The Trebuchet Design Project By: Nick Hansen, Thomas Smith, Matt Borges & Emily Byers University of the Pacific School of Engineering

Overview Problem Definition Problem Definition Approach/Initial Design Approach/Initial Design Calculations and Graphs Calculations and Graphs Results/Discussion Results/Discussion Suggested Improvements Suggested Improvements Conclusion Conclusion Acknowledgements Acknowledgements

What is a Trebuchet? In the medieval times the Trebuchet was designed to become the ultimate siege weapon In the medieval times the Trebuchet was designed to become the ultimate siege weapon It is a catapult like structure which uses a counterweight and a swing arm with a sling attached to fire a projectile as far & efficiently as possible It is a catapult like structure which uses a counterweight and a swing arm with a sling attached to fire a projectile as far & efficiently as possible

Constraints Must: Must: Be made of wood Be made of wood Fit in a 4 x 3 x 2.5 ft box Fit in a 4 x 3 x 2.5 ft box All wood parts connected with at least one metal fastener All wood parts connected with at least one metal fastener Be as light as possible Be as light as possible Wood members can’t be smaller then 1” x 2” Wood members can’t be smaller then 1” x 2”

Problem Definition Build a functional trebuchet Build a functional trebuchet Follow the set constraints Follow the set constraints Take into account weight and accuracy as negative factors Take into account weight and accuracy as negative factors

Objectives / Criteria What we wanted to accomplish: What we wanted to accomplish: Win the competition Win the competition Get $75 Get $75 Shooting for 75ft Shooting for 75ft Accurate as possible Accurate as possible What really happened: What really happened: 21 st place 21 st place Got $0 Got $0 Shot 50.5 ft Shot 50.5 ft Was super accurate Was super accurate

Preliminary Ideas

Top View

Front View

Side View

Attaching the base pieces

Drilling for the screws

Nick attaching the trough

Hurl Distance vs. Pivot Height

Hurl Distance vs. Counterweight Length

Hurl Distance vs. Missile Sling Length

Hurl Distance vs. Swing Arm Ratio

Range of Trebuchet vs. Ratio of Arm Length

Theoretical Energy Equations Projectile range with no air resistance: Projectile range with no air resistance: Energy balance: Energy balance: Combining range and energy equation: Combining range and energy equation: where, R = projectile range, V o = initial velocity, Θ = launch angle, g = gravity, h = height weight falls, m c = mass of counterweight, m m = mass of missile, R max = maximum projectile range. where, R = projectile range, V o = initial velocity, Θ = launch angle, g = gravity, h = height weight falls, m c = mass of counterweight, m m = mass of missile, R max = maximum projectile range.

Angles vs. Time

Refinement Pros Pros Added needed support on one of the sides that stabilized the bas Added needed support on one of the sides that stabilized the bas Added Nail release system with string attached Added Nail release system with string attached Took out middle supports Took out middle supports Constructed “pouch-like” wash cloth holder for hacky sack while using hemp string to attach it to the trebuchet Constructed “pouch-like” wash cloth holder for hacky sack while using hemp string to attach it to the trebuchet Cons Added additional weight! Only one possible swing arm length, not able to test multiple lengths without constructing another swing arm. Tried to maximize every possible measurement

Decision / Implementation

The Finished Product

Results / Discussion Placed 21 st Placed 21 st Distance: 50.5’ Distance: 50.5’ Accuracy:.9” off straight Accuracy:.9” off straight Same distance and accuracy for both trials Same distance and accuracy for both trials

Suggested Improvements Reduced the weight Reduced the weight Using a lighter wood Using a lighter wood Also eliminating unnecessary supports Also eliminating unnecessary supports Tested various sling and swing arm lengths Tested various sling and swing arm lengths Had a warmer, less windy day Had a warmer, less windy day Bigger may not always be better Bigger may not always be better

Conclusion Overall, a challenging worthwhile effort with much learned in the process Overall, a challenging worthwhile effort with much learned in the process Good teamwork qualities Good teamwork qualities Engineering Process Engineering Process Budgeting time, resources, becoming efficient Budgeting time, resources, becoming efficient Having a good time in the process Having a good time in the process

Acknowledgements We would like to thank Professor Golanbari and Professor Litton for their help and hard work. We would like to thank Professor Golanbari and Professor Litton for their help and hard work. Also, we would like to thank Mr. Hansen for providing tools and a quality work space in his home. Also, we would like to thank Mr. Hansen for providing tools and a quality work space in his home. Finally, we would like to thank Professor Turpin for taking photographs of the competition. Finally, we would like to thank Professor Turpin for taking photographs of the competition. Thanks to the student volunteers. Thanks to the student volunteers. Good job to all the trebuchet groups. Good job to all the trebuchet groups.