This is a trebuchet that we made. It is 1/2 a meter tall and 1.4 meters long. The arm is .91 meters long made out of wood on a pvc pipe axile. 

Watch it work at- http://www.youtube.com/watch?v=X6_lRgd781I

Render video at- http://www.youtube.com/watch?v=VIgBM83QV88

Put together video at- http://www.youtube.com/watch?v=UIP4ZXndpvA&feature=youtu.be

Slideshow at-https://drive.google.com/file/d/0B3mulA9tRWMUbFVKR3BGaHJrMnI0am1GZllMZFdtcjVHTk44/edit?usp=sharing