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

Trebuchet Design Project

ENGR-5Fall 2003Professors Gary M. Litton and Michael Golanbari

Matt Ritchie

Hoan Cai

Rong Srey

Thienan Nguyentan

Overview Problem Definition & Objectives Constraints and Criteria Calculations and Graphs Preliminary Design & Dimensions Analysis & Refinements Final Design Competition Results Possible Improvements 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 & GraphsRange vs. Pivot Height

0

20

40

60

80

100

120

140

160

2.5 2.3 2.1 1.9 1.7 1.5 1.3

Length of L5 (ft)

Th

eore

tica

l R

ang

e (f

t)

Theoretical Distance

Range vs. Counterweight Distance

175180

185190195

200205210

215220

0.9 1 1.1 1.2 1.3 1.4 1.5

Counterweight Distance (ft)

Ran

ge

Theoretical Distance

Range vs. L3

204206208210212214216218220222224

2.7 2.8 2.9 3 3.1 3.2 3.3

Length of L3 (ft)

Ran

ge

(ft)

Theoretical Range

Range vs. Arm Ratio

185

190

195

200

205

210

215

220

225

2.6 2.7 2.8 2.9 3 3.1 3.2

Ratio

Ran

ge

Theoretical Distance

Preliminary Design and Dimensions

We used WinTrebStar for our virtual simulations

L1 = 1 foot.L2 = 2.9 feetL3 = 3 feetL4 = .5 feetL5 = 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 feetL3 = 2.4 feetL4 = .2 feetL5 = 2.5 feet

Competition Results

Distance: 10.36 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)