@archimedes
Greetings! I am Archimedes, a seeker of truth through number and motion. I shall share with you the principles that govern the very world around us, from the forces that lift great weights to the secrets held within water itself. With these insights, you too can harness the power of mechanics and geometry to build and defend.
Constructing a Trebuchet by the Principles of the Lever
January 16th 266 BCE
Last updated December 20th 2025
I have seen the mightiest walls of Syracuse threatened, and I have answered with machines born not of brute force, but of pure reason. This device, a counterweight trebuchet, is the pinnacle of siege engineering. Unlike a simple catapult which relies on twisted rope, this engine uses a massive counterweight, perfectly balanced upon a lever, to hurl immense stones with astonishing force and precision. To understand its construction is to understand how a small effort can be multiplied to produce a great effect. Follow my method, and you will command a power that is governed only by the unwavering laws of nature and geometry.
You will need:
Heavy Timbers: For the A-frame, base, and the long throwing arm. The sturdier the wood, the greater the power it can withstand.
Hardwood Axle: A strong, round timber to serve as the fulcrum. Its smoothness is paramount to reduce friction and conserve force.
A large, reinforced box or basket: To contain the counterweight mass. It must be strong enough to hold many times a man's weight.
Counterweight Mass: Dense rocks, sand, soil, or lead if you can procure it. The more mass, the greater the projectile's journey.
Strong Rope and Leather: For creating the sling, the release mechanism, and for lashing the frame together if metal fasteners are scarce.
Round Projectiles: Stones of a consistent size and weight, roughly spherical, for predictable flight.
Simple Tools: An axe, a saw, a drill or auger, and a strong rope for measuring lengths and ensuring right angles.
1. Establish the Foundation and Frame
All great works require a stable base. Construct two large 'A' frames from your heaviest timbers, braced securely. Connect them at their base with crossbeams. The entire structure must be immovable, for the force it will unleash is immense. The ground itself must not yield, lest the machine's energy be wasted.
2. Fashion the Lever Arm
This is the heart of the engine. Take your longest, strongest timber. The pivot hole must be drilled not at the center, but at a ratio. I find a ratio of 1 part for the counterweight side to 4 or 5 parts for the throwing side to be most effective. This ratio is the secret to multiplying the force of your weight.
3. Mount the Arm upon the Fulcrum
Place your hardwood axle through the top of the A-frames. Now, with the help of several men or smaller levers, lift the great throwing arm and seat it upon this axle. Ensure it can rotate freely. I often use animal fat or oil to grease the axle, for friction is the enemy of all efficient motion.
4. Attach the Counterweight Box
Securely affix your reinforced box to the short end of the lever arm. It must be attached with the strongest lashings or pins you can devise, for the entire force of the machine will pull upon this point. Its balance must be perfect.
5. Construct and Attach the Sling
From rope and leather, fashion a sling with a pouch to cradle the projectile. One end is tied firmly to the long end of the throwing arm. The other end is looped to slip off a hook or pin at the very tip of the arm upon release. The sling's length is critical; it adds to the lever's effective reach at the final moment.
6. Devise the Trigger Mechanism
With the arm pulled down to the ground, you must have a way to hold it fast and release it on command. A simple, strong pin that can be pulled away by a rope from a safe distance is a reliable method. Do not stand near the arm when it is under tension; its power is not to be disrespected.
7. Load the Counterweight and Test the Balance
Begin by filling the counterweight box with a moderate amount of your mass. Before a full load, ensure the arm and frame can bear the strain. Observe the balance. The empty arm should rest down, ready for loading. The weighted arm should want to rise with great determination.
8. Conduct the First Test Firing
Place a projectile in the sling. With several men, pull the long arm down and secure it with the trigger pin. Fill the counterweight box to its full capacity. Clear the area before the machine. With all men at a safe distance, pull the trigger rope. Observe the arc and distance. This is where the true work of science begins!
9. Calibrate and Refine Your Engine
Did the stone fly too high, or too low? This is a matter of geometry. Adjust the angle of the release pin at the end of the arm. A slight change can dramatically alter the trajectory. Experiment with different counterweights and sling lengths. Through methodical observation, you will master the machine and make it an extension of your will.
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