For builders

Specs, free plans and simulators for each size of trebuchet we build, from a desktop model to a machine at least 10 feet tall.

Specs, plans and simulators

Medieval manuscript illustration of trebuchet by Villard de Honnecourt

A medieval trebuchet

Trebuchet sketch by Villard de Honnecourt, about 1230

Public domain, via Wikimedia Commons

Each size below shows an example machine, its specifications, and links to free (or low-cost) building plans and 3D-printing files. The plans belong to their creators; we link to them for reference. Photos are freely licensed and credited.

Diagram of how a counterweight trebuchet swings and releases
How every trebuchet works, at any size
Diagram: Onno / Д.Ильин, CC0 (public domain), via Wikimedia Commons

1. Desktop Models (6–8 inches)

  • Materials: 3D-printed PLA/PETG, wooden dowels, string
  • Projectile: grapes, ping-pong balls, or small foam balls
  • Range: 6–10 feet
  • Assembly time: 30–45 minutes
  • Cost per unit: $5–10 in materials

Build plans & 3D files

A student-built wooden “Small Yard” (12–18 in) trebuchet model
A student’s pine-and-dowel science-fair model (~12 in)
Photo: brittgow, CC BY 2.0, via Wikimedia Commons

2. “Small Yard” Models (12–18 inches)

  • Materials: laser-cut or hand-cut wood, hardware, string
  • Projectile: apples, tennis balls
  • Range: 15–30 feet
  • Build time: 2–4 hours
  • Cost per unit: $25–50

Build plans & 3D files

A homemade 2x4 A-frame trebuchet being tested in a field
A homemade lumber A-frame trebuchet (~4 ft)
Photo: Nathan Kit Kennedy, CC0 (public domain), via Wikimedia Commons

3. “Big Yard” Models (3–4 feet)

  • Materials: 2×4 lumber, plywood, hardware, rope
  • Projectile: grapefruit, water balloons
  • Splat Target idea (to test): biodegradable paintballs against a paper-covered target board. Paintballs may bounce at slower launch speeds, so this may only work at “Big Yard” (3–4 ft) and larger. Water balloons with washable paint work at any size. Safety glasses required
  • Range: 30–75 feet
  • Build time: 6–12 hours
  • Cost per unit: $75–150

Build plans & 3D files

A student-built wooden trebuchet launching a ball at an outdoor school event
A student-built lumber trebuchet firing at a school event
Photo: U.S. Army Corps of Engineers, Sacramento District, public domain, via Wikimedia Commons

4. 6-Foot Models

  • Materials: heavy lumber, steel brackets, rope/cable
  • Projectile: basketballs, small melons
  • Range: 75–150 feet
  • Build time: 3–5 days
  • Cost per unit: $200–400 (plus a turf-tire wheeled base for the Golf Challenge)

Build plans & 3D files

A trailer-mounted trebuchet launching a pumpkin at a fall festival
A trailer-mounted trebuchet launching a pumpkin (Damariscotta Pumpkinfest, Maine)
Photo: Matthew Bellemare, CC BY-SA 3.0, via Wikimedia Commons

5. 10+ Foot Machine (our 2027 goal)

  • Materials: heavy timber, steel hardware, concrete counterweight
  • Projectile: small pumpkins (2–8 lb)
  • Range: 150–300 feet
  • Build time: 1–2 weeks
  • Cost per unit: $500–1,000

Build plans & 3D files

A full-size timber trebuchet reconstruction at Urquhart Castle, Scotland
Full-size reconstruction at Urquhart Castle, Scotland (built for NOVA)
Photo: Yair Haklai, CC BY-SA 4.0, via Wikimedia Commons

Someday: a Full-Scale Trebuchet (15–20 feet)

  • Materials: heavy timber, steel hardware, concrete counterweight
  • Projectile: larger pumpkins
  • Range: 200–400 feet (someday)
  • Build time: multiple weekends with a team

Build plans & 3D files

There are no free, engineered plans at this size. Competition teams design their own. We’ll treat this as a design project using the simulators, and have an engineer review the build before any public launch.

Design tools for every size: Virtual Trebuchet and the Hastings Greer Trebuchet Simulator let you try arm lengths, sling lengths, and counterweights on screen before building.