STEERING & FRONT AXLE

FUNCTIONS OF STEERING SYSTEMPrimary requirement of a steering system is to achieve angular motion of front wheel to navigate a turn. 1. 2. 3. 4. 5. 6. To provide straight ahead stability. To provide perfect rolling motion of all wheels. To provide perfect steering condition. To facilitate straight ahead recovery after a turn. To minimize tyre wear. To absorb road loads and preventing them to reach to steering wheel. 7. To reduce effort for steering by providing higher mechanical advantage.

REQUIREMENTS OF GOOD STEERINGSYSTEM

Accurate mechanism and easy to handle. Minimum effort should be required for steering. Should provide directional stability and straight ahead recovery after turn

FRONT AXLETo take bending loads due to weight of the vehicle.

Spring seats

Brake drum

STEERING SYSTEMS & LINKAGESSteering linkage is a series or arms, rods, and ball sockets that connect the steering mechanism to the steering knuckles. The steering linkage used with most manual and power steering mechanisms typically includes a pitman arm, centre link, idler arm, and two tie-rod assemblies. This configuration of linkage is known as parallelogram steering linkage and is used on many passenger vehicles.

STEERING SYSTEMMANUAL Steering wheel Shaft column Manual gearbox Linkages Steering knuckles Ball joints Wheel spindle assembly POWER Steering wheel Shaft column Hydraulic pump Fluid reservoir Hoses Power steering gear assembly Power assist unit

STEERING GEARSThere are main 3 types of steering gears 1. Rack & Pinion 2. Worm & Wheel Steering Gear 3. Recirculating ball Other types are: Warm and nut Warm and roller type Cam and double liver

1. RACK & PINIONHere the steering wheel turns the pinion gear; the pinion moves the rack, which is a linear gear that meshes with the pinion, converting circular motion into linear motion along the transverse axis of the car.

Pinion Gear - rotated by the steering wheel and steering shaft; it s teeth mesh with the teeth on the rack. Rack - long steel bar with teeth along one section; slides sideways as the pinion gear turns Gear Housing - holds the pinion gear and rack Tie-rods - connects the rack with steering knuckles

WORM & WHEELA worm drive is a gear arrangement in which a worm (which is a gear in the form of a screw) meshes with a worm gear (which is similar in appearance to a spur gear, and is also called a worm wheel).

LINKAGE STEERING SYSTEM (WORM GEAR) PARTSSteering Wheel used by the driver to rotate a steering shaft that passes through the steering column. Steering Shaft transfers turning motion from the steering wheel to the steering gearbox Steering Column supports the steering column and steering shaft.

RECIRCULATING BALLThe recirculating ball steering mechanism contains a worm gear inside a block with a threaded hole in it; this block has gear teeth cut into the outside to engage the sector shaft which moves the pitman arm. The steering wheel connects to a shaft, which rotates the worm gear inside of the block. Instead of twisting further into the block, the worm gear is fixed so that when it spins, it moves the block, which transmits the motion through the gear to the pitman arm, causing the road wheels to turn.

TOE-IN, TOE-OUTIn automotive engineering, toe is the symmetric angle that each wheel makes with the longitudinal axis of the vehicle. Positive toe, or toe in, is the front of the wheel pointing in towards the centreline of the vehicle. Negative toe, or toe out, is the front of the wheel pointing away from the centreline of the vehicle. Toe can be measured in linear units, at the front of the tire, or as an angular deflection.

CAMBER ANGLECamber angle is the angle made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of the wheels used for steering and the vertical axis of the vehicle when viewed from the front or rear.

Camber angle

Generally 2 degrees of positive camber angle is provided. Positive camber angle results the tyre wear at out side edge Negative camber results the tyre wear at inside edge Equal camber on both wheels causes the vehicle to pullover the road. In right hand wheel drive country slightly high camber is provided on right wheel than left wheel

KING PIN INCLINATION, INCLUDED ANGLE, AND SCRUB RADIUS

KPI7 to 8 degree Helps the straight ahead recovery Providing directional stability During the turning the vehicle body tends to up

Scrub radiusNegative scrub radius tends to toe in Positive scrub radius tends to toe out Zero scrub radius tends to straight wheels- center point steering Large scrub radius tends to need more torque to turn the wheels Generally little bit positive scrub radius is preferred.

CASTER ANGLECaster angle is the angular displacement from the vertical axis of the suspension of a steered wheel in a car, bicycle or other vehicle, measured in the longitudinal direction. It is the angle between the pivot line (in a car - an imaginary line that runs through the centre of the upper ball joint to the centre of the lower ball joint) and vertical.

Castor angle

Generally 3 degrees are provided Helps in direction of vehicle Positive castor tends to higher torque for return steering and are provided in power steering only Zero Caster or negative castor is provided in manual steering.

UNDER STEER & OVER STEER

Under steer is a term for a car handling condition in which during cornering the circular path of the vehicle's motion is of a greater radius than the circle indicated by the direction its wheels are pointed. Oversteer is a phenomenon that can occur in an automobile while attempting to corner or while already cornering. The car is said to oversteer when the rear wheels do not track behind the front wheels but instead slide out toward the outside of the turn.

POWER STEERINGPower steering assists the driver of an automobile in steering by directing a portion of the vehicle's power to traverse the axis of one or more of its wheels. There are 3 basic types of power steering system 1. Hydraulic 2. Electric 3. Electro Hydraulic

1. HYDRAULIC POWER STEERINGHydraulic power steering (HPS) is a hydraulic system for reducing the steering effort on vehicles by using hydraulic pressure to assist in turning the wheels. It is intended to provide for easier driving direction control of the car while preserving "feedback", stability of the trajectory specified.

Power steering pump is driven by the engine produces the hydraulic pressure for steering system operation.

Four basic pumps: Roller pump. Vane pump Slipper pump Gear pump.

2. ELECTRIC POWER STEERINGElectric power steering (EPS or EPAS) is designed to use an electric motor to reduce effort by providing steering assist to the driver of a vehicle. Sensors detect the motion and torque of the steering column, and a computer module applies assistive torque via an electric motor coupled directly to either the steering gear or steering column.

3. ELECTRO-HYDRAULIC POWER

STEERING SYSTEMS

Electro-hydraulic power steering systems, sometimes abbreviated EHPS, and also sometimes called "hybrid" systems, use the same hydraulic assist technology as standard systems, but the hydraulic pressure is provided by a pump driven by an electric motor instead of being belt-driven by the engine.

"STEER-BY-WIRE" OR "DRIVE-BY-WIRE "These systems would completely eliminate the mechanical connection between the steering wheel and the steering, replacing it with a purely electronic control system. Essentially, the steering wheel would work like the one you can buy for your home computer to play games. It would contain sensors that tell the car what the driver is doing with the wheel, and have some motors in it to provide the driver with feedback on what the car is doing. The output of these sensors would be used to control a motorized steering system. This would free up space in the engine compartment by eliminating the steering shaft. It would also reduce vibration inside the car.

ACKERMANN STEERING GEOMETRYAckermann steering geometry is a geometric arrangement of linkages in the steering of a car or other vehicle designed to solve the problem of wheels on the inside and outside of a turn needing to trace out circles of different radii.

Steering Geometry Cot = (a + y )/ b

DEVIS STEERING GEOMETRY

Thank you