The Trebuchet Design The Trebuchet Design ProjectProject

By: Nick Hansen, Thomas By: Nick Hansen, Thomas Smith, Matt Borges & Emily Smith, Matt Borges & Emily

ByersByers

University of the PacificUniversity of the PacificSchool of Engineering School of Engineering

OverviewOverview

Problem DefinitionProblem Definition Approach/Initial DesignApproach/Initial Design Calculations and GraphsCalculations and Graphs Results/DiscussionResults/Discussion Suggested ImprovementsSuggested Improvements ConclusionConclusion AcknowledgementsAcknowledgements

What is a Trebuchet?What is a Trebuchet?

In the medieval times the Trebuchet In the medieval times the Trebuchet was designed to become the ultimate was designed to become the ultimate siege weaponsiege weapon

It is a catapult like structure which It is a catapult like structure which uses a counterweight and a swing uses a counterweight and a swing arm with a sling attached to fire a arm with a sling attached to fire a projectile as far & efficiently as projectile as far & efficiently as possiblepossible

ConstraintsConstraints

Must:Must: Be made of woodBe made of wood Fit in a 4 x 3 x 2.5 ft boxFit in a 4 x 3 x 2.5 ft box All wood parts connected with at least All wood parts connected with at least

one metal fastenerone metal fastener Be as light as possibleBe as light as possible Wood members can’t be smaller then 1” Wood members can’t be smaller then 1”

x 2”x 2”

Problem DefinitionProblem Definition

Build a functional trebuchetBuild a functional trebuchet Follow the set constraintsFollow the set constraints Take into account weight and Take into account weight and

accuracy as negative factorsaccuracy as negative factors

Objectives / CriteriaObjectives / Criteria

What we wanted to accomplish:What we wanted to accomplish: Win the competitionWin the competition Get $75Get $75 Shooting for 75ftShooting for 75ft Accurate as possibleAccurate as possible

What really happened:What really happened: 2121stst place place Got $0Got $0 Shot 50.5 ftShot 50.5 ft Was super accurateWas super accurate

Preliminary IdeasPreliminary Ideas

Top ViewTop View

Front View

Side ViewSide View

Attaching the base piecesAttaching the base pieces

Drilling for the screwsDrilling for the screws

Nick attaching the troughNick attaching the trough

Hurl Distance vs. Pivot HeightHurl Distance vs. Pivot HeightHurl Distance vs. Pivot Height

363

364

365

366

367

368

369

370

371

372

373

2.2 2.25 2.3 2.35 2.4 2.45

Pivot Height (ft)

Hu

rl D

ista

nce

(ft

)

hurls distance

Hurl Distance vs. Counterweight Hurl Distance vs. Counterweight LengthLength

Hurl Distance vs. Counterweight Length

0

50

100

150

200

250

300

350

400

0 0.2 0.4 0.6 0.8

Counterweight Length (ft)

Hu

rl D

ista

nce

(ft

)

hurl distance

Hurl Distance vs. Missile Sling Hurl Distance vs. Missile Sling LengthLength

Hurl Distance vs. M issile Sling Length

0

50

100

150

200

250

300

350

400

0 1 2 3 4 5

Missile sling Length (ft)

Hu

rl D

isa

nc

e (

ft)

hurl dis tance

Hurl Distance vs. Swing Arm RatioHurl Distance vs. Swing Arm Ratio

Hurl Distance vs. Swing Arm Ratio

358

360362

364

366368

370

372

374376

378

2.05 2.1 2.15 2.2 2.25 2.3 2.35

Swing Arm Ratio

Hu

rl D

ista

nc

e (

ft)

hurl distance

Range of Trebuchet vs. Ratio of Range of Trebuchet vs. Ratio of Arm LengthArm Length

Theoretical Energy EquationsTheoretical 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, Vwhere, R = projectile range, Voo = initial velocity, Θ = launch = initial velocity, Θ = launch angle, g = gravity, h = height weight falls, mangle, g = gravity, h = height weight falls, mcc = mass of = mass of counterweight, mcounterweight, mmm = mass of missile, R = mass of missile, Rmaxmax = maximum = maximum projectile range.projectile range.

g

VR o

2sin2

g

Vmghm omc

2

hm

mR

m

c2max

Angles vs. TimeAngles vs. Time

Angles vs. Time

-2

0

2

4

6

8

10

12

0 0.2 0.4 0.6 0.8 1 1.2

Time

Ra

dia

ns

th

psi

phi

RefinementRefinement

ProsPros Added needed support Added needed support

on one of the sides that on one of the sides that stabilized the basstabilized the bas

Added Nail release Added Nail release system with string system with string attachedattached

Took out middle supportsTook out middle supports Constructed “pouch-like” Constructed “pouch-like”

wash cloth holder for wash cloth holder for hacky sack while using hacky sack while using hemp string to attach it hemp string to attach it to the trebuchetto the trebuchet

ConsCons Added additional Added additional

weight!weight! Only one possible swing Only one possible swing

arm length, not able to arm length, not able to test multiple lengths test multiple lengths without constructing without constructing another swing arm.another swing arm.

Tried to maximize every Tried to maximize every possible measurementpossible measurement

Decision / ImplementationDecision / Implementation

The Finished ProductThe Finished Product

Results / DiscussionResults / Discussion

Placed 21Placed 21stst

Distance: 50.5’Distance: 50.5’ Accuracy: .9” off Accuracy: .9” off

straightstraight Same distance and Same distance and

accuracy for both accuracy for both trialstrials

Suggested ImprovementsSuggested Improvements

Reduced the weightReduced the weight Using a lighter woodUsing a lighter wood Also eliminating unnecessary supportsAlso eliminating unnecessary supports

Tested various sling and swing arm Tested various sling and swing arm lengthslengths

Had a warmer, less windy dayHad a warmer, less windy day Bigger may not always be betterBigger may not always be better

ConclusionConclusion

Overall, a challenging worthwhile Overall, a challenging worthwhile effort with much learned in the effort with much learned in the processprocess

Good teamwork qualitiesGood teamwork qualities Engineering ProcessEngineering Process Budgeting time, resources, becoming Budgeting time, resources, becoming

efficientefficient Having a good time in the processHaving a good time in the process

AcknowledgementsAcknowledgements

We would like to thank Professor Golanbari and We would like to thank Professor Golanbari and Professor Litton for their help and hard work.Professor Litton for their help and hard work.

Also, we would like to thank Mr. Hansen for Also, we would like to thank Mr. Hansen for providing tools and a quality work space in his providing tools and a quality work space in his home.home.

Finally, we would like to thank Professor Turpin Finally, we would like to thank Professor Turpin for taking photographs of the competition.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.