DESIGN METHODOLOGY FOR STEERING SYSTEM OF AN ATV

Transcription

1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 7, Issue 5, September October 2016, pp , Article ID: IJMET_07_05_027 Available online at Journal Impact Factor (2016): (Calculated by GISI) ISSN Print: and ISSN Online: IAEME Publication DESIGN METHODOLOGY FOR STEERING SYSTEM OF AN ATV Dhiraj Malu, Nikhil Katare, Suraj Runwal, Saurabh Ladhe Mechanical, Pune University, India. ABSTRACT The objective of steering system is to provide directional stability to the vehicle. The main consideration in design of the steering system is to produce pure rolling motion of the wheels while manoeuvring the tightest turns on the Dirt road tracks. The steering system must also provide adequate feel to the driver while turning. For maximum life of the tires the steering system is designed such that it maintains proper angles between the tires while turning and while braking in corner along with straight ahead position. The driver should be able to turn vehicle with minimum effort but it should not be directionally unstable. The steering system is thus designed in a very unique way by compelling many factors and formulating mathematic model. Key words: steering system, ATV, ICR geometry, Vehicle Dynamics Cite this Article: 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 INTRODUCTION An all terrain vehicle has to sustain rough road conditions. This design paper focuses on explaining engineering and design process behind steering system in the All Terrain vehicle to be developed. The design of the concept A.T.V. is in accordance with the specifications laid down by the rule book. 2. DESIGN PROCEDURE For the steering system design for the present vehicle the main aim was to minimize the turning radius for efficient performance of the vehicle in manoeuvrability. Initially we found if length of steering arm is reduced it results into minimum steering wheel turn for full tyre turn on one side, also turning radius can reduce drastically but it may result in increased steering wheel effort. After lots of arguments with the team members the steering arm length was decided as 90 mm (reduced by 10 mm of previous geometry). Same length with varying arm angle (ß) from 21 to 35 with the help of EES software a graph of Outer steer angle Vs. Inner steer angle was plotted with relation from book. The angles turned by inner and outer wheels are calculated, also iterations are carried out regarding the mounting position of the rack behind the front axle by using solid edge for modelling and Lotus 272

2 Design Methodology for Steering System of an ATV Suspension analysis (With the help of Suspension geometry). Also Turning radius was achieved near to 2.31 m. In order to minimize the bump steer effect the height of the rack with respect to chassis and the length of the tie rod are derived from the suspension geometry with upper and lower wishbone points and their ICR geometry. Exact steering effort was calculated by two methods. Dynamics of steering assembly along with front suspension was calculated by ADAMS software. Also by theoretical of error in front and rear slip angle Vs. Velocity was plotted with the help of EES. 3. DETERMINATION OF STEERING ARM INCLINATION Program developed on EES software:- {l=1473.2} wheel base of vehicle w=1143 wheel track of vehicle {1/tan(do)-1/tan(di)=w/l} Ackermann condition b=25 steering arm angle (w-2*90*sin(b))^2=(w-90*sin(b+di)-90*sin(b-do))^2+(90*cos(b-do)-90*cos(b+di))^2 relation for trapezoidal mechanism Figure 1 Graph of outer v/s inner wheel angle for different values of steering arm angle Parametric Table Arm angle=25 Table 1 Parametric Table- Outer v/s Inner wheel angle di (Inner wheel angle) do ( Outer wheel angle) Run Run Run Run Run Run Run Run

3 Dhiraj Malu, Nikhil Katare, Suraj Runwal, Saurabh Ladhe Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run Run ß=25 found closer hence, accordingly arm angle was selected. 4. DETERMINATION OF TIE-ROD LENGTH FROM ICR-GEOMETRY Bump-Steer In this phenomenon when the vehicle goes into bump the wheel steers if the ICR of wishbones and tie rod is not meeting at a same point Bump-steer cannot be completely avoided but reduced with help of ICR geometry as show in Figure 274

4 Design Methodology for Steering System of an ATV Figure 2 ICR geometry of wishbones and tie-rod From this Figure,which is constructed in solid edge software the length of tie-rod was selected to be in. 5. DETERMINATION OF ARM LENGTH BASED ON STEERING EFFORT Smaller the length of steering arm smaller is the steering wheel travel, but larger is the effort required. So, arm length is decided considering both the factors. Because, it can give two benefits, reduced steering angle rotation with larger angular rotation of tires. Once length is decided effort is calculated at static condition. Steering effort calculation: Diameter of Steering Wheel=152.4mm Weight on one wheel=51.8kg or N Radius of pinion =13.5mm Maximum coefficient of friction =1 Torque on pinion = *13.5 = N Force on steering wheel=torque/radius of steering wheel = / =52N Thus effort on Steering wheel is only 52N by one hand, which is within ergonomic consideration. Figure 3 Steering geometry with all dimensions 275

5 Dhiraj Malu, Nikhil Katare, Suraj Runwal, Saurabh Ladhe 6. DETERMINATION OF TURNING RADIUS FOR ATV Calculation from Thomas Gillespie, Fundamentals of Vehicle Dynamics [1] From geometry we have, Actual Angle turned by inner wheel (Ѳ i ) = Actual Angle turned by outer wheel (Ѳ o ) = Distance of C.G. from rear axle (b) = mm Distance between pivot point on front axle (L) = 1143 mm Wheel base (B)= mm We know that, R = R1 + b We have, R1 = B tanѳi + L = R R1 = mm = tanѳi Ideal Angle turned by inner wheel (Ѳ i ) = According to Ackermann condition, cot (Ѳ o ) cot (Ѳ i ) = cot (Ѳ o ) = + cot Ideal Angle turned by outer wheel (Ѳ o ) = Ideal Ackermann condition obtained, cot (Ѳ o ) cot (Ѳ i ) = Actual Ackermann condition obtained, cot (27.67) cot (40.26) = Difference in Ackermann, Eqn. (ii) Eqn. (i) = CONCLUSION While designing the all terrain vehicle the primary objective was to make the vehicle light, compact, ergonomic and safe for the driver. While designing the system all the conditions of an all terrain environment such as muddy surface, rough terrain with bumpy surface and hill climb were considered. A detail study was done of the possible failures that may occur in such vehicle and appropriate steps are taken to reduce or avoid such problems in the vehicle. Also the various driver comfort factors were considered. The resulting vehicle is safe, attractive, reliable, economical and fun to drive. (i) (ii) 276

6 Design Methodology for Steering System of an ATV ACKNOWLEDGMENT The design process is not a single handed effort but a team effort. We would also like to express our gratitude towards the Mechanical department and on the whole towards the college for the support. The team would also like to recognize the valuable assistance of the project guide, Mr. Vilash Shingare and faculty advisor for this project, Mr. U.I. Shaikh and the rest of the guiding staff at the Mechanical Engineering Department at PCCOE. REFERENCE [1] Thomas D. Gillespie, Fundamentals of Vehicle Dynamics, SAE Inc. [2] Milliken and Milliken, Race Car Vehicle Dynamics, SAE Inc. [3] John C. Dixon, Suspension Geometry and Computation, Wiley and Sons Ltd. [4] Reza N. Jazar, Vehicle Dynamics Theory and Application, Springer Publication. [5] Hans B. Pacejka, "Tyre and Vehicle Dynamics", Second Edition [6] Aman Doraya, Mohit Singh Panesir, Bhavya Bhardwaj and Aditya Bochare, 4-Wheel Steering System Mechanism Using DPDT Switch. International Journal of Mechanical Engineering and Technology (IJMET),6(11), 2015, pp [7] Aditya Patankar, Rohit Kulkarni, Sanket Kothawade and Sameer Ingale, Design and Development of a Transmission System for an all Terrain Vehicle. International Journal of Mechanical Engineering and Technology (IJMET),7(3), 2016, pp