TREBUCHET  , a

medieval siege engine, employed either to batter masonry or to throw projectiles over walls . It was developed from the post-classical Roman onager (wild ass), which derived its name from the kicking action of the machine . It consisted of a frame placed on the ground to which a vertical frame of solid timber was rigidly fixed at its front end; through the vertical frame ran an axle, which had a single stout spoke . On the extremity of the spoke was a Cup to receive the projectile . In action the spoke was forced down, against the tension of twisted ropes or other springs, by a windlass, and then suddenly released . The spoke thus kicked the crosspiece of the vertical frame, and the projectile at its extreme end was shot forward . In the trebuchet the means of propulsion was a counter-weight . The axle which was near the top of a high strutted vertical frame served as the bridge of a balance, the shorter arm of which carried the counter-weight and the longer arm the carrier for the shot . An alternative name for the trebuchet is the mangonel (mangonneau) .