I have some knowledge about siege weapons and
ballistae, catapultae, trebuchet are all weapons where you need the time to load them and aim them, they can't be used under pressure. To be of any use they need to be large and so take a few men to operate them. They are slow to load, and this increases the larger they get. If we are keeping to the thread point, then the only medieval weapon you need is a suitable bow of traditional design. A well trained archer drawing a suitable bow is capable of shooting arrows up to 250 yds, and landing them close enough to be lethal (if they hit you) half a dozen archers would would ruin your day before you get within 60yds. Once trained to shoot an arrow every couple of seconds you would be under fire for the entire time you are visable. This is not realms of fantasy as there are a lot of Archers who are capable of this and can be found in many clubs throughout the country. If you want to learn how to shoot like this, don't join a "target" archery club, join a Field archery club where you imitate hunting conditions, or join a club belonging to the BLBS British Longbow Society where you can learn to shoot "clout", the old English Longbow training of the Hundred Years War, where you shoot at 180yds. When you stand "on the line" and 50-60 longbow men open up from 180yds away, it's a sobering thing to think about being on the receiving end.
Learn the Bow