Trebuchet Basics
Post on 11-Jan-2016
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Trebuchet Basics
Fritz R. Fiedler
Basic Sling Trebuchet
Example Frame
Example Beam
Example Tip Detail
Release
Trigger
Sling
Basic Trebuchet
Basic Trebuchet
The Throw
Definitions v0
h
Energy Equations
2
10
202
1
2
:2
m
ghmv
KEPEif
vmKE
ghmPE
Range
2
120
20
2
deg45
cossin2
m
mh
g
vR
if
gv
R
m
Efficiency
What affects efficiency and what would you expect the actual efficiency to be?
Efficiency
Does not include effects of:mass of beamfrictionair resistance…?
Efficiency ~ 50% or less (compute for report!)
so Rm < hm1 / m2)
Required Information
• h : by design
• m1 : by design
• m2 : given
Projectile
• 3 lb exercise ball (m2)
• Compute range with different counterweights…
Example Simple Calculation
assume: h = 4 feetm1 = 50 lbs
given: m2 = 3 lbs
R < 67 feet
Design Flexibility
What aspects of the trebuchet can be varied (after primary construction) to change throw distance?
Design Flexibility
• Counterweight mass (m1)
• h:– fulcrum height– starting position– beam length – how?
• sling length
• release angle
Counterweight
Design Constraint: must fit in 5-gallon bucket.
What materials might be appropriate?
Counterweight
• 5 gallons = 0.67 ft3
• water: 62.4 lb/ft3
• sand (dry): ~110 lb/ft3
• sand (saturated): ~135 lb/ft3
• concrete (ordinary): ~120-150 lb/ft3
• steel: ~490 lb/ft3
• lead: ~710 lb/ft3
Other Considerations
• Will it tip over?
• Will the beam break?
• Will the sling snap?
• Will the throw be straight?
References
• http://www.ripcord.ws/
• http://www.algobeautytreb.com/
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