INTRODUCTION The steering wheel must be mechanically connected to the wheels, i.e. "steer-by-wire" is prohibited or electrically actuated steering, is prohibited. Allowable steering system free play is limited to seven degrees (7) total measured at the steering wheel . The steering wheel must be attached to the column with a quick disconnect. The driver must be able to operate the quick disconnect while in the normal driving position with gloves . In any angular position, the top of the steering wheel must be no higher than the top-most surface of the Front Hoop. This system provides directional changes in the automobile vehicle. This system converts rotary movement of the steering wheel into angular turn of the front wheel. It multiplies drivers effort by mechanical advantage,enabling him to turn the wheels easily. This changes the rotary motion of the steering wheel into straight line motion of the steering linkage. Most system includes the steering wheel, which the driver controls, the steering gear, which system were manual until a few years ago. Then power steering becomes popular.It is now installed on about 90 percent of car manufactured in the foreign country.

COMPONENTS OF STEERING SYSTEM Steering linkages consists of the following main components 1.Steering wheel 2.Steering column 3.Steering shaft4.Steering gear box5. Steering linkages1.STEERING WHEEL It is a circular wheel mounted at the steering shaft and acts as a control to steer the vehicle.A horn push button is fitted at its hub. In modern cars, the push button has replaced by a push ring which is placed inside the steering wheel. The steering hub sometimes contains trafficator swith,lighting swith (or) selectors lever for controlling automatic transmission. 2.STEERING COLUMNThis is a hollow shaft in which the steering shaft is housed. lower end of shaft is fixed on steering gear box, while the upper end is connected to the steering wheel.3.STEERING SHAFT It is made out of good quality steel. One end is fixed in steering wheel with the help of splines (or) key and kept tight by nut. The other end with worm is connected to the steering gear box.The changes in length of the shaft are accommodated by universal joints, pot joints (or) flexible couplings. The steering shaft is inclined at 50 in the case of cars and 20 in the case of commercial vehicle4.STEERING GEAR BOX The steering gear serves the following purposes. 1. It provided mechanical advantages and enables the driver to steer the vehicle easily. 2.It converts the turning motion of the steering wheel into the to-and-fro motion of the link rod of the steering linkages. 5.STEERING LINKAGES The steering linkage depends upon the type of the vehicle. It is commonly used in cars provided with rigid front axle. when the steering wheel is turned its motion is carried to the steering gear box through the steering gear box this motion is converted into angular motion of the drop arm which is connected to the steering arm by means of ball joints.

STEERING GEAR BOX

STEERING LINKAGES When the steering wheel is rotated the drop arm moves towards (or) away from the front wheel depending upon the direction of turn right (or) left.

STEERING MECHANISM They are two types of steering mechanism are used 1. Ackerman steering mechanism 2. Davis steering mechanismOnly Ackerman steering mechanism is used in vehicles now a days because of its simplicity and less wear of the parts.1. ACKERMAN MECHANISM The Ackerman steering gear mechanism consists of cross link KL connected to the short axles AC and BD of the front wheels through the short arms AK and BL, forming bell crank levers CAK and DBL respectively, when the vehicle is moving is moving straight,the cross link KL is parallel to AB, the short arm AK and BL both make angle to the horizontal axis of chasis. This is the fundamental equation for correct steering. If this equation is satisfied, there will not be any lateral slip of the wheels the vehicle is taking a turn.cot - cot =EI/AE IF/BF = IE IF / AE =AB / AE = b / l This is the fundamental equation for correct steering. If this equation is satisfied, there will not be any lateral slip of the wheels the vehicle is taking a turn.FRONT AFFETING STEERING The following factors affect the steering in an automobile 1. Steering gear ratio and backlash 2. Steering linkage connection 3.Tyre pressure 4. Play in the wheel bearings 5. Condition of king pins and bearings 6. Wheel alignmentFRONT WHEEL ALIGNMENT This relates to the relative position of the wheel for obtaining a true and free rolling movement over the road. The smooth operation of steering depends mush upon the wheel alignment. The important alignment factors are as under1. Caster 2.camber 3. King pin 4. Toe-in 5. Toe-out1.CASTER caster angle is the angle formed by the forward (or) backward tilt of the kingpin centre line from vertical when viewed from the side of the wheel. A backward tilt is known as positive caster and forward tilt is known as negative caster. The caster angle in modern vehicles range from 2 to 8 degrees. PURPOSES OF CASTER 1.To maintain directional stability and control 2. To increase steering returnability 3.To reduce the drivers effort to turn the vehicle 2.CAMBER The angle between the centre of the tyre and the vertical line when viewed from the vehicles is known as camber. If the top of the wheel tilts out, it has positive camber. The amount of tilt, measured in degrees from the vertical is called the camber angle. . Unequal camber on both the front wheel will cause should not generally exceed 2 degree factors affecting chamber.1. Hub bearing play 2. Kingpin bush wear3. Kingpin and play4. Front axle bend (or) twist3. KINGPIN INCLINATION The angle between the centre line of the kingpin and the vertical line is called kingpin inclination. The kingpin inclination in modern vehicles range from 4 to8 degrees. It must be equal on both the sides. If it is greater on one side then the other, the vehicle will tend to pull to side having the greater angle.PURPOSES OF KINGPIN INCLINATION 1. It provides directional stability along with the caster angle2. It help in self-centering of wheel after taking a turn.3.Reducing the wear on the tyre 4. TOE-IN when viewed from the top, if the front wheel are inclined inward at the front wheels are inclined inward at the front it is called toe-in. it means that the distance between the front wheels at the front is less than the distance at the back. Toe-in initially provided generally does not exceed 3mm.5. TOE-OUT when a car is stationary, the distance between the front wheels at the front end is greater than the distance between at the rear is called toe-out. When the vehicle taking a turn, the difference in angle between the front wheel and the chassis frame during turns is known as toe-out.

the inner wheel makes to an angle of 23 degrees with the car frame, while the outer wheel turns only 20 degrees with the car frame, while the car frame. This is achieved by arranging suitable linkage.STEERING GEAR BOXSteering gear is enclosed in a casing is known as steering gear box. It converts the rotary motion of the steering wheel into straight line motion of the linkage, these are two basic types of steering gears, the pitman arm type and the rack and pinion type. Either type can be used in 1.manual steering system(or) 2.power steering systemThe pitman-arm type has a gear box at the lower end of the steering shaft. The rack and pinion type at lower end of the steering shaft. this causes the front wheels to swing from one side to the other to steer the vehicle.TYPES OF STEERING GEAR BOX 1. Cam and double roller2. Recirculating ball type3. Rack and pinion4. worm and sector5. worm and nut6. cam and peg Manual rack and pinion steering A typical rack and pinion steering gear assembly consists of a pinion shaft and bearing assembly, rack gear, gear housing, two tie rod assemblies, an adjusterassembly, dust boots and boot clamps, and grommet mountings and bolts. Whenthe steering wheel is turned, this manual movement is relayed to the steeringshaft and shaft joint, and then to the pinion shaft. Since the pinion teeth meshwith the teeth on the rack gear, the rotary motion is changed to transversemovement of the rack gear.

rack and pinion steering Power assisted steering system Power steering makes a heavy car respond easily to the steering wheel, whether at highway speeds or inching into a narrow parking place, and it is normalequipment for large automobiles. . "Power steering" is really "power assisted steering." All systems are constructed so that the car can be steered manually when the engine is not running or if any failure occurs in the power source.

Most power steering pumps contain a flow control valve, whichlimits fluid flow to the power cylinder, and a relief valve which limits pressureaccording to system demands.Common types of power assisted steering systems are: 1. power rack and pinion; 2. power recirculating ball.

1. Power rack and pinion Power rack and pinion steering assemblies are hydraulic/ mechanical unit with an integral piston and rack assembly. An internal rotary valve directs powersteering fluid flow and controls pressure to reduce steering effort. This changes the position of the valve spool and sleeve, thereby directing fluid under pressure to the proper end of the power cylinder. The difference in pressure on either side of the piston (which is attached to the rack) helps move the rack to reduce turning effort.

Power rack and pinion steering system Power recirculating ball This power steering gear uses a recirculating ball system in which steel balls act as rolling threads between the steering worm shaft and the rack piston. The key to its operation is a rotary valve that directs power steering fluid underpressure to either side of the rack piston. The rack piston converts hydraulicpower to mechanical force. The rack piston moves up inside the gear when theworm shaft turns right. It moves down when the worm shaft turns left. Duringthese actions, the steel balls recirculate within the rack piston, which is power assisted in movement by hydraulic pressure.POWER STEERING SYSTEM Most steering systems used today are power assisted, though there are still some manual units produced. For easiersteering on manual units, the gear ratio is usually about 24 to 1, so you would have to turn the steering wheel 12 times toturn the sector shaft through one half a rotation. Power assisted units normally have a ratio of about 15 to 1, providing aquicker turning response. Turning the steering wheel only 7 times will move the sector shaft through nearly a half a rotation.POWER STEERING PUMP

Four main types of power steering pumps have been used. They are the roller, vane, slipper, and gear types. Thepump must provide sufficient pressure for steering assist at all engine speeds to meet the various steering demands. A fluid reservoir is often mounted on the pump housing, or it may be a separate component. Some power steering pumps are capable of producing up to 1,500 psi

TWO MAIN TYPEOF POWER STEERING

Power rack-and-pinion steering Integral power steering gearbox Conventionalrecirculating ball steering gear with a hydraulic controlsystem POWER RACK AND PINION STEERING SYSTEM Power cylinder a hydraulic cylinder inside the rackor gear housing Power piston a double-acting, hydraulic piston in thepower cylinder that acts upon the rack Control valve mechanism located in the steering gear; senses and controls power assist.

POWER RACK AND PINION STEERING SYSTEM

POWER STEERING PUMP Types of Power Steering Pumps 1.Power Rack-and-pinion System, 2.Integral Power Steering Gearbox System

Power Rack-and-pinion

Crossover Steering - Drag Link to Opposite Knuckle This is a common steering setup in solid front axles. The drag link to knuckle type crossover steering is also one of the most ideal aftermarket designs. With the drag link to knuckle type crossover steering, the drag link drops from the base of the pitman arm directly to the passenger side knuckle, either on top of the knuckle or below the knuckle's steering arm. This setup minimizes radial drag link and tie rod play due to ball joint movement. Crossover Steering - Drag Link to opposite end of Tie Rod Drag link to tie rod crossover steering is one of the most common factory steering systems. With a Drag link to tie rod crossover steering setup, the drag link connects the pitman arm and to a passenger side location directly on the tie rod. As the drag link controls steering by moving the tie rod, the tie rod serves to steer and maintain a parallel distance between the knuckles. Advantages Improved fuel efficiency due to less weight. Assembly efficiency: the powertrain can often be assembled and installed as a unit, which allows more efficient production. It is easier to correct trailing-throttle or trailing-brake oversteer.[3] The wheelbase can be extended without building a longer driveshaft (as with rear-wheel-driven cars). CALCULATION ACKERMANN CONDITION

For the ackermann analysis the ackermann condition is used to determine the relationship between inner and outer wheel in a turn and the radius of turn.

General equqtion:

(1/tano)-(1/tani)= B/L

Where: o= turn angle of the wheel on the outside of the turn i= turn angle of the wheel on the inside of the turn B= track width L= wheel base B= distance from rear axle to centre of mass

B= 2150mm L= 630mm i= 30 The minimum radius of turn can be determined from the geomentry; R1= (B/tani)+(L/2) = (2150/tan30)+(630/2) = 4038.9mm = 4.03m

R= ((R1^2)+(b)^2)^1/2 = (40389^2+760^2)^1/2 = 4109mm = 4.109m Therefore the minimum radius of turn of turn of the vechicle around its centre of gravity for a maximum inside wheel turn of 30 degree is about meters.

STEERING MOVEMENT RATIO The rack and pinion mechanism is designed to transfer the circular input motion of the pinion linear output movement of the rack. It was measured that for a full travel of the rack of 170mm pinion has to be rotated 4 turns. Therefore for the one turn, the rack travel Xo= 170/4 = 42.5mm One revolution then the input steering movement is Xi= 2r Where R=125mm is the radius of the steering wheel The output rack movement is Xi= 2r = 42.5 r = 42.5/2 = 6.76408mm Then, the movement ratio can be calculate as input movement over output MR= Xi/Xo = 2R/2 r = 125/6.764= 18 Therefore the movement ratio is 18:1 For an effort of 20N applied by each hand on the steering wheel and consider no friction the output load will be Fo= Fi *MR = 2*20*18 = 720NTherefore the load transmitted to the tie rods is 720N

HELICAL GEAR CALCULATION

Shaft angle ()= 25 Helical angle = /2 = 12.5 Angle of friction = 20

Efficiency = work output/work input = cos(+)/cos(-) = cos(12.5+20)/cos(12.5-20) = 0.85066*100 = 85.66%Circle pitch (Pc) = d/T (pinion) = *20/28 = 2.2439mmCircle pitch(Pc) = d/T (rack) = *20/7 = 8.9759mmNormal pitch = Pc*cos = 8.9759*cos(12.5) = 8.7631mmCentre distance = d1+d2/2 = (20+20)/2 = 20mm

RACK AND PINION CALCULATIONFACTORS

Rack travel 135 steering wheel angle = 29mmRack travel at 1 steering wheel angle = 29/135Rack travel at 360steering wheel angle= (29/135)*360 =77.20 Factor= travel(rack lengh)/360(pinion rotation) = 77.20/360 factor = 0.214814mmrack travel at 7 steering wheel angle = 0.21813*7 = 1.5036mm

RACK AND PINION CALCULATION

Addendum = 1m = 1*2.8571 = 2.8571mmDedendum = 1.25*m = 1.25*2.8571 = 3.57142mmWorkind depth= 2m = 2*2.8571 = 5.7142mmMinimum total depth= 2.25m = 2.25*2.8571 = 6.4284mmTooth thickness = 1.5708m = 1.5708*2.8571 = 4.4879mmMinimum clearance =0.25m = 0.25*2.8571 = 0.8325mmFillet radius at root = 0.4m = 0.4*2.8571 = 1.332mmAngle of teeth = 25Lengh of rack (L) = tooth thickness*2*no.of.teeth = 4.4879*2*28 L = 252mmFace width (b)= 3*Pc =3*8.9 = 26.7mmVelocity ratio = 4:1Wear load Fw = D1*Q*Kf*b Q = 2i/i+1 = 2*4/4+1 Q= 1.6 Fw = 20*1.6*1.42*26.7 = 1213.248N

Tp = 2A/sin^2 (or) AR*m=r sin^2

Tp= minimum number of teeth on the pinion r = mTp/2= pitch circle radius of tthhe pinion

Tp(min)= 2Ap/(1+G(G+2)sin^2)^1/2-1

G= gear ratio = Tr/Tp= R/r G= 28/7=4 Tp(min) = 2*3.33/(1+4(4+2)sin^2(20))^1/2-1

Ap= friction by the standard addendum of one module for the rack

Tp(min) = 7.007teeth

COST ESTIMINATIONCOMPONENDSQUALITYCOST

RACK AND PINION11,500

GEAR BOX13,000

STEERING WHEEL1400

BALL JOINT2600

TIE ROD2400

ROCKER ARM BEARING2150

TOTAL6,050

Conclusions

The project have been both challenging and rewarding. It required the knowledge gathered in many of the subjects pertaining to engineering studies and offered valuable practice in team working environment as well as good professional practice. At present, all the components have been manufactured, and the implementation of the two systems in the overall design will be soon finalised. The design complies with the SAE-A rules. A complete test of all the components is planned when the vehicles construction is completed.