Counterweight trebuchets, built and thrown in Colorado
Build a trebuchet that throws real pumpkins
Build videos, drawings, parts lists and the engineering behind three machines, from a backyard thrower to one that launches 10 lb pumpkins. The plans are free.
2023 build, 8 to 10 lb class
The wheeled A-frame that throws 10 lb pumpkins
Laminated 2x lumber arm, steel pipe axle, pneumatic wheels so the whole base rolls forward on release, and a counterweight box loaded with weight plates. Built in a driveway, thrown in a school parking lot.
| Counterweight | about 180 lb | estimated |
| Projectile | 8 to 10 lb pumpkin | measured |
| Arm length | not yet measured | unmeasured |
| Best range | not yet measured | unmeasured |
A larger 2026 machine is under construction now.
0:38Loading the counterweight box
0:22The release pin, explained
0:31Sewing a sling pouch that lasts
0:45Laminating the throwing arm
0:19First throw of the day
Titles above are placeholders for the 2026 build Shorts. Each tile links to the Short on YouTube.
Engineering
How a counterweight trebuchet works
A trebuchet is a lever with a very heavy short end and a very long light end. Drop the weight, and the long end whips a sling around faster than any arm could swing on its own. The release angle, the sling length and the mass ratio decide where the pumpkin lands.
- 01The counterweight drops and the arm rotates about the axle.
- 02The sling trails the arm tip, then swings out past vertical.
- 03The release pin slips off its hook and the pouch opens at the launch angle.
Fig. 1 Side elevation, not to scale
counterweight
sling and pouch
axle
Fig. 1 Side elevation, not to scale
counterweight
sling and pouch
axle
Plans
The plans are free.
Dimensioned drawings, a cut list and a parts list for the machine above, as a PDF. No sign-up. If you buy the hardware through the links on the parts list, the site earns a small commission at no cost to you.
Engineering
What the numbers mean
Every value on this site is labeled measured, estimated or unmeasured. The engineering page explains each label and how the machine works.
Read the engineering pageBuilds
Three machines, three build logs
What was built, what it threw, and what changed between versions. Every log ends with a parts and materials table.
Browse the buildsAbout
Why this site exists
One builder, over a decade of pumpkin machines, and the notes that would have saved a lot of broken lumber. Why the site exists and how to get in touch.
About RealTrebuchet