NC State Engineering Class Projects

Winter & Spring Quarters, 2004

Operation Trebuchet

The day students in the Project Design Class this year chose to design and build a medieval trebuchet, a counterweighted throwing machine capable of hurling five pound projectiles over 300 feet.  There are almost no formal design plans of original trebuchets from the middle ages, so the students researched various types and decided on building one modeled after the Bellifortis Trebuchet.  The throwing arm is approximately ten feet long, and used a ballast box of steel that weighed almost 700 pounds.  Actual medieval trebuchets were up to 50 feet tall!!

During winter quarter, the students used their engineering skills to calculate and design properly sized beams and steel shafts to comply with current-day safety factors.  They also used trebuchet simulation software to determine maximum expected loads, proper sling lengths and approximate throwing distances.  During spring quarter, the students fabricated the parts and assembled the trebuchet using 4 x 4 and 4 x 6 wood beams.  The entire frame weighs between and five and six hundred pounds.

Testing at the end of spring quarter resulted in five pound frozen water "cannonballs" being hurled up to 350 feet!

(Click on the pictures for full size shots)

Assembling the throwing arm onto the main shaft. The students transported the trebuchet on a 6 x 12 foot trailer.
The ballast box contains 700 pounds of steel, capable of hurling a five pound projectile up to 350 feet. The day class stands before their trebuchet.

Congratulations to all of the students on a job well done!


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