steering system

Function of steering;

To move the vehicle in required direction
 

Introduction: 

   

• The front wheels are supported on the front axle so that they can swing to the left or right 

  for steering 

• This movement is produced by gearing and linkage between the steering wheel in front of 

   the driver and steering knuckle or wheel.

• This complete arrangement is called steering system.

• The main function of the steering system is to convert rotary motion of the steering wheel

   in to angular turn of front wheel

• Steering system is mainly used to guide or to control the movement of a vehicle 

• The vehicle can be controlled even if ‘ABC’ fails. But vehicle cannot be turned if the 

   steering system fail

Tube Vulcanization

• A tube is made of  natural rubber whose monomer is isoprene

• It has two double out of which one is used in chain formation

• The other in producing an elastomer

• The elastomer is stronger than rubber and is formed during tube vulcanized

• Production of elastomer requires heating of raw rubber in the presence of sulphur under a 

  specified pressure

   
• Sulphur forms covalent bonds, and cross-links the chains 

• This process is called vulcanization 

• More the number of cross-links produced, more will be the degree of vulcanization 

• Various vulcanized agents are used in different types of rubber 

• These agents in neoprene rubber are S, Mgo or Zno; and di-isocyanates in urethane
   rubber

Tyre Retreading Processes

1.Conventional retreading process

• The tread rubber applied on the buffed tyre casing is uncured or raw

• The same is then vulcanized in the curing mould, using steam temperature and pressure

 

2. Cold-cure retreading process

• The tread rubber belt is already vulcanized

• It is stuck onto the cemented buffed tyre casing

• A curing bag is inserted inside the tyre and the whole assembly is encased in a rubber 
 
  envelope
 

• Then for proper bondage between cured tread rubber and the casing

• The tyre is placed in the tread bonder kept in it for a specified period of time and 

  temperature

Tyre Retreading

• Tyre retreading is a process of reconditioning an old tyre and giving it a new lease of life 

  again. 

• It is possible to retread a tyre 2 to 3 times or more since retreading cost is half that of a

  new  tyre price.Hence retreading tyres are economical

   

• Tyre retreading is done by a special tread rubber 

 

• The retreading requires abundant production of tread rubber in various sizes 

 

• Once the casing is damaged the tyre becomes unfit for retreading

•  Rear tyres are subjected to greater loads than the front tyres Consequently, they wear-out 

   rapidly

 

•  vehicle should have less worn tyres on its front and more worn tyres on the rear

 

•  It is required to change position of tyres after certain mileage of travel. This change is 

   called “tyre rotation”

 

•  To achieve more uniform wear for all tyres on a vehicle 

 

• The pattern of tyre rotation differs for the front wheel driven vehicles and rear wheel driven 

  vehicles

 

• A spare wheel generally a standard fitment on many vehicles but can be an optional 

  attachment on some vehicles

 

• The tyre rotation pattern differs for various makes of vehicles

Need of Tyre Rotation

• For satisfactory 4 wheel drive operation, a 4 wheel drive vehicle must be equipped with the 

 

  same size tyres of equal circumference on all four wheels. The tyres must then be 

 

  inflated to proper recommended pressures at all times

 

• Rotate the tyres for every 10000kms this practice make a set of tyres last longer than they 

 

  would without tyre rotation

 

Causes of Tyre Wear

• Incorrect inflation

• Incorrect caster, camber, or toe-in

• Excessive braking or violent acceleration

• Worn steering mechanism

• Worn king pins

• Out of balance wheel

• Misalignment

• Over-loading 

• Wrong loading 

• Defective brakes 

• Toe-out incorrect on turn 

• Bleeding of air in tyre 

• Careless driving 

• Unequal tyre 

• Incorrect rotation of tyres

Factors Affecting Tyre Life

The main factors which affect tyre performance and consequently their life 

• Tyre inflation

• Vehicle maintenance

• Manner of driving

• Miscellaneous factors (heat, Position in which tyre fitted, road conditions, Seasons)

 

Inflation pressure:

 

Tyre Inflation:

• This depends upon tyre size, tyre type,speed and load 

• The Inflation pressure are recommended by the vehicle manufacturer

 

Inflation:

 

• Under inflation

• Over inflation

• Proper inflation

 

Under Inflation:

   

Under Inflation causes the following defects:

 

• Uneven tread wear, more wear at the tyre sides 

• Lack of directional stability

• Increased rolling resistance leading to increased fuel consumption

• Excessive flexing of wall

 

Over Inflation:

   

Over inflation causes the following defects:

 

• Reduced tread contact area with the road surface

• This results in rapid wear in the tread at the centre 

• Reduced tyre grip

• Reduced impact resistance

• Increased vibration resulting in uncomfortable ride

• Increased stresses may cause tread separation and cracks in the side walls

    

Proper Inflation:

 

• The amount of pressure will be exact amount , required for good driving

 

Tread Pattern

• The grooves of different layouts on tyre

 

• Styles and orientations cut on the tread of a tyre are termed as tread pattern

 

• A proper tread pattern help in smooth steering, better mileage

 

• lower noise level, Increased road grip, Improved driving comfort, less wear

 

• Tyres have numerous varieties of tread pattern

   

• Special synthetic rubber is used for making tread on the tyre surface

 

• It has a high co-efficient of friction 

 

• It provides good grip on wet and dry road surface

Considerations in Tread Design

Grip:

• The braking grip of a tyre depends upon two factors

 

  a) Tread material

  b) Tread pattern

• The grip for a particular tread pattern is effected mechanically as well as through friction

 

• The tread must provide suitable sharp edges that will engage with the road

  

Noise:

   

• Various type of vibrations caused by roughness of the road surface 

 

• By the distortion  of the tyre carcass also produce noise 

 

• The type of tread pattern also contribute to tyre noise 

 

• Noise depends upon the nature of the rubber compound

 

Wear:

   

• For less wear the tyre must be such that the individual elements which undergo minimum 

 

  distortion during running 

 

• Tread wear indicators are provided at the bottom of the tread grooves