the trebuchet design project by: nick hansen, thomas smith, matt borges & emily byers university...
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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.