propaganda

I've googled it dozens of times probably got about 15 pages in and have found nothing useful at all.

I keep seeing those little tiny ones that are like 1 foot high but I can't seem to find any plan on one a little large (around 4 and a half feet tall). I see some where you have to buy but I don't want to buy plans this thing is supposed to be cheap. So alas I ask here. How would you build a medieval trebuchet with no modern crap in it thats about 4 and a half feet tall?

Thanks for the help