Trebuchet Basics Fritz R. Fiedler
Jan 02, 2016
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/