Steering Linkage for Vehicle With Independent Front Suspension

 In case of conventional rigid axle:

 

• The main axle beam ensures the movement of stub axle in the horizontal plane only

• Therefore, there is no vertical deflection of the suspension and hence there is no change 

  in effective track rod length takes place

 

In case of independent suspension:

   

• The two stub axles can move up or down independent of each other 

 

• Due to which distance between ball joint ends of the two track rod arms is continuously 

  varying 

 

• On account of this a single track rod as in conventional system discussed earlier, cannot 

  be used

 

• Above difficulty is avoided by using steering linkage for independent suspension 

 

• Here three piece track rod is used, the centre portion being called the relay rod 

 

• Relay rod is connected at one end to an idler arm supported on body structure and to the 

  drop arm of the steering gear at the other end through ball joints  

   

• The relay rod is restricted to move in horizontal plane only 

 

• Movement in vertical plane is provided by the other portions, i.e., the tie rods about the 

  end  ball joints

   

It is popularly used in 

 

• Cars 

• Most of the light vehicles

 

Rigid Axle Front SuspensionRigid Axle Front Suspension

Construction and working:

 

• In this type Stub axles are connected to the rigid front axle on either side by means of King

  pins

• The drop arm is rigidly connected to the cross shaft of the steering gear at its upper end

• The other end of the link rod arm is rigidly attached to the stub axle, on which the wheel is 

   mounted 

• Each stub axle has a forged track rod arm rigidly bolted to the wheel axis 

• The other ends of the track rod arms are connected to the track rod by means of ball joints

• The design of ball joints is such that the expanding spring compensates for wear or  

  misadjustments 

• An adjuster is also provided in the track rod to change its length for adjusting wheel 

  alignment 

• The steering gear provides mechanical advantage so that only a small effort is required at 

   the steering wheel to apply a much larger force to the steering linkage. 

• It also provides desired velocity ratio so that much smaller movement of the stub axle is 

  obtained with large angular movement of the steering wheel.

• When the steering wheel is turned, the swinging action of the drop arm imparts a near 

  linear movement to the link rod 

• This movement is transmitted through the link rod arm to the stub axle so as to turn the

   stub axle about its pivot, which may be a king pin or ball joints

• The other wheel is steered through the track rod 

• Thus only one wheel is positively steered 

Applications:

Used in Heavy vehicles such as    

• Passenger Bus 

• Lorry 

• Trucks etc.,

 

Types of Steering Linkages

• Rigid axle type front suspension

• Independent front suspension

1.Rigid Axle Front Suspension:

 It consists of 

 • Steering wheel 

 • Steering column drive shaft. 

 • Steering gear box 

 • Drop arm or Pitman arm 

 • Link rod or Drag link 

 • Ball joint

 • Steering arm 

 • Track rod end joint 

 • Track rod arm 

 • Track rod or Tie rod 

 • Stub axle 

 • Axle beam 

 • King pin 

 • Adjuster. Etc.,

 

 

Worm & Sector Steering gear:

Worm & Sector Steering gear:

 

• Steering gear box makes connection between steering shaft and steering linkage

• The worm on the end of the steering shaft meshes with a sector mounted on a sector shaft

• When the worm is rotated by rotation of the steering wheel, the sector also turns rotating  

  the sector shaft

• Its motion is transmitted to the wheel through the linkage.

• Sector shaft is also known as pitman arm shaft, roller shaft, steering arm shaft or cross    

  shaft

   

Application :

Used in old vehicles

 

Recirculating Ball Steering Gear

• Most widely used steering gear at one time

 

• Balls present in the gear greatly reduce friction

• This increase the efficiency of the mechanism

  

It consists of worm at the end of steering shaft:

• A nut is mounted on the worm with two sets of balls in the grooves of the worm, in 

  between the nut and the worm

• The balls reduce the friction during the movement of the nut on the worm

• The nut has a number of teeth on the outside, which mesh with the teeth on a worm wheel  

  sector

• Drop arm is mounted on the worm wheel sector, which steers the road wheels through the  

  link rod and the steering arms  

 

• When the steering wheel turned, the balls in the worm roll in the grooves and cause the 

  nut to travel along the length of the worm 

  

• The balls, which are in two sets, are recirculated through 

 

• The movement of the nut causes the wheel sector to turn at an angle and actuate the link 

  rod through the drop arm, resulting in the desired steering of the wheels

 

 Applications:

• Tata vehicles

• Dodge / Fargo

• Standard 20 vehicles

• Ashok Leyland Viking Trucks etc.,

   

Various Types of Steering Gears

Commonly used steering gears are:

•  Rack and pinion.

•  Worm and sector.

•  Recirculating ball.

•  Worm and roller.

•  Cam and double lever steering gear

•  Worm and ball baring nut steering gear

•  Cam and roller steering gear

•  Cam and peg steering gear  

Steering Gear

Steering Gear:

 

• Changes rotary motion of steering wheel into lateral movement of tie rod.

• Minimum effort of steering wheel exert a large force on the road wheels.

 

 

Drop Arm:

 

 

• Also known as pitman Arm.

• Connected between steering gear and drag link.

• Transfer motion from steering gear.

 

 

Drag Link:

 

• Connects drop arm and steering knuckle on either ends.

 

• Made of forged alloy steel.

 

Steering Gear

Steering Column:

 

• Circular column houses steering shaft.

• Connected to steering shaft in bush, ball or roller bearing .

• Column supported to vehicle by brackets.

• Some of the vehicle controls carried on to the columns.   

• Collapsible columns are used in modern vehicles.

 

 

Steering Shaft:

 

 

• Top end connected to steering hub.

• Bottom end goes into the steering box.

 

• Ball or bush bearing supports the shaft inside the column.

• Inclined at 50 in case of cars 20 in case of commercial vehicles.

 

Steering Gear

Mainly Consists of :

1.Steering Wheel 

2.Steering  Column

3.Steering shaft. 

4.Steering Gear Box

5.Drop Arm/Pitman arm 

6.Drag Link / Pull & Push Rod

Steering Wheel:

 

• Made of polyurethane or Hard plastic.

• Consists of circular rim with hub at center.

• Slightly elliptical in cross section for good hand grip & strength.

• Rim diameter based on drivers comfort.

• Input torque depends on size of Rim. 

 

 

 

Steering Wheel Diameters:

 

 

 In light vehicles :

 

1. Ambassador  43.2    cm.

2. Willys Jeep  43.8    cm.

3. Premier  43  cm.

4. Standard 10  39  cm.

5. Maruti-800  37  cm.  

Requirements of steering system

• The steering mechanism should be very accurate and easy to handle.

• The effort required to steer should be minimum.

• The effort required to steer  must not be tiresome to the driver.

• The steering mechanism should Provide directional stability.

 

•The steering mechanism implies the tendency to return to its straight ahead position after 

 

  turning.

• Steering system must be semi reversible.

• It should multiply the turning effort applied on the steering wheel by the driver