kalispera ballista,
dunno whether or not you're interested in literature on the topic and these are available on the net,
but maybe the following might lead furtheron one way or the other. so here's a little bibliography on
ancient, e. g. greek artillery
G. T. Griffith, The Mercenaries of the Hellenistic World, London 1935
E. W. Marsden, Greek and Roman Artillery. Historical Development, Oxford 1969
Sir Ralph Payne-Gallwey, The Projectile Throwing Engines of the Ancients, London 1907 [ND London 1973].
Sir Ralph Payne-Gallwey, A Treatise on the Construction, Power and Management of Turkish and Other Oriental
Bows of Mediaeval and Later Times, London 1907 [ND London 1973]
Michael M. Sage, Warfare in Ancient Greece. A Sourcebook, London 1996
Hans van Wees, Greek Warfare. Myths and Realities, London 2004
Henry Balfour, The Archer’s Bow in the Homeric Poems, in: Journal of the Royal Archeological Institute 51 (1921), S. 289-309
Hilda L. Lorimer, Homer and the Monuments, London 1950
sto kalo