Hi,
in fact I don`t realy think that this is a good contribute but I think that this might be also interresting for you guys (especially when you are working on some sort of middle age strategie game).
Searching through the web I have found this site:
Siege Engine Blueprints This site contains blueprints and descriptions how these old siege engines worked like the "tribock" (don`t know the english name sry) from Age of Empires II.
I had much fun reading through this site so maybe you also have!
~Gurke