The Onager

The Roman engineers knew that the Ballista was very complicated and expensive, and they needed a design that was simple and cheap. So, in 50 a.D., the onager was created. Because of it's kickback action when it was fired, it was called after a wild donkey that kicked back stones when it was attacked. A Roman writer, called Ammianus Marcellius, roughly gave gave the following explanation: "The onager's framework is made out of two beams from oak, which curve into humps. In the middle they have quite large holes in them, in which strong sinew ropes are stretched and twisted. A long arm is then inserted between the bundle of rope, at it's end it has a pin and a pouch. It strikes on a huge buffer with a sack stuffed with fine chaff and secured by tight binding. When it comes to combat, a round stone (often clay balls with Greek fire in them, which explode on impact and burst into flames) is put in the pouch and the arm is winched down. Then, the master artilleryman strikes the pin with a hammer, and with a big blow, the stone is launched towards it's target." In my onager, the side beams do not have humps, they're just straight which works fine. The overal dimensions aren't that big, it's 120 cm long, 70 cm wide and 100 cm high. The Roman onagers were much bigger, a normal one would stand over 2,5 meters high! The name of the onager is interesting. When it was first invented, it already had two names, scorpion because of the metal pin sticking out of the end of the arm, and onager because it kicked back when it was fired. During the Dark Ages, almost all knowledge of siege weapons became lost, but the French in that time "reinvented" the onager and named it mangonneau, which comes from the Greek word manganon. In England, it became known as mangonel, a name that is still used today. Another big mistake people make when they think about or draw an onager, is that it has a sort of spoon on the end of the arm in which the ball is laid. The Romans knew that a sling would work much better than that because it extended the arm and gave the projectile more force, increasing the range.

If you want to see more of my Onager, go to News or Photo's.

People who have built the Onager:
A German site full of reconstructions, by E. Schramm.
A Punkin Chunkin' Onager, by Bob Carbo.