1. Mbeya Institute of Science and
Technology
Department of Mechanical
Engineering
Automotive Technology
STEERING SYSTEM

2. STEERING SYSTEM
• A vehicle is not much use if it cannot be
steered or guided. The act of guiding the
vehicle is called steering
• Wheeled vehicles are steered by aiming or
pointing the wheels in the direction we want
the vehicle to go.The driver of a car or truck
guides it by turning the steering wheel.

3. STEERING SYSTEM
•The function of a steering system is to
convert the rotary movement of the
steering wheel in driver's hand into the
angular turn of the front wheels on
road.
•Additionally, the steering system
should provide mechanical advantage
over front wheel steering knuckles,
offering driver an easy turning of front
wheels with minimum effort in any
desired direction.

4. • The steering system of cars and trucks consists of levers, links,
rods, and a gearbox and sometimes a hydraulic system that
assists the driver's steering
effort.
• The steering system is of critical importance in the safe
operation of the vehicle. There must be no looseness
between the steering wheel and the front wheels if the driver
is to keep control over the direction the wheels point. The
tires must meet the road at the correct angle to get good
traction and to prevent unnecessary tire wear. Also, the
driver should be able to hold the wheels in the straight ahead
position and change them to the right or left with very little
effort.

5. Steering layout
• The following are commonly used layouts
• Swinging beam steering
• Fixed beam steering
• Ackermann steering principle

6. Swinging beam steering
• In this layout the front axle is mounted onto
the vehicle by means of a central turntable
which allows the whole axle to pivot
• As each of the steered wheels is at right
angles to the centre of the turn, the vehicle
can follow a curved pathway. This gives true
rolling motion in which the wheels has
minimal resistance.

7. Swinging beam steering

8. Swinging beam steering

9. Fixed beam steering
• In fixed beam steering the front axle is unable
to turn. Instead the wheels are mounted on
pivoting sub axles, mounted on each end of
the axle beam.
• This method is the basis of all steering
systems. Vehicles with independent
suspension have their stub axles mounted in
the same relative positions.

10. Fixed beam steering

11. Ackerman steering principle
• To ensure that the front steered wheels rotate
around a common centre the inner and outer
roadwheels must be moved by differnt
amounts. This achieved by setting the steering
arms at an angle so that their projected
centrelines meet on or near the centre of the
rear axle.

12. Ackerman steering principle

13. Ackerman steering principle

14. Ackerman steering principle
• The intention of Ackermann geometry is to avoid the
need for tyres to slip sideways when following the
path around a curve.[2]
The geometrical solution to
this is for all wheels to have their axles arranged as
radii of a circle with a common centre point. As the
rear wheels are fixed, this centre point must be on a
line extended from the rear axle. Intersecting the
axes of the front wheels on this line as well requires
that the inside front wheel is turned, when steering,
through a greater angle than the outside wheel

15. Ackerman steering principle

16. Wheel alignment
• Wheel alignment is part of standard
automobile maintenance that consists of
adjusting the angles of the wheels so that they
are set to the car maker's specification
• The purpose of these adjustments is to reduce
tire wear, and to ensure that vehicle travel is
straight and true (without "pulling" to one
side).

17. Wheel alignment
• Alignment angles can also be altered beyond
the maker's specifications to obtain a specific
handling characteristic. Motorsport and off-
road applications may call for angles to be
adjusted well beyond "normal" for a variety of
reasons

18. Wheel alignment

19. Wheel alignment

20. Wheel alignment

21. Steering angles
• The steering geometry of a vehicle is
purposely designed with certain steering
angles these have an important effect on how
the vehicle steers and handles
1.Caster angle
2.Camber angle
3.Kingpin inclination(KPI)

22. Caster angle
• Caster angle or castor angleis 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 center of the upper ball joint
to the center of the lower ball joint) and vertical. Car
racers sometimes adjust caster angle to optimize
their car's handling characteristics in particular
driving situations

23. Caster angle

24. Caster angle
• When an automotive vehicle's front
suspension is aligned, caster is adjusted to
achieve the self-centering action of steering,
which affects the vehicle's straight-line
stability. Improper caster settings will cause
the driver to move the steering wheel both
into and out of each turn, making it difficult to
maintain a straight line.

25. Caster angle

26. Camber angle
• Camber 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.
• It is used in the design of steering and suspension. If
the top of the wheel is farther out than the bottom
(that is, away from the axle), it is called positive
camber; if the bottom of the wheel is farther out
than the top, it is called negative camber

27. Camber angle

28. Camber angle
• Camber angle alters the handling qualities of a particular
suspension design; in particular, negative camber improves
grip when cornering. This is because it places the tire at a
more optimal angle to the road, transmitting the forces
through the vertical plane of the tire, rather than through a
shear force across it. Another reason for negative camber is
that a rubber tire tends to roll on itself while cornering. If the
tire had zero camber, the inside edge of the contact patch
would begin to lift off of the ground, thereby reducing the
area of the contact patch. By applying negative camber, this
effect is reduced, thereby maximizing the contact patch area.
Note that this is only true for the outside tire during the turn;
the inside tire would benefit most from positive camber.

29. Camber angle

30. Camber angle

31. Camber angle

32. Kingpin inclination
• The kingpin, also king-pin and king pin,[
is the main
pivot in the steering mechanism of a car or other
vehicle. Originally this was literally a steel pin on
which the moveable, steerable wheel was mounted
to the suspension.
• On most modern designs, the kingpin is set at an
angle relative to the true vertical line, as viewed
from the front or back of the vehicle. This is the
kingpin inclination or KPI (also called steering axis
inclination, or SAI).

33. Kingpin inclination
• KPI is the angle at which the centrline of the
kingpin or the axis of the steering swivels
leans inwards from the vertical.

34. Kingpin inclination

35. Kingpin inclination

36. Kingpin inclination

37. Steering gear
• The purpose of steering gear is to enable the
driver to alter the vehicles steered direction
with a minimum of effort. Three of the most
common types in use are
1.Worm and peg
2.Recirculating ball
3.Rack and pinion

38. Steering gear
• Worm and peg steering
• A 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). The terminology is often
confused by imprecise use of the term worm
gear to refer to the worm, the worm gear, or
the worm drive as a unit.

39. Worm and peg steering

40. Worm and peg steering
• With with this type of steering mechanism the
lower part of the steering column shaft is
machined with a worm-type screw thread,
which meshes with a peg protuding from the
arm of the cross-shaft
• When the steering wheel is rotated, worm
moves the peg along , and the arm transfered
to a steering drop arm and linkage to move
the roadwheels.

41. Steering gear

42. Recirculating ball steering
• The 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 (also called a sector gear)
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
roadwheels to turn.

43. Recirculating ball steering

44. Recirculating ball steering

45. Recirculating ball steering
• The recirculating-ball steering gear contains a
worm gear. You can image the gear in two parts. The
first part is a block of metal with a threaded hole in
it. This block has gear teeth cut into the outside of it,
which engage a gear that moves the pitman arm
(see diagram above). The steering wheel connects to
a threaded rod, similar to a bolt, that sticks into the
hole in the block. When the steering wheel turns, it
turns the bolt. Instead of twisting further into the
block the way a regular bolt would, this bolt is held
fixed so that when it spins, it moves the block, which
moves the gear that turns the wheels.

46. Recirculating ball steering

47. Steering gear

48. Power steering
• Power 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 the roadwheels. As vehicles
have become heavier and switched to
front wheel drive, particularly using negative
offset geometry, along with increases in tire
width and diameter, the effort needed to turn
the steering wheel manually has increased —
often to the point where major physical

49. Power steering
• To alleviate this, auto makers have developed
power steering systems: or more correctly
power-assisted steering — on road going
vehicles there has to be a mechanical linkage
as a fail safe. There are two types of power
steering systems—hydraulic and
electric/electronic. A hydraulic-electric hybrid
system is also possible.

50. Power steering
• A hydraulic power steering (HPS) uses hydraulic
pressure supplied by an engine-driven pump to assist
the motion of turning the steering wheel.
Electric power steering (EPS) is more efficient than
the hydraulic power steering, since the electric
power steering motor only needs to provide
assistance when the steering wheel is turned,
whereas the hydraulic pump must run constantly. In
EPS, the assist level is easily tunable to the vehicle
type, road speed, and even driver preference.

51. Power steering
• There are a couple of key components in
power steering in addition to the rack-and-
pinion or recirculating-ball mechanism
• Pump
The hydraulic power for the steering is
provided by a rotary-vane pump (see diagram
below). This pump is driven by the car's
engine via a belt and pulley. It contains a set
of retractable vanes that spin inside an oval
chamber.

52. Power steering

53. Power steering
• Rotary Valve
A power-steering system should assist the
driver only when he is exerting force on the
steering wheel (such as when starting a turn).
When the driver is not exerting force (such as
when driving in a straight line), the system
shouldn't provide any assist. The device that
senses the force on the steering wheel is
called the rotary valve.

54. Power steering
• The key to the rotary valve is a torsion bar.
The torsion bar is a thin rod of metal that
twists when torque is applied to it. The top of
the bar is connected to the steering wheel,
and the bottom of the bar is connected to the
pinion or worm gear (which turns the wheels),
so the amount of torque in the torsion bar is
equal to the amount of torque the driver is
using to turn the wheels. The more torque the
driver uses to turn the wheels, the more the

55. Power steering

56. Power steering

57. Steering linkage
• The steering linkage is a combination of rods, and
arms, that transmit the movement of the steering
gear to the front wheels.
• It must transmit this movement to the front wheels,
while still allowing for any up-and down movement
they may make, while the vehicle is in motion.
• The type of steering mechanism, and the number of
linkages, depends on the type of steering box, its
location, and the type of suspension on the vehicle.

58. Steering linkage

59. Steering linkage

60. Ball joint
• In an automobile, ball joints are spherical bearings that
connect the control arms to the steering knuckles. More
specifically, a ball joint is a steel bearing stud and socket
enclosed in a steel casing. The bearing stud is tapered and
threaded. It fits into a tapered hole in the steering knuckle. A
protective encasing prevents dirt from getting into the joint
assembly. Motion control ball joints tend to be retained with
an internal spring, which helps to prevent vibration problems
in the linkage. Commonly found in automotive throttle
linkages, throttle body set ups, these are also widely used on
construction equipment, the end of gas springs and in
children's toys.

61. Ball joint

62. Ball joint

63. Purpose of ball joint
• Ball joints are the pivot between the wheels
and the suspension of an automobile. Ball
joints play a critical role in the safe operation
of an automobile's steering and suspension.
Ball joints can also be found in most linkage
systems for motion control applications, and
should not be confused with spherical rod end
bearings, which are a different design.

64. Ball joint

65. END OF PRESENTATION
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