www.mocpages.com/moc.php/188396
and this video-
http://www.youtube.com/watch?v=b_qVvuVqXWw
From 4:17 to 4:20, you see where(approximately) and how the thanix cannon unfolds. On the lego model...