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Senior Design Presentation
- 1. Baja Steering SystemDesign By: Adam M Conrad
- 2. IntroductionCurrent State •No SteeringSystem in Place •Original Mount is Present •Steering wheel mount is present •No suspension in place Goals for Project •Design a steering system that utilizes as much of the current frame •System must be able to withstand SAE racing conditions •System should provide a competitive advantage
- 3. Customer Requirement Requirement DescriptionImportance Rating Reliability The design must be able to perform under racing conditions. 30% Cost The cost needs to be low and fall within the customers budget 25% simplicity The design should be simple enough to build given the resources and materials that the design team has access to. 20% Weight The weight needs to be low in order to provide a favorable power to weight ratio 15% Size The size of the assembly must be small enough to accomadate the driver given the materials at hand 10%
- 4. Circulating Ball Worm-gear Strengths •High Reliability • Low Friction Weaknesses • Low simplicity • Heavier
- 5. Rack and PinionConcept Strengths • High Reliability • High Simplicity • Low Weight Weaknesses • Fast-Ratio rack and pinions are more expensive
- 6. Pitman Arm Linkage Strengths •Low Cost • Low Weight • High Reliability Weaknesses • Low Simplicity • Unfavorable size
- 7. Steer-By-Wire Strengths • none Weaknesses • LowSimplicity • Low Reliability • Expensive • Takes up a lot of space • Heavy
- 8. Double Crank Rocker Strengths •Low Cost • High Simplicity • Low weight • Takes up little space Weaknesses • Questionable reliability
- 9. Concept Selection Criteria Weight (%) rating weighted rating rating weighted rating rating weighted rating rating weighted rating rating weighted rating Cost 252 0.5 3 0.75 4 1 0 0 4 1 Simplicity 20 2 0.4 4 0.8 2 0.4 2 0.4 4 0.8 Reliability 30 4 1.2 4 1.2 4 1.2 2 0.6 3 0.9 Size 10 2 0.2 4 0.4 2 0.2 2 0.2 4 0.4 Weight 15 3 0.45 4 0.6 3 0.45 2 0.3 4 0.6 100 na 2.75 na 3.75 na 3.25 na 1.5 na 3.7 Unsatisfactory 0 Just Tolerable 1 Adequate 2 Good 3 Very Good 4 Crank Rocker Alternative Concepts / Embodiments Concept Evaluation Using Weighted Rating Method (Pahl & Beitz Method) Ball and Nut Rack and Pinion Linkage and Pitarm Steer by Wire
- 10. Criteria for RackLocation • Low Transmission Angle – 30 degrees or below – reduce bending moments – reduce needed effort for turning • Small Tie Rod Length – 14 inches or below – Low Material Costs – Reduce buckling • Low Turn Radius – 8 feet or below
- 11. Location Concept 1 •12 Inch Tie Rods • Dismissed because of tie rods exposure • Dismissed because steering shaft exposure • Wheels pushed forward • Rack Mounted on the front of vehicle • 14 Inch Rack (12 to 1 Steering Ratio)
- 12. Location Concept 2 •Wheels pushed forward • Rack Mounted in original mounting Location • 14 inch rack (12 to 1 Steering Ratio) • 50 degree horizontal transmission angle • 4 degree vertical transmission angle • 21 inch tie rods • 17.3 foot turn radius
- 13. Location Concept 3 •New Control Arms • Rack Mounted in original mounting Location • 14 inch rack (12 to 1 Steering Ratio) • 30 degree horizontal transmission angle • 5 degree vertical transmission angle • 15 inch tie rods • 11.17 foot turn radius
- 14. Location Concept 4 •New Control Arms • Rack Mounted 5 inches forward from original mounting Location • 16.25 inch rack (12 to 1 Steering Ratio) • 12 degree Horizontal transmission angle • 7 degree Vertical transmission angle • 12 inch tie rods • 8.75 foot turn radius • 15.08 foot radius with half turn
- 15. Location Concept 5 •New Control Arms • Rack Mounted 7 inches forward from original mounting Location • 16.25 inch rack (12 to 1 steering ratio) • 0 degree Horizontal transmission angle • 10 degree Vertical transmission angle • 12 inch tie rods • 6.978 foot turn radius • 13.08 foot radius with half turn
- 16. Location Concept 6 •New Control Arms • Rack Mounted 7 inches forward from original mounting Location • 11.25 inch Rack (6.4 to 1 steering ratio) • 0 degree Horizontal transmission angle • 9 degree Vertical transmission angle • 13 inch tie rods • 5.33 foot turn radius
- 17. Position Selection Summary Description RackLength "Inches" Approximate Tie Rod Length "Inches" Lock-Lock Turn Radius "feet" Half Turn, Turn radius "feet" Horizontal Transmission Angle "degrees" Vertical Transmission angle "degrees" Concept 1 Wheels forward, Rack in front 14 12 na na na na Concept 2 Wheels forward, rack in original mount 14 21 17.294 na 50 4 Concept 3 New Control Arms, Original Mount 14 15 11.17 na 30 5 Concept 4 New Control Arms, Moved forward 16.25 12 8.75 15.08 12 7 Concept 5 New Control Arms, Moved forward and horizontal 16.25 11 6.978 13.08 0 10 Concept 6 New Control Arms, Concept 5 with fast ratio rack 11.25 13 5.3324 5.3324 0 9
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- 20. Bump Steering Check •Approximately Halfway between control arms • 2 inch clearance
- 21. Tie Rod MaterialSelection • Length: 13 inches • Diameter: 3/4 inches • Hole Diameter: 5/16 inches • Threading: UNC 24 • Material: 6351 aluminum (Yield at 40,000 PSI) • Cost:
- 22. Tie Rod StressCalculations 114 Lbs10.5’’ 4’’ 300 Lbs
- 23. Tie Rod StressCalculations 300 Lbs 9 degrees 304 Lbs
- 24. Steering Shaft Material Selection •Length: 25 Inches • Diameter: 5/8 Inches • Material: Mild Carbon Steel
- 25. Component List • HeimJoints (2) • Clevis Rod End (2) • Tie Rod Ends (2) • 13’’ Aluminum Threaded Tie Rods • 25’’ Mild Steel Steering Shaft • Steering Wheel • Fasteners
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