DESIGN AND FABRICATE A FULLY CAPABLE OFF-ROADER
By
SAYANTAN DAS Name of the Student
Roll No.
SAYANTAN DAS
11ME013
Internship – Internship – I/ I/ Internship-II Course At
BAJA STUDENT INDIA-2015
DEPARTMENT OF MECHANICAL ENGINEERING LINGAYA’ S UNIVERSITY, FARIDABAD SESSION 2011-2015.
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A REPORT ON
DESIGN, SIMULATION AND FABRICATION OF A FULLY CAPABLE SINGLE SEATER OFF-ROAD VEHICLE WITH AUTOMATIC TRANSMISSION By
SAYANTAN DAS Name of Student SAYANTAN DAS
Roll No. 11ME013
Discipline th
4 year B-tech (M.E.)
PROJECT REPORT SUMMITED IN FULFILLMENT OF THE REQUIREMENTS OF THE COURSE INTERNSHIP-I; INTERNSHIP-II At
BAJA STUDENT INDIA-2015
Guides / Professional Expert(s) – Expert(s) – Prof Prof R. K. Deb; Prof Vibhuti Jha; Prof K. Srinath Faculty/ Associate Faculty(s) – Prof Prof B.B. Malhotra; Associate Prof Ankur Kashyap
DEPARTMENT OF MECHANICAL ENGINEERING LINGAYA’S UNIVERSITY, FARIDABAD SESSION 2011-2015.
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CERTIFICATE This is to certify that the project report titled “DESIGN AND FABRICATE A FULLY ”, submitted by SAYANTAN DAS, 11ME013 in partial fulfilment CAPABLE OFF-ROADER ”, of the requirements
of courses, ME-483(Internship-I) and ME-484(Internship-II) at BAJA
STUDENT INDIA, as part of the degree of Bachelor of Technology in Mechanical Engineering
of Lingaya’s University, session 2011-2015 2011 -2015 Is a record of bona fide work carried out under my/ our supervision and has not been submitted anywhere else for any other purpose.
Name of Faculty/Associate Faculty/Associate Faculty: Prof. R. K. Deb
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ACKNOWLEDGEMENT
This project on DESIGN AND FABRICATE A FULLY CAPABLE OFF-ROADER, is intended to give a detailed insight of the understanding of Automobile Engineering, and processed required to fabricate a vehicle. I hope that this treatise will prove useful to readers seeking an understanding of building an All-Terrain Vehicle. It gives me an immense pleasure to express my gratitude towards all who have helped me to experience this training program with their support. Firstly, I’d like to thank the Almighty God for rendering the divine favour throughout this endeavour and immense gratitude we recognise the moral support provided by my parents. I express my sincere gratitude to the Head of the Department. Prof. B. B. Malhotra for the opportunities provided for the completion of this project. I would like to thank Prof. R.K Deb and Prof. Vibhuti Jha for their immense support and guidance throughout the course of the project.
I would also like to express my sincere thanks to our Project Guide Mr. Ankur Kashyap and Prof. K. Srinath who provided us with essential knowledge required for commencement and completion
of this project. There constant encouragement and valuable suggestions are the key factor behind this great success. I’m also very much thankful to all the faculty members o f the mechanical and automobile department and all our friends for their valuable suggestions and cooperation that they have extended to us without any inhibition.
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TABLE OF CONTENTS
1. Cover Page……………………………………………..…………….………………………..1 2. Title Page…………………………………………………..…………………………….……2 3. Certificate……………………………………………………..………………………...……..5 4. Acknowledgement…………………………………………..…………………………………6 5. Abstract……………………………………………………………….……………………….7 6. Introduction…………………………………………….………………………………….......8 7. About our Design………………………………………….…………………………..............9 8. Goals and Objectives………………………………………..………………………………..10 9. Vehicle Design Aspects…………………………………………………….………….……..11 10. Technical Specifications…………………………………………………………..…….……12 11. Frame Design……………………………………………………………………..…….……13 12. Analysis of Front Impact………………….………………….……………………………...14 Analysis of Side Impact……………………………………………..………………………..15 13. Analysis of Roll Over …………………………………………………………………...…...16 14. Analysis of Load during Acceleration……………………………………………...………..17 15. Vehicle Ergonomics…………………………………………………………………..……..18 16. Ergonomic Angles…………………………………………………………..……………….19 16.1.
Vehicle Prototype……………………………………….………………………..20
16.2.
Driver Vision while seated……………………………………….…………........20
16.3.
Reach Envelope……………………………………………….………………….21
17. Suspension System………………………………………………………..…………………22 17.1.
Design Process……………………………………….…………………………..25
17.2.
Anti-Squat and Anti-Dive……………………………….……………………….26
17.3.
Bump Steer …………………………………………….…………………………27
17.4.
Motion Ratio………………………………………………….………………….27
17.5.
Shock Ride Height……………………………………………….………………28
17.6.
Sprung & Un-sprung Weight………………………………………………….…28
17.7.
Corner Weights…………………………………………………….…………….28
17.8.
Spring Angle & Spring Rate…………………………………….……………….29
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17.9.
Wheel Rate…………………………………………………….…………………29
17.10.
Suspension Part Analysis………………………….……………………………..30
18. Steering System…………………………………………………………..………………….31 18.1.
Steering Kinematics……………………………………………….……………..31
18.2.
Ackerman Steering Geometry………………………………………….………...32
18.3.
Vehicle Axis System……………………………………....……………………..33
18.4.
Roll Centre Height………………………………………..……………………...34
18.5.
Knuckle Load Analysis…………………………………………………….…….34
19. Power Train……………………………………………………..…………………………...35 19.1.
Engine………………………………………………………………………….....35
19.2.
Power Curve………………………………………………………………….…..35
19.3.
Gear Box Calculations…………………………………………………………...37
20. Braking System…………………………………………………………………………..….41 20.1.
Brake Calculation…………………………………………………………….…..43
21. Project Plan ………………………………………………………………………………....47 22. D.F.M.E.A… …………………………………………………………………………..……48 23. Pictures………………………………………………………...………………………...…..49 24. Conclusion………………………………………………………………………………..….60 25. References………………………………………………………..………………………….61
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INTRODUCTION
BAJA Student India is a college level engineering design competition, held every year at the NIT Jamshedpur campus. Participating teams comprise of undergraduate & post graduate engineering students and as a team they are tasked to design, build, test, race, and promote a single-seater 4 wheeler all-terrain vehicle. BAJA Student India follows the BAJA SAE International rules and procedure. All the delegates and judges are internationally acclaimed faculties and engineers from the best Colleges and Automobile Industries. This event is meant 'FOR THE STUDENTS' and main focus is on the educational aspect of the competition. Department of industries, Government of Jharkhand, being the principle sponsors and Tata Being the title sponsors for this there will be a great amount of exposure between the technical groups and automobile industrialists. BAJA student India started in 2013 at NIT Jamshedpur, organised by the Federation of Motor Sports Council India, Members of NIT Jamshedpur and Baja aluminous and technical inspectors from different country’s across the world. The Chief technical inspectors include Mr. Claude Roulle, President of OptimumG, and Judge for Formula SAE series, USA. Mr. James. Pat Clarke, Semi-retired Consultant, Sydney, NSW. And Mr. Stephen.M.Fox, President/Director of engineering powertrain technology, USA. This year Baja Student India has 44 Teams participating in the final event from all over India and is expecting a footfall of more than 50,000. Teams include the best from India who have been participating in Indian and International Motorsports Events.
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ABSTRACT
The objective of the Lingaya’s University’s “ Team Saksham” is to design, fabricate and test a new vehicle which can endure the off-track designed by Delta Inc, organizers of Baja Student India-2015, held at NIT, Jamshedpur. This vehicle will be used to compete in this competition
and hence it is designed in accordance with 2015 SAE Mini-Baja Rules and Regulations . The design process of the vehicle is iterative and is based on various engineering and reverse engineering processes depending upon the availability, cost and other such factors. So the design process focuses on: Safety, Serviceability, Cost, Standardization, Strength and ruggedness, Driving feel and ergonomics, Aesthetics The design criterion followed here is design for the worst and optimize the design while avoiding over designing, which would help in reducing the cost.
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OUR DESIGN
The design process of the vehicle is iterative and is based on various engineering and reverse engineering processes depending upon the availability, cost and other such factors. So the design process focuses on: Safety, Serviceability, Cost, Standardization, Strength and ruggedness, Driving feel and Ergonomics, Aesthetics. The design criterion followed here is design for the worst and optimize the design while avoiding over designing, which would help in reducing the cost. We proceeded by setting up the budget for the project. Throughout the design process we distributed the budget in such a way that if we assign more money to one system, we reduce that amount from some other system. Our last year vehicle design was based on the criterion of prevention of failure, as that year no one knew the track and the obstructions prevalent over there. So the procedure of over designing was followed as the safety of the driver is of utmost importance. The main aim this year was to decrease the overall weight with keeping in mind the overall durability of the vehicle and increase the overall performance.
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GOALS AND OBJECTIVES
1. To fabricate a fully operational vehicle in a time period of 5 months, the vehicle was designed in accordance to the SAE International Baja -2015 rule book. The time period will divided, 33% for designing, 33% for fabrication and 33% for testing.
2. Reinstall a mechanical drivetrain with a CVT and chain reduction and tune the CVT to maximize performance.
3. Design and install a new front suspension that has better travel and is lighter, and still just as strong as the current design.
4. To design and install a trailing arm suspension system in the rear.
5. Design and install a new steering system that properly balances the effects of caster and camber to improve the handling of the vehicle in an off road environment. Maintain the original design requirements set for the vehicle: steering wheel rotation limited to 180 degrees in each direction with maximum steering angle of 30 degrees.
6.
Design and install a braking system with “at least two (2) independent hydraulic circuits capable of locking ALL FOUR wheels, both in a static condition as well as from speed on pavement and on unpaved surfaces,” as stated in the Baja SAE Collegiate Design Series Rules.
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VEHICLE DESIGN ASPECTS
1. Vehicle must be capable of carrying one person 75 in. tall, weighing 250 lbs. 2. Vehicle must be safe for a 95th percentile male operator. 3. Width of the vehicle must not exceed 162 in. 4. The vehicle must be capable of safe operation over rough land terrain including, but not limited to, obstructions such as rocks, sand jumps, logs, steep inclines, mud and snow and ice. 5. No components of the vehicle must come loose during a rollover. 6. All wiring must be sealed, protected and securely attached. 7. Vehicle must contain front and rear hitch point along the longitudinal centerline. 8. There must be a firewall between the cockpit and the engine and fuel tank compartment. It must cover the area between the lower and upper lateral cross members on the Rear Roll Hoop. 9. The vehicle must have a hydraulic braking system that acts on all wheels and is operated by a single foot pedal. The pedal must directly actuate the master cylinder through a rigid link. 10. The brake system must be capable of locking all four wheels, both in a static condition as well as from speed on paved and unpaved surfaces. 11. Vehicle must be capable of completing a four hour endurance test.
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TECHNICAL SPECIFICATION
S. No
Vehicle Specifications
Old Vehicle
New Vehicle
1
Wheel Base
55’’
59’’
2
Wheel Track
53’’ Front; 52’’ Rear
53’’ Front; 50’’ Rear
3
Overall Length
90’’
87’’
4
Ground Clearance
12’’ Front; 11’’ Rear
12’’ Front ; 12’’ Rear
5
Kerb Weight
294 Kg
220 Kg
6
Brake Type
All four disc brakes with Tandem cylinder.
All four disc brakes with Tandem cylinder.
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Stopping Distance
9m
6.97 m
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Max Power
10 HP @ 3600 rpm
10 HP @ 3600 rpm
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Max Torque
19.6Nm @ 2800 rpm
19.6 Nm @ 2800 rpm
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Transmission Type
Mahindra Alfa 4 Speed
Continuously Variable Transmission (CVTech)
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Front Suspension
SLA Double Wishbone
SLA unparalleled Double Wishbone
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Rear Suspension
SLA Double Wishbone
Trailing Arm
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FRAME DESIGN
The Chassis is the component in charge of supporting all other vehicle subs ystems and taking care of the driver safety at all times. The Chassis design need to be prepared for impacts created in any certain crash or roll over. It must be strong and durable, taking in account the weight distribution for better performance. This year our team used AISI 1020 Steel tubes with outs ide diameter of 28.3 mm and thickness of 2mm. AISI 1020 was used because it has the required ca rbon percentage, i.e. 0.18-0.24%, and substantial amount of bending strength. Finite Elements analysis In order to prove the safety of our chassis design we decided to use Catia and Solidworks, due to its low memory requirement and ease of use.
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Analysis was done for the following impacts:
1. Front impact:
Load Applied: 23240 N; Max Stress: 2.49*10 8 N/m2 ; Max Displacement: 0.175”
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2. Side Impact:
Load Applied: 15303 N; Max Stress: 2.32*10 8 N/m2 ; Max Displacement: 0.116”
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3. Roll Over:
Load Applied: 15303 N; Max Stress: 2.32*10 8 N/m2 ; Max Displacement: 0.116”
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4. Load during Acceleration:
Acceleration Applied: 9.8m/s2 ; Max Stress: 5.47*106 N/m2 ; Max Displacement: 0.0043”
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VEHICLE ERGONOMICS
The ergonomics of a cockpit of any vehicle is a crucial part. It the vehicle controls are not strategically placed, the operator will not be able to reach to the peak performance. In extreme cases, the safety of the operator and other could be jeopardy, if controls are not readily available at all times. For our vehicle we had created a prototype and had collected data from diffe rent drivers and found out the optimal angles that have to be set to attain the most comfortable and safe ride for a prolonged period of time and in extreme conditions.
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Final Design Values for the Cockpit: S.No
Parameters
Std Range
Design Value
1
Angle at Elbows
120-140o
122.921o
2
Angle at Knee
120-150o
120.026o
3
Angle at Back
8-15o
14o
4
Pedal Space
N/A
33 litres
5
Min Visibility
<1.5-2.5 m
1.386 m
Ergonomic Angles:
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Vehicle Prototype:
Driver Vision while Seated :
20
Reach Envelope:
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SUSPENSION SYSTEM One of the stated goals of this Major Qualifying Project was to re-design the front suspension and steering systems in order to improve handling and performance. Each component from the mounting points out was re-engineered. The mounting points could not be altered without extensive modification to the frame so the system was designed around this constraint. In the course of designing an off-road vehicle, much attention must be paid to the terrain it will be navigating in order to develop a fitting suspension system. A Baja vehicle suspension must provide the car with the ability to compete in every event including the hill climb, endurance, and manoeuvrability competitions. A sufficient suspension will have the necessary practical features such as adequate ground clearance and suspension travel to allow navigation of the terrain as well as provide comfort and control to the driver. The goal of any suspension is to maximize the contact between the tire and the track surface. Two basic methods of accomplishing this goal include reducing the weight of the suspension, which is called the un-sprung mass and increasing the stiffness of the mounting points on the vehicle or sprung mass. Reducing the un-sprung mass will decrease the effects of inertia in the system allowing it to react more rapidly to bumps. There are several different types of suspensions, each with their own advantages; however the double wishbone designs allows for the most control of ride behaviour and isolation of individual tire movement. For this reason, most performance vehicles employ double wishbone suspensions on the front axis and this design was no different. In off-road vehicle design, some attributes that provide necessary ride height and manoeuvrability must be prioritized over other parameters that might improve handling but cannot be optimized under the necessary design requirements. After researching and ranking the suspension characteristics discussed above, the team was able to define both static and dynamic goals for the new design. The design of the front suspension and steering will be explained as one since the two are closely related and changes made to one system can greatly affect the other. The suspension is one of the most critical component in a BAJA buggy. It is vital that the suspension is responsive enough and has sufficient travel to handle a wide variet y of off-road terrain at speeds of 30 to 45 mph. Overall goal of suspension is to keep the vehicle as stable as possible and provide sound ergonimical ride over rough and unpredictable terrain and ensure that all exposed undercarriage members are provided enough elevation to avoid impact with mentioned obstacles.
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Vehicle Level Target:
Total Mass:
:
280 Kg
Unsprung Mass
:
82 Kg
Sprung Mass
:
192Kg
S. No:
Parameters
Front
Rear
1.
Ride Height
12”
12”
2.
Ride Frequency
1.69 Hz
2.02
3.
Jounce
4.8”
3.5”
4.
Rebound
3.7”
2.5”
5.
Wheel Rate
17.54 Kg/in
29.066 Kg/in
6.
Natural Frequency
1.074 Hz
1.27 Hz
7.
Motion Rotio
0.75
0.6
8.
Spring Rate
41.34 Kg/in
84.893 Kg/in
Supension Hardpoints:
1.
Toe:
+1.7 o
2.
Camber:
-2 o
3.
Roll Centre Height(F)
10.059”
5.
SAI
9 o
6.
Scrub Radius
28.3mm
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DESIGN PROCESS First we have to decide which suspension is better for us in according with different benefits of different suspension. In most of the Baja Buggies we go with the Double Wishbone in the front suspension. For designing it, we first have to see what should be the length of our arms, in that length what should be the vertical distance between the two arms. Think of it as Four-Bar mechanism, 2 arms and 1 roll cage and 1 upright side links. Roll cage side link is fixed. We will first see how much travel we want from the suspension. Normally, 6” up down is enough. Then, we decide equal arms or non-equal arm or parallel arm. By simulating it in designing software like adams or lotus, we check if we can get proper travel or not. Shocker is mounted on the lower arm, so it would be good to have longer lower to have maximum travel. To make it longer, lower arm is kept longer than the upper arm. This has disadvantage that on travelling, it gains more camber angle, to compensate it, initially some negative camber is given. While iterating we much consider how much roll centre, scrub radius, caster angle, king pin axis angle we want, all the parameters were kept in mind.
Few Topics are explained: Anti-Squat and Anti Dive: Squat is the backward tipping of vehicle. As car accelerates weight is transferred to the back of the car whose magnitude is the product of mass, acceleration and the ratio of Cg distance from front wheel and total wheel base. Whereas, dive is the forward tipping of vehicle while braking. Here weight is transferred from back to front wheel whose magnitude is the product of mass, acceleration and the ratio of Cg distance from rear wheel and total wheel base. This result into very rough riding so we use Anti dive and Anti squat geometry. If we consider front side as double wishbone and rear side as trailing arm, the IC for front side is intersection of two arm lines as shown in fig. and the line joining IC and centre of wheel gives you the anti-dive percentage .4L and .6L is the breaking ratio. Line drawn perpendicularly through that point is major responsible for percentage of anti-dive. If any dive line passes through the top of perpendicular line, it’s 100% anti-dive. As it comes down, it keep on decreasing. It’s impossible to give 100% anti-dive because of other geometries like steering, roll. We kept it 50%.
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Anti-Squat & Anti Dive Design
Bump Steer:
Bump steer is the toe in-toe out of vehicle when it encounters bump. When vehicle comes in contact with any bump it causes tie rod to move in or out which results into steering effect. To avoid this there should not be any movement of tie rod during bumps. Keeping these things in mind we have to place tie rod in such a way that when wheel rotates about IC, the tie rod should also rotate without any radial movement i.e. tie rod should lie on the line joining the IC and outer tie rod joint. In other words inner tie rod end must lie on the line connecting the tie rod outer ball joint with the instantaneous centre of suspension system. For double wishbone parallel arms tie rod should also be parallel to arm.
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Calculating Different Parameters of Suspension: Motion Ratio: Motion ratio is the ratio of spring travel and wheel travel or it is also the ratio of distance of wheel and distance of spring from pivot point. It is some time called Installation ratio.
M otion Ratio = (a / b) * si ne (Spri ng An gle) a = distance from lower arm axis to spring mount. b = distance from lower arm axis to ball joint. According to Herb Adams in Chassis Engineering equation is
2 2 M R = (a/b) * (c/d)
c = distance from IC to ball joint. d = distance from IC to wheel centre.
Shock Ride Height: Spru ng Weight = Corn er Weight – Un -spru ng Weight.
Sprung Weight: It is the height of travel left after sprung mass is applied. A shocker gives 4-5 inch travel when sprung mass is applied as 40 to 50 percent of shocker gets compressed. So shock ride height is 40 to 50 percent of travel of shocker. It is the weight of the vehicle that is supported by the spring and is the only weight used when calculating spring rates.
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Un-Sprung Weight: Un-sprung weight is the vehicle weight that is not supported by the springs. It includes Tire-wheel assembly, brake rotors and callipers (or drums and components), wheel bearings; st eering knuckle, differential and axle weight, hanging weight of the control arm (or trailing arms on rear axles), 1/2 of the spring and shock absorber weights.
Corner Weights: It is the weight measured by the contact patches present at the four wheels. By adjusting the corner weight we can adjust understeer and over steer tendency of vehicle. Increase the ride height at a corner will increase the weight at that corner and its diagonally opposite corner. And similarly decreasing the ride height at the corner will decrease the weight at that corner and it’s diagonally opposite corner. The other two corner will gain weights. Change in stagger, tire pressures and springs will change the ride height.
Corner Weight = Total Weight /4
Spring Angle: It is the angle made by spring to the control arm, it is between 75 and 90 degree.
Spring Rate: Spring Rate = Static Load / Shock Ride Height. Static Load = Sprung Weight / Motion Ratio k = d*G / (8ND3)
k: The spring rate. d: The wire diameter. G: The spring’s Shear Modulus.
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N: The number of wraps. D: The diameter of the coil.
Wheel Rate: Wheel Rate = Spri ng Rate * (M otion Ratio ^ 2) * spri ng
Angle Correction:
Spring Angle Correction Factor : ACF = {cos (Spri ng An gle) * Spri ng Rate} Spring parameters in market Yamaha-Spring parameters
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Suspension Parts Analysis:
Front Control Arm:
Force Applied: 3952N F.O.S: 2.58
Rear Trailing Arm with Upright Assembly:
Force Applied: 4100N F.O.S: 1.6
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STEERING SYSTEM Steering Kinematics:
Steering was designed with an aim of providing minimum turning radius, minimum slippage, maximum rolling, and optimum steering ratio, which provides an ergonomically sound steering system.Steering system is based on Ackerman principle and uses centrall y located Rack and Pinion steering gear box which is typically used in dune buggies. 1.
Wheel Track
53”
2.
Wheel Base
61”
3.
Ackerman Angle
21.28 o
4.
Inner Lock Angle
44.8o
5.
Outer Lock Angle
29.236o
6.
Turning Radius
3.25m
7.
Steering Ratio
5.08:1
8.
Ackerman Percentage
92.5%
9.
Steering Arm Length
3”
10.
Castor Angle
+6 o
30
Last year, steering arm length was 7” which resulted in catastr ophic structural failure of the steering system, so learning from last years’ experience, steering arm length is 3” and proper support has been provided.
31
Front Wheel Assembly:
32
Steering Geometry
33
Steering Hard Points Location:
Front Knuckle Load Analysis:
Load Applied: 3000 N; Max Von Mises Stress: 5.23*10 7 N/m2
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POWER TRAIN
The Primary Goal of the drive train is to maximize the power delivered to the rear wheels for all practical vehicle speeds. This goalpeciallyimportant when attempting to power a off road buggy with a small. Single cylinder engine. All components used in drivetrain should be durable enough to last the endurance race, as light as possible, and they should occupy am acceptable space given the restrictions derived from the rest of the vehicle sub-systems, namely the rear suspension. The drivetrain should also contribute to the vehicle’s center of gravity while maintaining minimum of 12 inches of ground clearance. The team wil be using a Cvtech CVT coupled with a four stage reduction FNR Gearbox with a gear reducton of 13.55:1.
Engine: All vehicles competing in the Society of Automotive Engineers’ (SAE) Mini Baja Competition must use the same engine: the Briggs and Stratton OHV Intek model 20. This single cylinder, four cycle, air-cooled, 52 pound engine is rated for 10 HP at 3800 rpm. SAE uses this engine to level the playing field between teams. To be competitive, the car needs to be designed to maximize the output available from this engine. The power curve for this engine, provided by Briggs and Stratton, is shown below in Figure 1
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Targets:
1.
Maximum Velocity
58kmph
2.
Uniform Acceleration
2.63 m/s 2
3.
Maximum Gradability
35 o
4.
Power to Weight Ratio
45.45HP/tonne
5.
Maximum Torque Required
1604.1 N
6.
Maximum Torque Available
1902.92 N
Assumptions for drive train Calculations:
1.
Tyre diametre
22”
2.
Wheel Resistance
107.45 N
4.
Gross Weight
280Kg
5.
Max Power
10 HP
6.
Reduction
13.55:1
7.
CVT Hiighest Ratio
3.1:1
8.
CVT Lowest Ratio
0.43:1
9.
CVT Efficiency
84%
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Power Train Exploded View
GEARBOX CALCULATIONS:
Engine power @ 3600 rpm = 7.38 KW P → Engine Power → Engine rpm → Engine Torque P = 2*π*3600*19.6 60,000 = 7.46KW
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Assumptions: • 22 in diameter tire • 13:1 gearbox • Rolling Resistance (wet) = 0.061 • Rolling Resistance (dry) = 0.045 • Gross weight=280kg • K erb weight=220kg • Maximum power = 7.38kW (10 HP) • 98% efficiency of the gears • 99% efficiency of the bearings. • 97% efficiency of the constant velocity joints • 88% efficiency of the Van Doore type CVT
CVT ratio = 3 - 2.5 ∗ ( −800) 2800
Total ratio = ∗ = ∗ 13 Torque on the wheel = Torque Output * Total Ratio
Vehicle Speed = Rpm of Axle * Perimeter of the Tyre*60
for 800
=553.846*0.00176*60 =58.486 km/h Perimeter = 2* *r r
= radius of tyre = 0.28m
Perimeter = 1.76m = 0.00176 km Rpm of axle = 3600
= 553.846
(13*0.5)
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Table 1: This table displays our numerical data as it relates to our assumptions and the equations
Engine rpm 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600
Torque output (N-m) 17.88 18.49 19.11 19.30 19.50 19.60 19.57 19.44 19.17 18.63
CVT ratio
Total ratio
2.107 1.929 1.750 1.571 1.393 1.214 1.036 0.857 0.679 0.500
27.391 25.077 22.750 20.042 18.109 15.782 13.468 11.141 8.827 8.82 7 6.5
Torque on wheel(N-m) 489.75 463.67 434.75 394.16 353.12 309.32 263.56 216.58 169.21 121.10
Speed (km/h) 6.93 8.42 10.21 12.64 15.16 18.73 23.52 30.33 40.67 58.48
Force required to push the vehicle →
Force Required = Wheel Resistance ( F w ) + Air Resistance ( F a ) + Gradient Resistance ( F g ) + Acceleration Resistance ( F ac )
Wheel resistance = Rolling resistance + Road resistance + Slip resistance
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Neglecting slip resistance:Then rolling resistance = f r * mv * g * incli nation . nation angle f r = coefficient of rolling resistance = 0.045 mv = mass of the vehicle = 280 Kg
Rolling resistance = 0.045 * 280 280 * 9.81 * cos30 = 107.045 N Road resistance=0.045*280*9.81=123.606 N Wheel resistance ( F w ) = 107.045+123.606 N Neglecting, acceleration resistance: Air resistance or drag (Fd) = cd* ρ*v2*A=247.59 N 2 Gradient resistance ( F g ) = mv * g * sin30= 1373.4N Hence, Required force = 123.60+107.045 + 1373.4 1373.4 = 1604.046N A total f orce of 1604.046 1604.046 N i s r equi r ed to push push th e vehi vehi cle at in cl i nati on of θ =30 =30
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BRAKING SYSTEM
The objective to bring the vehicle to rest when desired, under the condition that all four wheels should lock simultaneously as the brake pedal is pressed. Key points for implementing Disc brakes in both front & rear is based on the following points:
Heat Dissipation
Low Weight
Centrifugal Cleaning Action
Maximum Deceleration
Parameters
Old
New
Type
Disc ( Front & Rear)
Disc (Front & Rear)
Outer Diameter of disc
Front: 8” ; Rear: 6”
Front: 6.25” ; Rear: 6.5”
Brake Type
Front-Rear Split
Front-Rear Split
Brake Biasing
60(f): 40(r)
50:50
Stopping Distance
9 m at 45 Km/h
6.78 m at 45 Km/h
Leverage Ratio
4:1
7:1
Pedal Force
386 N
350 N
Deceleration
9.8 m/s2 or 1 g
11.51 m/s 2 or 1.17 g
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Brake Components
Old
New
Calliper Used
Driver front right and rear left: Apache 160 Driver front left and rear right: Suzuki GS 150
Driver front right and rear left: Apache 160 Driver front left and rear right: Suzuki GS 150
Master Cylinder Used
TVS Girling Tandem Master Cylinder
TVS Girling Tandem Master Cylinder
Disc Used
Aviator: front (8”); and Apache 160: rear ( 6”)
Imported disc for ATV. Front: 6.25” ; Rear: 6.50”
Braking Mounts On the front Wheel Assembly
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Braking Calculations: Assumptions & Requisition:
TVS Girning Tandem Master Cylinder
Brake Type: Front- Rear Split
Leverage Ratio: 7:1
Pedal force: 350 N
Front Disc: 6.50’’ (0.165m)
Rear Disc: 6.25’’ (0.158m)
Front Wheel & Tire:
Rear Wheel & Tire:
Tire Pressure: 7psi
Coefficient of Friction ( pad wrt disc) = 0.3
Coefficient of Friction ( tire wrt road)= 0.7
Gross Weight = 280 Kg
Taking Moment about Pivot Point, => Force on Master Cylinder * 1 = Force on Pedal (350 N) * 7 => Force on Master Cylinder = 2450 N Pressure Delivered on Master Cylinder: = Force on Master Cylinder/ Bore Area of Master Cylinder = 2450/ 0.031415 = 77988.23 N/m2
Front: Rear Biasing= 60:50 Pressure on Front Line = 46792.938 N/m 2 Pressure on Rear Line = 31195.292 N/m 2
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Force Applied by Calliper Piston: FFront = Pressure on front line * bore area of calliper = 46792.938 * 0.0491 = 2297.533 N Similarly, FRear = Pressure on front line * bore area of calliper = 31195.292 * 0.0491 = 1531.688 N
Force applied on disc by the calliper: FfrontDisc = 2 * Force applied by calliper piston * µ (disc wrt pad) = 2 * 2297.533 * 0.3 = 1378.519 N Similarly, FRearDisc = 2 * Force applied by calliper piston * µ (disc wrt pad) = 2 * 1531.688 * 0.3 = 919.01 N
Torque on each Disc: TFront = Force applied on front disc by calliper * Radius of front disc = 1378.519 * 0.1651 = 227.59 N-m TRear = applied on front disc by calliper * Radius of front disc = 919.01 * 0.1524 = 140.057 N-m
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Force per Wheel: FWFront = Torque on Front Wheel/ Radius of the Wheel = 227.59/ 0.558 = 407.86 N FWRear = Torque on Rear Wheel/ Radius of the Wheel = 140.057/ 0.558 = 250.99 N
Normal Force = µ (tyre wrt ground) * Gross weight of Vehicle N= 0.7 * 280 * g = 1920.8 N
Deceleration= Force/ Mass of Vehicle: Dx= [2( FFrontWheel + FRearWheel) + Normal Force] / Mass of Vehicle = [2(407.86 + 250.99) + 1920.8] / 280 = [2(658.85) + 1920.8] / 280 = [1317.7 + 1920.8] / 280 = 3238.5 / 280 = 11.56 m/s2 or 1.18g
Stopping Distance: SD= v2 / (2 * D x) = 12.52 / (2* 11.56) SD = 6.75m
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Mass Transfer: Wt = (µ*h*W*Dx) / b =>Wt= (0.7*0.457*280*11.56)/1.500 =>Wt= 690.30 N
Weight of Vehicle: W= 280*9.8 =>W=2744 N Percentage Mass Transfer= 25.15 %
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PROJECT PLAN
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D.F.M.E.A Components
Failure Mode
Causes
Failure Effect
Actions Taken
S O
D
RPN
Brakes
Leakage, Master Cylinder Failure
Lose hoses, punctured brake lines
Loss of braking force and control
Using separate Master cylinder for Front & Rear brakes, and use of genuine parts
5 2
4
40
Wishbone
The arm breaks or bends from the ball joint or bushing
Sudden impact, stresses in case of collision
Damage to the entire wheel assembly, loss of control
Analysis done with high factor of safety.
6 1
6
36
CVT Belt
Belt stretches, burns, slips.
Incorrect distance b/w pulleys, misalignment of shafts, no proper vents for heat dissipation
Power cannot be transmitted to the wheels
5 2
2
20
Tie Rod
Breaking of Tie rod from joints
Due to excessive cornering forces and excessive bump stresses.
Loss of control
6 3
1
18
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Final Design: Front View:
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Top View:
50
Side View:
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Isometric View:
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Weld Destructive Test:
Welding Process:
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Front Uprights Machining:
Front Wheel Assembly:
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Testing Phase:
55
56
Vehicle at the Event:
57
58
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CONCLUSION
The Vehicle was completed well in time and had a month’s testing time to it, the vehicle had gone through rigorous terrains but it proved to be a good off-roader, the vehicle participated in BAJA Student India-2015 at NIT Jamshedpur Campus, organized by Government of Jharkhand and FMSCI. On 7th Jan, team presented their design to the technical inspectors. The team scored decent points in the design event and went on for the cost event. On 8 th January, Team was ready for the Acceleration Event and Traction Event. In acceleration Event, teams had to complete a 100 feet track in the least timing, Lingaya’s University finished ‘fourth’ in acceleration. Next was the sledge pulling event, where we had to pull a 1500 Kg Maruti Gypsy through a 100 feet track, in this event our college finished at 7 th position. On 10th January Teams went through manoeuvrability track and hill climb track, our team went for the hill climb, where it had to climb up a hill with an inclination of 24 deg. Our team did well and completed the hill in 8 sec, and was at 8th position. At the end, team geared up for the manoeuvrability event where the team had to showcase a great combination of suspension, power train and driving skills. Our Team completed manoeuvrability in 1min 10 sec and was placed 3 rd position with College of Engineering, Pune at first and Vishwakarma Institute OF technology, Pune at 2 nd position. On the last day Team was all set to participate in the 4 hour Endurance Race, and since we had a good rank in the manoeuvrability our car stood at the third pole position. We had a good start but due to broken CVT cover we lost 30 min in the race, but we still managed to finish at fifth position and a total of 66 Laps. Lingaya’s University stood 11th in overall out of 44 teams from All over India. Overall it was a great learning experience, using different software for analyses and simulation and furthermore using different machining equipment such as CNC, Lathe, Drilling Machine, Notching Tool, Gear Hobbing and many more. This project has helped to learn more about the basic of automobile and mechanical engineering.
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