EGR 400: Senior Design IFinal Report Presentation

Summer 2008

2009 Frame Front Rev B.

Introduction

• Objective– Design, build, and compete with a

small, formula style, race car.

• Plan– Divide into four teams:

• Frame and Suspension• Brakes and Controls• Engine and Drive Train• Body and Miscellaneous

– Work in sub-groups as well as collectively with the entire class.

2009 Frame

• Used 2008 frame model as foundation for our design

• Many changes were implemented and there are more to come

Design Goals

• Improve driver safety– Prevent driver’s arms from hitting sides of cockpit

• Eliminate “C-notch”• Follow 2009 rules

– Two templates for cockpit– Knee clearance for front roll hoop– Two inches of clearance over driver’s head between front and

main roll hoops

• Decrease weight of frame• Decrease wheel base from 64” to 60”• Shorten front of car while leaving room for pedals• Fit every component needed

Benchmarks in the road we’ve traveled

• June 22: build prototype frame out of MDF

• Week of June 23: learn how to manipulate 2008 frame model

• Week of July 24: make 2 different revisions of the model to compare concepts

• Week of July 28: receive final front and rear suspension points from suspension team

• August 6: selection revision B as design

Prototype Goals

• Elbow clearance

• Foot pedal positions

• Height of roll hoops

• Line of sight

• Angle of drivers seat

• Adjustable for changes

• Steering wheel mounting

Prototype Success

Rev A vs. Rev B

Revisions made to model to correct weight distribution problems

Revision A: • 62.75” wheelbase• Rear tire back 2”

Revision B:• 63.75” wheelbase• Rear tire back 1”• Driver forwards 1”

Driver safety

2008 Frame 2009 Frame

Side impact structure

C-notch

Templates

Must fit in seating area Must fit in leg area

Templates

Suspension Points

Interaction withengine team

• Met with engine team • Engine compartment

has approximately equal room to 2008 car, space won’t be an issue

• Engine mounts will be added to the model after they are designed

FEA withCosmosWorks

Material Properties

• Material properties obtained from MatWeb.

• Custom material created in SolidWorks.

• Material Properties:– Sut = 128 ksi

– Sy = 113 ksi

Torsional Stiffness

• Methodology:– Back and left front were restrained.– Torque of 2000 ft-lbs was applied at the right front.– Deflection of right front was measured in inches.– Torsional Stiffness was calculated as follows:

Torsional Stiffness 57

2400 19 32Torsional Stiffness

57 0 177

Torsional Stiffness 45959

Torque Distance

Deflection

in lbf . in

. in

in lbf / deg

Torsional Stiffness

Worst Case Stress

• Methodology:– Back restrained

and a weight hung from the front.

– At 90 lbs max stress was 104.2 ksi

– At 110 lbs max stress was 127.3 ksi

Case 1 Suspension

• Methodology– Force vectors for the three main scenarios

were obtained from the suspension team.– Force vectors were applied to each of the 16

suspension points.– The rear was restrained.

Case 1: Worst Case Stress

• Max stress occurred at the left rear lower A-arm suspension point• Max stress was 35.92 ksi• Factor of safety against yielding is 3.15• Factor of safety against failure is 3.56

Case 1: Displacement

Case 1: Bending Stress

• Max stress occurred at the right rear A-arm front suspension point• Max stress was 14.37 ksi• Factor of safety against yielding is 7.86• Factor of safety against failure is 8.91

FEA w/ ANSYS

Prepping the model

Creating the Mesh

Applying the forces

Results

What’s Next?

• Analysis needs to be completed for case 2 and case 3.

• Results from ANSYS analysis need to be compared.

• Anticipate similar results.

Conclusions from FEA

We have a frame that will meet or exceed all the physical requirements.

Changes Planned

• Main roll hoop – Radii of bends– Height

• Front roll hoop– Radii of bends– Number of bends

• Main roll hoop bracing• Front suspension point member• Shoulder harness and back brace• Add gussets for shoulder harness and back brace • Engine mounts

Engine Sensors

• Sensors– Throttle Position– Air Temperature– Water Temperature– Crank Position

• Each sensor delivers feedback to the ECU

• Plan to add a Manifold Absolute Pressure sensor.

Engine Tuning

• Goals– Began with acquiring a FSAE 4cly. Engine

map from Performance Electronics.– Read the tuning manual for the ECU to

understand the different parameters of the engine

– Engine started– Tune engine

Engine Tuning

Engine Tuning

• We tuned the engine– Real World– Stand testing

• The fuel map is tuned to be the correct ratio

• Spark map was left alone because that has more chance of damaging the engine

Engine Goals

• Acceleration and Deceleration compensations need more tuning

• Re-tune the fuel and spark maps once the MAP sensor is installed

• Also, need re-tune for our intake and exhaust designs

• Swap engines with 2008 FSAE car

Drive Train: Goals

• Improve upon current design– Lighter/smaller

differential

• Account for torque steer and misaligned sprocket

• Improve acceleration– Gear ratio– Larger rear sprocket

Drive Train: Sprocket

• Use basic concept from current car

• 11 tooth pinion• At least 48 tooth rear

sprocket– Testing must be done

to determine effectiveness of more teeth

• Gear ratio: 4.364

Drive Train: Differential

• Design choices:

– Honda ATV diff.

– Audi diff. (2007 FSAE)

– Miata diff. (2008 FSAE)

– New diff.

• Considerations:

– Ease of adaptation

– Weight

– Simplicity

Drive Train- Axles

Sprocket misalignment

• Solution/Alternatives– Center the differential

• Multi-stage gear• Larger differential housing

– Use different diameter axles– Provide calculations to prove design choices

Drive Train- Axles

• Factory Specifications:– Peak horsepower-

123hp– Peak RPM- 13000rpm– Pinion torque- 49ftlbf

• Gears:– Np= 11 teeth

– Ng= 48 teeth

• Assumed dimensions:– Short shaft- 16in, 1in

diameter– Long shaft- 24in, 1 in

diameter

Drive Train- Axles

• Calculations:• Gear RPM- 2979rpm• Gear torque- 216ftlbf• Angle of twist

– Φshort= 1.04deg

– Φlong= 1.56deg

– Difference= .519deg

• Calculate the new diameter of the longer shaft:– Dlong= 1.10in

• With:– Dshort= 1.0in

• Not large enough to have an impact

• Would require 2 different sized bearings

Intake

• Philosophy

• Components of Intake

• Calculations

• Preliminary Design

• Future Plans

Philosophy

• Effectively designed intake will improve volumetric efficiency– Torque

– Horsepower

– Fuel efficiency

Components of Intake

• Air Filter– Removes impurities

• Throttle Body– Manage air flow

• Restrictor– FSAE mandated

• Plenum– Air reservoir

• Fuel Injectors– Fuel regulation

• Runners– Cylinder air delivery

Restrictor

• 20mm Venturi Restrictor

• Placed after throttle body

• Severely limits air flow

Restrictor

D 35 mm

L1 35 mm

R1 48.125 mm

α1 21 Degrees

R2 72.5 mm

Dt 20 mm

L3 6.67 mm

R3 100 mm

α2 7 Degrees

R4 100 mm

L5 35 mm

Plenum

• Smooth out turbulence

• Even flow distribution

• 4-6X engine displacement– 3000cc

• Shape not yet determined

Runners

• Employed resonance equations– Ltotal=18”

• Primary tuning peak=5000 RPM– Helmholtz peak=7500 RPM– Helmholtz peak=11250 RPM

Preliminary Design

• Overhead Entrance– Straight delivery=Minimal flow loss– Easier construction

• Side Entrance– More bends=More flow loss– More difficult construction

Preliminary Design

Future Plans

• Verify runner length– Ricardo – Ohata & Ishida

• Better CAD model

• CFD’s

• Fabrication

Exhaust Design Overview

• Components

• Header Design Considerations

• Selected design

• Muffler design Considerations

• Selected Muffler

Exhaust Components

• Header

• Collector

• Muffler

Pictures from team-integra.net

Header Design Concerns

• Type of Header– 4 to 2 to 1– 4 to 1

• Primary Pipe Length

• Pipe Inner Diameter– Stepped Pipe

Charts from team-integra.net

Header Design

• Competition Requirements

• Final Design – Primary Pipe Length– Pipe Diameter – Collector

Muffler Design Concerns

• Muffler Types– Resonance– Absorptive– Back Pressure

• Materials– Titanium– Stainless Steel– Carbon Fiber

Picture from Motor cycle superstore .com

Pictures from starcycle-usa.com

• Supertrapp– Universal fit– Adjustable– Stainless Steel

Suspension

• Goals: – Maximize Friction

• Establishes ability to steer, brake, and accelerate

– Provide steering stability and feedback

• Determines the handling of the vehicle

SuspensionGeometry

• King Pin Inclination– 2.5°

• Helps with packaging• Provides steering

feedback• Increases steering

effort

• Scrub Radius– .75”

• Similar effects as KPI

Suspension Geometry

• Static Camber– Front: -1°, Rear: -.5°

• Negative camber maximizes the size of the tire patch

• Caster– 4°

• Provides beneficial camber gain during steering

• Increases steering effort

Front View Geometry

• Solidworks/Excel– Parameters set in

Excel and imported into Solidworks

• Solidworks used to cycle suspension through range of motion

– Results graphed in Excel

Camber Curves

Stress Analysis

• Excel sheet used to find wheel loads

• MathCAD file used to find forces in each member

• Excel sheet used to calculate safety factors in tension, compression, and buckling

Suspension Dynamics: Tire Behavior

• Slip angle• Cornering force

curve• Pneumatic trail• Aligning torque• Steering torque

Cornering Force vs. Slip Angle: Avon 1.0/20.0-13, 1 deg Camber

-5

-4

-3

-2

-10

1

2

3

4

5

Slip Angle (deg)

Cor

neri

ng F

orce

(kN

)

'

350 kg

250 kg

150 kg

Suspension Dynamics: Ride & Roll Rates

• Lateral Load Transfer

• Wheel center rate• Ride rate• Roll rate

90909090

LLT RHT

WRWL

FL FR

W

-WAY AY

• Worst case scenario:– Critical speed at tightest turn

• Weight & CG Assumptions

• Iterative design process

• Preliminary results– Roll gradient & body roll angle– Wheel, spring & anti-roll bar rates– Slip angle, aligning torque & steering torque

Suspension Dynamics: Ride & Roll Rate Calculations

• Pull rod vs. push rod– Lower CG & reduce weight

• Rocker arm– Installation ratio of 1: increased sensitivity

• Anti-roll bar– Blades: increased adjustability

• Shocks– 1’’ jounce, 1’’ rebound

Suspension Linkage Design Overview

Suspension Linkage Design Overview II

Suspension Linkage Design Overview III

Pull Rod

Rocker ArmAnti-Roll Bar

Blade

Shock/Spring

Suspension Linkage Motion Visualization

Upward Motion due to Vertical Wheel Displacement

RotationJounce/Compression

Bending

Torsion

Upright Design

• Design Goals

– Material• Weight / Strength / Cost

– Easy to manufacture– Similar manufacturing

procedure– KPI, Brakes, A-Arms,

Steering– Prototypes

Front Uprights

Rear Uprights

• Design Goals

– Interchangeable– Lightweight– Design Considerations

• A-arms• Tie-Rod• Bearing

Steering

• Design Goals

– No > 180º for any turn– 60º - 80º steer = 9.5m turn– Ratio for manageable steer– Rack total travel ≤ stock

Steering

• Basic GeometrySteering Calculation

• Find point B WRT A

• Calculate angle CAB

• Subtract arm angle

• Subtract angle to vertical

• Steering angle

• Calculate Steering ratio

Steering

• Ackermann Steering

Brakes

• Design Goals

– Max pedal force < 100lbf – No lock < 60lbf pedal force– Lock front wheels first– Built-in Bias– Light, Compact, Inexpensive

Brakes

• System Layout

Aerodynamics

• Benefits– Stability & Control– Increase Downforce

• Better Traction

– Air Flow Control– Drag Reduction

Aerodynamics

• Drag Components– Basic External Shape

• Less than Perfect Shape• Interference

– Internal Flow Devices– External Flow Devices

• Wheels & Wheel Wells

Aerodynamics

• Internal Flow Devices– Goal: Optimize Cooling Efficiency

• Types– Ram Air Ducts

• Nose• Side

– Scoops (High-Mounted Units)– Flush Duct (NACA Submerged Inlet)

Aerodynamics

• Side Ram Air Duct– Benefit: Easy Input &

Output Adjustments

• Scoop– Benefit: Low Speed

Operations– Coverts Air Velocity to

Pressure

Aerodynamics

• External Flow Devices

• Surface Roughness– Permissible Grain Diameter = 0.0021in

• Same as for Unpainted Sheet Metal

• Vortex Generators– Control & Delay Flow Separation

Aerodynamics

• Rear Wings– Rear Downforce & Increased Deceleration

• Rear Spoilers– Separate Air Flow & Rear Downforce

• Slotted Front Wings– Frontal Downforce & Very Little Drag

• Rear Wheel Curved Guide Vanes– Decrease Drag & Increase Downforce on Tires

Aerodynamics

• Ground Effects– “Sucker Car”

• Increased Downforce from 1.3 to 1.7g’s• Low Speeds

– Nose Angle• Horizontal to 10° Down

– Lift Coefficient from -0.95 to -2.3

Aerodynamics

• Venturi Upsweep– Controls strength of

two vortices• Height of Side Skirts

– Drawback• Open Wheeled

Vehicles Diminish Effects

Aerodynamics

• Testing– Wind Tunnel

• Employ Correction Factors

– CAD Program• Know Programs Limitations

– Calculate Frontal Area• Guess Overall Drag Coefficient

– Estimate Drag Components• Guess Interference Effects

Aerodynamics

• Conclusion– Explored Variety of Aerodynamic Designs

• Promising Low Speed Design Options– Side Ram Air Duct– Slotted Front Wings– Venturi Upsweeps

• Will Effect Handling– Ability to “Grip” the Road

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