Roman Balista

Standard 3 and 1/2 span Classical Arrow Shooter

Features and Data


A fully functional real-size greek-style palintone (straight-spring) arrow-shooter, as used in Classical times. Its features include a slider rail with a dove-tail connection to the main beam, two central stanchions and straight bow-arms. The draw of the bow-string is made with a winching system with side ratchets along the main beam and the release mechanism is of the claw and lever type.

The design follows Heron/Philon’s proportions relating to “D”, that is diameter of the "spring" (the inside diameter of the washers): the stanchions are 3,5D x 1,5D, the hole-carriers are 6,5D x 2D and the central-beam is 16 D.

The standard CERCO21’s machine has been dimensioned for a D of 90 mm, so its intended projectile is 9D, that is 810 mm long (aprox. 3,5 greek span).
The stand is of a design seen in bigger stone-shooter euthytones, which have the advantage of disassembly into flat components: easy to pack, transport and store (it is also sturdier than a single hexagonal stand).

Technical Data

Net Weight:
85 kg
D(washers inside ø):
90 mm
Max Lenght:
1500 mm
Draw Strenght:
300 kg
Max Width:
750 mm
Spring Ropes:
10 mm ø Nylon Rope
Max Height:
1400 mm
Exit Velocity (m/s):
85-105 m/s
Break Strain (Wood Frame) minimum:
Max Range (30º):
350-400 m
Break Strain (Washers):
150 kN
Efective Range (0-10º):
Break Strain (Bow String):
-10º / +50º
Break Strain (Winch Rope):
Wood Frame :
Pine Wood treated with fungicide and 2 coats of UV and water resistant varnish.
Metal Parts:
Steel St37.2 passivized to prevent rust. Washers made of Naval Brass also to resist corrosion. All steel pins encased in epoxy.


- Can be folded and disassembled to fit an everyday car (at least 1550 litres of trunk space with the folded seats);
- Disassembled components can be transported by a single person;
- Security features allows disabling the winch or the trigger, or both (so that no-one is tempted to shoot it without permission).


The assembly can be done in 10 minutes or less*:
- screw the 3-piece stand;
- insert the crossbeam in the head section;
- insert the winch in the crossbeam;
-insert the bow arms with the string;
- use the spanner to twist the washers for the desired tension;
- place the ballista in the stand;
- connect the elevation “y” frame,
and you’re done.   

(* - with the pre-tension option)

(see the assembly video)


Operating the ballista:
- release the winch lock and pull the arming claw and slider to grab the bow string;
- lock the winch and spin the lever until the bow string is in it's further most position;
- aim and shoot.

(see shooting video)


Included in the Pack

·         A ballista

·         Stand and elevation y-frame

·         Tools needed for assembly /disassembly

·         Six one-meter long bolts, one of them being a special tracer bolt (for ranging)

·         Comprehensive manual

Everything is shipped by international carrier in two units: the crossbeam, due to its size, and a wood pallete with the rest (the power frame, bow arms, string, winch, stands, spanner and bolts). The full pack will have a brute weight around 100 kg.


Costumization Options


Assembly of the "head" (power unit) and pre-strech of all ropes.

Assembly of the stand in it's 3 portable parts.

You’ll just need to insert the crossbeam and in the head section, place it on the stand and you’re done.


Bigger size

Sometimes bigger is better. By choosing this option bigger model, this design will fit a van like a Ford Transit.

It will weight up to 150kgs

For even bigger sizes, please contact us because there are some restrictions for international shipping.


Natural fibbers ropes

As a standard, CERCO21 ballistas come with nylon (twisted) rope for the torsion springs. Nylon has a good Young’s Modulus, its impervious to humidity with it's only the drawback being degradation through sun exposure.
The historically correct sinew rope or horse-hair rope are not available( we much like others avoid gutting cats to produce rope). Plant fibber ropes are also an historical alternative (they were used in Western Europe in torsion springs in the Middle Ages), and are widely available.
If you wish your machine to have a more appealing historical look, the string ropes can be made from manila, hemp or linen.
Because they have a smaller Young’s Modulus this option diminishes the machines performance. Of the alternatives, hemp is by far the better, but some restrictions apply in export to some countries.


 Brass Washers

As a standard, CERCO21 ballistae are fitted with ST37 steel washers and naval brass counter-plates. In classical times those washers would be made of casted bronze and lathed.
As a more historical looking alternative, we offer as an option brass washers and steel counter-plates. There are drawbacks: the brass breaking strain is roughly half that of the steel and the price is can be almost ten times higher (the brass market floats much more than the steel market).


If you require a machine that is more period-specific there is available the adaptation to a later roman design and to Vitruvius’ set of proportions. It will include changes to the following components:

- Replacing the two central stanchions with one central perforated one;
- Changing the proportions of length and width of the hole-carriers frames;
- Changing the height of stanchions;
- Replacing the strait ratchet in the central beam with a circular ratchet in the winch mechanism.

This option decreases the machines’ safety of operation, as it provides lesser visibility for the gunner and makes the machine susceptible to critical breakdown in case of failure of the winch rope.
Please note that this options still maintains the strait arms configuration, it does not used arched ones as depicted in some scorpios. CERCO21 has not yet find a reliable way to make them composite and safety comes first.

Front Shielding

On commission we can provide an engraved copper front plate shield for the romanized ballista (similar to the findings in Cremona and depicted) through cooperation with a local artist.

Iron Plating

The Roman ballistae archaeological findings of Camin Real and Ampurias had iron plating reinforcements and classical authors insist upon its use, so it’s thought to have been a common usage.
As a standard, CERCO21 ballistae are not fitted with plates, as our math and tests show that the wood frame is already over-dimensioned for the 300 kg draw weight it was designed for.
This option will entail encasing the head-frame with 8 riveted plates of 2 mm steel. It has the drawback of greatly increasing the machine’s total weight and changing the centre of gravit
y (which we will compensate).


Choice of wood and finishing

The balista itself is made of pine, treated with wood-preserving products (fungicide) and two layers of varnish for outdoors (UV and humidity resitance). 

The choice of Oak for the frame will make it and heavier but sturdier machine.

You can indicate the desired colour and hue of the varnish. As an option it can be dark-waxed instead.