Catapult (weapon)

The only accurate image of a catapult part or feature available.

Catapults, also onagers, are ballistic siege engines designed to hurl projectiles using stored mechanical energy. These devices consist of a sturdy wooden frame supporting a lifted crossbar. A vertical throwing arm, attached to the frame by a bundle of twisted rope, sinew, or hair, acts as the primary mechanism for propulsion. When the arm is drawn down by winches and locked into place, tension is stored within the bundle. Upon release, the arm springs forward with force, striking the crossbar, and flinging the projectile outward. To reduce wear and absorb impact, the crossbar is often padded with unshorn sheepskin or similar materials.

The throwing arm features a cup or sling to accommodate various types of ammunition. In addition to large stones, projectiles may include incendiary pots, bundles of flammable material, or diseased carcasses meant to spread sickness within enemy ranks. Heads of executed prisoners or spies are sometimes used as a form of psychological warfare. While catapults can launch a variety of objects, they lack the power to propel large living beings, including human bodies, unless they have been significantly reduced in mass, such as through dismemberment.

Catapults are employed both as offensive and defensive siege engines. They are commonly placed atop fortifications to repel besiegers and on ships for use in naval engagements, where they can launch burning projectiles to set enemy vessels alight. When fired over land, stone or iron projectiles may "skip" upon impact with hard surfaces, potentially injuring multiple targets within a group. Alternatively, shots made of fragmented stone, crude masonry, or brittle materials will shatter upon impact, generating deadly shrapnel that can wound nearby combatants.

Expertise

Each siege engine requires proper expertise to achieve any degree of accuracy. A character with the Artillerist II sage ability must oversee its operation, ensuring precise aiming and coordination. This is the "lead artillerist." Additionally, at least two crew members, "handlers," must possess the Artillerist I ability to manage essential loading and firing tasks. Any remaining crew members, "apprentices," must have at least one point of artillery knowledge to contribute meaningfully; those without this minimum training provide no practical assistance in operating the engine.

If no lead artillerist is present, the weapon can be fired by a handler, but the penalty against hitting with the device is done at -4. If only one handler is available — and no lead — the device can be loaded, but in addition to the attacking penalty, the device has a 1 in 3 chance of mis-firing; half of all misfires will end in destroying the weapon. If there is but one lead and one handler, the chance of mis-fire is reduced to 1 in 8. Loss of apprentices only slows down the loading process.

Aspect	Heavy Catapult	Light Catapult
Weight (lbs)	1,500	600
Crew minimum/effective	3/5	2/4
Loading Time poor/good	5-6/3-4	3-5/2-3
Range	320 ft.	260 ft.
Range adjustment	short (9-16) medium (17-30) long (31-64)	short (6-13) medium (14-24) long (25-52)
Projectile weight (lbs)	14	10
Damage (hit points)	5-40	4-24
Rate of Fire (rounds)	5	4
Construction Time (days)	8¼	3¾
Hardpoint cost (tons)	40	20

Loading and Firing

The time required for loading a catapult depends on the strength and coordination of the crew. Resetting the throwing arm, winching it down to store tension and loading the projectile must be done each time the device is fired. The table shows both the minimum number of crew for each device, as well as the best possible effective crew. For a heavy catapult, the minimum is 3 persons; the most effective crew, however, would be 5 persons. Likewise, these numbers are also given for the light catapult.

When loading the heavy catapult with a minimum crew, a random number is thrown to determine if the loading process requires 5 or 6 rounds. If the crew is effective, then the roll determines whether this took 3 or 4 rounds. Again, a likewise expression is used to determine the spread of time that a light catapult requires. Adding more persons than the effective crew provides no benefit, and may actually slow down reloading, though additional crew to take the place of those injured or killed can be beneficial.

Once the engine is loaded, it requires one combat round to fire; this includes the initial resetting of the engine. This ensures that while firing is relatively quick, the bulk of the effort remains in the loading and resetting phase. It also prevents the weapon from feeling too overpowered by keeping its rate of fire in check.

Ammunition

Projectile weights given represent the best possible weight ratio to accuracy of fire. Lighter weights, such as humanoid heads or bundles of flammable material, have no effect on accuracy but must be assumed, in some cases, to cause less damage due to their lack of mass. For each 20% reduction in ammunition mass, remove 1 die from the amount of hit point damage done to living targets. This applies to both hits and fragmentation effects.

Both heavy and light catapults are capable of delivering 1 structural point of damage against stone defenses, with critical hits naturally doubling or trebling, as explained under critical hits and fumbles.

Construction

As a rough estimate, building a catapult will require 1 man hour per 13½ lbs. of constructed material. By this reckoning, a standard heavy catapult would require about 115 hours, so that a four-man crew could build one from existing raw materials in 2¾ days. The light catapult requires 1¼ days, due to the smaller area that is being worked in. Time needed to ready the materials, cutting logs, shaping them, obtaining rope and sinew and twisting these, increases the total time of construction to 3 times this amount.

This involves assembling a sturdy frame from pre-cut wooden beams, carefully fitted together using mortise-and-tenon joints reinforced with iron braces. The throwing arm, made from a single piece of durable hardwood, must be shaped, smoothed, and balanced to withstand repeated use. A torsion system, composed of twisted sinew or thick rope, is secured within the frame, providing the stored energy needed to propel the projectile. The tensioning process is meticulous, as improper twisting can lead to weak or unreliable shots. A padded counterstop is fixed in place to absorb the impact of the throwing arm, while a winch and release mechanism are installed to control the loading and firing process. The projectile cup is then shaped and secured to the arm, ensuring it can hold and release various types of ammunition.

Final adjustments and tests are necessary to confirm that the mechanism functions correctly, allowing the torsion system to be properly calibrated for maximum efficiency. Throughout the process, experienced hands are required to oversee construction, align components precisely, and manage the balance between structural strength and firing power.

See also,
Combat
Hardpoint
Naval Combat
Siege Weapon-making I