Construction Details

Disclaimer : Do not attempt to build this yourself. These machines are very dangerous and capable of harming, maiming, dismembering, and even killing (after all this is what they were originally designed to do when built and fired by Medieval soldiers).

     The Making of an Onager

The 1997 Onager is poised to fling another Pumpkin at our secret testing site, where Team Carbo conducts important "high tech" Research and Developement.

The Onager is constructed with very heavy materials to withstand the tremendous stresses it undergoes when cranking it up and firing it. The frame is built out of railroad ties that are 7" x 9" thick. The frame is about 8 feet long. The arm of the Onager is an 8 ft. long log of oak, 7 inches in diameter. The torsion spring is made from 600 ft of 3/4" poly rope. The side pieces, or skeine pipes, around which the rope is wrapped have been custom built by Ray Wheeler of Bay Design in Baltimore, Md. (I had to give a plug since this is my brother Bill's company). These pieces are made from 8" diameter steel pipe each about 12" long. These pieces of pipe, which I refer to as Skiene pipes have a piece of 1" thick iron bar, 4 inches wide, running through them around which the poly rope is twisted.

Here's the 1997 version of the Skiene Pipe (Aye, it's a manly lookin piece of iron work too!) You can see the yellow poly rope wrapped around the steel bar, which when twisted creates the torsion spring. In the 1998 version, a set of 2 steel washers have been welded around the outside of the pipe with a series of holes in them for the steel pins.

Below is a diagram of the 1998 version of the skeine pipe and pursuader bar.

Here is the new aand improved Onager Skiene pipe.

Below you see a couple of Team grunts torquing up the skiene pipe. With the (orange) pursuader bar being 9 feet long, you can get some decent leverage.

My bother Bill's company, Bay Design, did the above modifications with no problem, thanks to the skilled craftsmanship of Ray Wheeler.

Here is a top view of the Onager mounted on it's trailer. The winch pedaling mechanism is attached at the rear.

The entire catapult is mounted on a 2-wheel, single axle trailer allowing the Onager to be quite mobile, a definite strategic advantage in both siege warfare and Punkin Chunkin.

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When the skiene pipes are twisted forward with the pursuader bar to torque up the rope torsion spring( with great force and sweat), 1" thick iron pegs are inserted through the holes in the washers around the pipes and into holes in the Onager frame (to stop the skiene pipes from twisting back). Steel cable from a pedal powered winch is attached to the end of the oak arm.

The arm is then winched back until it is horizontal. A sling made out of rope and leather is attached to the end of the oak arm with the projectile(usually a pumpkin or watermelon - cause they make the neatest splat when they land) in it. A release mechanism is pulled which releases the arm from the winch cable, and the forward motion of the arm causes the sling to throw the projectile. Stand back when this baby is fired - it packs quite a wallop.

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