trebuchet basics fritz r. fiedler. basic sling trebuchet

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/