Redesign of the STOL CH 701 Redesign of the STOL CH 701 Landing Gear StrutLanding Gear Strut

Group Members: Peter ChiuCameron Clark

Dave MaharajOkason Morrison

Problem DefinitionProblem Definition

Design a single-piece double cantilever leaf Design a single-piece double cantilever leaf spring capable of surviving the landing spring capable of surviving the landing conditions set forth by the FAR.conditions set forth by the FAR.

SpecificationsSpecificationsDescent velocity range 7 - 10 ft/s (2.134 m/s - 3.048 m/s)

Descent load factor range 1.67g – 2.67g

Wing Area 122 ft2 (11.2 m2)

Empty Weight 580lbs (263 kg)

Gross Weight 1,100 lbs (500 kg)

Payload 520 lbs (236 kg)

Max Reaction Load on tire 1350 lbs (6005 N)

Tire Diameter 16 in (0.406 m)

Theoretical Analysis 1: Theoretical Analysis 1: Newton’s Equation of MotionNewton’s Equation of Motion

AssumptionsAssumptions

Plane can be treated as point massPlane can be treated as point mass

Constant deceleration (vertical component Constant deceleration (vertical component only)only)

Neglecting material propertiesNeglecting material properties

Plane has zero final velocityPlane has zero final velocity

CalculationsCalculations

mma

us

a

us

mmrs

sss

strut

total

tiretire

struttiretotal

2.712

2

2.71*%35

2

2

The displacement, s is a The displacement, s is a function of 2 variables: u & a function of 2 variables: u & a

sstrut = f (u, a) surface plot

sstrut

stire

Maximum Displacement: 3-dMaximum Displacement: 3-d

S is max at

a =1.67g

u= 10 ft/s

Sstrut(max) = 212 mm (8.36 in)

s total

Theoretical Analysis 2: Theoretical Analysis 2: Beam DeflectionBeam Deflection

Geometry SimplificationGeometry SimplificationStrut can be modeled as a cantilever beamStrut can be modeled as a cantilever beam

Only a portion of strut needs to be analyze due Only a portion of strut needs to be analyze due to symmetry to symmetry

Beam subjected to 1 load and 1 momentBeam subjected to 1 load and 1 moment

R = 1350 lbs

Ry

YX

M

Deflection EquationsDeflection Equations

Deflection Equations 2Deflection Equations 2

I b( )b h

312

Y1 b( )R y

6 E I b( )L

33 L

3 Y2 b( )M

2 E I b( )

L2

y b( ) Y1 b( ) Y2 b( )

b

h

Beam AnalysisBeam AnalysisStrut Width vs Deflection: Beam Analysis

0

100

200

300

400

500

600

700

800

10 60 110

Width (mm)

De

fle

cti

on

(m

m)

Beam Analysis

Newton's Law

Suitable strut width 65 mm (2.6 in)

Width

Finite Element AnalysisFinite Element Analysis

ModelingModeling

Material: Al 2014

σyield: 414 MPa

Optimization StudyOptimization Study

Engineering Drawings of Final DesignEngineering Drawings of Final Design

Deflection VideoDeflection Video

DeflectionDeflection

Sstrut(max) = 45 mm (1.77 in)

Von Mises StressVon Mises Stress

σvm: 307 MPa S.F. = 1.3

Summary TableSummary TableMaterialMaterial Al 2014Al 2014

Strut WidthStrut Width 120 mm120 mm

Strut HeightStrut Height 354 mm354 mm

Strut thicknessStrut thickness 17 – 20 mm17 – 20 mm

Max Strut Deflection (Newton’s Law)Max Strut Deflection (Newton’s Law) 212 mm212 mm

Max Deflection (Beam Analysis)Max Deflection (Beam Analysis) 111 mm111 mm

Max Deflection (FEA)Max Deflection (FEA) 45 mm

Max Von MisesMax Von Mises 307 MPa307 MPa

Yield StrengthYield Strength 414 MPa414 MPa

Safety FactorSafety Factor 1.31.3

% of max allowable Displacement % of max allowable Displacement 14.2 %14.2 %

QuestionsQuestions