BAJA SAE 2010
Conceptual Design Review
Statement of Work

Baja SAE is an international collegiate design
competition sponsored by the Society of Automotive
Engineers. The program simulates real-world
engineering design projects and the related challenges
with the goal of developing and building a small offroad vehicle. Teams from around the world compete
in static and dynamic events to have their design
accepted for manufacture by a fictitious firm.
Team Responsibilities

Sam Moran – Chief Executive Officer; Frame Designer;
Welder/Grinder

Michael Guilfoy – Steering Engineer; Chief Financial Officer;
Welder/Machinist

Sam Weitkemper – Drivetrain Engineer; Executive
Secretary

Ben McNealy – Braking Engineer; Analyst; Director of
Internet Services

Matt Wantland – Analyst; Materials Acquisition Specialist;
Fabricator

Dan Pickering – Suspension Engineer; Chief Mechanic

Ahmed Al-Gattan – Chief Safety Officer
Customers

SAE Competition Fictitious Firm





Sponsors



Safe vehicle
Maneuverability, Traction, Suspension, Acceleration
Design/Manufacturability
Cost
Competitive vehicle
Promotion
Faculty Advisors


Competition success
Educational experience
Benchmarking


Vehicle Engineering Specifications

Front Track Width

Rear Track Width

Wheelbase

Weight

Suspension

Drivetrain
Data from 2009 Baja SAE Alabama competition
Benchmarking
Number of Teams Using a Specific Wheelbase
8
7
Number of Teams
2010 TU car
6
5
4
2009 TU car
3
2
1
0
42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86
Wheelbase (in.)
Benchmarking
Number of Teams Using a Specific Front Track Width
16
14
Number of Teams
12
10
8
6
2010 TU car
4
2
2009 TU car
0
48
49
50
51
52
53
54
55
56
57
58
59
Front Track Width (in.)
60
61
62
63
64
65
Benchmarking
Number of Teams Using a Specific Rear Track Width
16
14
Number of Teams
12
2010 TU car
10
8
6
2009 TU car
4
2
0
49
50
51
52
53
54
55
56
57
58
Rear Track Width (in.)
59
60
61
62
63
64
Benchmarking

Analysis of top 11 overall performing cars from 2009 Baja
SAE Alabama competition
Specification
Value
Wheelbase (in.)
62.2
Front Track Width (in.)
57.6
Rear Track Width (in.)
54.9
Weight (lbs.)
396.3
Frame Concept 1 – The Nose Box

Advantages:



simple
few packaging constraints
Disadvantages:

inefficient use of space
Frame Concept 2 – Integrated Cockpit

Advantages:




more legroom
efficient use of space
light
Disadvantages:

Complicated design
Frame Concept 3 – “The Cage”

Advantages:




simple design
requires the least amount
of planning
allows for last-stage
drivetrain changes
Disadvantages:


heavy
difficult drivetrain
maintenance
Frame Concept 4 – Double Loop

Advantages:




lightweight
efficient
easy drivetrain maintenance
Disadvantages:



difficult to design
not conducive to double aarm suspension
stuck with drivetrain
choices
Frame Concept & Design

Front




Rear






Length designed for the reach of the team’s smallest driver
Clearance designed for the 95th percentile male
Integrated cockpit design
Double loop design inspired by Queen’s University
Frame members do not interfere with removal of drivetrain
components
Weight: 73 lbs
Length: 80.5”
Width: 31.0”
Height: 52.9”
Final Frame Design
Frame Material


Given in 1018 PCS
2 different specifications Strength/Stiffness


Critical Components – Roll
Cage
Non-Critical Components
– frontal/side impact
Sizing Calculations
Roll Cage Requirements
mm
Inches
1018 Steel
Outer Diameter
25
0.984
Density (g/c3)
7.87
Wall Thickness
3
0.1181
E-Modulus (Gpa)
205
Sultimate (Mpa)
440
Syield (Mpa)
365
I (mm4)
12777.64
c (mm)
12.5
Bending Strength
Bending Stiffness
M = Syield*I/c
Stiffness = E*I
Min---> Max Moment (N-m)
373.11
Min---> Max Moment (lb-ft)
274.96
Min--->
Stiffness (N-m2)
2619.42
Tubing Possibilities
Tubing Size (in)
Minimum
0.75 X .080
1.00 X 0.095
1.25 X 0.095
1.28 X 0.071
1.00 X 0.060



Source
X
Tenaris
Tenaris
Tenaris
QuikService
QuikService
Yield (Mpa)
X
480
620
550
365
365
Strength (N-m) Stiffness (N-m2) Weight (lbs/ft)
375
2620
X
225
817
0.57
627
2385
0.91
903
4937
1.17
462.1
4218.7
0.91
235
1676
0.6
Hi Performance – Expensive/Light
Economical – Cheap/Heavy
Compromise – In between
Frame Specifications
Lengths of Different Tubing
Large Req. Tubing (ft)
25
Small Req. Tubing (ft)
68
Non Required (ft)
Option
1 - Economical
2 - Hi-Performance
3 - Compromise
0
Cost
$0.00
$650.00*
$40.00
Final Tubing Sizes
Lrg OD (in)
1.28
Lrg t (in)
0.071
Sm OD (in)
1
Sm t (in)
0.06
*http://www.airpartsinc.com/products/4130-steel-tubing.htm
Frame Wt. (lbs)
92
44.2
63.8
Drivetrain Benchmarking
Team
Oregon State
South Florida
Sherbrooke
Cornell
Maryland
SUNY Buffalo
Rochester Tech
SUNY Stony
Brook
Transmission
CVT w/ transaxle
6-speed gearbox
CVT w/ chain drive
Differential
driver-lockable open
solid rear axle
limited slip
CVT
not specified
CVT w/ transaxle
CVT
CVT w/ transaxle
auto-locking
not specified
auto-locking
CVT w/ transaxle
limited slip
Drivetrain Concept #1



CVT with chain drive
Pros: lightweight, simple, cheap
Cons: no reverse gear, requires tensioning system
Drivetrain Concept #2



Motorcycle gearbox with
chain drive
Pros: easy to find, includes
reverse gear
Cons: more difficult for the
driver
Drivetrain Concept Chosen



CVTech CVT with Dana H-12 transaxle
Pros: Simple, proven reliability, F/N/R, auto-locking
differential
Cons: Heavy
Drivetrain Layout
2010 Axle Design
Drivetrain Specifications
Max Ratio
Min Ratio
Top Speed
Max Gradient
Max Engine Power
Max Engine Torque
Idle
Max RPM
Weight
Tire Diameter
39.75 (35.60)
5.70 (6.98)
34 mph (35 mph)
52 % (70%)
9.1 HP
13.8 ft-lbs
1750
3800
120 lbs
22”
Front Suspension

Double A-arm configuration


The front suspension system for a majority of the cars at last
year’s competition
Benefits


The length and orientation of the arms can be designed for the
vehicle’s application.
Computers can be used to design the suspension geometry
Front Suspension

The vehicle was designed around the suspension
mounting points


To prevent conflicts between the suspension and other vehicle
components
Mechanism synthesis was performed in SolidWorks with the
help of Dr. Daily
Front Suspension

Mounting points
 Geometric constraint analysis was performed to determine the suspension
mounting points for a given tie rod length and designed for no bump steer
 Constraints: 5 degrees of camber and 10 inches of vertical travel for a 52-inch
front track width
 Top arm length: 16.375”
 Bottom arm length: 16.50”
Front Suspension

Roll center


The front roll center was determined using SolidWorks
For the desired mounting points, the roll center was found to
be about 3.05 inches above the ground
Rear Suspension

Solid Rear Axle/ Swing Arm


Top finishers such as Queen’s University and Michigan
University used a swing arm with a solid rear axle.
Double A-arm




A majority of the cars at last year’s Mini Baja used a double
wishbone configuration.
More appropriate for cars without a solid rear axle
Simple
After discussing options with the team, a double wishbone
configuration was chosen
Rear Suspension

Mounting points
 Geometric constraint analysis was again performed to determine the suspension
mounting points
 Constraints: no camber change and 8 inches of vertical travel for a 50-inch rear
track width
 Top arm length: 16.50”
 Bottom arm length: 16.50”
Rear Suspension

Roll center


The rear roll center was determined using SolidWorks given
parallel equal length arms
For the desired mounting points, the roll center was found to
be at the ground
Shocks and Springs


The shock mounting points were set by the frame design
and restrained by the control arm movement.
The ideal shock travel for the given wheel travel was
determined from mechanism synthesis.
Steering Concepts


Power Steering

Additional components

Requires power

Complicated integration
inside steering box
Four-Wheel Steering

Challenging integration

Untested in competition
conditions
Steering Concepts

Rack and Pinion Steering

Simplified system

Light

Ease of integration with suspension

Used by nearly every Baja SAE team
Ackerman Geometry
51”
62.5”
Modeling Steering Angles
27.73°
Outside Wheel Lock Position
45.49°
Inside Wheel Lock Position
Turning Radius Results
Turning Radius Composition
12
Turning Radius (ft)
10
8
6
4
2
0
Track Width
Wheelbase
Track Width (in)
52.00
Wheelbase (in)
60.00
Steering Angle (deg)
36.61
Turning Radius (ft)
10.55
Steering Specifications

Chosen Concept: Rack and Pinion








14 inch length; 4.5 inches of travel
1.5 turns lock-to-lock
Turning radius of approximately 10.5 feet
Ackerman Geometry
Tie Rod Connection
Rack mounting to minimize lateral loads
Rack mounting considered in frame design
Front Suspension design clearance issues addressed
Braking Concepts


Rules require two independent
hydraulic systems
Disc brakes




Light
Compact
Used by nearly all Baja teams
Drum brakes


Heavy
Bulky
Braking Concepts

Single cylinder, dammed reservoir



Pros: simple, packaging flexibility
Cons: longer than dual cylinders
Dual cylinders, overhead mount


Pros: shortest overall length
Cons: aesthetics

Dual cylinders, floor mount


Pros: elegant packaging
Cons: longer, may conflict with steering
components
Braking Concepts

Rigid lines



Pros: Rigid, look good
Cons: Difficult to install
Braided flex lines


Pros: Flexible, easier to install
Cons: Heavier
Braking Concept Selected




Polaris discs and calipers
Dual US Brake master cylinders
Wilwood reverse mount pedal
Braided steel flex line
Safety

Braking




Drivetrain



Two independent hydraulic braking systems
Capable of locking the wheels
No plastic brake lines
CVT cover – made of polymer
Gas catch – made of polymer
Kill Switches


Two kill switches required
One in cockpit, one in rear
Safety

Frame pads




The minimum required thickness is ½”.
The cost is $17.95 per 3 feet.
Need 6 feet.
Safety helmet

Motor cross style, Snell M2005 specification
Safety

Fire extinguisher



Two 5 B-C extinguishers.
One must be mounted next to the driver and the other in
the pit area.
Head restraint
Goals and Deadlines

January 25 – complete design



February 28 – drivable vehicle



rolls under its own power
basic safety gear
March 28 – competition-ready vehicle



stress analysis
CAD models
meets all rules
fully functional, painted, polished, done.
April 8-11 – 2010 Baja SAE Carolina competition
Schedule
Budget
Retail Cost
Customer Cost
Vehicle System Costs
Frame
Tubing - Donated
$
750.00 $
-
Tubing - Purchased
$
350.00 $
100.00
$
1,100.00 $
100.00
Transaxle
$
1,320.00 $
-
Engine
$
450.00 $
450.00
CVT
$
130.00 $
130.00
Rear Drive Axles
$
1,000.00 $
1,000.00
Miscellaneous
$
885.00 $
680.00
$
3,785.00 $
2,260.00
Shocks
$
1,160.00 $
1,160.00
A-Arms
$
250.00 $
250.00
Wheel Uprights
$
768.29 $
374.00
$
2,178.29 $
1,784.00
Rack and Pinion
$
98.00 $
98.00
Accessories
$
247.00 $
247.00
$
345.00 $
345.00
Braking
$
1,124.09 $
433.00
Tires and Maintenance
$
396.00 $
160.00
Miscellaneous
$
500.00 $
500.00
$
9,428.38 $
5,582.00
System Total
Competition Expenses
Travel to South Carolina
Hotel
$
1,000.00 $
-
Transportation and More $
1,000.00 $
1,000.00
$
2,000.00 $
1,000.00
$
1,000.00 $
1,000.00
$
3,000.00 $
2,000.00
Driving/Safety Gear
$
800.00 $
400.00
Team Uniforms
$
300.00 $
300.00
Office Supplies
$
100.00 $
100.00
Fabrication Tools
$
250.00 $
250.00
$
1,450.00 $
1,050.00
Total Engineering
$
97,500.00 $
-
Total Fabrication
$
43,350.00 $
-
Total Testing
$
10,500.00 $
-
$
151,350.00 $
-
TOTAL
Drivetrain
System Total
Suspension
System Total
Steering
System Total
TOTAL VEHICLE EXPENSES
Customer
Cost
Retail Cost
Entry Fee
TOTAL COMPETITION
EXPENSES
Team Operation Expenses
TOTAL OPERATION
EXPENSES
Team Labor Expenses
TOTAL LABOR EXPENSES
Retail Cost
Total Anticipated Costs $ 165,228.38
Customer Cost
$
8,632.00
Budget
Retail Cost
Competition Expenses
Customer Cost
$
3,000.00
$
2,000.00
Frame
$
1,100.00
$
100.00
Drivetrain
$
3,785.00
$
2,260.00
Suspension
$
2,178.29
$
1,784.00
Steering
$
345.00
$
345.00
Braking
$
1,124.09
$
433.00
Tires and Maintenance
$
396.00
$
160.00
Miscellaneous
$
500.00
$
500.00
$
9,428.38
$
5,582.00
Team Operation Expenses
$
1,450.00
$
1,050.00
Team Labor Expenses
$
151,350.00
$
-
Vehicle System Costs
TOTAL VEHICLE EXPENSES
Total Anticipated Costs
$
165,228.38
$
8,632.00
Budget
Hourly Rate
Extended Cost
Item
Description
Engineering
Design & Analysis
$75.00
$0.00
1300
$97,500.00
$0.00
Fabrication
Machining Time
$50.00
$0.00
30
$1,500.00
$0.00
Welding Fixtures
$45.00
$0.00
12
$540.00
$0.00
Tube Bending
$45.00
$0.00
6
$270.00
$0.00
Welding
$45.00
$0.00
72
$3,240.00
$0.00
Assembly
$45.00
$0.00
840
$37,800.00
$0.00
Testing & Analysis
$75.00
$0.00
140
$10,500.00
$0.00
2400
$151,350.00
$0.00
Testing
Total Labor Costs
Retail Rate Customer Rate Quantity Retail Cost Customer Cost