Design of an Off-Road Front Suspension and Steering System OFF-ROAD INNOVATIONS Design of an Off-Road Front Suspension and Steering System GROUP M2: ANDREW SNELGROVE  CALVIN HOLLOWAY  JEREMY SHEPHERD  KATE PRICE

Outline 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: Provide more driver room Improve ground clearance Absorb frontal impact forces Maintain safety, reliability and low weight

2013 Memorial Baja Steering 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 Criteria Rack and Pinion Recirculating Ball Gear Hydraulic Power-Assisted Electric Power-Assisted Score Weighted Score Cost (0.1) 5 1 4 0.8 2 0.4 Weight (0.2) 1.5 4.5 1.35 0.45 1.2 Manufacturability (0.2) 2.5 0.5 0.1 0.3 Performance (0.35) 0.375 3.5 0.525 Maintenance (0.1) 0.6 0.15 Weighted Total 4.275 3.55 1.625 2.725 Final Selection: Rack and Pinion

Suspension System Validation To validate that the chosen system was the best choice for our application we compared alternatives using a decision matrix. Alternatives considered include: Swing Arm Double Wishbone MacPherson Strut Trailing Links 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 Criteria Swing Axle Double A-arms MacPherson Strut Trailing Link Score Weighted Score Cost (0.1) 1 0.1 2 0.2 4 0.4 Durability (0.2) 0.8 5 3 0.6 Weight (0.2) Manufacturability (0.15) 0.3 0.75 0.15 Performance (0.35) 0.7 1.75 1.05 0.35 Maintenance (0.1) Weighted Total 4.9 2.95 2.5 Final Selection: Double A-arms

Design Methodology

Design Methodology Ackerman Steering Track Wheelbase

Design Targets Design Parameters Previous Design Clarification Value Static Camber -4 deg   Camber Change -6 deg Steering Axis Inclination 8 deg Scrub Radius 30 mm Static Toe 0 deg Toe Change (over travel) Static Caster Angle 3 deg 6 deg Leans into Turns  Caster Change (over travel) Track 1350 mm Wheel Base 1558 mm 1450 mm  Improves Handling Static Ride Height 230 mm 281 mm Raising Ground Clearance  Vertical Wheel Travel (Jounce) 152.4 mm 200 mm Shock Compression Vertical Wheel Travel (Rebound) 100 mm Recessional Travel 0mm 51 mm Absorbs Frontal Impact Unsprung Weight 16.5 Kg

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/encyclopediaimages/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-camber-and-toe-alignments/

Questions? More information is also available at: www.OffRoadInnovations.weebly.com