PREFACE This Master Thesis are considering the design, analysis and testing of the steering system on a Formula Student racing car. The car is built at the University of Stavanger during the spring 2013 and will compete at the Silverstone Circuit in July 2013. I would like to thank the following persons: Jan Kåre Bording, chief engineer at the workshop at University of Stavanger, for his helpful advice and support during the project Hirpa Lemu Gelgele, associate professor at the University of Stavanger, for being my supervisor during the project and for his help and support during the project Rosenberg Worley Parsons Group for the decision to be our main sponsor and helping us financially to achieve our goals with the car Stavanger, 24.06-2013 Christoffer Leidland Andersen Romertal ii Table of Contents PREFACE ............................................................................................................................................. I TABLE OF CONTENTS .................................................................................................................... III SUMMARY ..................................................................................................................................... VIII 1 INTRODUCTION ................................................................................................................... 10 1.1 Background ...................................................................................................................................... 10 1.2 The Objective ................................................................................................................................... 10 1.3 The Aim ............................................................................................................................................ 11 1.4 Conclusions ....................................................................................................................................... 11 1.5 Recommendations ............................................................................................................................ 11 2 TIRE ........................................................................................................................................... 12 2.1 Lateral force ..................................................................................................................................... 12 2.2 Pneumatic trail ................................................................................................................................. 12 2.3 Mechanical trail ................................................................................................................................ 13 2.4 Slip angle .......................................................................................................................................... 13 3 STEERING SYSTEM ............................................................................................................ 14 3.1 Power Assisted Steering Systems ..................................................................................................... 14 3.1.1 Power Assisted Rack and Pinion ......................................................................................................... 14 3.2 Manual Steering Systems ................................................................................................................. 15 3.2.1 Worm and Roller ................................................................................................................................. 15 3.2.2 Worm and Sector ................................................................................................................................. 16 3.2.3 Worm and Nut ..................................................................................................................................... 16 3.2.4 Cam and Lever .................................................................................................................................... 17 3.2.5 Rack and Pinion ................................................................................................................................... 17 3.3 Stability and Control ........................................................................................................................ 18 3.3.1 Ackerman ............................................................................................................................................ 18 3.3.2 Toe In/Out ........................................................................................................................................... 20 3.3.3 Camber Angle ...................................................................................................................................... 22 3.3.4 Caster Angle ........................................................................................................................................ 22 iii 3.3.5 Bump-steer .......................................................................................................................................... 22 3.3.6 Neutral-/under-/oversteer ..................................................................................................................... 23 4 STEERING SYSTEM DESIGN GUIDELINES .............................................................. 26 4.1 Formula Student SAE 2013 Rules .................................................................................................... 26 4.1.1 Wheels ................................................................................................................................................. 26 4.1.2 Tires ..................................................................................................................................................... 26 4.1.3 Steering ................................................................................................................................................ 26 4.1.4 Steering Wheel .................................................................................................................................... 27 5 STEERING SYSTEM DESIGN ........................................................................................... 28 5.1 Steering System Considerations ....................................................................................................... 28 5.2 The Seering System .......................................................................................................................... 30 5.3 The Acting Forces............................................................................................................................. 31 5.3.1 Down-Forces ....................................................................................................................................... 32 5.3.2 Bump Forces ........................................................................................................................................ 33 5.3.3 Cornering Forces ................................................................................................................................. 33 5.3.4 Braking Forces ..................................................................................................................................... 37 5.4 The Design ........................................................................................................................................ 39 5.4.1 The Offset Arm .................................................................................................................................... 39 5.4.2 Steering Rack Position ......................................................................................................................... 40 5.4.3 Bolt Calculation ................................................................................................................................... 45 5.4.4 Rod End ............................................................................................................................................... 46 5.4.5 Tie rod ................................................................................................................................................. 46 5.4.6 Quick Release Fastening and Position ................................................................................................. 48 5.4.7 The Design’s Influence On The Car .................................................................................................... 48 6 ANALYSIS AND SIMULATIONS ..................................................................................... 50 6.1 Multi-body simulation model ........................................................................................................... 50 6.1.1 Upper control arms .............................................................................................................................. 51 6.1.2 Lower control arms .............................................................................................................................. 51 6.1.3 Tie rod ................................................................................................................................................. 51 6.1.4 Pushrod ................................................................................................................................................ 51 6.1.5 Rocker/Damper ...................................................................................................................................