Trebuchet Design Project ENGR-5 Fall 2003 Professors Gary M. Litton and Michael Golanbari Matt Ritchie Hoan Cai Rong Srey Thienan Nguyentan

Overview  Problem Definition & Objectives Problem Definition & Objectives  Constraints and Criteria Constraints and Criteria  Calculations and Graphs Calculations and Graphs  Preliminary Design & Dimensions Preliminary Design & Dimensions  Analysis & Refinements Analysis & Refinements  Final Design Final Design  Competition Results Competition Results  Possible Improvements Possible Improvements  Conclusions Conclusions

Problem Definition & Objectives  Build a trebuchet that will hurl a Hacky Sack.  Distance, accuracy, and trebuchet weight will be incorporated into the final performance design score.  Other design elements (e.g., aesthetics, safety, written report and oral presentation quality) will be judged and combined with the performance score to determine the overall project grade.  Research the history and design features of the trebuchet, develop a design using a comprehensive computer analysis program, build a prototype and optimize it.  Score = flight distance (m) - centerline offset distance (m) - 3 * mass (kg)  Two firings permitted. Only the best hurl will count.

Constraints & Criteria  When fully assembled with the swing arm in a horizontal position, the entire trebuchet must fit within a 4 x 3 x 2.5 foot container.  There is no weight restriction, only a penalty.  The sole energy source shall be a provided 12-lb lead ball.  No other operator contact or intervention will be permitted once the trebuchet is aligned and loaded.  The trebuchet will be activated with the operator 10 ft from the side.  Trebuchet must be fully designed and constructed only by members of the team.  No Hazardous Materials may be used.  Testing of the trebuchet shall only be conducted on Hand Hall Lawn, Brookside Field, Zuckerman Field, or the sunken field during daylight hours.  Only Hacky Sacks may be hurled at any time.

Initial Calculations & Graphs

Preliminary Design and Dimensions We used WinTrebStar for our virtual simulations L1 = 1 foot. L2 = 2.9 feet L3 = 3 feet L4 =.5 feet L5 = 2.5 feet

Analysis and Refinements  Shortened sling  Refined sling release  Changed remote release mechanism  Moved pivot hole on the swing arm in order to optimize arm ratio.

Final Design

Final Design (continued) L1 = 1 foot. L2 = 2.9 feet L3 = 2.4 feet L4 =.2 feet L5 = 2.5 feet

Competition Results Distance: meters Offset:.61 meters Weight: 5.35 kilograms Final Score: -6.2

Possible Improvements  Use a bearing for the swing arm to rotate on. (Reduce friction)  Spend more time and effort on the release mechanism and sling release.  Use less wood on the base. (Reduce weight)

Conclusions  More time should be spent on the design and improvement of the sling than on anything else.  The release mechanism is very important. (Ours failed)  The point reduction for weight was crucial.  It’s good to go first on competition day. (It was pretty cold)