THE BASIC STRUCTURE



          The basic structure is a unit on which the remaining unit are build to make a complete automobile.

  it consists of the frame,suspension, axles, wheel and tyers   
                   FRAME                                                          1: frame; the frame provides a foundation for the engine and  the body of the vehicle. the commonly used frame are
                       

(i) the conventional square or box shape steel frame. it supports the engine, wheel and other component parts while the body is superimposed on it.

(ii) the integral or frame less construction in which the structure is designed in such a manner that is combines function  of body and frame.all the unit are attached to the frame which is the n directly attached to the body.





                       

                                      ADVANTAGE OF FRAMELESS CONSTRUCTURE
*  light in weight and hence fuel efficient.
* manufacturing cost is less.
* safe for the passenger during collision , since the body crumbles thereby absorbing the shock due    to impact.
* more stable automobile can be made because of the lower body constructure

                       DISADVANTAGE OF FRAME LESS CONSTRUCTION
* less strength and durability.
* cost of repair is hight
* economical only if adopted in mass production
* car without roof are difficult to design.

        APPLICATION OF FRAME LESS CONSTRUCTION
it is possible only in case of closed car, since the roof, screen pillars,door pillars and rear panel are essential load taking parts of the structure.

(iii) a third type of body construction is the space frame. it is made by steel stamping welded together this is similar to tube chassis and roll cage in a race car plastic panels fasten to the space frame to complete the body.


                                  2:   SUSPENSION SYSTEM

spring shock absorbers and related parts between the wheel  and the car body make up the suspension system the main function of a suspension system are

*to prevent the road shock from being transmitted to the vehicle frame.
*to preserve the stability of the vehicle in pitching or  roll, while in motion.
*to maintain proper steering geometry.
*to provide good road holding while driving, cornering and braking.
   the suspension system is classified as
*Rigid system: in this system the road spring are attached to a rigid beam axle  of all types  of vehicles.
* Independent:   it dose not have a rigid axle. in this system each wheel is free to move vertically without any reaction on it mating  wheel.such types are used in small cars.


                                              3:  AXLE

these are the shafts on which road wheel are mounted.the required drive for the road wheel is provided through these axles. axle are subjected to the following loads:

* vertical load at the spring centers due to weight  of vehicle.
* torque reaction due to drive or brakes.
* a fore and aft load at the wheel  center due to driving or braking effort.
*side thrust at the radius  of the tyre due to centrifugal force when rounding a curve.

 Live rear axles are of the following types:

* fully floating type
* three-quarter floating type
*semi-floating type

                                               4: WHEEL

  there are used to take the load of the vehicle and also produce tr-active force to move the vehicle. the wheel also used for retardation and for stopping the vehicle.