Automobile Steering system

The Automobile steering system is to help the driver to manure the vehicle in the desired direction with less effort & good accuracy

1. Session: Vehicle Steering System 4/24/2019 16MT407 - Theory of Automobile Engineering 1 MODULE 1

2. SESSION OBJECTIVES 4/24/2019 16MT407 - Theory of Automobile Engineering 2 On the completion of this session, the students might be able to understand , Proper selection of steering mechanism for vehicle Good chosen of steering gear box for easy steering Important of wheel alignment factors for good Steerability & stability of vehicle.

3. Topics Introduction Steering Mechanism Steering Ratio Steering Lock Steering Gear Box Power Steering Steering Geometry 4/24/2019 16MT407 - Theory of Automobile Engineering 3

4. Introduction 4/24/2019 16MT407 - Theory of Automobile Engineering 4 Simple steering system: Change the direction of motion of a vehicle. Simply converted the Rotary motion of steering wheel into angular turn of front wheels. The motion of steering shaft is transferred to the steering gear box. Gear box convert the rotary motion into lateral motion And it will transferred it to steering linkage. Components of steering system

5. Introduction 4/24/2019 16MT407 - Theory of Automobile Engineering 5 Simple steering system: The left & Right linkages are connected to the steering knuckle on the left & right wheels respectively. Each knuckle is pivoted on the suspension’s upper & lower arms and rotate about the axis. This cause the wheel to move left or right, allowing the direction of the vehicle to be changed. Components of steering system

6. Introduction 4/24/2019 16MT407 - Theory of Automobile Engineering 6 Important terms used in S teering: Steerability: Measure of the vehicle’s responsiveness to the steering operation of the driver. Stability: Dynamic Meaning of vehicle Capability of a vehicle to restore original motion by itself without intervention of driver. When there is some external disturbance during steady driving.

7. Introduction 4/24/2019 16MT407 - Theory of Automobile Engineering 7 Principle of C orrect Steering: When the vehicle take a turn, the front wheel along with the respective axles turn about the respected pivot points The rear wheel remains straight and do not turn. The steering is done by means of front wheels.

8. Introduction 4/24/2019 16MT407 - Theory of Automobile Engineering 8 Principle of C orrect Steering: For avoid skidding, the two front wheels must turn about the same instantaneous center I, Which lies on the axis of the back wheels If “I” for two front wheels do not coincide with the “I” of the rear wheels, skidding of the front wheel takes place This will leads to more wear & tear of the tyres

9. Introduction 4/24/2019 16MT407 - Theory of Automobile Engineering 9 Principle of C orrect Steering: Let, a = Wheel Track B = Wheel Base C = Distance b/n the pivot points of wheel From Triangle IBP, From Triangle IAP,   B A C D

10. Introduction 4/24/2019 16MT407 - Theory of Automobile Engineering 10 Principle of C orrect Steering: This is the fundamental equation of correct steering, If this condition is satisfied, then there will be no skidding of the wheels, when the wheel take a turn.   B A C D

11. STEERING MECHANISM 4/24/2019 16MT407 - Theory of Automobile Engineering 11 Steering Mechanism: Good turning means, all the four wheels must rotate about the common “I”. In order to achieve this two types of mechanism is followed by automakers. Davis Steering Mechanism Ackerman Steering Mechanism

12. STEERING MECHANISM 4/24/2019 16MT407 - Theory of Automobile Engineering 12 Davis Steering Mechanism: Located in front of front axle. It has sliding pairs It’s fulfills the fundamental equation of correct steering in all directions. Drawback: Due to more friction, leads to easy wearing. It becomes inaccurate after sometimes So Davis steering is not common in use A,B – Pivot points of front wheels AM,BH – Slotted link α – Angle of inclination of the links AC and BD, to the vertical α α

13. STEERING MECHANISM 4/24/2019 16MT407 - Theory of Automobile Engineering 13 Davis Steering Mechanism: The slotted link AM and BH are attached to the front wheel axle at the pivots A & B to turn its on. The rod C & D is constrained by the sliding members P & Q to move along it’s length direction. These constraints are connected to the slotted link AM & BH by a Sliding & Turning pair at each end α α ϴ Φ a – Vertical distance b/n AB and CD b – Wheel Base C – Distance b/n the pivots A and B of the front Axle

14. STEERING MECHANISM 4/24/2019 16MT407 - Theory of Automobile Engineering 14 Davis Steering Mechanism: The steering is affected by moving CD to the right or left of its normal position. C’D’ shows the position of CD for turning to the left. α α ϴ Φ d – Horizontal distance b/n AC and BD x – Distance moved by AC to AC’ = CC’ = DD’ α – Angle of inclination of the links AC and BD, t o the vertical

15. STEERING MECHANISM 4/24/2019 16MT407 - Theory of Automobile Engineering 15 Davis Steering Mechanism: From triangle AA’C’, From triangle AA’C From triangle BB’D’ We know that,   α α ϴ Φ

16. STEERING MECHANISM 4/24/2019 16MT407 - Theory of Automobile Engineering 16 Davis Steering Mechanism:   α α ϴ Φ

17. STEERING MECHANISM 4/24/2019 16MT407 - Theory of Automobile Engineering 17 Davis Steering Mechanism: Similarly, from We know that for correct steering,   α α ϴ Φ

18. STEERING MECHANISM 4/24/2019 16MT407 - Theory of Automobile Engineering 18 Davis Steering Mechanism: The range of c/b is 0.4 to 0.5. Thus, the value of α lies b/n 11.3 o to 14.1   α α ϴ Φ

19. STEERING MECHANISM 4/24/2019 16MT407 - Theory of Automobile Engineering 19 Ackerman Steering Mechanism: Invented by German carriage builder Mr. Georg Lankensperger. Patent by Anglo – German, Mr. Rudolph Ackermann. The mechanism is placed inside the Front Axle. It has only turning pair. Drawback: Fulfills the fundamental equation of correct steering at the middle and at the two extreme position But not for remaining positions. Georg Lankensperger Rudolph Ackermann

20. STEERING MECHANISM 4/24/2019 16MT407 - Theory of Automobile Engineering 20 Ackerman Steering Mechanism: Four Link Mechanism ABCD. The shorter Link BC and AD are of equal length And are connected with stub Axles BF & AE respectively. The longer link AB & CD are of unequal length. CD link< AB link During Straight motion of vehicle, the links BC and AD are parallel and subtend equal angles with the center line of the vehicle.        

21. STEERING MECHANISM 4/24/2019 16MT407 - Theory of Automobile Engineering 21 Ackerman Steering Mechanism: During vehicle turn, The stub Axle AE & BF make an different angles, in respect to their previous positions. The stub axle BF will turn through a greater angle ϴ , The stub axle AE, which will turn through a greater angle Ф At this moment, the lines from the front wheels axle intersect on the rear wheels axle at the instantaneous center I.         This arrangement is known as Ackerman Steering Mechanism

22. STEERING MECHANISM 4/24/2019 16MT407 - Theory of Automobile Engineering 22 Ackerman Steering Mechanism: Let r = Length of the shorter links BC and AD L = Length of the track rod, i.e link CD Now, from the geometry of fig,   - i - ii

23. STEERING MECHANISM 4/24/2019 16MT407 - Theory of Automobile Engineering 23 Ackerman Steering Mechanism: Let Adding equations (i) and (ii), we have   Sin α =   This mechanism has three value of ϴ for correct steering While turning right, While turning left, While running straight ahead. ( ϴ = 0) However, for other angles also, it gives a close approximation to the ideal condition.

24. STEERING RATIO 4/24/2019 16MT407 - Theory of Automobile Engineering 24 Steering Gear Ratio: Ratio of angle turned by the steering wheel to the corresponding angles of stub axle (Steering Knuckle or front wheels) Now a days, for cars steering gear ratio 12:1, for heavy vehicles 35:1, Larger steering gear ratio will reduce the amount of steering effort required But the steering wheel needs to be turned through a larger angle. It says steering will not very responsive. On the other hand smaller steering ratio will improve the steering response. But increasing the steering effort

25. STEERING LOCK 4/24/2019 16MT407 - Theory of Automobile Engineering 25 Steering Lock: To ensure the vehicle safety from theft. The put the lock for steering, also switch off the ignition. It will lock the gear shift lever of the transmission.

26. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 26 Steering Gear Box: Consists of two gear enclosed in a housing One of them is attached to the steering shaft & the other is attached to the steering linkages Function of steering box: Converts the rotary motion of steering wheel into straight line motion to move steering linkage. Provides mechanical advantages gear reduction for easy vehicle steer.

27. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 27 Steering G ear Box: Worm Gears It used worm gears A worm drive is a gear arrangement in which a worm meshes with a worm gear Major advantages of worm gear drive units are can transfer motion in 90 o Like other gear arrangement, a worm drive reduce rotational speed or transmit high torque. Worm Screw Worm Wheel

28. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 28 Steering G ear Box: Types Worm & Worm wheel (Sector Steering). Worm & Nut steering gear Worm & Roller steering gear Recirculating ball type Cam and lever type steering gear Rack & Pinion

29. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 29 Steering G ear Box: Worm & Worm wheel (Sector Steering ) Worm is placed at the end of the steering shaft And it is constant mesh with worm wheel Worm wheel mounted on a shaft, which is attached to the pitman arm (Drop arm) Worm shaft is supported in the housing with the help of two bearings by placed above & below the worm It helps the worm rotate easily

30. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 30 Steering G ear Box: Worm & Worm wheel (Sector Steering ) When driver rotates the steering wheel, drop arm moves forward & backward resulting in motion of stub axle. The arc movement of the drop arm usually from 60 o to 90 o Commonly seen in tractors

31. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 31 Steering G ear Box: Worm & Worm wheel (Sector Steering ) This is similar to worm & worm wheel type. Here instead of worm wheel, a sector gear is placed

32. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 32 Steering G ear Box: Worm & Nut Steering Gear Steering rod end have worm. Worm is connected with nut arrangement When the worm rotates, the nut is able to move. Movement is along the axis of the column either up or down. This move cross shaft in arc, which also moves drop arm. This can be commonly seen in all steering

33. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 33 Steering G ear Box: Worm & Roller Steering Gear Worm and roller gear have two teethed roller which are fastened to the cross shaft called roller shaft or sector shaft. The threads of the worm gear are meshed with roller shaft at the end of the steering tube Diameter of worm is greater at end and reduced at center When the worm shaft is turned by the steering tube, the roller will also be moved in an arc for rotating the roller shaft

34. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 34 Steering G ear Box: Worm & Roller Steering Gear The bearings are designed to resist both radial and end thrust. Used in Leyland & American Passenger car

35. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 35 Steering G ear Box: Recirculating Ball type Steering Consist of worm at the end of steering rod. Nut is mounted on the worm with two sets of balls in the groves of the worm. Ball reduce the friction b/n Nut & Worm The teeth of nut is meshed with teeth of worm wheel sector to which drop arm is mounted.

36. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 36 Steering G ear Box: Recirculating Ball type Steering By turning steering wheel , the balls in worm roll in the grooves and cause nut to move along the length of worm, balls recirculates through the guide. Movement of nut causes the wheel sector to turn and actuate the link rod through the drop arm resulting in desired steering of wheels. Teeth on the nut are tapered to minimize the wear Used in TATA motors, etc..

37. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 37 Steering G ear Box: Cam & Lever steering gear. The worm is cut in the form of a cylindrical cam at the steering shaft lower end. The cam is held in housing by thrust bearing. The inner end of drop arm (pitman arm) has a lever that contains a tapered stud. Stud engages in the cam, so the lever is moved up & Down when the cam is turned. Lever Cam Thrust bearing Stud

38. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 38 Steering G ear Box: Rack & Pinion steering gear (End Take off type) Rotary Motion of the steering wheel is transmitted to the pinion of the steering gear through universal joint. Now circular motion is transferred as linear motion. That lateral movement transferred to the stub axle through Tie rod & Ball joint arrangement.

39. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 39 Steering G ear Box: Rack & Pinion steering gear (Center Take off type) Here Tie rods are connected at the center of the rack instead of at the ends. It is called of center take off rack & pinion steering gear. Large boot covers center part of rack & pinion housing. A slot in the housing permits the inner tie rod end to move with the rack

40. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 40 Steering G ear Box: Rack & Pinion steering gear (Center Take off type) Advantage : Save spacing Shortening the length of the steering column. During vehicle moves over road bump (Bump Steer) steering gets affected in end take type is reduced in Center take off. Bump Steer : tendency of wheels to steer themselves without driver input. When the toe of wheels changes as they go over a bump or through a depression on the rod.

41. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 41 Steering G ear Box: Rack & Pinion steering gear: Geometry Tooth profiles of both the pinion as well as rack are of the Involute form. Side profile of teeth is curved. Side profile of rack teeth is straight line. Rack pitch circle being straight line Helical teeth ensure the quiet & Smooth operation It enable the steering to withstand higher loads compared to spur gears. It uses larger gear ratio can be used for rack travel.

42. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 42 Steering G ear Box: Rack & Pinion steering gear: Geometry Helical teeth & Inclination of pinion axis, causes the sliding action b/n the teeth which increases friction and hence teeth wear. But it provides damping to the road shocks & Ensure not to transmitted to the steering wheel.

43. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 43 Steering G ear Box: Rack & Pinion steering gear: Geometry Let, r s = Radius of the steering wheel r p = Radius of the pinion pitch – circle T = Number of teeth on pinion P = Circular pitch of the pinion = Linear pitch of the rack For one revolution of steering wheel, Input - Output moment of the rack, Output -  

44. STEERING GEAR BOX 4/24/2019 16MT407 - Theory of Automobile Engineering 44 Steering G ear Box: Rack & Pinion steering gear: Geometry Movement Ratio MR = Also, MR = If there is no friction in the gears, Movement ratio = MR =  

45. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 45 Power steering: Reduce the effort required to operate the steering wheel. Most of the front engine mount vehicle requires power steering because of more weight on front side. It also has fail safe design, which allows manual steering to be done. If the system develops some problem

46. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 46 Power steering: Advantage: Reduce the number of turns of the steering wheel. Easy steering at parking, at low speeds or tight turns. Disadvantages: Little cost than conventional steering system

47. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 47 Power steering: Types Hydraulic Power steering Electrical assisted, Electronic power steering system.

48. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 48 Power steering: Hydraulic Power Steering Hydraulic booster that reduces the forces required to operate the steering wheel. Pump : It generates hydraulic pressure Control Valve : It switches the oil passage to the power cylinder according to the rotational direction of the steering wheel. Power Cylinder : It moves the piston in the cylinder to tight right or left with hydraulic forces and there by assists the steering wheel operation.

49. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 49 Power steering: Hydraulic Power Steering Fluid Reservoir : Stores the fluid & Cleans it using a built in filter. Working : When steer wheel rotates CCW/CW the hydraulic pressure from the pump is shifted by the control valve & Drawn into the power cylinder left (or Right) Chamber. The power cylinder piston is moved by the hydraulic pressure to the left This will assist the steering wheel operation & There by steering wheel can operated with light force.

50. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 50 Power steering: Hydraulic Power Steering – Types Linkage Type – Has separate hydraulic cylinder controlled by a valve & it is attached to the drop arm to assist in steering.

51. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 51 Power steering: Hydraulic Power Steering – Types Integral Type – Power steering has the power cylinder & the control valve as the integral part of the steering system.

52. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 52 Power steering: Linkage Hydraulic Power Steering : It includes Fluid Reservoir, and pump, a control valve (Spool Type), a power cylinder, Connecting Fluid lines and the necessary steering Linkage. Hydraulic pump is drive by Engine mechanical means Pressure relief valve with the pump controls the pressure in the system as per the load The control Valve is operated by the movement of the steering wheel and supplies the fluid to the power cylinder by switching the oil passage according to the rotation of the cylinder Valve in Central (Neutral) Position i.)Steering wheel is not operated condition

53. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 53 Power steering: Linkage Hydraulic Power Steering : During Steering wheel is operated ii.) Steering wheel is operated condition: Steering wheel rotates in CW direction. The fluid passage is open by Spool valve & Filled the Chamber B. This will assist the steering action in Right turn Similar operation is reversed for steering Wheel CCW for Left turn . If no force on steering wheel means, spring force make the spool valve in neutral position. Now the vehicle in Straight ahead position.

54. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 54 Power steering: Integral Type Hydraulic Power Steering : It includes fluid reservoir & Pump Pump is connected to the power cylinder with flexible hydraulic lines through control valves Here the control valve is an integral part of a gear box. Control valve is rotary spool type & is located above gear box. Control valve simple in construction & Compact size It consists of Input shaft, Torsion bar and a valve. All of these are mounted in co-axial manner.

55. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 55 Power steering: Integral Type Hydraulic Power Steering : Valve consists the below two section. Steering wheel & input shaft Pinion shaft & valve Input shaft & the pinion shaft are each connected to an opposing end of the torsion bar. Valve is mounted over the input shaft and is connected with pinion shaft through a pin. During steering wheel rotation, the torsion bar twist & cause the input shaft and valve to rotate with steering wheel. Relative position of the valve & the input shaft is changed in response to twisting

56. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 56 Power steering: Integral Type Hydraulic Power Steering : Now the flow of fluid and pressure is controlled in accordance with this motion and is directed to the proper side of power cylinder to assist the turning action

57. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 57 Power steering: Integral Type Hydraulic Power Steering : i.) When the steering wheel is not operated condition: No force applied on steering wheel Input shaft in neutral position and fluid from the pump returns to the reservoir through the rotary valve No flow of oil to either side of cylinder, but each side kept the equal pressure of oil.so it doesn’t move. Now the fluid act as a cushion to absorb the shocks, so they are not transferred to the steering wheel.

58. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 58 Power steering: Integral Type Hydraulic Power Steering : ii.) When the steering wheel is operated: When steering wheel is turned counter-clock wise, the input shaft will also turn in same direction. The torsion bar is twisted & creates a gap b/n the input shaft and the valve. Now fluid enters into chamber A & i ncrease the pressure on cylinder piston, forcing it to move. This provides assistance for steering wheel operation At the same time, chamber B valves opens, causes the fluid to move into reservoir through the valve.

59. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 59 Power steering: Integral Type Hydraulic Power Steering : ii.) When the steering wheel is operated: When the turning effort is removed from the steering wheel, the torsion bar untwists, returning the valve to a straight ahead position. Now oil pressure is equal on both sides of the power cylinder. No power assist is present on steering. Now vehicle move on straight ahead, due to the steering geometry and wheel alignment. For right turn (Steering wheel – CW direction) – same process occur in reverse manner.

60. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 60 Power steering: Electronic Power Steering : Operating principle is same as hydraulic power steering with some changes in system components The torque sensor instead of valve body unit Hydraulic power cylinder is replaced by electric motor EPS control unit is added

61. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 61 Power steering: Electronic Power Steering : Construction: Consists of rack & pinion steering gear with an electric motor(i.e DC Motor) Installed around the rack, which supplies the power. The rack shaft passes through the motor’s armature and is held by recirculating ball screw The motor transmits its power to push the rack right or left. Pinion shaft contains two sensors are torque sensor & speed sensor

62. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 62 Power steering: Electronic Power Steering : Construction: Sensors converts the torque, speed & direction of motion into voltage signal & send it to EPS unit

63. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 63 Power steering: Electronic Power Steering : Working: Vehicle speed input & Steering sensors input are processed by microprocessor control unit. The ECU unit compares the sensor input & calculate the force requirement from the look up table in the memory. Now the control unit sends the signal to the motor to assist the steering action by DC - motor with the proper current flow direction. The motor pushes the rack to the right or left side depending on which the way the current flow.

64. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 64 Power steering: Electronic Power Steering : Fail safe design of EPS: Over load causes the m otor to damage. It could be avoid by controlling the current to the motor with help of ECU. Voltage surges problem due to faulty alternator or charge problem rectified by ECU unit. If any abnormal situation detects /No possible to operate EPS means – The steering will done by manually

65. POWER STEERING 4/24/2019 16MT407 - Theory of Automobile Engineering 65 Power steering: Electronic Power Steering : Advantage: It is compact, light and quiet in operation. Precise control of steering at different speed is achieved. It requires less maintenance as there no hydraulic line to break

66. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 66 Wheel Alignment : Relative positioning of the wheel for obtaining a true and free rolling movement over the road. If the wheels were mounted directly on the vehicle at right angles, then that vehicle would be actually be very difficult to handle. It would steer poorly and would be particularly dangerous at high speeds Moreover, the tyre exhibit rapid wear Diagonal Wear

67. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 67 Wheel Alignment : The important wheel alignment factors are, Camber Toe in & Toe out Steering Axis inclination (King pin Inclination) Cater

68. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 68 Wheel Alignment : Camber The camber is an inward or outward tilting of the wheels at the top from the vertical axis If the wheel tilt outwards at the top, the camber is positive. If the wheel tilt inwards means, the camber is negative. The camber is measured in degrees. Positive camber is reduce the steering effort

69. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 69 Wheel Alignment : Camber Race cars/Rally cars have negative camber on Tarmac road & No camber on Gravel. Negative camber ensure the tyre has full contact with road during cornering. As the car turns on corners, the body rolls, as the body rolls, the suspension compresses the tyre roll. This action makes the negative camber into zero camber. Zero camber during body roll, ensure the maximum tyre contact patch with road. Tarmac road Gravel Road

70. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 70 Wheel Alignment : Camber On the gravel road grip is reduced. So traction is main priority for car. This achieved by Zero camber. Because gravel road are normally undulating and rough. The car use large suspension to keep the tyre contact with road surface. Tarmac road Gravel Road

71. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 71 Wheel Alignment : Camber Vehicle weight cause the wheels to tile inwards, here the camber is used to compensate the tilting. The positive camber is used to compensate this type of tilting. During vehicle motion on corner the positive camber changes as zero camber. Zero camber gives maximum tyre life Here the tyre treads contact with road equally on both side of the tyre.

72. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 72 Wheel Alignment : Camber offset (Scrub Radius) The distance b/n the wheel centerline and steering axis centerline at the point where they intersect at the road surface called as camber offset. The smaller the offset is the lower the effort required to steer the vehicle Excessive camber causes the uneven tyre wear and loss of traction

73. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 73 Wheel Alignment : Camber offset (Scrub Radius) So modern vehicle designed with wider tyres and power steering Most vehicle have only small degree of camber angle (1 o to 3 o )

74. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 74 Wheel Alignment : Toe in & Toe out Toe is angle of tyre pointing inwards or outwards. It should be visualize by Birds perspective. Positive Toe is – Toe in = Front of the tyre is facing each other (inwards) Preferred in Rear wheel drive. Tyre straightness with body roll Negative Toe is - Toe Out = Front of the tyre is facing outwards Preferred in Front wheel drive Created moment straightness the tyre

75. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 75 Wheel Alignment : Toe in & Toe out The purpose of Toe – in is to ensure parallel rolling of wheels, steering stability, and to prevent both side of slipping and excessive wear of tyre . It is set for stand still condition of vehicle. During vehicle motion, the front portion of wheel comes straight ahead position because of road resistance. This will ensure the parallel Rolling. Toe in & Camber are properly combine means to ensure the rolling of the wheel in straight line

76. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 76 Wheel Alignment : Toe in & Toe out The greater the camber angle more toe – in is needed & Vice-versa. The toe-in can be adjusted by modifying the length of the left and right tie rods. During adjustment that the length of both tie rods are set equal. Otherwise, the vehicle may tend to pull in either direction due to the steering wheel being out of center.

77. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 77 Wheel Alignment : Steering Axis Inclination The steering axis inclination is the angle b/n the steering axis and the vertical axis. Helps the vehicle wheels straight ahead position after the turn has been made. Also called as Kingpin inclination. Because in older vehicle, the stub axle is fixed with front axle with the help of Kingpin considered as Steering axis.

78. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 78 Wheel Alignment : Steering Axis Inclination When the steering wheel is turned, the front of the vehicle is lifted up by a small amount. When the driver releases the steering wheel, the weight of the vehicle actually tries keep the wheel straight ahead position. This is because of force generated by the steering axis inclination, to move the wheels back, is known as steering-aligning torque. Helps to reduce the excessive camber. By reducing the Camber offset, can reducing the force required by the steering wheel. Allowable angle limit – 6 o to 8 o .

79. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 79 Wheel Alignment : Caster Angle It is an angle viewed from the side of the car. It’s lie b/n steering axis & Vertical axis. Direction control angle can be either positive or negative. Positive caster angle – Steering axis is tilted backward. Negative cater angle – steering axis is tilted forward.

80. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 80 Wheel Alignment : Caster Angle This will provide the degree of self – centering for the steering. This makes the car easier to drive & improves the directional stability. The excessive caster angle will make the steering heavier & less responsive. + ve caster – 3 o to 6 o . - ve caster – 1 o -2 o .

81. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 81 Effects of incorrect wheel a lignment : Problem Effect on Vehicle Incorrect camber setting Uneven tire wear Vehicle pulls to the side of the most positive or least negative camber Incorrect Toe - in Excessive tire wear Unstable steering Uneven Toe - in Vehicles tends to pull to one side Incorrect steering axis inclination Instability of vehicle Poor steering Vehicle pull to the side of lesser inclination Hard steering Too much cater Hard steering Excessive road shock Wheel shimmy - Wobbles

82. STEERING GEOMETRY 4/24/2019 16MT407 - Theory of Automobile Engineering 82 Effects of incorrect wheel a lignment : Problem Effect on Vehicle Insufficient caster Instability at high speed Unequal caster Vehicle pulls to the side of the most caster

83. 4/24/2019 16MT407 - Theory of Automobile Engineering 83 END