1. Team: Clyde Baker Ken Brown Alex Cherukara Kevin Eady Sponsor: Dr. Patrick Hollis SAE 1: Mini-Baja Four Wheel Steering

2. Problem Statement Reduce Turning Radius Applicable to Formula SAE Car Budget of $500

3. Needs Assessment As defined by group: –Turning radius of 7’ or less –Strong enough to withstand forces experienced during competition –Must not interfere with other components –Must remain stable –Least weight possible

4. Concepts Steering Configuration –Opposite Wheel Steering –Parallel Wheel Steering –Combination

5. Concepts Front Wheel Angle –35 degrees: Toggling becomes a concern –20 degrees: Must have high front to rear wheel angle ratio to satisfy turning radius –30 degrees: Standard for most production cars. Good compromise

6. Concepts Wheel Angle Ratio –1:1 : Greatly reduces turning radius, unstable during high speed turns. –2:1 : Good compromise. Will meet turning radius requirement, more stable than 1:1. –3:1 : Cannot satisfy turning radius requirement

7. Steering Ratio

8. Concepts How to achieve front to rear ratio? –Geometry: Easier to construct, more reliable, less components. –Gearing: Easier to design, identical geometry and components for subsystems.

9. Final Concept The complete concept is a combination of all other concepts. –Opposite wheel steering –30 degree front wheel angle –2:1 front to rear wheel angle ratio –Gearing to achieve ratio

10. System Configuration Layout/Operation of the system: –Two subsystems: Rack and pinion for front and rear, identical geometry and components. –Steering column fitted with 2” bevel gear. Meshes with 2” bevel gear on shaft to front system and 4” gear on shaft to rear system. –As steering wheel is turned the shafts turn. Front rack will travel 5” total, the rear 2.5”.

11. Front Steering Assembly

12. Center Gearbox

13. Rear Steering Assembly

14. Force Analysis Performed by hand initially, vector analysis of statically loaded system. Equations written in Mathcad equation solver software, angle of wheels and impact changed. Given stresses through components and design strengths of components based on factor of safety.

15. Vector Analysis Vector analysis performed in following way: Performed for each individual component: Steering arm, tie rod, tie rod ends, bolts and rack

16. Initial Force Initially force was taken as the force with the largest expected driver and a 30 – 0 mph velocity with an elapsed time of.7 seconds. Following more research the initial velocity was lowered to 20 mph and the E.T to.55 seconds.

17. Force Breakdown Forces in steering arm as wheel travels from 0-30 degrees

18. Force Breakdown Forces on bolt as wheel travels from 0-30 degrees

19. Force Breakdown Forces on tie rod as wheel travels from 0-30 degrees

20. Force Breakdown Forces in tie rod end as wheel travels from 0-30 degrees

21. Force Breakdown Forces on rack as wheel travels from 0-30 degrees

22. Stress Reduction Initially the design strengths of the components were too high. The stress and therefore design strength of the components were lowered by increasing their sizes.

23. Design Strength The final design strengths of components

24. Modeling All parts and assemblies were modeled in Pro- Engineer ADAMS was inoperable during the first half of the semester, therefore work is still being done to confirm the hand calculated force analysis numbers. Predict our force analysis values are 50% high.

25. Modeling

28. Component Selection Components selected based on force analysis results. Picked to match the design strength of the components. –Tie Rod Ends: ¾” Chrome-moly ends –Rack: 11” steel rack with 5” total travel –Gears: 2” Steel bevel pinion(2), 4” Steel bevel gear –All other components will be fabricated by team

29. Final Car Specs Turning Radius6.5’ Front Wheel Angle30 degrees Rear Wheel Angle15 degrees Cost$475 (est.) Car Weight800 lbs. (estimated)

30. Current Work Complete ADAMS modeling. Reselect components if needed Order Components

31. Spring Agenda Test current steering system. Construct system. Test new steering system. Analyze test results. Rework system if necessary. Downhill From Here