International Journal of Research in Advent Technology, Special Issue, December 2018
International Conference on Mechanical and Civil Engineering (ICOMACE-2018)
E-ISSN: 2321-9637
Available online at www.ijrat.org
Design and Fabrication of ackerman steering For Hybrid
Car
Katla Praveen Kumar1 B.H.Sridhar2
1
Assistant Professor, Department of Mechanical Engineering,
K.G. Reddy College of Engineering &Technology, Moinabad, Telangana State: 501504, INDIA
2
Assistant Professor, Department of Mechanical Engineering,
Vignana Bharathi Institute of Technology, Ghatkesar, Telangana State: 501301, INDIA
Email: praveenkatla@gmail.com
Abstract- Steering is the collection of components, linkages, etc. which allows any Vehicle (i.e. Car, Bike etc.)
to follow the desired path. The primary purpose of the steering system is to allow the driver to guide the vehicle.
The most conventional steering arrangement is to turn the front wheels using a hand–operated steering wheel
which is positioned in front of the driver, via the steering column, which may contain universal joints, to allow it
to deviate from a straight line. The aim of this project is to highlight the design, modeling and explore the
theories and techniques behind procedures of manufacturing a rack and pinion steering system for Hybrid vehicle
car. This newly manufactured mechanism will be used in 2018 ISIE EVENT. Various systems were studied but
very effective rack and pinion steering system was manufactured with the consideration of the driver.The normal
standard steering systems available in the market are in ratio 16:1 which means for complete turn of vehicle the
steering wheel must be rotated 4 times, a power steering overcomes the problem of rotation and does the full turn
in 2 revolutions of steering wheel. Hence a need arise to manufacture a steering system that could take a full turn
in half rotation of steering wheel, this was accomplished by using a rack and pinion steering system with low
steering ratio to 12:1. The mechanism is designed with a view to keep the steering ratio low as possible so the
various tentative events like auto cross can be easily be faced. The mechanism has been, analyzed, manufactured,
tested and installed successfully.
Key words: steering mechanism, Hybrid car, universal joints, design, rack and pinion
1. INTRODUCTION with the vertical plane also influences steering
The most conventional steering arrangement is to turn dynamics as do the tires.
the front wheels using a hand–operated steering The car steering system is a widely studied
wheel which is positioned in front of the driver, via system by automobile manufacturers and research
the steering column, which may contain universal institutes across the globe. Current research shows that
joints, to allow it to deviate somewhat from a straight the modern vehicle may sport a steering wheel which
line.Other arrangements are sometimes found on will not be physically connected with the car wheel
different types of vehicles, for example, a tiller or through linkages, but the driver will still receive haptic
rear–wheel steering. Trackedvehicles such feedback from a complex array of sensors and control
as bulldozers and tanks usually employ differential system feedback. The steering feel based on a rack and
steering — that is, the tracks are made to move at pinion type steering mechanism is still important
different speeds or even in opposite directions, because most midrange consumer vehicles will
using clutches and brakes, to bring about a change of continue to bear a rack and pinion type steering
course or direction. mechanism.
The basic aim of steering is to ensure that the
wheels are pointing in the desired directions. This is 2. DESIGN OF STEERING SYSTEM:
typically achieved by a series of linkages, rods, pivots
and gears. One of the fundamental concepts is that 2.1 Steering System
of caster angle – each wheel is steered with a pivot A schematic of the steering system is shown in Figure
point ahead of the wheel; this makes the steering tend 2.1. The steering system comprises of a steering wheel
to be self-centring towards the direction of travel. turning a steering column. The steering column is
The steering linkages connecting the steering connected to an intermediate shaft through a universal
box and the wheels usually conform to a variation joint. The universal joint transmits torque to a lower
of Ackermann steering geometry, to account for the shaft through another universal joint. A pinion at the
fact that in a turn, the inner wheel is actually travelling end of the lower shaft mates with the rack and
a path of smaller radius than the outer wheel, so that converts the column rotary motion into translator
the degree of toe suitable for driving in a straight path motion of the rack.
is not suitable for turns. The angle the wheels make For modelling purposes, the rack can be visualized as
two similar sections on either side of the pinion. A
5
International Journal of Research in Advent Technology, Special Issue, December 2018
International Conference on Mechanical and Civil Engineering (ICOMACE-2018)
E-ISSN: 2321-9637
Available online at www.ijrat.org
ball joint is used to connect the end of the rack to a shown in Figure 2.3 It is commonly used in shafts that
tie rod, which connect to a knuckle through another transmit rotary motion. It consists of a pair of hinges
revolute joint. The kingpin axis is aligned with the located close together, oriented at 90° to each other,
global Z axis. The knuckle carries the road wheel connected by a cross shaft.
which turns due to the translator motion of the rack.
This complete system had been divided into three
subcomponents for analysis, namely the universal
joint, the rack & pinion assembly and the tie rod &
knuckle assembly.
Figure 2.3 Universal Joint
Relation between different parameters for a Universal
joint as shown in figure have been stated in and are as
follows:
Fig.2.1 steering system
2.2 Rack And Pinion Type Steering System
The rack and pinion steering gear has become
increasingly popular for today’s small cars. It is
simpler, more direct acting, and may be straight
mechanical or power assisted in operation. Figure 2.2
shows the schematic of a rack and pinion steering
system. As the steering wheel and the shaft are turned,
the rack moves from one side to another. This pushes
or pulls on the tie rods, forcing the knuckle to pivot
about the kingpin axis. This turns the wheel to one
side or the other so that the car is steered. The steering
gear and the tie rod are visible in the figure.
The universal joint is at the upper end of the steering
shaft and the flexible coupling at the lower end. In
small cars, rack and pinion steering is quick and easy.
It provides the maximum amount of road feel as the
tires meet irregularities in the road. Where;
θ= angle of the driving shaft
∅= angle of the driven shaft
β= angle between the shaft axis
ω1=angular velocity of the driving shaft
ω2 = angular velocity of the driven shaft
α2 = angular acceleration of the driven shaft
2.4 Tie Rod And The Knuckle
The tie rod is part of the steering mechanism in a
vehicle. A tie rod is a slender structural rod that is
used as a tie and is capable of carrying tensile loads
Fig 2.2 only as shown in Figure 2.4. It is a rod with a "ball and
schematic of socket" at one end that is connected to the steering
rack & arm or the knuckle. The other end is connected to the
pinion rack. When the steering wheel moves, causing the rack
to move, the ball and socket allows the wheel to turn.
Stud swing from side to side allows the tie rod to
2.3 Universal Joint: function as the vehicle moves up and down. When two
A universal joint, U joint, Cardan joint, tie rods are used, their length are kept adjustable,
Hardy-Spicer joint, or Hooke's joint is a joint in a rigid allowing the wheels to be aligned. Proper tie rod
rod that allows the rod to 'bend' in any direction, as function is important, as excessive movement can
6
International Journal of Research in Advent Technology, Special Issue, December 2018
International Conference on Mechanical and Civil Engineering (ICOMACE-2018)
E-ISSN: 2321-9637
Available online at www.ijrat.org
contribute to toe change, which can affect tire wear Cot Φ – Cot θ= Φ = outer wheel angle
and car stability. The knuckle is mounted about the
θ = inner wheel angle
kingpin axis. It is mounted between the shockers and
b = track width
the stub axel. The car wheel is installed on the knuckle
L = wheelbase
and as it turns about the kingpin axis it turn the
α = Ackermann angle
vehicle.
In Figure 2.4 axis is at the point O along the
Z-axis which is perpendicular to the XY plane.
The intention of Ackermann geometry is to prevent
the tyres from slipping outwards when the wheels
follow around a curve while taking a turn. The
solution for this is that all wheels to have their axles
settled as radii of circles with a common Centre point.
Since the rear wheels are fixed, this Centre point must
lie on a line extended from the rear axle. So we need
to intersect the front axle to this line at the common
Fig 2.4 Tie Rod and Ball Joint Centre point. While steering, the inner wheel angle is
greater than outer wheel angle. So for obtaining
different results we need to vary the parameters in
Where order to obtain desired steering geometry.
= lateral rack displacement
= lateral distance between the pinion and the king
pin axis
= lateral distance between rack and the king pin
axis
d = longitudinal distance between the rack
and kingpin axis
= length of the tie rod
= length of the knuckle arm
= acute angle made by the tie rod
= acute angle made by the knuckle arm
3. FABRICATION OF ACKERMAN
STEERING
Ackerman steering is used to change the dynamic toe
setting, by increasing front wheel toe out as the car is
turned into the corner. The typical steering system, in
a road or race car, has tie-rod linkages and steering
arms that form an approximate parallelogram, which
skews to one side as the wheels turn. If the steering
arms are parallel, then both wheels are steered to the
same angle. The Ackermann steering geometry takes
its name from a London agent that patented the design Fig 3.3 Steering rod
in 1816. The geometry allows the outer front wheel to
cover a larger radius than the inside wheel. As a result 4. EXPERIMENTATION
both wheels will follow individual radii without 4.1 Working Principle:
skidding or scrubbing as the vehicle corners. To achieve true rolling for a four wheeled
vehicle moving on a curved track, the lines drawn
According to Ackermann Steering geometry, through each of the four wheel axes must intersect at
the outer wheels moves faster than the inner wheels, the instantaneous centre. The actual position the
therefore, the equation for correct steering is: instantaneous centre constantly changes due to the
alternation of the front wheel angular positions to
7
International Journal of Research in Advent Technology, Special Issue, December 2018
International Conference on Mechanical and Civil Engineering (ICOMACE-2018)
E-ISSN: 2321-9637
Available online at www.ijrat.org
correct the steered vehicle’s path. Since both rear R = L/sinθ
wheels are fixed on the same axis but the front wheel = 64.5/sin〖(38.44)〗
axles are independent of each other, the instantaneous = 2635mm
centres lies somewhere along an imaginary extended
line drawn through the axis of the rear axle. 4.2.4 Steering wheel diameter:
The Ackermann principle is based on the two front [3*(3.14)*R]/rack travel lock to lock = 12:1
steered wheels being pivoted at the ends of an axle- R=5.41 inches
beam. The original Ackermann linkage has parallel set
track-rod-arms, so that both steered wheels swivel at Diameter =10.82 inches
equal angles. Consequently, the intersecting projection
lines do not meet at one point. If both front wheels are Where:
free to follow their own natural paths, they would θo = turn angle of the wheel on the outside of the turn
converge and eventually cross each other. Since the θi = turn angle of the wheel on the inside of the turn
vehicle moves along a single mean path, both wheel B= track width
tracks conflict continuously with each other causing L = wheel base
tyre slip and tread scrub. Subsequent modified linkage b = distance from rear axle to centre of mass
uses inclined track-rod arms so that the inner wheel R=√ (R12+B2)
swivels about its king-pin slightly more than the outer R12=R2+B2
wheel. Hence the lines drawn through the stub-axles R1=√ (R2+B2)
converge at a single point somewhere along the rear- R=4.5
axle projection B=1.55
4.2 Calculations: R1=4.43m
In the figure below it is shown that the R1=B/tan θi +L/2
total length of the vehicle from the centre of the front R1=1.55/tan θi +1.195/2
wheel to centre of the rear wheel is called Wheel Base Ɵ1 = 22.02
(b). Similarly, the total length between centreof the Through the calculations we can find out that for a
front left wheel to centre of front right wheel is called turn of maximum radius 4.5 m the steer angle for the
Wheel Track (t). The distance between the two pivot inner tire is 22.02 degrees and the outer tire is 17.13
joints of steering system is called Kingpin Centre to degrees.
Centre distance (k). The calculation of Ackermann 5. RESULTS AND DISCUSSIONS
angle is shown below: 1) The Fabrication of Ackerman Steering
4.2.1 Ackerman angle: system for ISIE was successfully done.
Tan (Ackermann angle)= kingpin to kingpin 2) The ratio of Ackerman Steering has been
distance/2*wheel base calculated as 16:1.
Ackerman angle = tan inverse of (kingpin to kingpin 3) Ackerman steering geometry can achieve
distance/2*wheel base) less Gear ratio when compared to Modern
=tan inverse of(41.82/2*64.5) Steering Geometry.
Ackermann angle (alpha) = 17.971°
4.2.2Ackermann percentage calculation: 6. CONCLUSIONS
We have steering ratio as 12:1 1. After all the calculations were completed and
Steering lock condition 1.5 turns i.e. 540° the final steering assembly was designed in
So angle turned by the wheel tire is = Solid works.
12/1=540/X 2. This steering system designed for the turns
So,X=45° which is considered as the angle generally encountered in the ISIE events was
made by inner wheel while making a turn. optimal to counter negative impacts of bump
We know that for a perfect steering condition, and roll steer and also possessed self-
Cot (Y)-cot (X)=w/l returning capability. Universal joints have
Where,Y=angle made by outer wheel been added in the steering column to line it
X=angle made by the inner wheel up nicely with the pinion shaft.
From this we have both w=41.82, l=64.5 3. An innovative feature of this steering linkage
From this we obtain the angle made by the outer design and its ability to drive all four (or two)
wheel as Y=31.24° wheels using a single steering actuator. Its
successful implementation will allow for the
development of a four-wheel, steered power.
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International Journal of Research in Advent Technology, Special Issue, December 2018
International Conference on Mechanical and Civil Engineering (ICOMACE-2018)
E-ISSN: 2321-9637
Available online at www.ijrat.org
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