DESIGN AND ANALYSIS OF STEERING COMPONENTS FOR A RACE CAR

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 6, June 2017, pp , Article ID: IJMET_08_06_013 Available online at aeme.com/ijmet/issues.asp?jtype=ijmet&vtyp pe=8&itype=6 ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed DESIGN AND ANALYSIS OF STEERING COMPONENTS FOR A RACE CAR P. Bridjesh, Subramanyam B and Madhu S Department of Mechanical Engineering, MLR Institute of Technology, Hyderabad, India ABSTRACT This article presents the steering system used in a race car is customized rack and pinion which is generally mounted to the base of the frame. The rack is bottom mounted to lower the Center of gravity of rack, pinion and tie rods. The chosen housing inner diameter designed to optimize steering responsiveness, allowing minimal steering wheel input to steer the car. High speed cornering is important factor for optimum performance in the race track. It can be achieved only with Reverse Ackermann type steering geometry which compensates for the large difference in slip angle between the inner and outer front tires while cornering at high speed. It was also decided to attain responsive steering at the expense of steering effort to the driver by varying the gear ratio of the simple rack and pinion assembly used. In this paper a detailed summary of how to design and analysis of steering components for modified turning radius to attain shortest radius compared to the normal passenger cars. EN27 steel materials are used for the selection of material. Key words: Agile turning, Caster, Camber, Effective Camber. Cite this Article: P. Bridjesh, Subramanyam B and Madhu S. Design and Analysis of Steering Components for a Race Car. International Journal of Mechanical Engineering and Technology, 8(6), 2017, pp MET/issues.asp?JType=IJMET&VType=8&ITy ype=6 1. INTRODUCTION The steering system components are a common source of driver complaints. Tire wear is almost completely dependent on the condition and adjustment of the steering components [1]. New generation of active steering systems distinguishes a need of steering of rear wheels for the reason of directional stability from a need of steering of rear wheels for the reason of cornering at slow speed [2]. Condition for True Rolling While tackling a turn, the condition of perfect rolling motion will be satisfied if all the four-wheel axes when projected at one point called the instantaneous center, and when the following equation is satisfied: cotᶲ-cotᶿ=c/b. Selection of the steering mechanism from all manual steering systems, the more suitable is rack and pinion steering for the following reasons: -has a simple construction, - is cheap and readily available, editor@iaeme.com

2 Design and Analysis of Steering Components for a Race Car - has a high mechanical efficiency, - has a reduced space requirement. To rotate the car on corner entry we are talking about creating increasing drag at the inside tyre [3]. As the cornering force builds the inside tyre must at some point reach it optimum lateral grip. We then use Ackerman to toe the tyre out further - say increase the slip angle a couple of degrees. The tyre grip doesn t change that much but the longitudinal component of tyre grip, the tyre drag, does increase in line with the increased slip angle. For this to work we would need to know that we have sufficient steering angle to generate the [4]. Ackerman needed. If in the process above, we started to lose outside tyre grip, and the driver wound on some more lock, we would have increased drag at the outside tyre. We would then loose the effect. The oversteer torque we were looking for would be overcome by the larger understeer torque [5]. The above indicates that pro-ackerman would probably not work with low powered cars in fast corners. It might also be a problem generally with heavy cars with spool or locker diffs that might want to push a bit, such as V8 Supercars. With pro-ackerman, the higher slip angle on the inside tyre will put more heat into the tyre [6]. This will help bring the tyre up to temperature, but could overheat the tyre on a longer run. If our race car is faster with toe in, we will use anti-ackerman [7]. This implies a tyre curve where the lightly loaded inside tyre has maximum grip at a lesser slip angle [8]. Sprint cars and similar speedway, dirt short circuits, can make a lot of use of varying degrees of pro-ackerman. With dirt tyres we expect very large slip angles [9]. Nasar s and similar will use anti-ackerman. With low profile tyres the slip angles will be a lot less. The tyre drag will be less. The slip angle on the inside tyre will have a smaller drag component. So, it may be more difficult to use pro- Ackerman to create the oversteer torque. The toe out from the slip angles will be less. The slip angle variation from outside to inside tyre will be a smaller number, requiring different Ackerman to achieve what we want [10]. We will probably use initial toe out to help turn in. The idea is to get the inside tyre working as discussed earlier [11]. Other settings you would use to help initial turn in are stiffer front shocks, and higher front roll center height. By delaying the roll, we help to keep the weight on the inside, to again keep the inside tyre working. The better way to couple any of your steering components together is with splined joints. So, it requires testing and analyzing the parts before it got manufactured [12,13]. The stress and displacement pictures of the components are shown in Figs.4, 5, and 6,7,8,9. 2. INDENTATIONS AND EQUATIONS C FACTOR = Rack travel / one rotation of pinion =75mm STEERING RATIO = C factor/( Steering arm length/pinion rotation)=7.86:1 TURNING RADIUS = Wheel base/sqrt(2-2*cos(2*steering wheel angle/steering ratio)) =2.6mtrs INNER WHEEL ANGLE=Wheel base /(Turning radius (Track width/2)) =38deg OUTER WHEEL ANGLE=Wheel base /(Turning radius +(Track width/2)) = 27deg ACKERMANN ANGLE = (Outer wheel+ Inner wheel) /2 ACKERMANN PERCENTAGE = Ackermann angle/ Inner wheel angle = 99.96% GEAR CALCULATIONS Constraints for both gears Pitch geometry (D) = mm, Pressure Angle (ψ) = 20 Module (m) = 2mm, Calculate Diametric Pitch (P) editor@iaeme.com

3 P. Bridjesh, Subramanyam B and Madhu S P = N/D = Number of Teeth/Pitch Diameter, Chosen N & D = 12/37.56 = 0.32 P = 0.32 Calculate Addendum (a) a = 1/P = 1/0.32 = Calculate Whole Depth (ht),ht = (2.188/P) ht = (2.188/0.32) = 6.83 Calculate Dedendum (b), b = ht a b = = Base Circle Diameter (Db) Db = D*cos(20) Db = 37.56*cos(20) = 35.3 Root Diameter Dr = D - 2b Dr = (3.125) = FIGURES AND TABLES Figure 1 Pinion Figure 2 Steering arm Figure 3 Mating of Rack and Pinion editor@iaeme.com

4 Design and Analysis of Steering Components for a Race Car Figure 4 VonMises Stress Contour Plot of Pinion Figure 5 Displacement Contour Plot of Pinion Figure 6 VonMises Stress Contour Plot of Steering Arm Figure 7 Displacement Contour Plot of Steering Arm Figure 8 Von Mises Stress Contour Plot of Rack Table 1 Required Particular values PARTICULARS VALUES C-factor Rack travel 75mm 35mm Steering ratio 7.86:1 Turning radius Inner wheel angle Outer wheel angle Steering arm length mm 38.59deg deg 78mm Ackermann percentage 99.96% Lock to lock rotation editor@iaeme.com

5 P. Bridjesh, Subramanyam B and Madhu S 4. CONCLUSIONS The designing process for static conditions is completed. The numerically solved values are near approximate the simulated values hence our design procedure is correct for such kind of vehicle design. This paper includes static and dynamic parameters according to the objectives. The work successfully achieved the objective. Result implies that car designing using solid works has very good scope of improving vehicle geometry, behavior and performance. The overall analysis satisfies the constraints and of Formula SAE International rulebook, so the vehicle modeling under the dynamic analysis is considerable. REFERENCES [1] Robertson, Dennis, George J. Delagrammatikas, The suspension system of the 2009 cooper union FSAE vehicle: A comprehensive design review. No SAE Technical Paper, [2] Khurmi. R.S and Gupta. J.K., A Textbook of Machine Design, 25 th Ed, S Chand publications. [3] Bhandari. V.B., Design of machine elements, 3 rd Ed, Mc Graw hill publications, [4] Design data hand book, PSG Coimbatore, kalaikathir Achchagam. [5] Gillespie, Thomas D., Fundamentals of Vehicle Dynamics. Society of Automotive Engineers, Inc., Pennsylvania, [6] Smith, Carroll, Engineer to Win. MBI Publishing Company, Minnesota, [7] Norton, R. Machine design. Pearson Prentice Hall, Upper Saddle River, NJ, [8] Heisler, H. Advanced Vehicle Technology, Arnold, 338 Euston Road, London NW1 3BH, [9] Fenton, J, Vehicle Body Layout and Analysis, Mechanical Engineering Publications Ltd. London, [10] Smith, C, Tune to Win: The Art and Science of Race Car Development and Tuning, Aero Publishers, Inc. 329 West Aviation Road, Fallbrook, CA 29028, [11] V. B. Bhandari, Design of Machine Elements, McGraw Hill Education India Pvt. Ltd., vol. 3, 11th Edition, 20. [12] Kezia.P, Krishna Sai.B.L.N, Analysis of gas turbine blade assembly to evaluate the performance of various nickel based alloys, International journal of mechanical engineering and technology, 8(5), [13] Subramanyam.B, P.Bridjesh, Design and Analysis of Student Formula Car Roll Cage, Indian Journal of Science and Technology, 9(48). DOI: /ijst/2016/v9i48/ [14] Anshul Dhakar and Rishav Ranjan, Force Calculation In Upright of A FSAE Race Car. International Journal of Mechanical Engineering and Technology, 7(2), 2016, pp [15] Dhiraj Malu, Nikhil Katare, Suraj Runwal, Saurabh Ladhe, Design Methodology for Steering System of an ATV. International Journal of Mechanical Engineering and Technology, 7(5), 2016, pp [16] Mandar Soman, Sumit Sonekar, Saurabh Upadhye and Prof. Pathan Farha Mubeen. Designing and Manufacturing of Foot Operated Steering For Disabled People, International Journal of Mechanical Engineering and Technology, 6(12), 2015, pp editor@iaeme.com