This trebuchet was the second one I had ever constructed.  Two large A-frame structures were built to support the axle, throwing arm, and counterweight.  Outriggers were then constructed to improve stability.  The throwing arm was also a small pine tree, like trebuchet 1, but I built an adjustable release pin mechanism at the end of the throwing arm to control the pin angle.  By changing the angle of the release pin, one can make the trebuchet release the projectile earlier or later.  Early releases correspond to high trajectories, and late releases correspond to flat trajectories.  The total counterweight was 250 pounds.