Ancient Roman Ballista Torsion Artillery Lab

60 mins Ages 10-14 Indoor

A challenging, hands-on discovery and STEM project designed for curious young minds aged 10 to 14.

Materials Needed

  • • Sturdy corrugated cardboard or wood scrap chassis (1 set)
  • • Nylon paracord or thick braided twine (2 meters)
  • • Wooden craft dowels (15 cm long) (2 units)
  • • Lightweight cotton balls or foam balls (4 units)
  • • Hot glue and utility scissors (1 set)

Pro Tips

  • → Unlike medieval counterweight trebuchets, Roman ballistas stored potential energy in twisted skeins of animal sinew or rope.
  • → Twist the vertical cords using dowels until tight torsional resistance builds before inserting the throwing arms.
  • → Connect the two throwing arms with a flexible central drawstring to launch projectiles down the central flight trough.

Safety First

Launch only soft foam balls or cotton balls. Never aim projectiles at people or pets.

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Step-by-Step Instructions

1

Step 1

Build an open rectangular wooden or rigid cardboard chassis featuring a central launch guide trough.

2

Step 2

Thread two vertical loops of nylon paracord through top and bottom holes on both sides of the chassis.

3

Step 3

Insert wooden dowel arms through the center of the cord loops and twist them tightly to build torsional spring tension.

4

Step 4

Tie a drawstring between the arm tips, pull the string back to draw the torsion arms, load a foam ball, and release to measure launch distance.

What they are learning

Torsional spring potential energy storage Hooke’s law in twisted fibrous skeins Projectile trajectory ballistics