21st Century Pacific Students Construct A Great Launcher of Siege Assembled by: See Yang Hans Roelle Nicole Solari Rim Madani (Thursday 4-6) December 04, 2003

Overview/Outline I. Project Description II. History III. Modern Improvements IV. Design Tips and Guidelines V. Safety Considerations VI. Design & Construction VII. Analysis & Proposed Design VIII. Completion & Performance IX. Suggestions X. Acknowledgement

Project Description To design and construct a TREBUCHET that is able to launch a hacky sack as far and accurate as possible. Trebuchet: “an ancient siege engine used for throwing objects” TASKS 1. Research 2. Design development 3. Build actual model. 4. Performance Test 5. Final/Competition 6. Presentation 7. Final Report

History  Used for destroying barricading walls  4th century BC - first invented in China  6th century AD - made its way to Europe (used to hurl stones, cows, rotting flesh, etc.)  In England, it was referred to as Ingenium  16th century - became obsolete

Modern Improvements  Usage of Newton’s Second Law of Motion to modify designs (principles of physics)  The addition of wheels to increase momentum  Development of new materials for counter weight (massive solid vs. rocks)  Different/stronger sling material  Usage of light weight building materials

Design Tips and Guidelines  Find ratio of counter weight vs. arm that best optimizes hurl distance  Hinge the weight so it is free falling  Have the weight fall as vertically as possible for maximum acceleration  Have counter weight arm at a minimum weight  Have stable based frame  When drilling the hole for the dowel, make sure it’s as straight at possible  Use as much simplicity as possible

Safety Considerations  Always wear safety goggles at every step of the construction process and launching of the trebuchet  Keep a safe distance from the trebuchet when launching, somewhere around six feet  Keep all appendages away from the sling or release mechanism of the trebuchet to prevent injury to yourself or others  Prevent yourself and others from putting harmful objects into the sling as they may be hurled and injure someone  Do not use sharpened metals in construction as they may injure someone during operation

ALWAYS TAKE SAFETY PRECAUTIONS BEFORE OPERATING!!!

Design and Construction Requirements and Scoring Criteria  Limitations/Constraints  Hurl a Hacky Sack of weight 28.8g or 1 oz  Cannot exceed 4ft long x 3ft wide x 2.5 ft tall  Must use a counter weight that does not exceed 12 lbs  Must release arm from a distance no less than 10 ft  Weight penalty incurred per pound

Analysis and Proposed Design

Analyses Overview I. Design criteria discussion II. Analytical discussion A. Theoretical energy analysis B. Dynamic Computer Simulation III. Proposed Design A. Proposed Materials to be used B. Estimated Cost

Design Criteria Discussion In this portion of our project, we discussed how the truss should be put together, the base strength, the height, the arm length, the distance at which the counter weight is hanging from the arm, the length of the sling, and what material to use for the pouch.

Analytical Methods Projectile range with no air resistance: Energy balance: Combining range and energy equation: * R = projectile range * g = gravity * h = height * m c = mass of counter weight * m m = mass of missile (hacky sack) * V 0 = initial velocity * In order to maximize the range, the total height needs to be maximized

Analytical Methods (cont.) Dynamic Computer Simulation Discussion  In order to maximize the range, we experimented with all the variables in the figure to the left.  First, we started with all the given information. From there on, we experimented with different lengths of L1, L2, L3, L4, and L5. After finding the most efficient values for the variables, we experimented with the most efficient angles to be used.

Analytical Methods (cont.) Computer Simulation Results

Proposed Design In our proposed design, we made the base wide so the trebuchet would be stable. We also set our dimensions and lengths in accordance with the computer simulation. It seemed that in the simulation, by changing one measurement, the rest of the trebuchet lengths were changed.

Proposed Design (cont.) Materials Used…  Pine (1”x 2”) & (2”x 2”)  Screws  Wooden dowel (1)  Nylon rope  Shami  Wood putty  Eye bolts (appr. 4)  PVC pipe (1- 3.5” dia.) Estimated Cost…  Due to the fact that Nicole already has supplies at her house, we are fortunate enough to have our supplies donated.  If we do need supplies, we have estimated an amount of $25.

Construction and Performance

Construction methods To begin the project, we first sat down together and gathered all our thoughts. Before beginning to cut the pieces, we drew out a rough sketch of how we were going to put the trebuchet together.  Step 1: measure all the pieces  Step 2: we put the base together  Step 3: measure and cut all angles for the legs that are to fit at an angle  Step 4: screwing all the pieces together  Step 5: getting the holes in for the dowel  Step 6: cut the dimensions of the arm  Step 7: fix the track  Step 8: fix the sling, pouch, and release mechanism  Step 9: fix the counterweight

Pictures

Construction methods (cont.) In our actual building of the trebuchet, we changed a lot of the dimensions and design. The reason we changed our design and dimensions was so make it easier on our part. We ARE humans and cannot be exact, and our changes did make a difference. ProblemsSolutions Angles of BracingsAdd wedges and end caps Angling of trussModify design so trusses would stand vertical Use of nails to attach piecesUse screws instead of nails Drilling the hole on the arm for the dowel Added an extra piece to straighten the dowel Release mechanism wouldn’t lock into place Moving the release attachment Size of swing armShorten the end of the swing arm where the counter weight is attached

Completion of the Trebuchet

Optimizing hurl distance * For our first trials, we kept the all the measurements as calculated by the simulation. Step 1: experimented with different sling length to find the optimum performance length (between ft) Step 2: experimented with shortening and lengthening the distance between the counterweight and the ground (between ft) Step 3: experimented with different release angles (distance varied between 0-40) Step 4: shorten the length of the arm connected to the counterweight (50 ft) Step 5: repeated steps 1, 2, and 3 Other factors that affected the range were the weight of the arm, the overall weight of the trebuchet, and air resistance.

What would we do differently? Group  Started earlier on the construction portion of the project  Figured out the angles and lengths at reasonable measurements Trebuchet  Maximizing height of trebuchet  Use a lighter arm  Add wheels  Reduce the total weight  Use different release pin  Use different sling material  Make the counterweight drop as straight at possible  Drilling a straight hole through the arm

Conclusions and Recommendations Most helpful design processes:  Our design goals were met in terms of weight and size  We learned a number of interesting aspects in math and physics to help aid us in the design  The construction process helped us understand that the computer simulation was just a theoretical estimation of the results  Collaboration of ideas  Examples of trebuchets on the web Least helpful design processes:  There weren’t different measurements  The drawings we made were not detailed enough  The weight of the arm

Recommendations (cont.) Recommendations for future trebuchet builders:  Using better materials, connections, and construction tools  Run as many test trials as you can  Time management  Try not to get off task  Don’t be afraid to argue with your teammates to get your point across  Leave criticism with the project (don’t take it personally)  Have spare parts available  Be flexible  Have fun!!!

Acknowledgement Bullock, Tom. 11 January Trebuchet. 8 October Carliste, Paul. 1 February The Trebuchet. 8 October Geiselman, Kevin A. 27 May Ingenium. 8 October Gray Company Trebuchet Page. February October 2003.\ Grimminck, Micheal. 16 April Basic Physics Formulae. 8 October Ludlam, Eric M. 1 June Siege-Engine.com. 8 October Radlinski, Filip. Welcome to the Physics of the Trebuchet. 8 October Valley/Park/6461/trebuch.html

Acknowledgement (cont.) Ripcords Trebuchet Stuff. 23 August October Trebuchet. 10 February October Trebuchet. 8 September Wikipedia. 8 October Trebuchet.com. 8 October Trebuchet at NF/Observatory. 8 October Vaarma, Jari. 20 July Siege Engine Page. 8 October

Acknowledgement (cont.)  Thank you Linda, Charlene, Hanh, and James for letting us borrow your power drill and donating screws.  Thank you to Professor Litton and Professor Golinbari for all your help.