OFF-ROAD INNOVATIONS
Outline
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The SAE Baja Competition
Problem Definition
The Current System
Suspension System Validation
Steering System Validation
Design Methodology
Design Targets
Moving Forward
Management Plan
The SAE Baja Competition
The Baja SAE Series is an international competition testing the
limits of off-road vehicles designed and built by engineering
students from around 100 universities each year.
Introduction to SAE Baja Competition
Suspension and Traction
Introduction to SAE Baja Competition
Rock Crawl
Mud Pit
Introduction to SAE Baja Competition
Design Competition
Problem Definition
Off-Road Innovations’ goal is to develop a front suspension and
steering system for the Memorial Baja team that will:
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Provide more driver room
Improve ground clearance
Absorb frontal impact forces
Maintain safety, reliability and low weight
The Previous System
2013 Memorial Baja Steering
2013 Memorial Baja Suspension
Steering System Validation
Manual Rack and Pinion
Pro: Lightweight and Robust
Con: More Effort to Steer
Steering System Validation
Recirculating Ball Gearbox with Pitman Arm
Pro: Less Effort to Steer
Con: Complicated and no driver feedback
Steering System Validation
Electric Power-Assisted
Hydraulic Power-Assisted
Pro: Less Effort to Steer
Con: Complicated and Heavy
Steering System Validation
Rack and Pinion
Recirculating
Ball Gear
Hydraulic
Power-Assisted
Electric
Power-Assisted
Criteria
Score
Weighted
Weighted
Weighted
Weighted
Score
Score
Score
Score
Score
Score
Score
Cost (0.1)
5
1
4
0.8
2
0.4
2
0.4
Weight (0.2)
5
1.5
4.5
1.35
1.5
0.45
4
1.2
Manufacturability (0.2)
4
0.8
2.5
0.5
0.5
0.1
1.5
0.3
Performance (0.35)
2.5
0.375
2.5
0.375
3.5
0.525
3.5
0.525
Maintenance (0.1)
4
0.6
3.5
0.525
1
0.15
2
0.3
Weighted Total
4.275
3.55
1.625
Final Selection: Rack and Pinion
2.725
Suspension System Validation
Swing Axle
Pro: Robust
Con: Heavy
Double A-arm
Pro: Large Motion Range
Con: Complexity
Suspension System Validation
Trailing Arms
Pro: Compact
Con: Difficult Mounting
MacPherson Strut
Pro: Simplistic
Con: Limited Range
Suspension System Validation
Swing Axle
Criteria
Score
Double A-arms
MacPherson
Strut
Trailing Link
Weighted
Weighted
Weighted
Weighted
Score
Score
Score
Score
Score
Score
Score
Cost (0.1)
1
0.1
2
0.2
2
0.2
4
0.4
Durability (0.2)
4
0.8
5
1
3
0.6
2
0.4
Weight (0.2)
4
0.8
4
0.8
3
0.6
4
0.8
Manufacturability (0.15)
2
0.3
5
0.75
2
0.3
1
0.15
Performance (0.35)
2
0.7
5
1.75
3
1.05
1
0.35
Maintenance (0.1)
3
0.3
4
0.4
2
0.2
4
0.4
Weighted Total
3
4.9
2.95
Final Selection: Double A-arms
2.5
Design Methodology
Design Methodology
Track
Wheelbase
Ackerman Steering
Design Targets
Design Parameters
Previous
Value
Design
Target
Static Camber
Camber Change
Steering Axis Inclination
Scrub Radius
Static Toe
Toe Change (over travel)
Static Caster Angle
Caster Change (over travel)
Track
Wheel Base
Static Ride Height
Vertical Wheel Travel (Jounce)
Vertical Wheel Travel (Rebound)
Recessional Travel
Unsprung Weight
-4 deg
-6 deg
8 deg
30 mm
0 deg
0 deg
3 deg
0 deg
1350 mm
1558 mm
230 mm
152.4 mm
100 mm
0mm
16.5 Kg
-4 deg
-6 deg
8 deg
30 mm
0 deg
0 deg
6 deg
0 deg
1350 mm
1450 mm
281 mm
200 mm
100 mm
51 mm
16.5 Kg
Clarification
Leans into Turns
Improves Handling
Raising Ground Clearance
Shock Compression
Absorbs Frontal Impact
Moving Forward
Next steps include:
• Finalizing geometry
• Generating Models
• Simulation and FEA
Management Plan
To mitigate the risks to driver safety and project completion:
• Closely follow SAE standards for the Baja SAE series
• Monitoring progress with respect to planned milestones
References
http://www.uniquecarsandparts.com.au/how_it_works_steering.
htm
http://image.absoluteastronomy.com/images/encyclopediaimage
s/a/ac/ackermann.svg.png
http://forums.bajasae.net/forum/caster_topic1126.html
http://www.subaruofkeene.com/specials/service.htm
http://www.townfairtire.com/wheel-alignment/caster-camberand-toe-alignments/
Questions?
More information is also available at:
www.OffRoadInnovations.weebly.com