Ancient Engineering
Ballistic Technologies of Antiquity

X-treme Onager

New low price!

Designed and made in the USA for
better quality, better performance!

Now made from top-quality solid oak non-toxic, formaldehyde-free plywood for a more
dimensionally stable, stronger, and less expensive model than if made from natural wood.

Modeled after the Roman Onager, this torsion-based machine can hurl golf balls and tennis balls over 50

This modern design for an Onager uses the exact same principles as the ancient Roman war machines. It
is capable of hurling small stones, golf balls, walnuts, eggs, tennis balls and even potatoes from 20 feet
to more than 50 feet! It all depends on how much power you build into it and the weight of your
projectiles. Precision crafted of high quality hard wood, the kit contains everything you need to build a
working model in one evening.*

The advantages of this new design are:
  • Double cross-grain frame for added strength.
  • Higher skein and arm rest allows for longer slings.
  • The arm can travel farther, well beyond the vertical limit of a traditional onager.
  • A soft arm arrestor eliminates hard impacts between the arm and the frame.

The ONAGER (also called a Mangonel) uses a bundle of twisted ropes (called a skein) for real torsion
power. This torsion engine is so powerful, a full-sized machine can hurl a bowling ball almost 1/4 of a

The finished model stands 17" long, 14" high and 12" wide. The kit is precision crafted from top-quality
engineered hardwood plywood and includes a working winch and real leather sling-pouch.

The detailed instructions are complete with diagrams, photos and tuning tips so you can get the most out
of this fun project. All parts are pre-cut, pre-drilled and can be assembled to a finished model in one

We've put a lot of time and effort into making this kit as easy and complete as possible. It's a fun way to
learn about history and engineering!

* Golf ball and tennis ball missiles are not included.
* Can throw over 50 feet when properly constructed and tuned. Your performance may vary.

WARNING! This is a representative model of a real ancient military weapon. It contains a fast moving arm
that can cause injury if you make contact when firing. Use only under adult supervision.

Tools required:
Scissors, Glue, Ruler, and a utility knife. Sandpaper is optional.

Assembly time:
For a Master carpenter doing a sloppy job: about 2 hours.
A person with no kit building experience being extremely meticulous: about 10 hours.
The model in these photos was built by Ron Toms in about four hours.

Assembled Size:
- Height: 14"
- Length: 17"
- Width: 12"

- 20 to 50 feet with golf balls as projectiles, about half that with tennis balls. (Optimal range assumes a
well built and well tuned machine)

Shipping weight: 5 lbs.
Box dimensions: 24" x 12" x 4"

Quantity pricing info:
0 to 4 kits, standard price.
5 to 9 kits, 10% off
10 or more kits, 15% off

Orders of $200 or more get FREE ground shipping!

WARNING! This is a representative model of a real ancient military weapon. It contains a fast moving arm
that can cause injury if you make contact when firing. Use only under strict adult supervision.

* Can throw 50 feet when properly constructed and tuned. Your performance may vary.
* Golf ball and tennis ball missiles are not included.
* Actual item may differ slightly from the images on this page.
* X-treme Onager is a trademark of RLT Industries.

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    Price: $70.00
    Minimum age: 14
    Availability: out of stock

    Item code: 10301

More Stuff




A catapult is any kind of device that shoots or launches a projectile by mechanical means. In England, a catapult is what we call a slingshot in the US. A catapult is also the part of an aircraft carrier that launches airplanes off the deck.

But for our purposes, a catapult is any of the ancient types of artillery, including Onagers, Scorpions, Trebuchets, Ballistae, Springalds, Coullards, Bricoles Perriers and more.

But most people tend to think of a catapult as the one-armed torsion machine used by the Romans. This is also known as the Onager or Mangonel.


The word Mangonel derives from the ancient Greek word "Manganon", literally meaning "engine of war". The Romans called it a Manganum. In pre-medieval French the word Manganum was changed to Manganeau, and the English changed that to Mangonel in the 1300s.

The history gets a little sketchy in the middle ages, but some historians believe that "mangonel" was shortened to the word "gonnel" about the same time that cannons were being developed, and later still, "gonnel" was shortened to "gun." And still today, in the military a "gun" is strictly a piece of big artillery.


Onager is originally the name for the wild Asian donkey. This donkey bucks like a bronco if anyone gets too close to it, and it is known to kick stones at people and predators too. So when the Romans needed a name for their one-armed torsion catapult, they called it the Onager!

The Onager (catapult) has a single arm that is powered by a large skein of twisted ropes. The ropes were usually made from hair or sinew for their elastic properties.


The word "Trebuchet" is originally French, and meant something like "to fall over or rotate about the middle" as in a see-saw rotating on its axle. It also seems to have meant a big, heavy beam. Today a Trebuchet is any kind of catapult that is powered by a massive counterweight on one end of an arm, and a sling on the other end. This includes Perriers, or "traction" trebuchets which are powered by a mass of people pulling one end of the arm with ropes.


This is a two-armed torsion device invented by the Greeks. It works similar to a crossbow, but instead of a flexible bow, it uses two stiff arms powered by twisted rope skeins like an Onager. The ballista predates the Onager by several centuries and was used to hurl stones (lithobolos style ballista) and also bolts or darts.

Obviously, this is where we get the word "ballistic".

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