Design Review #2
Statement of Work
 Baja SAE is an international engineering
design competition. Student teams design,
build, and test a single seat, four-wheel offroad vehicle. We will compete in the Baja SAE
Carolina competition in April 2010.
Team Responsibilities
 Sam Moran – Team Captain; Frame; Welder/Fabricator
 Michael Guilfoy – Treasurer; Steering; Machinist/Fabricator
 Sam Weitkemper – Powertrain; Secretary
 Dan Pickering – Suspension; Machinist/Fabricator
 Matt Wantland – Analyst; Materials Acquisition; Fabricator
 Ben McNealy – Brakes; Dynamic Analysis
 Ahmed Al-Gattan – Safety
Project Background: Baja SAE
 Baja SAE Carolina will be held
April 8th-11th, 2010, in Greenville,
South Carolina
 106 teams registered
 Dynamic Testing Events:
 Acceleration
 Suspension
 Traction/Pulling
 Maneuverability
 4-hour Endurance Race
 Static Events:
 Design Presentation/Report
 Prototype Cost
Project Background: Baja SAE
 Why is this project important?
 Real-world engineering design project

Concept Selection

Design decisions based on pre-determined competition
specifications and safety concerns

Three-Dimensional Modeling

Limiting Factor – 10 horsepower Briggs & Stratton Engine
 Fabrication Experience

Welding

Machining
Vehicle Engineering Specifications
Overall Vehicle Dimensions
Specification
Specified by
Designed
Ground Clearance
10"
Team
10"
Track Width
55"
Team
55"
Wheelbase
60"
Team
60"
Weight
< 500 lbs.
Advisors
~500 lbs.
Frame
Material
Steel, Sy = 52.9 ksi
Baja SAE
Sy = 52.9 ksi
Size A
1.25" 1018 steel
Baja SAE
32.0 feet
Size B
1.00" 1018 steel
Baja SAE
65.5 feet
Length
≤ 80”
Team
81.5”
Width
≤ 35”
Team
30.25”
Height
≤ 52”
Team
51.8”
Weight
< 100 lbs.
Team
67.8 lbs.
Vehicle Engineering Specifications
Powertrain
Specification Target
Designed
Max Ratio
35.60
39.75
Min Ratio
6.98
5.7
Top Speed
35 MPH
34 MPH
Max Gradient
70%
52%
Max Engine Power
9.1 HP
9.1 HP
Max Engine Torque
13.8 ft-lbs.
13.8 ft-lbs.
Idle
1750 RPM
1750 RPM
Max RPM
3800 RPM
3800 RPM
Weight
< 150 lbs.
120 lbs.
Tire Diameter
22 inches
22 inches
Vehicle Engineering Specifications
Suspension
Specification
Specified by
Designed
10”
Team
10”
Suspension
Synthesis
Bump Steer
Front:
105 lb/in
Rear:
145 lb/in
Front:
5.0°
Rear:
0.0°
0.0°
Team
Front:
120 lb/in
Rear:
140 lb/in
Front:
5.0°
Rear:
0.0°
0.0°
Weight
< 65 lbs.
Team
~50 lbs.
Specification
Specified by
Designed
Turning Radius
≤ 10 feet
Team/Advisors
10.02 feet
Rack & Pinion Travel
4.25 inches
Team
4.75 inches
Lock-to-Lock
1.5 turns
-----
1.5 turns
Ackerman Angle
39.75°
Team
39.55°
Suspension Travel
Spring Rates
Camber
Team
Steering
Final Vehicle Concept
Frame Bends
Frame
Drivetrain Design - Transmission
 CVTech CVT mated to a Dana H-12 transaxle
 Pros: Simple, proven reliability, F/N/R, auto-locking
differential
 Cons: Heavy
Drivetrain Design – Axle
Drivetrain Stress Analysis
 Conservative analysis:
 Max axle torque = Max motor torque * max gear ratio = (14.5 ft-
lbs) * (39.75) = 580 ft-lbs
 Shear stress = T*C/J * Kt= (580 ft-lbs) * (0.362) ft / 0.0270 ft^4 *
1.78 = 138 ksi
 Shear strength (4340 @ HRC 52) ≈ 0.577 * (260 ksi) = 150 ksi
 Factor of Safety = 150 / 138 = 1.1
 Fatigue life (calculated using FatigueCalculator tool) > 1500
cycles
Drivetrain Stress Analysis
 Using same CV joints that worked well in the 2009
competition
 Axle assemblies are rated by manufacturer to 700 ft-lbs
(includes a factor of safety), and that vehicle uses an
engine that produces twice as much power
 Using hollow axles would at best save 0.5 lbs per axle
and would increase part cost
 In our case, conservative analysis did not add to cost
Drivetrain Design - Axle
 4340 Q&T steel
 Splined ends to fit CV joints
Suspension System
Su sp en sion A nalysis O ve rvie w
Fro nt Sus pe ns ion :
T ra ve l:
10
in
Jo unce :
8
in
Re b oun d:
2
in
G rou nd C le a ra nce :
10
in
Ro ll C e nte r:
3.05
in
C am b e r
5.5
d e gre e s
J oun ce:
4.3
d e gre e s
R e bo und:
1.2
d e gre e s
C ha nge :
a bov e the gro und
R e a r Sus pe ns ion:
T ra ve l:
8
in
Jo unce :
6
in
Re b oun d:
2
in
G rou nd C le a ra nce :
10
in
Ro ll C e nte r:
A t th e gro und
C am b e r
0
d e gre e s
J oun ce:
0
d e gre e s
R e bo und:
0
d e gre e s
C ha nge :
Suspension System
Sho ck a nd Sprin g A n aly sis :
Loa din g:
S pring Co nsta nt
Fron t:
S pring Co nsta nt
R e ar:
Fo rce in S pring
Fron t:
Fo rce in S pring
Fron t:
4
g 's
Lo ad ing :
From Syn th es is :
5
g 's
131.7149
l b/in
Sprin g
105 .3719
lb/ in
C ons ta nt
F ront:
F ront
S hock s:
Re a r
S hock s:
T ra ve l
T ra ve l
20.27514.55
20.00-
lb/ in
C ons ta nt
S pring 105 l b/i n
3.79" Stroke
S pring 145 l b/i n
16 .215
Pola ris W e bs ite
Sprin g
142 .3406
5.73" Stroke
177.9258
l b/in
T ra ve l
Re a r:
18.00 12.0 0
6" S tro ke
S pring 120 l b/i n
Fo rce in
903
lb s
Sprin g
11 29
l bs
F ront
Sho ck - Fox Pod ium X
S hock s:
F ront:
Sprin g - 120# /IN , 10.5" ,
Fo rce in
832
lb s
Sprin g
R ed
10 40
l bs
18.0 1 (E xte nde d Le n gth) x 6.00 (Strok e)
F ront:
T ra ve l
Re a r
S hock s:
18.00 12.0 0
6" S tro ke
S pring 140 l b/i n
Sho ck - Fox Pod ium X
Sprin g - 140# /IN , 10.5" ,
R ed
18.0 1 (E xte nde d Le n gth) x 6.00 (Strok e)
Suspension System
 Front Suspension View
Suspension System
 Rear Suspension View
Suspension Stress Analysis
A-Arm Material Specifications
Tubing Size
1 Inch
1.25 Inch
Diameter (in)
1
1.25
Wall (in)
0.075
0.075
c (in)
0.5
0.625
I moment (in4)
0.02346
0.04797
Fmax Bending (lbs)
156.5
256.0
A-Arm tube Length
15.875 in
Tubing Yield Strength
53 Ksi
Suspension Stress Analysis
M ou nting Bracket Stress Analysis:
σy =
53700
psi
Sh ear and C om pression:
Loading :
2
g 's
W eig ht of Car:
680
lbs
D ynam ic Lo ad ing (P) :
136 0
lbs
σ=
P
A=
2w t
A
A=
0.75t
P
A=
t=
σ
t=
0 .034
t=
σ=
0.062 5
in
1/16
in
2 9013.33
psi
t=
σ=
0.125
in
1 /8
in
14506.67 psi
σy
F .S. =
σ
P
0.7 5σ
in
F.S. =
1.85
t=
F .S. =
1/8
3.7 0
in
Steering System
 Major Goal – turning radius less than 10 feet

Procured rack and pinion drive had greater travel than
specified by vendor
 4.75 inches rather than 4.25 inches of travel
 1.5 turns lock-to-lock
 Allows for a greater steering angles
 Allows for shorter turning radius
Outside Wheel Steering Angle
37.5
degrees
Inside Wheel Steering Angle
41.6
degrees
Ackerman Steering Angle
39.55
degrees
Turning Radius
10.02
feet
Braking system
Components:
• Dual US Brake master cylinders,
7/8” bore
• Wilwood reverse mount pedal
• Polaris Outlaw front rotors and
calipers
• Polaris Ranger rear rotors and
calipers
• AN-3 flex steel brake lines
• Polaris 10mm pressure switch
• Polaris brake light
Weight Distribution Analysis
 Design Specifications:
 55% rear weight bias
 Center of Mass as low as possible to ground level
 Design Results:
 54.3% rear weight bias
 Center of Mass = 25.3 in above ground level
Rollover Potential Analysis
Dynamic Rollover Threshold
Maximum Safe Velocity (mph)
30
25
20
15
10
5
0
0
5
10
15
20
25
30
35
40
45
50
Turning Radius (ft)
 Dynamic analysis based on COM height, roll center, and spring rate
 Vehicle will be rollover-resistant when cornering at reasonable speeds
Torque Analysis
Torque vs. Incline
1600
Resistive Torque (lb-ft)
1400
1200
1000
800
600
400
200
0
0
5
10
15
20
25
30
Percent Grade
 Based on front/rear weight distribution and torque at wheels
 Result: Front wheels will stay on the ground under foreseeable
circumstances
35
Vehicle Safety Considerations
 Engine Spill Shield – made of HDPE
 CVT Cover – eliminate hand access, made of HDPE
 Kill Switches – 2 required, cockpit and external
 Transponder – “MYLaps” rechargeable power
 Safety Harness – 5 strap system, 3” lap belt, quick release
connecters
 Fire Extinguisher – 5 BC rating, dial pressure gauge
 Tube Padding – standard 1.5” foam padding
Vehicle Safety Considerations
 Welding Helmet – new auto-darkening mask
 Safety Glasses – always required during fabrication
 Ear Plugs – required for cutting/grinding metal
 Helmet – motor-cross style, 1-piece composite
 Neck Collar – SFI 3.3, full 360° coverage
 Arm Restraints – SFI 3.3, attach to driver harness
 Head Restraint – SFI 42.2, foam pad
activity
week
Jan 18
Jan 25
Feb 1
Feb 8
Feb 15
Feb 22
Mar 1
Mar 8
Mar 15
Mar 22
Mar 29
April 5
April 12
DESIGN
frame
suspension
steering
design review I
braking
complete design
Jan 20
Jan 25
PURCHASING
PURCHASING
FABRICATION/ASSEMBLY
FABRICATION/ASSEMBLY
tubing
tools
drivetrain
suspension
brakes
drivetrain
steering
safety equipment
engine
nuts 'n' bolts
tube bending
welding fixtures
fabricate frame
suspension
brakes
drivetrain
steering
safety equipment
design review II
drivable vehicle
bells and whistles
paint
competition prep
competition-ready
design review III
Feb 17
Feb 28
Mar 13
Mar 28
Mar 31
TESTING
on-road
off-road
competition
design review IV
April 8-11
April 21
activity
week
Feb 15
Feb 22
Mar 1
Mar 8
Mar 15
Mar 22
Mar 29
PURCHASING
tubing
tools
drivetrain
suspension
brakes
drivetrain
steering
safety equipment
engine
nuts 'n' bolts
FABRICATION/ASSEMBLY
tube bending
welding fixtures
fabricate frame
suspension
brakes
drivetrain
steering
safety equipment
design review II
drivable vehicle
bells and whistles
paint
competition prep
competition-ready
design review III
Feb 17
Feb 28
Mar 13
Mar 28
Mar 31
Budget
Original Budgeted
Retail Cost
Competition Expenses
Retail Cost
Customer Cost
$
3,000.00
$
3,100.00
$
2,100.00
Frame
$
1,100.00
$
1,100.00
$
50.00
Powertrain
$
3,785.00
$
6,290.34
$
3,033.69
Suspension
$
2,178.29
$
3,600.00
$
1,648.00
Steering
$
345.00
$
269.95
$
269.95
Braking
$
1,124.09
$
1,124.09
$
653.00
Tires and Maintenance
$
396.00
$
500.00
$
200.00
Miscellaneous
$
500.00
$
1,750.00
$
1,000.00
TOTAL VEHICLE EXPENSES
$
9,428.38
$
14,634.38
$
6,854.64
Team Operation Expenses
$
1,450.00
$
900.00
$
900.00
Team Labor Expenses
$
151,350.00
$
154,950.00
$
-
Total Anticipated Costs
$
165,228.38
$
9,854.64
Vehicle System Costs
$ 173,584.38
Budget
Hourly Rate
Extended Cost
Item
Description
Retail Rate
Customer
Rate
Quantity
Retail Cost
Customer Cost
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
20
$900.00
$0.00
Tube Bending
$45.00
$0.00
6
$270.00
$0.00
Welding
$45.00
$0.00
144
$6,480.00
$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
2480
$154,950.00
$0.00
Testing
Total Labor Costs
Donations Received
 Polaris Industries:


$5,647.23 in parts for $2,533.00
Suspension, brake, safety, and driveshaft components
 CVTech-IBC:

$232.00 CVT for $130.00
 Tubing:


Tenaris Coiled Tubes – 150 feet of tubing
QwikService Steel – 200+ feet of various tubing and steel
 Ariens:


$2,074.60 in parts for $371.69
Dana Transaxle, locking differential, and driveshaft components
 The University of Tulsa Student Association

$1,000 towards travel costs to competition in South Carolina
Tulsa Baja Racing Sponsors
•
•
•
•
•
•
•
•
•
•
Hurricane Motor Works
The University of Tulsa Department of Mechanical Engineering
The University of Tulsa Student Association
Bendco
Polaris Industries
QuikService Steel
Tenaris Coiled Tubes
Briggs & Stratton
Ariens Corp.
CVTech-IBC
Original Retail
Cost
Vehicle System Costs
Frame
Updated Retail
Customer Cost
Cost
Tubing - Donated
$
750.00
$
750.00
$
-
Tubing - Purchased
$
350.00
$
350.00
$
50.00
$
1,100.00
$
1,100.00
$
50.00
Transaxle
$
1,320.00
$
1,653.12
$
-
Engine
$
450.00
$
628.00
$
-
CVT
$
130.00
$
232.00
$
130.00
Rear Drive Axles
$
1,000.00
$
2,965.00
$
2,503.69
Miscellaneous
$
885.00
$
812.22
$
400.00
$
3,785.00
$
6,290.34
$
3,033.69
Shocks
$
1,160.00
$
1,700.00
$
810.00
A-Arms
$
250.00
$
800.00
$
438.00
Wheel Uprights
$
768.29
$
1,100.00
$
400.00
$
2,178.29
$
3,600.00
$
1,648.00
Rack and Pinion
$
98.00
$
94.95
$
94.95
Accessories
$
247.00
$
175.00
$
175.00
$
345.00
$
269.95
$
269.95
Braking
$
1,124.09
$
1,500.00
$
653.00
Tires and Maintenance
$
396.00
$
500.00
$
200.00
Miscellaneous
$
500.00
$
1,750.00
$
1,000.00
$
9,428.38
$
15,010.29
$
6,854.64
System Total
Powertrain
System Total
Suspension
System Total
Steering
System Total
TOTAL VEHICLE EXPENSES
Original Retail Updated Retail
Customer Cost
Cost
Cost
Competition Expenses
Travel to South Carolina
Hotel
$
1,000.00
$
1,100.00
$
100.00
Transportation and More
$
1,000.00
$
1,000.00
$
1,000.00
TOTAL
$
2,000.00
$
2,100.00
$
1,100.00
$
1,000.00
$
1,000.00
$
1,000.00
$
3,000.00
$
3,100.00
$
2,100.00
$
9,428.38
$
15,010.29
$
6,442.95
Driving/Safety Gear
$
800.00
$
200.00
$
200.00
Team Uniforms
$
300.00
$
300.00
$
300.00
Office Supplies
$
100.00
$
100.00
$
100.00
Fabrication Tools
$
250.00
$
300.00
$
300.00
$
1,450.00
$
900.00
$
900.00
Total Engineering
$
97,500.00
$
97,500.00
$
-
Total Fabrication
$
43,350.00
$
46,950.00
$
-
Total Testing
$
10,500.00
$
10,500.00
$
-
$
151,350.00
$
154,950.00
$
-
$
9,442.95
Entry Fee
TOTAL COMPETITION EXPENSES
Vehicle System Costs
TOTAL VEHICLE EXPENSES
Team Operation Expenses
TOTAL OPERATION EXPENSES
Team Labor Expenses
TOTAL LABOR EXPENSES
Total Anticipated Costs
$ 165,228.38
$ 173,960.29