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Most Important Terms of Automobile Engineering





Clutch :-
This is a mechanism, which enables the rotary motion of one shaft to be transmitted, when desired , to a second shaft the axis of which is coincident with that of the first.





Gear Ratio :-
The ratio of turning speeds of the two gears.


Functions of transmission :-
1.To vary the torque ratio between the engine and the road wheels as required under different conditions.
2.To provide a neutral position.
3.To enable the vehicle to move in the reverse direction.


Free Wheel :-
A mechanical device that engages the driving member to impact motion to a driven member in one direction but not the other: also called overrunning clutch.


Transfer Box :-
A gear box which transfers drive between front and rear axles in a 4-wheel drive vehicle.


Propeller Shaft :-

This is the shaft which transmits the drive from the transmission to the bevel pinion or worm of final drive in front engine, rear drive vehicles. It consists of a shaft, one or two universal joints and a slip joint.


Half shafts :-

Either one of the two shafts connecting the differential (front or rear) to the road wheels through which power is transmitted in a live axle.





Universal Joint :-
It is a particular type of connection between two shafts, whose axes are inclined to each other. Most common example is the Hook's joint.


Differential :-

The arrangement to ensure equal speeds of the inner and the outer wheels of an axle while taking turns. In an ordinary differential, the torque transmitted is always equally divided between the two wheels on the axle, even when their speeds are different.


Final drive ratio :-
The ratio of the road wheel speed to the speed of the gear box (transmission ) output shaft.


Radius Rod :-
The member connecting the axle casing and the chassis frame in the longitudinal direction , which transmits the driving thrust from the axle casing to the chassis frame and body of the vehicle . This is also called Thrust Member.





King Pin Inclination :-
Inclination of the king pin from vertical .In modern cars with independent suspension, the king pin has been replaced by the ball joints.As such this term has been renamed as Steering Axis Inclination.


Castor :-
The angle between the king pin center line (or steering axis) and the vertical, in the plan of the wheel. If the steering axis meets the ground at a point ahead of the vertical wheel center line, it is called positive castor , while if it is behind the vertical wheel center line, it is called negative.




Toe-in Toe-Out :-
Toe-in is the amount by which the front wheels are set closer together at the front than at the rear when the vehicles is Stationary. On the other hand if the wheels are set closer at the rear than at the front , the difference of the distance between the front wheels at the front and at the rear is called Toe-out.


Turning Circle Diameter :-

The diameter of the smallest circle which the outer front wheel of the car can traverse and obtained when the wheels are at their extreme positions.


Thrust Angle :-
The angle made by the Thrust line with the Longitudinal center line of the vehicle . Obviously for trust angle to be zero, all the four wheels should be parallel to the frame.


Power Steering :-
It provides automatic assistance to the turning effort applied to the manual steering system. Earlier, hydraulic power steering systems were used, through lately electronic power system are talking their places, due to following advantages :
1.No problem of fluid-Leakage.
2.Energy consumed only while steering.
3.Steering assistance available even when the engine is not ruining.
4.In manual mode, lesser force is required for steering,compared to the hydraulic system since there is no fluid to be forced through the valves.


Steering Ratio :-

It is the ratio of the angle turned by the steering wheel to the corresponding turning angle of the stub axle.



Steering Gear :-
The steering component which converts the turning motion of the steering wheels into the liner motion of the link.Most commonly used steering gear in modern vehicles is the rack and pinion type.


Steering Arm (Track rod Arm) :-
The arm attached to the steering Knuckle at one end and Tie Rod end at the other end.



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