DESIGN AND FABRICATION OF FOUR WHEEL STEERING MECHANISM TO IMPROVE MANEUVERABILITY

STUDENT NAME REGISTER NO M.Nandha Kishore 31109114057

B.Nagaraja Sankar 31109114055B.Mohammed Iburahim 31109114049

Guided byMr.K.G. Maheswaran

DIFFICULTIES IN PRESENT STEERING SYSTEM

Drivers find it difficult in controlling the vehicle at lower speeds

(<30kmph).

Turning radius of the vehicle is fairly high.

Response in the changing curvature is very low at lower speeds.

Handling the vehicles at narrow corners and sharp turns are

difficult in a normal steering.

These disadvantages can be overcome to a great extent by

using four wheel steering (4WS). 

IDENTIFICATION OF SOLUTION

(a)Counter Steering System (b) Active Steering System.

•Online Reference : ieeexplore.ieee.org•Book Reference : Automotive Mechanics By William H.Crouse

DESIGN METHODOLOGY

Additional steering unit added to the rear wheels. Bevel gears (4) used effectively as It can transmit the rotary motion perpendicularly. One bevel gear is introduced in the front steering rod(1). Other bevel gear is connected to the transfer rod(2). 

Customized gear box with three modes i.e. forward (Active), reverse (Counter) and neutral ( Normal).

Three modes in gear box Neutral Mode (Normal Steering)

◦ In this mode the rotary motion will not transfer to the rear wheels.◦ So only Front wheels are steered as like normal cars.Forward Mode (Active Steering)◦ In this mode the front and rear wheels will rotate in the same direction.Reverse Mode (Counter Steering)◦ In this mode both the rear wheels will turn in the opposite direction to the

front wheels.

.

DESIGN CALCULATION AND DESIGN

LIST OF SYMBOLS

SYMBOL DESCRIPTION

o Instantaneous Centre, m

θ Angle of the Inside ‘Lock’ degree

φ Angle of Outside ‘Lock’, degree

c Distance between the Pivot Centers, m

b Wheel Base of the Vehicle, m

d Length of the Track Road, m

a Wheel Track, m

r Tie rod length, m

α Angle of the knuckle arms, degree

δf Angle of the front wheel, degree

δr Angle of the rear wheel, degree

ξ Rear steering proportioning factor

WHEEL BASE CALCULATIONd = 0.610mc = 0.780 ma = 0.908 mr = 0.21m assume θ = 40`sin α= (c-d)/ 2r = 0.4048α =23.88`sin(α+θ) +sin (α-φ) = 2sinα0.8979+sin(23.88-φ) = 0.8096φ = 28.94`For correct steeringcotφ –cotθ = (c/b)1.8085-1.1918 = (0.78/b)Base b = 1.6 mRef:- AUTOMOBILE MECHANICS by DR N.K.GIRI

VEHICLE DESIGN

TURNING RADIUS CALCULATION NORMAL STEERINGb = 1.6ma = 0.908mc = 0.780mφ = 28.94`Considering outer wheel,Turning radius of the outer wheel Rf = (b/sinφ)+((a-c)/2) = (1.6/sin28.94)+((0.908-0.780)/2) = 3.307+0.064 = 3.371mTurning radius of the vehicle is Rf = 3.371mRef:- AUTOMOBILE MECHANICS by DR N.K.GIRI

FOUR WHEEL STEERING

δf = 28.94` Take ξ = 0.5δr = ξδfδr = 0.5(28.94`)δr = 14.47`Rf cosδf = Rr cosδr3.371cos28.94 = Rr cos14.472.95 = 0.968RrRr = 3.05mTurning radius of the vehicle is Rr = 3.05m

So nearly 10% of the turning radius is reduced

Ref:- FUNDAMENTALS OF VEHICLE DYNAMICS by THOMAS

D GILLESPIE

Gear Box CalculationTake Module (m)= 1.5mm Adentum = 1m Dedentum = 1.157 mModule = (Pitch/ 3.14)Pitch = Module * 3.14= 1.5 * 3.14Pitch= 4.712mm

Assume No of Teeth (z1) = 82OD = (No of teeth + 2) * module = (82+2)* 1.5 = 126mmID = OD-2(adentum+dedentum)

= 126-2(1.5+1.74) = 119mmPCD = OD-2m

= 126-2(1.5) = 123mmTooth Thickness = m*z*sin(90/z)

= 1.5*82*sin(90/82) = 2.35mm

Similarly for Z2 = 40OD = 63mmID = 56mmPCD = 60mmThickness = 2.35mm

Z3 = 50OD = 78 mmID = 71mmPCD = 75mmThickness = 2.35mm

Z4 = 24OD = 39mmID = 32 mmPCD = 36 mmThickness = 2.35 mm

Design Of Engage And Disengage Mechanism With Variable Modes

Graph – Steered Angle Vs Turning Radius

FABRICATED WORKFRONT WHEEL MOUNTING:

Material Used : Mild Steel Plate 4mm thickProcess undergone : Cutting , Drilling, Grinding, Arc welding.M10 bolt and lock nut

Tyres Used : Tvs Sunny tyres.

REAR WHEEL MOUNTING:

Material Used : Mild Steel Plate 4mm thick, Square Channel – 1.6mm thick.Process undergone : Cutting , Drilling, Grinding, Arc welding.M10 bolt and lock nut.

Mild Steel Rod – 25mm thickMild steel plate – 4mm thickProcess Undergone : Cutting, Facing, Turning, Arc Welding.

Tyres Used : Bajaj Scooter Tyres..

STEERING UNIT AND BEVEL GEARS MOUNTING:

Steering Unit Used:TATA Indica Steering Unit. ( Both Front And Rear )Alterations Made : Tie rod Length Reduced.

M10 Bolt And Nut.

Bevel Gear Setup Used : Major alterations in Fiat Differential Unit.Process undergone : Cutting , Grinding, Arc welding, TIG Welding.

GEAR BOX MOUNTING :

Gear Type Used : Spur Gear/ Material : Mild SteelModule = 1.540T Teeth / O.D =63mm 82 Teeth/OD= 126mm24Teeth/OD= 39mmGear Ratio : 1 (Input) : 0.487 (output) E.g: Steering outputIf the front wheel is steered to an angle of 40 degree.The rear wheel will have a max turning angle of 20 degree.

Frame Construction: Material Used : Mild Steel Square Channel -1.6mm Thick..Process undergone : Cutting , Grinding, Arc welding.

STEERING MODES

Normal Steering Mode

Counter Steering ModeActive Steering Mode

TESTINGU-Turn

L-Turn

PARKING ASSISTANCE

COST ESTIMATIONMaterials Total Price(Rs)

Steering unit(2) 3000Universal joint(5) 500

Tyres(4) 2000Bevel gears 1000

Frame 3000Steering wheel 500Bolt and Nut 500

Engage and disengage mechanism 5000Shaft 500

Welding and Machining charges 2000Front wheel mounting 1000Rear wheel mounting 1500

Total 19500

IMPLEMENTATION COST IN PRESENT SYSTEM

Materials Total Price(Rs)

Steering unit(1) 1500

Universal joint(5) 500

Bevel gears 1000

Engage and disengage Mechanism 5000

Total 8000

Thank You