sbragonier, you got it. I'm working more towards a functional model than Something that just works. The design is from a wood cut on the internet. It's 3 ft. long. The rest is by eye from the drawing.Haven't figured out the arm or the pivot yet. The counterweight will be 5-7 lbs of lead. Boxed in with wood. The projectile will be a marble or a 1/2" Diam. Lead ball. .50 cal. (May be illegal soon) There is a real trebuchet in England that launches pianos and mini-coopers. Ain't Physics grand?