basic about steering

1. STEERING
The essentials still remaining the same, the importance of the steering mechanism cannot be
compromised with. The BAJA track consisting of sharp turns and bumpy roads, the stability of the
system and the response time (Feedback) are vital factors in deciding the vehicles’ run. The Worm
and Sector mechanism, Rack and pinion and the Re-circulating ball mechanism were among our
options to go with. But on consideration of mounting ease, simplicity in design and considering that
our vehicle is of the compact category; rack and pinion was chosen over the others. The rack and
pinion being a simple system; can be easily maneuverer and the defect, if any, can be spotted and
taken care of. Moreover the steering wheel and other relevant apparatus are so placed in the
design, for easy entering and exit of the driver.
Steering Geometry:
The Ackermann geometry is the easiest to implement and has been tested for BAJA vehicles all over
the globe and hence it was a unanimous choice for the steering geometry. With Ackermann Steering
all four wheels of the vehicle pivot around the same point making sharp turns relatively easy to
accomplish. This ensures that the vehicle tires do not slip during turns that are sudden.
Steering Gearbox:
We shall be manufacturing a customized centred steering mechanism, the basis of which shall be
derived from the rack and pinion of MARUTI 800. Direct usage of the Maruti 800 gear system is not
done, mainly because of its eccentric placement of the gearbox that disrupts the C.G. balance of the
vehicle
The major parameters in steering design are,
1. The Caster angle has been adjusted to 3 to 5 degree as it increases directional stability and
handling of the vehicle in bumpy sections.
2. The Camber should be kept negative to ensure maximum contact of tire with ground during
cornering and to reduce chances of flipping over.
3. Ackermann type of steering geometry ensures consistent and smoother ride and prevents the
slipping of tires during cornering.
4. We should have a scrub radius of 40-48 mm approximately. This is acceptable as it is neither a
negative value nor too large of a positive value. Such a small value will leave the car slightly harder
to steer at very low speeds. It is important for this value to be equal on both tires to avoid the car
“pulling” to one side.
We should have kept a small Toe-in in the front. This will stabilize the car while moving straight and
while coming out of turns. It will smooth out the steering response, making the car very easy to
drive.

2. Approximate specification
Sl.no. property Value between
1 Caster 4-5 degree
2 Camber 1-2 degree (negative)
3 Toe In 10-12 mm
4 King-pin inclination 12-13 degree
5 Scrub radius 42-45mm
6 Lock Angle Around 38-42 degree
Terminology
 The Steering Wheel – The Bit the driver holds on to! It also incorporates the Air Bag.
 Steering Column – The shaft connecting the steering wheel to the steering box or steering
rack.
 Steering Rack – A combination of a small gear and a toothed rack. This changes the rotation
of the steering wheel into a back and forth movement of the rack which in turn moves the
road wheels.
 Steering Box – This does a similar job to the rack but needs extra linkages and rods to
connect it to the road wheels. Mostly used on old cars, but still is in use on larger vehicles.
 Track rod/Tie rod – A rod to connect the left and right steered wheels. The steering rack is
also the track rod.
 Track rod end – A ball joint to allow steering and suspension movement.
 Ball joint/Swivel joint – Part of the suspension, but these are joints which allow the steered
wheels to left and right.
 PAS – Power assisted steering. An engine driven pump or electric motor, provides extra force
to help the driver turn the steering.
 Tracking – toe in or toe out setting for the steered wheels.

3. Ackerman Principle
Ackermann stated the principle that when a vehicle travels in a curved path,its
wheels should describe circles around the same centre. A wheel which follows
a markedly different path will slide to some extent, this would cause excessive
tyre wear. The steering mechanism is designed to insure that when the vehicle
turns left or right, the inner wheel is turned through a larger angle to prevent
tyre wear
Steering assembly in operation, as the
steering linkage is shorter than the axle, the inner wheel is turned through a larger angle.
Steering Shafts and Columns
Nearly all steering systems use a steering column or shaft to link the driver (steering wheel) to the
steering rack or gear/box.
Flexible coupling isolates steering wheel from road shocks.
Universal joints allow steering shaft angles to change
Most steering columns are designed with a collapsible section that helps prevent forces generated in
a collision being transferred to the driver.
Bottom of steering column normally has a master spline where it mounts onto the steering rack-and-
pinion or steering gear/box.

4. Basic Steering Systems
Two main types of steering
 Linkage or Conventional type (also known as Parallelogram)
 Rack-and-pinion type.
Linkage type uses a worm gear inside the steering gear/box, this operates the drop arm, then
couples to a centre link, idler arm, track rods and the steering knuckles.
Rack-and-pinion type uses track rods to couple the rack to the steering knuckles.

5. Rack-and-Pinion Steering Principle
Part of rack contains a piston.
Two fluid ports, one on each side
The side with high pressure pushes the piston to the opposite side (turning the wheel).

6. Steering Linkage

7. .

8. Steering System( we can use power steering in the car)
Power Steering normally use an engine driven pump and a hydraulic system to assist steering action.
Three major types of power steering systems
• Integral-piston linkage system.
• External power steering system.
• Rack-and-pinion system

9. Ball Joints
Ball joints are common on most steering systems and provide a controllable link to the other
steering components.
Ball joints allow linkage components to swivel freely.
Suspension (vertical) and steering (horizontal) movements
Nearly all ball joints have some form of adjustment.
Most steering rack ends have adjustable ball joints and some incorporate shock dampers.
Linkage Type Steering System

11. As compare to last year we can apply power brake in the car, but I need to
study its mechanism . I need a bit time to understand it and to design it.