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automotive mechanics lab manual

automotive mechanics lab manual for diploma automobile students

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automotive mechanics lab manual

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  1. DIPLOMA AUTOMOBILE ENGINEERING TUTORIAL BOOK AUTOMOTIVE MECHANICS (4340202) Semester 4 Directorate of Technical Education Gandhinagar – Gujarat.

  2. 4340202 DTE’s Vision: • To provide globally competitive technical education; • Remove geographical imbalances and inconsistencies; • Develop student friendly resources with a special focus on girls’ education and support to weaker sections; • Develop programs relevant to industry and create a vibrant pool of technical professionals. Institute’s Vision: Institute’s Mission: Department’s Vision: Department’s Mission: Automotive Mechanics (Tutorial) P a g e | 2

  3. 4340202 Institute Name: ……………………………………………………… Automotive Mechanics (Tutorial) CERTIFICATE This is to certify that Shri / Kum. __________________________________, Enrollment No._____________________________ of Semester_______ Diploma program in Automobile Engineering has satisfactorily completed his / her term work in the subject Automotive Mechanics (4340202) for the Academic year:……………Term:…………………..As prescribed in the curriculum. Place :……………..... Date :………………. Staff in-charge Head of Department P a g e | 3

  4. 4340202 Automotive Mechanics (Tutorial) Preface Main motto of any tutorial work is for enhancing required skills as well as creating ability amongst students to solve real time problem by developing relevant competencies in affective domain. A tutorial, in education, is a method of transferring knowledge and may be used as a part of a learning process. More interactive and specific than a book or a lecture, a tutorial seeks to teach by example and supply the information to complete a certain task. By keeping in view, GTU has designed competency focused outcome-based curriculum - 2021 (COGC-2021) for engineering diploma programmes. In that, more time is allotted to tutorial work than theory work. It shows importance of enhancement of skills amongst students, and it pays attention to utilize every second of time allotted for tutorial amongst students and lecturers to achieve relevant outcomes by practice. Tutorials are designed to give student a space to engage more actively with the course content. It is must for effective implementation of competency focused outcome- based green curriculum- 2021 that every tutorial has been keenly designed to serve as a tool to develop & enhance relevant analytical competency in each and every student. It also gives an idea that how students will be assessed by providing Rubrics. Mechanics is a branch of Physics, which incorporates science concerned with the motion of bodies under the action of forces, including the special case in which a body remains at rest. Study of automotive mechanics includes the underlying study of various forces, motion analysis of mechanisms, braking performance, engine performance, vibration analysis, direction control, etc. This course is mainly concerned with the movements of a vehicle on a road surface. The movements of interest are acceleration, braking, ride and turning. Course is designed to acquaint students with effects of various forces on the vehicle, sources of vibration and its isolation, steering geometry for true rolling and engine performance measurement. Calculation on wheel reaction, braking force impact, traction available at wheel, maximum possible acceleration for given situation, heat balance sheet etc. are also covered in the course with a view to develop problem solving capacity of student in the field of automotive mechanics. Although we have tried our level best to design this Tutorial book, there are chances of improvement. We welcome any suggestion for improvement. P a g e | 4

  5. 4340202 Automotive Mechanics (Tutorial) Programme Outcomes (POs) to be achieved through Practical of this Course Following programme outcomes are expected to be achieved through the practical of the course: 1. Basic and Discipline specific knowledge: Apply knowledge of basic mathematics, science and engineering fundamentals and engineering specialization to solve the engineering problems. 2. Problem analysis: Identify and analyse well-defined engineering problems using codified standard methods. 3. Design/ development of solutions: Design solution for well-defined technical problems and assist with the design of systems components or processes to meet specified needs. 4. Engineering Tools, Experimentation and Testing: Apply modern engineering tools and appropriate technique to conduct standard tests and measurements. 5. Engineering practices for society, sustainability and environment: Apply appropriate technology in context of society, sustainability, environment and ethical practices. 6. Project Management: Use engineering management principles individually as a team member or a leader to manage projects and effectively communicate about well-defined engineering activities. 7. Life-long learning: Ability to analyse individual needs and engage in uploading in the context of technological changes. P a g e | 5

  6. 4340202 Automotive Mechanics (Tutorial) PO-COMPETENCY-CO MAPPING Automotive Mechanics (4340202) Semester IV POs Competency PO 1 Basic & Discipline specific knowledge PO 2 Problem Analysis PO 3 Design/ development of solutions PO 4 Engineering Tools, Experimentation &Testing PO 5 PO 6 Project Management PO 7 Life-long learning Engineering practices for society, sustainability & environment & Course Outcomes Use knowledge of automotive mechanics to improve vehicle performance. 3 2 1 2 2 2 Interpret various terminologies used in Automotive Mechanics. 3 1 Appreciate the importance of true rolling condition for steering to minimize side forces, vehicle vibrations and vibration isolation. 3 2 1 2 2 Evaluate the vehicle performance based on given situation. 3 1 1 2 1 Evaluate various parameters affecting Engine performance 3 1 1 3 2 2 Legend: ‘3’for high, ‘2’ for medium, ‘1’ for low and ‘-’ for no correlation of each CO with PO. Teaching and Examination Scheme Teaching Scheme (In Hours) (L+T+P/2) Theory Marks L T P C CA Total Credits Examination Scheme Practical Marks ESE CA Total Marks ESE 2 2 0 4 30* 70 - - 100 Legends: L-Lecture; T – Tutorial/Teacher Guided Theory Practice; P -Practical; C – Credit, CA - Continuous Assessment; ESE -End Semester Examination. P a g e | 6

  7. 4340202 Automotive Mechanics (Tutorial) Course Outcomes CO1 Interpret various terminologies used in Automotive Mechanics. CO2 Appreciate the importance of true rolling condition for steering to minimize side forces, vehicle vibrations and vibration isolation. CO3 Evaluate the vehicle performance based on given situation. CO4 Evaluate various parameters affecting Engine performance. Tutorial Outcome - Course Outcome matrix Sr. No. 1. Tutorial Outcome CO1 CO2 CO3 CO4 a.Interpret and write various terminologies related to mechanics. b.Describe various mechanisms used in automotive mechanics. c.Explain important terms related to Automotive mechanics i) Aerodynamic forces ii) SAE Vehicle axis system iii) Rolling, Pitching and Yawing moments iv) SAE Tire axis system v) Side force 2. Steering System: a.Derive the equation for Ackerman steering Mechanism. b.Derive the equation for the true rolling conditions c. Understand the equation of turning radius. 3. a.Recall various terminologies related to Vibration. b.Prepare a list of sources of vibration in vehicle. c.Describe various types of vibration. d.Enlist various factors affecting vehicle vibration and human comfort. 4. Vehicle Performance: a.Explain various resistances acting on a vehicle. b.Illustrate the relation between the Engine speed and vehicle speed. c.Draw the road performance curve (road speed vs power available at wheel & road speed vs tractive effort) for, •Acceleration •Drawbar Pull •Gradability d.Derive equations for weight distribution in •Three wheeled Vehicle •Four wheeled Vehicle √ - - - - √ - - Vibration: - - - √ - - - √ P a g e | 7

  8. 4340202 Automotive Mechanics (Tutorial) 5. Vehicle Performance: a.Derive equations for the stability of a vehicle on slope. b.Calculation of maximum acceleration, maximum tractive effort and relation for different drives c.Calculation of stopping distance. •Only front wheel, •Only rear wheels •All four wheels 6. Engine Performance: Calculation related to basic terminology of engine. 7. Engine Performance: a.Describe Morse test along with its procedure. b.Calculation of Power of multi cylinder along with example Solve problems related to heat balance sheets - - √ - - - √ - - - √ - P a g e | 8

  9. 4340202 Automotive Mechanics (Tutorial) TUTORIAL RUBRICS LEVEL OF PERFORMANCE & SCORE iteria Poor Average Good Very Good (4 Marks) Excellent (1 Marks) (2 Marks) (3 Marks) (5 Marks) Average basic knowledge of topic Adequate knowledge of most topics. Demonstrates deep knowledge. Basic Knowledge of Tutorial Not basic knowledge of topic Good knowledge of topic Somewhat Understanding of theoretical concept and little idea of where to use concept and why In-depth Understanding of theoretical concept and idea of where to use concept and why Somewhat understanding of theoretical concept and No idea of where to use concept and why Good Understanding of theoretical concept and idea of where to use concept and why Adequate Understanding of theoretical concept or idea of where to use concept and why Understanding of tutorial Do whatever is assigned with active participation. Do whatever is assigned with some resistance Participation in tutorial Ask for more work. Not active Less active Neatness in assigned work Poor Average Good Very Good Excellent Submitted at the end of semester else students will score zero. Timely Submission Submitted at the end of semester. Submitted after due date. Submitted on due date. Submitted before due date. Total Marks per practical - 25 Guidelines to Teachers 1Tutorials should have their own learning goals. Check that tutorial goals are congruent with those of the rest of the course and that they clearly define what students will do. Communicate these goals to your students. Focus not on “covering material” but rather encourage active learning among your students. Give them the opportunity to practice, with feedback, the core concepts or skills for the course. 2Establish guidelines at the beginning. Devote time early in the term to familiarizing students with your guidelines for how the tutorial will be run. 3Prepare a lesson plan for each session. Begin with your learning objectives for the session to help you limit your content to 2-3 main concepts for a 120-minute session. Make sure to include time estimates for each section of the tutorial. 4Have your supporting materials ready. If you plan to use visual aids (e.g., slide show, handouts), make sure they are legible and concise. If you plan to use the chalkboard in on-campus tutorials, determine how to partition and use it. It’s also a good idea to prepare a few extra problems and examples in case students need additional practice. P a g e | 9

  10. 4340202 Automotive Mechanics (Tutorial) Instructions for Students 1Listen carefully the lecture, curriculum, learning structure, skills to be developed. 2Organize the work in the group and make record of all work. 3Students shall develop analytical skill as expected by industries. 4Student shall attempt to do work at his/her own and build confidence. 5Student shall refer technical magazines and data books. 6Student should develop habit to submit the tutorial on date and time. 7Student should well prepare while submitting problems of exercise. 8Students are required to understand the rubrics of tutorial at the starting of their term. P a g e | 10

  11. 4340202 Automotive Mechanics (Tutorial) Progressive Assessment Sheet Practical Outcome Sr. No. Date of Date of Marks Dated Sign Page Remarks Perform Submission (25) a.Interpret and write various terminologies related to mechanics. b.Describe various mechanisms automotive mechanics. c.Explain important terms related to Automotive mechanics vi)Aerodynamic forces vii)SAE Vehicle axis system viii)Rolling, Pitching and Yawing moments ix)SAE Tire axis system x)Side force 2. Steering System: a.Derive the equation for Ackerman steering Mechanism. b.Derive the equation for the true rolling conditions c. Understand the equation of turning radius. Vibration: a.Recall various terminologies related to Vibration. b.Prepare a list of sources of vibration in vehicle. c.Describe various types of vibration. d.Enlist various factors affecting vehicle vibration and human comfort. 4. Vehicle Performance: a.Explain various resistances acting on a vehicle. b.Illustrate the relation between the Engine speed and vehicle speed. c.Draw the road performance curve (road speed vs power available at wheel & road speed vs tractive effort) for, •Acceleration •Drawbar Pull •Gradability d.Derive equations for weight distribution in •Three wheeled Vehicle •Four wheeled Vehicle 1. used in 3. P a g e | 11

  12. 4340202 Automotive Mechanics (Tutorial) 5. Vehicle Performance: d.Derive equations for the stability of a vehicle on slope. e.Calculation of maximum acceleration, maximum tractive effort and relation for different drives f. Calculation of stopping distance. (When brakes are applied to) •Only front wheel, •Only rear wheels •All four wheels 6. Engine Performance: Calculation related to basic terminology of engine. 7. Engine Performance: c.Describe Morse test along with its procedure. d.Calculation of Power of multi cylinder along with example Solve problems related to heat balance sheets Total marks obtained out of 25 HOD Sign: Faculty Sign: P a g e | 12

  13. 4340202 Automotive Mechanics (Tutorial) Date: ___ / ___ / _______ Tutorial 1 Aim: - Interpret and write various terminologies related to Automotive Mechanics. Relevance/Objective: - After this tutorial, the student will be able to, Understand Various terms and mechanism related to Automotive mechanics Relevant CO: -. Interpret various terminologies used in Automotive Mechanics. Apparatus/Equipment required: - Models ofVarious mechanism related to Automobile. INTRODUCTION: Theory of machine is a branch of engineering science, which deals with the study of relative motion between the various parts of a machine, and forces which act on them. Scalar quantities: are those quantities which have magnitude only e.g. mass, time, volume, density etc. Vector quantities: are those quantities which have magnitude as well as direction e.g. velocity, acceleration, force etc. Sub- divisions of theory of Machines: 1- Kinematics: is that branch of theory of machines which is responsible to study the motion of bodies without reference to the forces which cause this motion, i.e. it relates the motion variables (displacement, velocity, acceleration) with the time. 2- Kinetics: is that branch of theory of machines which is responsible to relate the action of forces on bodies to their resulting motion. 3- Dynamics: is that branch of theory of machines which deals with the forces and their effects, while acting upon the machine parts in motion. 4- Statics: is that branch of theory of machines which deals with the forces and their effects, while the machine parts are at rest. Mechanism: is a combination of rigid bodies which are formed and connected together by some means, so that they are moved to perform some functions, such as the crank- connecting rod mechanism of the I.C. engines, steering mechanisms of automobile etc. Rigid Body: is that body whose changes in shape are negligible compared with its overall dimensions or with the changes in position of the body as a whole, such as rigid link, rigid disc etc. Links: are rigid bodies each having hinged holes or slots to be connected together by some means to constitute a mechanism which is able to transmit motion or forces to some another locations. Each part of a machine which moves relative to some other part is called a kinematic link. From the Reciprocating steam engine Slider crank mechanism) kinematic links are: Link (1): Frame & guides, Link (2): Crank, Link (3): Connecting rod, Link (4): Slider P a g e | 13

  14. 4340202 Automotive Mechanics (Tutorial) Kinematic Pair / Joint: Combination / Assembly of two links kept in permanent contact, permitting particular kind(s) of definite relative motion(s) between them. Kinematic Chain: Combination / Assembly of links and pairs such that each link has minimum two pairs, permitting controlled definite output motion for a specified input motion. Mechanism: A kinematic chain with one link fixed / stationary. A device to transfer or transform given input motion to specified output motion. Structure: A single body with no motion / combination of bodies with no relative motion. Machine: A device, which has one or more mechanisms, transferring / transforming motion and energy to do required useful work easily. The degree of freedom: Parameters that define its configuration. It is the number of independent parameters that determine the state of a physical system and is important to the analysis of systems of bodies in mechanical engineering. The degree of freedom of a system can be viewed as the minimum number of coordinates required to specify a configuration. Applying this definition, we have: For 1.A single particle in a plane two coordinates define its location so it has two degrees of freedom; 2.A single particle in space requires three coordinates so it has three degrees of freedom; 3.Two particles in space have a combined six degrees of freedom; Degree of Freedom for various Pairs Basic Mechanisms used in Automobile Systems Four Bar Chain: The simplest and the basic kinematic chain is a four-bar chain or quadric cycle chain, as shown in Fig. 1. It consists of four links, each of them forms a turning pair at A, B, C and D. The four links may be of different lengths. It consists of four rigid links which are connected in the form of a quadrilateral by four pin-joints. A link makes complete revolution is called Crank (4). The link which is fixed is called fixed link (1). The link opposite to the fixed link is called Coupler (3). The fourth link is called Lever or Rocker (2). P a g e | 14

  15. 4340202 Automotive Mechanics (Tutorial) Four Bar Chain Mechanism Single Slider Crank Mechanisms A single slider crank mechanism is a modification of the basic four bar chain. It consists of one sliding pair and three turning pairs. It is, usually, found in reciprocating steam engine mechanism. This type of mechanism converts rotary motion into reciprocating motion and vice versa. Single slider crank mechanism In a single slider crank chain, as shown in Fig. 2, the links 1 and 2, links 2 and 3, and links 3 and 4 form three turning pairs while the links 4 and 1 form a sliding pair. The link 1 corresponds to the frame of the engine, which is fixed. The link 2 corresponds to the crank; link 3 corresponds to the connecting rod and link 4 corresponds to cross-head. As the crank rotates, the cross-head reciprocates in the guides and thus the piston reciprocates in the cylinder. Double Slider Crank Mechanisms Double slider crank mechanism A kinematic chain which consists of two turning pairs and two sliding pairs is known as double slider crank mechanism, as shown in Fig. We see that the link 2 and link 1 form one turning pair and link 2 and link 3 form the second turning pair. The link 3 and link 4 form one sliding pair and link 1 and link 4 form the second sliding pair. P a g e | 15

  16. 4340202 Automotive Mechanics (Tutorial) Cam and Follower Mechanism A cam and follower mechanism is a profiled shape mounted on a shaft that causes a lever or follower to move. Cams are used to convert rotary to linear (reciprocating) motion. As the cam rotates, the follower rises and falls in a process known as reciprocating motion. Cam and Follower Mechanism The motion of the follower is restricted to a pre-determined pattern by a guide. The follower maintains contact with the cam through the force of gravity or by a spring. The total range of movement produced by the cam is called the stroke. The range of movement of the follower will depend on the distance from the shaft supporting the cam to the upper and lower points of the rotation circle. Cams are commonly used in engines to control valves (in which the valve is the follower), sewing machines, children's toys and many other mechanical applications. Automotive Mechanics and Related Important Terms Aerodynamic Forces in vehicle: Aerodynamics is the study of how gases interact with moving bodies. Aerodynamics is primarily concerned with the forces of drag and lift, which are caused by air passing over and around solid bodies. Aerodynamic drag: Aerodynamic drag is one of the main obstacles to accelerate a solid body when it moves in the air. When a racing car or road vehicle burns fuel to accelerate, drag force pulls it from back to reduce the speed and hence the fuel efficiency is adversely affected. Aerodynamic lift: The lift force is due to the pressure difference between the upper and lower surface of the airfoil, which reduces the total load on the wheels. Rolling: The angular oscillation of the vehicle about the longitudinal axis. Pitching: The angular oscillation of the vehicle about lateral (horizontal) axis. Yawing: The angular oscillation of the vehicle about the vertical axis. P a g e | 16

  17. 4340202 Automotive Mechanics (Tutorial) Aerodynamic Forces in vehicle SAE Wheel Axis System SAE Wheel Axis System P a g e | 17

  18. 4340202 Automotive Mechanics (Tutorial) Assignment Exercise – 1 Give the definition of following terms: (a) Kinematic Link: _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ (b)Kinematic Pair: _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ (c) _____________________________________________________________________________________ Kinematic Chain: _____________________________________________________________________________________ _____________________________________________________________________________________ (d)Degree of freedom: _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ Exercise – 2 Explain single slider crank mechanism with neat sketch. P a g e | 18

  19. 4340202 Automotive Mechanics (Tutorial) Exercise – 3 Explain double slider crank mechanism with neat sketch. Exercise – 4 Explain cam and follower mechanism with neat sketch. P a g e | 19

  20. 4340202 Automotive Mechanics (Tutorial) Exercise -5 Explain various aerodynamic Forces and moments acting on the vehicle with a neat sketch. Assessment Assessment criteria Poor Average Indicators Good Very good Excellent Basic Knowledge of Tutorial 1 2 3 4 5 Understanding of tutorial 1 2 3 4 5 Participation in tutorial 1 2 3 4 5 Neatness in assigned work 1 2 3 4 5 Timely Submission 1 2 3 4 5 Total marks / 25 Faculty Name & Sign: P a g e | 20

  21. 4340202 Automotive Mechanics (Tutorial) Date: ___ / ___ / _______ Tutorial 2 Aim: - Derive the equations related to steering system of Automobile. Relevance/Objective: - After this tutorial, the student will be able to, Derive various equations of steering system of Automobile and understand importance of each parameters used to derive equation. Relevant CO: -. Appreciate the importance of true rolling condition for steering to minimize side forces, vehicle vibrations and vibration isolation. Apparatus/Equipment required: - Various steering mechanism models related to Automobile INTRODUCTION: The steering system controls the directional movements of the vehicle. The steering system, in conjunction with the suspension system, provides control and stability of the vehicle. The motion the operator makes at the steering wheel is transferred to the front wheels. This is typically achieved by a series of linkages, rods, pivots and gears. One of the fundamental concepts is that of caster angle. Each wheel is steered with a pivot point ahead of the wheel, which tends to make the steering self-centring towards the direction of travel. Condition for True Rolling Always there should be absolute rolling contact between the wheels and the road surface. Any sliding motion will cause wear of tyres. When a vehicle is taking turn, absolute rolling motion of the wheels on the road surface is possible, only if all the wheels describe concentric circles. Therefore, the two front wheels must turn about the same instantaneous centre I which lies on the axis of the back wheel. The condition for perfect steering is that all the four wheels must turn about the same instantaneous centre. While negotiating a curve, the inner wheel makes a larger turning angle θ than the angle φ subtended by the axis of the outer wheel. In the fig. 2.1, a = wheel track, b = wheel base, c = distance between the pivots of front axles. x Fig 2.1 True Rolling condition P a g e | 21

  22. 4340202 Automotive Mechanics (Tutorial) Considering triangles formed by two angles, and applying cot functions to them, cot? = ? + ? ? cot? = ? ? cot? − cot? = ? + ? − ? ? ? ???? − ???? = ? ? When this condition gets satisfied then all four wheels will roll without sleep while taking turn. A steering gear should be designed in such a way that this condition is satisfied. ACKERMAN STEERING MECHANISM When you turn the steering wheel, the steering column translates the motion to the steering axis. The steering axis is connected to the moving link of the steering mechanism, which is at the centre. The moving link, in turn, changes the direction of the wheels by transferring motion to the link that is attached to the wheels. This is how Ackermann's steering kinematics works. It is referred to as kinematics because Ackermann's principle of steering doesn’t get influenced by any external forces. It involves only the relative motion between force links and doesn’t involve the study of the effect of forces. The Ackermann steering geometry is designed in such a way that the two front wheels are always aligned towards the common centre of the turning radius. Fig. 2.2 Ackerman Steering Mechanism for True Rolling Consider Figure 2.3, Where, a = c = r = Wheel Track Distance of Pivot points Length of track arm Horizontal distance from pivot point before steering α θ ∅ = Initial angle (Track rod to Longitudinal Reference) = Inner Angle = Outer Angle x = y = Horizontal distance in distance after steering P a g e | 22

  23. 4340202 Automotive Mechanics (Tutorial) θ θ Φ α α x y y x Fig. 2.3 Ackerman Steering Mechanism Analytic Solution Applying Sine functions to all angle before and after steering action, sin(? + ?) =? + ? ? sin(? − ∅) =? − ? ? sin(?) =? ? Hence, a relation is obtained as following: ???(? + ?) + ???(? − ∅) = ????? ???(? + ?) + ???(? − ∅) = ?? ? Above equation represents Ackerman’s Principle, which is useful to decide steering geometry for True rolling condition of steering. Turning Radius of a Vehicle Turning circle radius gives an indication of the space required to turn a particular vehicle. Hence, the higher the value of turning circle radius, the higher is the space you need to turn the vehicle completely and vice versa. This parameter is closely related to the steering geometry and the suspension system of the vehicle under consideration. For entire vehicle, it is the radius of the circle made by the outer wheels of the vehicle while making a complete turn. Naturally, turning circle differs for every kind of vehicle. Legally, manufacturers must specify the turning circle radius or diameter. Hence, it appears in the specification sheet of every vehicle. For each wheels, turning circle radius is equal to distance of wheel contact point from an instantaneous circle. With slight consideration Fig 2.1 is useful to derive equations for Turning Circle Radius. sin?− (? − ? ? ??? Outer Front, = ) 2 sin?− (? − ? ? tan?− (? − ? ? ??? Inner Front, = ) 2 Outer Rear, = ) ??? 2 tan?− (? − ? ? Inner Rear, = ??? ) 2 P a g e | 23

  24. 4340202 Automotive Mechanics (Tutorial) Exercise – 1 Derive the equation for Ackerman steering Mechanism. P a g e | 24

  25. 4340202 Automotive Mechanics (Tutorial) Exercise –2 Derive the equation for the true rolling conditions. P a g e | 25

  26. 4340202 Automotive Mechanics (Tutorial) Exercise – 3 Explain turning circle radius of vehicle and write equations of all wheels turning radius. P a g e | 26

  27. 4340202 Automotive Mechanics (Tutorial) Exercise – 4 A motor car has a wheel-base of 2.743 m and pivot centre of 1.065 m. The front and rear wheel track is 1.217 m. Calculate the correct angle of outside lock and turning circle radius of the outer front and inner rear wheels when the angle of inside lock is 40°. P a g e | 27

  28. 4340202 Automotive Mechanics (Tutorial) P a g e | 28

  29. 4340202 Automotive Mechanics (Tutorial) Exercise – 5 A track has pivot pins 1.37 m apart, the length of each track arm is 0.17 m and the track rod is behind front axle and 1.17 m long. Determine the wheel base which will give true rolling for all wheels when the car is turning so that the inner wheel stub axle is 60 degrees to the centre of the car. P a g e | 29

  30. 4340202 Automotive Mechanics (Tutorial) Assessment Assessment criteria Indicators Good Very good Excellent Poor Average Basic Knowledge of Tutorial 1 2 3 4 5 Understanding of tutorial 1 2 3 4 5 Participation in tutorial 1 2 3 4 5 Neatness in assigned work 1 2 3 4 5 Timely Submission 1 2 3 4 5 Total marks / 25 Faculty Name & Sign: P a g e | 30

  31. 4340202 Automotive Mechanics (Tutorial) Date: ___ / ___ / _______ Tutorial 3 Aim: Interpretand write various terminologies related to Vibration, Relevance/Objective: After this tutorial, the student will be able to, Understand various terms related to automotive vibration and source of vibration, its impact on human and vibration isolation in a vehicle. Relevant CO: Appreciate the importance of true rolling condition for steering to minimize side forces, vehicle vibrations and vibration isolation. Apparatus/Equipment required: Various models and charts related to vehicle vibration and isolation. INTRODUCTION OF VIBRATION: Vibrations: “Vibration is when the motion arising in an engineering system with a body with mass and elasticity is repeated over a given period of time.” Vibration can cause noise in a vehicle, sudden breakdown of vehicle units, and unnecessary motion transmission in a nearby unit. Various Terminologies related to Vibration. 1.Period: The time period for repetition of motion is called period. 2.Periodic Motion: It is the time interval after which the motion is repeated itself. The period of vibration is usually expressed in seconds. 3. Cycle: It is the motion completed during one time period. 4. Frequency: It is the number of cycles described in one second. In S.I. units, the frequency is expressed in hertz (briefly written as Hz) which is equal to one cycle per second. 5.Amplitude: The maximum displacement of the vibrating body from its equilibrium position. VI. Degree of Freedom: The minimum number of independent coordinates requires for specifying the motion of a system at any instant is known as the degree of freedom. 6.Natural Frequency (Natural Frequency): When no external force acts on the system after giving it an initial displacement, the body vibrates. The vibration is called as free vibration and the frequency is called Natural frequency. This is expressed in rad/sec or Hertz. 7.Resonance: When the frequency of external excitation is equal to the natural frequency of the vibrating body, the amplitude of vibration becomes excessively large. This concept is called resonance. 8.Critical Speed: The speed, at which the shaft runs so that the additional deflection of the shaft from the axis of rotation becomes infinite, is known as critical or whirling speed. 9.Damping: It is resistance to the motion of a vibrating body. The vibration associated with the resistance is known as Damped Vibration. 10.Free or natural vibrations: When no external force acts on the body, after giving it an initial displacement, then the body is said to be under free or natural vibrations. The frequency of the free vibration is called free or natural frequency. 11.Forced vibrations: When the body vibrates under the influence of external force, then the body is said to be under forced vibrations. The external force applied to the body is Periodic Disturbing force created by unbalance. The vibrations have the same frequency as the applied Force. 12.Ergonomics: Ergonomics is a discipline that studies the interactions between human activity and the components of this activity (tasks, tools, methods, work environment, etc.) to develop systems that allow people to work in conditions of optimal efficiency, safety and comfort. P a g e | 31

  32. 4340202 Automotive Mechanics (Tutorial) TYPES OF VIBRATION When a rigid or elastic body is forcibly moved from a position or state of equilibrium, that force creates a motion that we know as vibration. A vibrating motion can be oscillating, reciprocating, or periodic. Vibration can also be either harmonic or random. Harmonic vibration occurs when a vibration’s frequency and magnitude are constant. A vibration is random when the frequency and magnitude vary with time. Consider a weightless constraint (spring or shaft) whose one end is fixed and the other end carrying a heavy disc, as shown in Fig. 3.1. This system may execute one of the three below mentioned types of vibrations. 1.Longitudinal vibrations, 2.Transverse vibrations 3.Torsional vibrations. Fig 3.1 : Types of vibrations 1.Longitudinal vibrations: When the particles of the shaft or disc moves parallel to the axis of the shaft, as shown in Fig. 3.1 (a), then the vibrations are known as longitudinal vibrations. In this case, the shaft is elongated and shortened alternately and thus the tensile and compressive stresses are induced alternately in the shaft. 2.Transverse vibrations: When the particles of the shaft or disc move approximately Perpendicular to the axis of the shaft, as shown in Fig. 3.1 (b), then the vibrations are known as transverse vibrations. In this case, the shaft is straight and bent alternately and bending stresses are induced in the shaft. 3.Torsional vibrations: When the particles of the shaft or disc move in a circle about the axis of the shaft, as shown in Fig. 3.1 (c), then the vibrations are known as torsional vibrations. In this case, the shaft is twisted and untwisted alternately and the torsional shear stresses are induced in the shaft. SOURCES OF VIBRATION IN VEHICLE: When spring supported mass such as that of a motor vehicle chassis is given an impulse, it is set in to vibratory motion & it keeps on vibrating until the energy of the impulse completely dies out in overcoming damping forces. There are different sources of vibration of vehicle i.e. road roughness, the unbalance of the engine, whirling of shafts the cam forces & tensional fluctuations. Depending upon the cause the vibration may be free or forced. The free vibration may occur when the vehicle passes over an isolated irregularity in the road surface, which may die off as a result of dissipation of energy in damping. Then the forced vibration may result when disturbances occur persistently such as passing over obstacles on a proving road. In this case even if there may be damping, the vibration may persist & build up an undesirable level. P a g e | 32

  33. 4340202 Automotive Mechanics (Tutorial) In reality an automobile in its conventional form represents a very complicated vibration system. It is we known that a rigid mass free in space has a six degrees of freedom; three translation, such as 1) Bobbing up & down 2) Swaying back a form 3) Moving forward & backward & Three rotational such as 1) Rolling about longitudinal axis, 2) Pitching about a lateral axis & 3) Yawing about vertical axis Since automobile has three such masses A) The body B) The trot & rear axles & C) Eight distinct spring (Four spring & four tyres), therefore it has eighteen degree of freedom. Major sources of vibration in a vehicle are as follows: (1)Unbalanced force arising in the engine: The maximum values of the primary force and the secondary force produced by the acceleration of the reciprocating mass of the engine's slider frank mechanism are as follows. Maximum primary force = mω2r Maximum secondary force = mω2 r ? Where, m = mass of reciprocating parts (kg) ω = angular speed of the crank (rad / sec) n = the ratio of connecting rod length to frank radius r = crank radius (m) (2)Dry Friction Dry friction occurs between exposed surfaces when no lubricant is applied. These frictions include sliding and rolling frictions, which are a source of vibration. (3)Loose Fittings: Every loose fitting of the vehicle chassis and body causes vibration of the attached parts. (4)Propeller Shaft: Imbalance in the propeller shaft causes vibration or noise, like in tires. The propeller shaft turns faster than tires by the gear ratio of the differential gear. Therefore, the frequency of the vibration or noise increases, and is often accompanied by a booming noise. Gear box: As the gear system of the gearbox moves, torsional vibration is produced. The main reasons for gearbox vibration are lack of lubrication and worn out gears and bearings. (5)Lack of Vibration Isolation: The engine mountings, body fittings, window glass fittings, etc. are insufficient to insulate vibration. (6)Improper Engine Foundation Improper engine foundations make the engine unable to absorb vibrations or prove insufficient capacity. Such engine foundations are a source of vehicle vibration. (7)Disturbing force produced instantly or accidentally: Engine mounting breaks, engine is misfired, vehicle passes over irregular road surface, and transmission system defect occurs, center bearing fails and fittings are damaged. This causes vehicle vibration to occur. P a g e | 33

  34. 4340202 Automotive Mechanics (Tutorial) (8)Wheels and tyres: The most prevalent cause of vibration is problems with your wheels or tires. The potential problems include improper wheel and tire balance, uneven tire wear, separated tire tread, out of round tires, damaged wheels and even loose lug nuts. (9)Whirling of Shafts: A rotating shafts carries different mountings and accessories in the form of gears, pulleys etc. The centre of gravity of pulley or gear is at a certain distance from the axis of rotation and due to this the shaft is subjected to centrifugal force. This force will bend the shaft and causes vibrations. TYPES OF ENGINE VIBRATION AND THEIR CONTROL: Engine vibration accelerates engine wear, breaks engine parts, and robs us of horsepower. There are three specific types of engine vibration that professional engine builders concentrate on minimizing. Each vibration type has its own method to control it. They are: 1. Unbalances vibration Unbalanced vibration is a weight-imbalance vibration that occurs once per engine revolution. Like the consistent thumping you feel when you lose a wheel weight. A balancing service refers to precision matching the pistons, connecting rods, and crankshaft counterweights to minimize unbalanced vibration. 2. Axial vibration Axial vibration is forward and backward movement of the crankshaft. The main bearing support plate and thrust bearings are in place to avoid this movement. 3. Torsional vibration Torsional vibration is the end-to-end twisting and rebounding of the crankshaft caused by combustion. The harmonic balancer (damper) controls the twist to achieve durability and efficiency. IMPACT OF VIBRATION ON HUMAN COMFORT: The evidence suggest that short time exposure to vibration causes small physiological effects such as increase in heart rate, increase in muscle tension. Long term exposure to vibration causes effects such as disk to spine & effects on digestive system peripheral veins & the female reproductive organ. Whole- body vibration can cause fatigue, stomach problems, headache, loss of balance and "shakiness" shortly after or during exposure. The symptoms are similar to those that many people experience after a long car trip. After daily exposure over a number of years, whole-body vibration can affect the entire body and result in a number of health disorders. Studies of bus and truck drivers found that occupational exposure to whole-body vibration could have contributed to a number of circulatory, bowel, respiratory, muscular P a g e | 34

  35. 4340202 Automotive Mechanics (Tutorial) and back disorders. The combined effects of body posture, postural fatigue, dietary habits and whole- body vibration are the possible causes for these disorders. Mechanical Damage: Damage is produced when the accelerative forces are of sufficient magnitude. Chronic injuries may be produced by vibration exposure of long duration. Physiological Responses: The vibration of frequency range 4 to 10 Hz procures pain in the chest after backaches seem to occur very particularly at 8 to 12 Hz Headaches, eye strain & irritations in the intestines and bladder are usually associated with frequencies between 10 to 20 Hz. Visual Performance: Visual performance is generally impaired most by vibration frequencies in range of 10 to 25 Hz. Neural Processes: Tasks that involve primarily central neural processes, such as reaction time, monitoring & pattern recognitions, appear to be highly degrade during vibration. VEHICLE VIBRATION ISOLATION: Vibration isolation is a commonly used technique for reducing or suppressing unwanted vibrations in a vehicle. With this technique, the vehicle is isolated from the source of vibration through insertion of a resilient member or isolator. The purpose of vibration isolation is to control unwanted vibration so that its adverse effects are kept within acceptable limits. Vibration isolation materials are generally springs and resilient mounts that are inserted between the driving Object and the driven Object. Materials may be elastomers, elastomeric foam, cork, felt, fiberglass boards and steel springs, pads or hangers. Springs are commonly used as isolators to minimize the transmitted vibrational force. These springs may involve steel coil, rubber, pneumatic, fluid damping, or combination of one or more. When designing vibration isolator mounts, There are two types of systems that require analysis. 1. The first is a Mass Excited system. Think of when the engine (mass) produces vibration and needs to be isolated from the vehicle’s frame. The vibration mounts protect the frame of the car from movement. 2. The second is a Base Excited system. Consider an operator cab in the same vehicle. The goal would be to isolate all inputs (road, terrain, and engine). In this scenario, the base itself must be isolated. For many mounts, spring and damper are contained in the same mount. The purpose of the springs is to provide safety and make the journey comfortable. The stiffness of the front springs needs to be kept high, as the soft springs at the front put the steering in an uncertain position. More soft springs can be used in the independent suspension of the front wheels in the passenger car, which gives a comfortable ride. The use of coil springs and torsion bars has a minimal amount of damping force but in leaf springs there is a special damping device known as spring dampers in the passenger car and bus for the required damping force and to achieve comfortable travel as only the friction of the inner leaf gives the damping force. Vehicle shock absorber, absorbs mechanical energy from the vibration is converted to thermal energy in the fluid, decreasing the amount of energy transmitted to the body of the car. P a g e | 35

  36. 4340202 Automotive Mechanics (Tutorial) , Figure 3.2: Model of Car Body and Dampers P a g e | 36

  37. 4340202 Automotive Mechanics (Tutorial) EXERCISE A. Recall various terminologies related to vibration. 1. Period: 2. Periodic motion: 3. Cycle: 4. Frequency: 5. Amplitude: 6. Degree of freedom: 7. Natural frequency: P a g e | 37

  38. 4340202 Automotive Mechanics (Tutorial) 8. Resonance: 9. Critical speed: 10. Damping: 11. Free vibration: 12. Forced vibrations: P a g e | 38

  39. 4340202 Automotive Mechanics (Tutorial) B. Prepare a list of sources of vibration in vehicle. P a g e | 39

  40. 4340202 Automotive Mechanics (Tutorial) C. Describe various types of vibration. P a g e | 40

  41. 4340202 Automotive Mechanics (Tutorial) D. Discuss effect of vehicle vibration on human comfort. P a g e | 41

  42. 4340202 Automotive Mechanics (Tutorial) E. Discuss vibration isolation in a vehicle. Assessment Indicators Good Assessment criteria Very good Excellent Poor Average Basic Knowledge of Tutorial 1 2 3 4 5 Understanding of tutorial 1 2 3 4 5 Participation in tutorial 1 2 3 4 5 Neatness in assigned work 1 2 3 4 5 Timely Submission 1 2 3 4 5 Total marks / 25 Faculty Name & Sign: P a g e | 42

  43. 4340202 Automotive Mechanics (Tutorial) Date: ___ / ___ / _______ Tutorial 4 Aim: Evaluate and explain various terminologies related to vehicle performance. Relevance/Objective:After this tutorial, the student will be able to, Understand various resistances acting on a moving vehicle and weight distribution in a vehicle. Relevant CO: Evaluate the vehicle performance based on given situation. Apparatus/Equipment required: Various charts related to vehicle performance. VARIOUS RESISTANCES ACTING ON A VEHICLE The 3 different Resistances acting to the vehicle are as follows. 1. Rolling Resistance: The value of rolling resistance is mainly based on the following. (a)Type of road surface (b)Types of tires such as pneumatic or solid rubber type (c)Vehicle weight (d)Vehicle Speed The formula for vehicle speed rolling resistance is as follows. Rolling resistance, Rr = KW Where, W K = = = = = Total weight of the vehicle, N Coefficient of Rolling Resistance 0.0059 for good roads 0.18 for sandy roads 0.015 Sample value 2. Air Resistance: This is the Resistance given by the air to the movement of the vehicle. It has an effect on the performance of the vehicle, its travel and stability. This Resistance is affected by following factors. (a)Body size and shape of the vehicle (b)Vehicle Speed (c)Wind speed (d)Relative direction of air Where, A = Projected area of front, m2 V = Vehicle speed km / h Ka = = 0.045 for trucks and similar heavy vehicles = 0.031 for average car = 0.023 for excellent streamlined cars. Air resistance, Ra = Ka x A x V2 Coefficient of air resistance, N-h2 / m2 -Km? 3. Grade Resistance:  If a vehicle is climbing a slope then weight component of the vehicle is known as Gradient Resistance. P a g e | 43

  44. 4340202 Automotive Mechanics (Tutorial)  So, it depends on the straightness or inclination of the grade / slope.  If the slope is shown as 1 in 6, it means that when the vehicle rises 1 meter per 6 meters run. Grade resistance is denoted by the following formula. Grade resistance, Rg = W x sin θ  Where, θ = Slope angle with a horizontal surface Percentage grade = 100 x tan θ (But for the lower value of angle) tan θ = sin θ Total Resistance = Rolling Resi. + Air Resi. + Grade Resi. = Rr + Ra + Rg + (Ka x A x V2) = (KW) + (W x sin θ) POWER REQUIRED FOR PROPULSION: A Vehicle experiences different Resistances due to which Power is required to move a vehicle against these Resistances, this power is known as “Power required for Propulsion”.  The power required to propel a vehicle is proportional to the Total Resistance on it and its speed. PV = Power required for a vehicle, kW PR = Engine Power Requirement, kW V = Vehicle speed, km / h ηt = Transmission efficiency R = Total resistance, N Ra = Air resistance, N Rr = Rolling Resistance, N Rg = Gradient Resistance, N  From the basic definitions, Using above relation for power required to propel a vehicle can be written as follows. Pv = R × V/3600 The transmission loss is taken into account when calculating the engine power requirement. Hence, TRACTION AND TRACTIVE EFFORT: P a g e | 44

  45. 4340202 Automotive Mechanics (Tutorial) “Tractive effort”is a force available between the tires of the drive wheels and the road contact “Traction” is an ability of the dive wheels to transmit Tractive effort without drive wheel slipping.  Tractive effort must overcome the Total resistance to the vehicle in order to get vehicle propulsion. Engine torque, TE = 60000 PE / (2πN) Wheel Torque, Tw Gearbox Ratio g.r. Differential Axle Ratio TE x (g.r.) x (a.r.) a.r. TE TE . (g.r) TE x (g.r.) x (a.r.) x ηt Overall Transmission efficiency ηt TW = TE × (?. ?. ) × (?. ?. ) × ηt Wheel torque, Where, G = (g.r.) x (a.r) = Overall Gear Ratio TW = TE × (?) × ηt Tractive effort (N), ? =?? ? ??× ? × η? ? ? = Where, PE TE ηt g.r. a.r. G r N = Engine brake power (BP) = Average engine torque, N = Overall transmission efficiency = gearbox gear ratio = axle ratio = Overall gear ratio = tire radius, m = crankshaft rpm  When F > R then Additional Tactical Effort is used for acceleration, slope climb and draw bar pull. RELATION BETWEEN ENGINE SPEED AND VEHICLE SPEED:  If, N = engine crankshaft speed, rpm V = Vehicle speed, km/h G = Gear ratio r = Tire radius, m  The relationship between N and V can be obtained by using the following relation. 2 π r N = 1000 V 60 ? P a g e | 45

  46. 4340202 Automotive Mechanics (Tutorial) ? ?= 1000 ? 2 π r × 60 N ? = 2.65 ? ?  From the above formula it can be said that the N / V ratio depends upon the overall Gear Ratio and on the diameter of the wheel.  There are four different values of the N / V ratio of a vehicle with four different gear ratios. ACCELERATION, DRAWBAR PULL AND GRADEABILITY: Acceleration:  When the vehicle is accelerated, its rotating parts accelerate based on their own moments of inertia and the gear ratio of the drive line.  Thus increasing the weight of the vehicle to WE. This increased weight is known as “effective weight of the vehicle”.  While the extra Tractive effort is used to provide acceleration to the vehicle against effective weight. ? ??????? ????? = ??×? × 3600 1 × (??????? ?????) ×3600 ??????? ????????????,? = ?? ? 1 × (??− ??)?? ×3600 ??????? ????????????,? = ?? ? 1 × (????− ??) ×3600 ??????? ????????????,? = ?? ? 1 × (???????? ?????? − ???? ??????????) ??????? ????????????,? = ?? ? × (? − ?) ??????? ????????????,? = ?? Gradability:  The maximum percentage grade that a vehicle can negotiate in a full rated condition  It means that the maximum percentage slope, a vehicle can climb is called Gradability.  Hence, ??????? ????? = ? ×??????????? × ? 100 × 3600 100 × ? ? × 3600 (??− ??) ??????????? = ??????????? = 100 ? (Tractive effort – Road Resistance) ??????????? = ??? ? (? – ?) P a g e | 46

  47. 4340202 Automotive Mechanics (Tutorial) Drawbar Pull:  When the extra power used to carry the extra load attached to the vehicle. Maximum Draw Bar Pull Maximum Draw Bar Pull = = Tractive Effort - Road Resistance (F - R)  In this case rolling resistance and air resistance together form road resistance.  Maximum surplus tractive effort is obtained when the speed of the vehicle is very slow.  Therefore, first gear is very suitable for accelerating, steep climbing and more drawbar pull. ROAD SPEED V/S AVAILABLE POWER:  The maximum road speed can be achieved in a gear when the value of available power is equal to the required power.  This only happens when the value of the tractive effort is equal to the value of the resistance in level road.  If the vehicle is required to run at a slower speed, the corresponding throttle adjustment should be made in such a way that the throttle power is obtained by intersecting the required power curve at given road speed. P a g e | 47

  48. 4340202 Automotive Mechanics (Tutorial) WEIGHT DISTRIBUTION THREE WHEELED VEHICLE: A stationary vehicle is shown in below figure, different forces are acting on it are also indicated. Where, W b l = = = Vehicle weight, N wheel base, m distance of CG from rear axle, m height of CG from ground, m distance of CG from center line in top view, m wheel track, m Vertical reaction at front wheel Vertical reaction at rear wheel 1 Vertical reaction at rear wheel 2 h = c = a RF = = RR1= RR2=  To get unknown reactions, Apply conditions,∑ V = 0 and ∑ M = 0  For, vertical forces ∑V = 0 W = RF + RR1 + RR2  For, Moments around rear axle, ∑ MR1,R2 = 0 RF × b = W × l RF = ?×l ? For, Moments around central axis (rear view) ∑MCG = 0 (RR2−RR1 ) × ? 2= W × c (RR2−RR1 ) = 2W ×? ?  For, Moments around Front wheel central axis (side view), ∑MF = 0 (RR2 + RR1) × b = W × (b − l) (RR2 + RR1) =W × (b – l) ? P a g e | 48

  49. 4340202 Automotive Mechanics (Tutorial) (RR2 + RR1) = W (1 −? ?)  Adding equations, and simplifying them... ???=? 2 (2? ?−1 ?+ 1) 2(1−1 ?−2? ?) ???=? ??= ?− (???+ ???) FOUR WHEELED VEHICLE:  The forces exerted on a four-wheeled vehicle while standing is shown in figure. Where, W= Vehicle weight, N b= wheel base, m l = distance of CG from rear axle, m h= height of CG from ground, m RF= Vertical reaction at front wheel RR= Vertical reaction at rear wheel   Only three independent formulas are required in this case to find the four un-known here.  All four reactions on wheels can be calculated with these formulas.  Therefore, assuming a two wheeler in this case, the problem will be eased.  It is assumed that, the reactions of the two rear wheels (left & right) will be the same and the reactions of the two front wheels (left & right) will also be the same.  Suppose RF and RR, are front and rear reactions respectively. To get unknown reactions, Apply conditions, ∑ V = 0 and ∑ M = 0  For, vertical forces ∑ V = 0 W = RF + RR  For, Moments around Rear wheel (side view), ∑ MR = 0 RF × b = W × l ?? = W × l  From above equations, ??= ?(1 −1  It is to be noted that, Weight distribution depends upon wheel base and distance of CG from rear axle. ? ?) P a g e | 49

  50. 4340202 Automotive Mechanics (Tutorial) EXERCISE: A.The coefficient of rolling resistance of truck weighing 62293.5N is 0.018. Find a rolling resistance of a truck while it is travelling on a road surface. B.The coefficient of air resistance of truck weighing 64000 N is 0.0276, frontal area of truck is 5.574 m2, and vehicle speed is 88 km /hr. find an air resistance of a truck while it is travelling on a road surface. P a g e | 50

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