High School  ·  Physics

Trebuchet

Whipper trebuchet for grade 12 physics — launched a tennis ball 103m on 35 lbs of counterweight.

Year 2019
Role Designer & Builder
Type Whipper-arm trebuchet
Trebuchet

A grade 12 physics build: design a trebuchet to launch a tennis ball as far and as accurately as possible. We skipped heavy up-front calculation and went straight to building, choosing a whipper trebuchet because it converts counterweight energy into projectile speed remarkably well.

I didn't capture progress photos and the final launch videos are low quality — but turn the audio up and you can hear the whip crack of the arm, which gives a sense of how much energy the design released.

Tuning centered on the release-point setting, which controls the launch angle. We bracketed both extremes to learn the trajectory response, then dialed in toward a ~45° launch.

Backyard test — first throw, no counterweight, and it worked
Fail #1 — release point too early
Fail #2 — release point at the other extreme
Success — dialed in toward a ~45° trajectory

The final videos are rough, but they document the result: we shattered the school distance record, and at the in-class demo won the accuracy award with a direct hit that knocked down pins 10 ft away.

Best launch — 103m
School demo — shorter into a headwind; won the accuracy award
103m
Best launch distance
35 lb
Counterweight
1st
Class accuracy award

Shattered the class distance record and won the accuracy award with a direct-hit pin knock-down.