Design Evaluation of a Two-Wheeler Suspension System for Variable Load Conditions

1 International Journal for Modern Trends in Science and Technology
Design Evaluation of a Two-Wheeler Suspension
System for Variable Load Conditions
S. Vidhyathar, M.E.,
Assistant Professor, Mechanical Department, Sri Sunflower college of Engineering and technology, Lankapalli, Andhra
Pradesh, India.
To Cite this Article
S. Vidhyathar, “Design Evaluation of a Two-Wheeler Suspension System for Variable Load Conditions”, International
Journal for Modern Trends in Science and Technology, Vol. 05, Issue 03, March 2019, pp.-01-08.
Article Info
Received on 11-Feb-2019, Revised on 06-March-2019, Accepted on 16-March-2019.
A suspension system or shock absorber is a mechanical device designed to smooth out or damp shock
impulse, and dissipate kinetic energy. The shock absorbers duty is to absorb or dissipate energy. In a
vehicle, it reduces the effect of travelling over rough ground, leading to improved ride quality, and increase in
comfort due to substantially reduced amplitude of disturbances. The design of spring in suspension system
is very important. In this project a shock absorber is designed and a 3D model is created using CATIA V5. The
model is also changed by changing the thickness of the spring. Structural analysis and modal analysis are
done on the shock absorber by varying material for spring, Spring Steel and Beryllium Copper. The analysis
is done by considering loads, bike weight, single person and 2 persons. Structural analysis is done to
validate the strength and modal analysis is done to determine the displacements for different frequencies for
number of modes. Comparison is done for two materials to verify best material for spring in Shock absorber.
KEYWORDS: Introduction, applications, Types of Shock Absorber, Introduction to Catia V5,Introduction to
Ansys, Generic Steps to Solving any Problem in ANSYS, Preparing the analysis part.
Copyright © 2019 International Journal for Modern Trends in Science and Technology
All rights reserved.
I. INTRODUCTION
A shock absorber or damper is a mechanical
device designed to smooth out or damp shock
impulse, and dissipate kinetic energy.
Description
Pneumatic and hydraulic shock absorbers
commonly take the form of a cylinder with a sliding
piston inside. The cylinder is filled with a fluid
(such as hydraulic fluid) or air. This fluid-filled
piston/cylinder combination is a dashpot. the
dissipated energy can be stored and used later. In
general terms, shock absorbers help cushion cars
on uneven roads.
II. APPLICATIONS
Shock absorbers are an important part of
automobile and motorcycle suspensions, aircraft
landing gear, and the supports for many industrial
machines. Large shock absorbers have also been
used in structural engineering to reduce the
susceptibility of structures to earthquake damage
and resonance. A transverse mounted shock
absorber, called a yaw damper, helps keep railcars
from swaying excessively from side to side and are
important in passenger railroads, commuter rail
and rapid transit systems because they prevent
railcars from damaging station platforms. The
success of passive damping technologies in
ABSTRACT
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International Journal for Modern Trends in Science and Technology
ISSN: 2455-3778 :: Volume: 05, Issue No: 03, March 2019

S. Vidhyathar : Design Evaluation of a Two-Wheeler Suspension System for Variable Load Conditions
suppressing vibration amplitudes could be
ascertained with the fact that it has a market size
of around $ 4.5 billion.
FIG.1: REAR SHOCK ABSORBER AND SPRING OF
A BMW R75/5 MOTORCYCLE
Vehicle suspension
In a vehicle, it reduces the effect of traveling over
rough ground, leading to improved ride quality,
and increase in comfort due to substantially
reduced amplitude of disturbances. Without shock
absorbers, the vehicle would have a bouncing ride,
as energy is stored in the spring and then released
to the vehicle, possibly exceeding the allowed range
of suspension movement. Control of excessive
suspension movement without shock absorption
requires stiffer (higher rate) springs, which would
in turn give a harsh ride. Shock absorbers allow
the use of soft (lower rate) springs while controlling
the rate of suspension movement in response to
bumps.
They also, along with hysteresis in the tire itself,
damp the motion of the un sprung weight up and
down on the springiness of the tire. Since the tire is
not as soft as the springs, effective wheel bounce
damping may require stiffer shocks than would be
ideal for the vehicle motion alone. Spring-based
shock absorbers commonly use coil springs or leaf
springs, though torsion bars can be used in
torsional shocks as well. Ideal springs alone,
however, are not shock absorbers as springs only
store and do not dissipate or absorb energy.
Vehicles typically employ springs or torsion bars as
well as hydraulic shock absorbers. In this
combination, "shock absorber" is reserved
specifically for the hydraulic piston that absorbs
and dissipates vibration.
Structures
Applied to a structure such as a building or
bridge it may be part of a seismic retrofit or as part
of new, earthquake resistant construction. In this
application it allows yet restrains motion and
absorbs resonant energy, which can cause
excessive motion and eventual structural failure.
III. TYPES OF SHOCK ABSORBER
There are a number of different methods of
converting an impact /collision into relatively
smooth cushioned contact.
 Metal Spring
 Rubber Buffer Hydraulic Dashpot
 Collapsing safety Shock Absorbers
 Pneumatic Cylinders
 Self-compensating Hydraulic
Metal springs
Simply locating metal springs to absorb the
impact loads are a low cost method of reducing the
collision speed and reducing the shock loading.
They are able to operate in very arduous conditions
under a wide range of temperatures. These devices
have high stopping forces at end of stroke. Metal
springs store energy rather than dissipating it. If
metal sprint type shock absorbers are used then
measures should be provided to limit Oscillations.
Metal springs are often used with viscous dampers.
There are a number of different types of metal
springs including helical springs, bevel
washers(cone-springs), leaf springs, ring springs,
mesh springs etc. Each spring type has its own
operating characteristics.
A spring is an elastic object that stores
mechanical energy. Springs are typically made of
spring steel. There are many spring designs. In
everyday use, the term often refers to coil springs.
When a conventional spring, without stiffness
variability features, is compressed or stretched
from its resting position, it exerts an opposing force
approximately proportional to its change in length
(this approximation breaks down for larger
deflections). The rate or spring constant of a
spring is the change in the force it exerts, divided
by the change in deflection of the spring. That is, it
is the gradient of the force versus deflection curve.
An extension or compression spring's rate is
expressed in units of force divided by distance, for
example or N/m or lbf/in. A torsion spring is a
spring that works by twisting; when it is twisted
about its axis by an angle, it produces a
torque proportional to the angle. A torsion spring's
rate is in units of torque divided by angle, such as
N-m/rad or ft-lbf/degree. The inverse of spring rate
is compliance, that is: if a spring has a rate of 10
N/mm, it has a compliance of 0.1 mm/N. The

stiffness (or rate) of springs in parallel is additive,
as is the compliance of springs in series.
Elastomatic shock absorbers
These are low cost options for reducing the
collision speed and reducing the shock loading and
providing system damping. They are conveniently
moulded to suitable shapes. These devices have
high stopping forces at end of stroke with
significant internal damping. Elastomeric dampers
are very widely used because of the associated
advantages of low cost and mouldability together
with performance benefits. The inherent damping
of elastomers is useful in preventing excessive
vibration amplitude at resonance – much reduced
compared to metal springs. However elastomeric
based shock absorbers are limited in being affected
by high and low temperatures. And are subject to
chemical attack. Silicone rubber is able to provide
reasonable mechanical properties between
temperatures of -50O to +180O deg. C- most other
elastomer has inferior temperature tolerance.
A shock absorber (in reality, a shock "damper")
is a mechanical or hydraulic device designed to
absorb and damp shock impulses. It does this by
converting the kinetic energy of the shock into
another form of energy (typically heat) which is
then dissipated. Most shock absorbers are a form
of dashpot (a damper which resists motion via
viscous frict
Hydraulic dashpot
This type of shock absorber is based on a simple
hydraulic cylinder. As the piston rod is moved
hydraulic fluid is forced through an orifice which
restricts flow and consequently provides a
controlled resistance to movement of the piston
rod. With only one metering orifice the moving load
is abruptly slowed down at the start of the stroke.
The braking force rises to a very high peak at the
start of the stroke and then falls away rapidly. On
completion of the stroke the system is stable - the
energy being dissipated in the hydraulic fluid as
heat. This type of shock absorbers are provided
with Springs sufficient to return the actuator to its
initial position after the impacting load is removed.
Collapsing safety Shock absorbers
These are single use units which are generally
specially designed for specific duties. They are
designed such that at impact they collapse and the
impact energy is absorbed as the materials distort
in their inelastic/yield range. They therefore are
more compact compared to devices based on
deflections within their elastic range.
Air spring
These devices use air as the resilient medium. Air
has a high energy storage capacity compared to
metal or elastomer materials. For duties with high
loads and deflections the air spring is generally far
more compact that the equivalent metal or
elastomer device. Due to the compressibility of air
these have a sharply rising force characteristic
towards the end of the stroke. The majority of the
energy is absorbed near the end of the stroke. The
force on an air cylinder buffer is determined by the
relation PVn=constant. Air springs require more
maintenance than meal or elastomer based springs
and the temperature range is restricted compared
to metal springs.
Air spring is a type of vehicle
suspension powered by an electric or
engine-driven air pump or compressor. This
compressor pumps the air into a flexible bellows,
usually made from textile-reinforced rubber. The
air pressure inflates the bellows, and raises the
chassis from the axle.
Self compensating hydraulic
These devices are similar to the hydraulic
dashpot type except that a number of orifices are
provided allowing different degrees of restriction
throughout the stroke. These devices are
engineered to bring the moving load is smoothly
and gently to rest by a constant resisting force
throughout the entire shock absorber stroke. The
load is decelerated with the lowest possible force in
the shortest possible time eliminating damaging
force peaks and shock damage to machines and
equipment. These type of shock absorbers are
provided with springs sufficient to return the
actuator to its initial position after the impacting
load is removed.
A hydraulic positioner for seats includes a
cylinder and piston structure with a piston rod
secured to the piston and extending from the
cylinder. A reservoir is provided in the cylinder by a
gland jointly biased by a first spring located within
the cylinder and a second spring which also urges
the piston rod to an extended position. A sleeve is
movable by the gland for visual indication of the
hydraulic fluid in the cylinder.
Design Calculation For Helical Coil Spring Of
The Shock Absorber
Material: Spring Steel (modulus of rigidity)
G= 4100N/mm2
Mean diameter of a coil, D=62mm
Diameter of wire, d = 8mm
Total no of coils, n1= 18

Height, h = 220mm
Outer diameter of spring coil, D0 = D +d=70mm
No of active turns, n= 14
Weight of bike = 125 Kgs
Wight of 1person = 75Kgs
Weight of 2 persons
= 75×2=150Kgs
Weight of bike + persons = 275 Kgs
Rear Suspension = 65% 65% of 275
Considering dynamic loads it will be double
W= 330Kgs = 3234N
For single shock absorber weight = w/2= 1617N
= W
We Know that, compression of spring (δ ) = WD3n
G.d4
C = spring index = D/d = 62/8=7.75=8
( δ ) = 282.698
Solid length, Ls =n1×d=18x8=144
Free length of spring,
Lf = solid length + maximum compression +
clearance between adjustable
coils=144+282.698+0.15x282.698=469.102
Spring rate, K = W =5.179
Pitch of coil, P = Lf – Ls + d n1=26
Stresses in helical spring: maximum shear
stress induced in the wireτ = Ks × 8WD 𝜋.d3 Ks
Buckling of compression springs =499.519
Spring rate or Stiffness of spring kB=7.5
Values of Buckling Factor(for hinged and spring)
K=0.05
The buckling factor for the hinged end and built-in
end springWcr =1.719x0.05x469.102
=134.139 N
IV. INTRODUCTION TO CAD
Throughout the history of our industrial society,
many inventions have been patented and Whole
new technologies have evolved. Perhaps the single
development that has impacted Manufacturing
more quickly and significantly than any previous
technology is the digital computer. Computers are
being used increasingly for both design and
detailing of engineering components in the drawing
office. Computer-aided design (CAD) is defined as
the application of computers and graphics
Software to aid or enhance the product design from
conceptualization to documentation. CAD is most
commonly associated with the use of an interactive
computer graphics system, referred to as a CAD
system. Computer-aided design systems are
powerful tools and in the Mechanical design and
geometric modeling of products and components.
There are several good reasons for using a CAD
system to support the engineering design
function:
o To increase the productivity
o To improve the quality of the design
o To uniform design standards
o To create a manufacturing data base
o To eliminate inaccuracies caused by
hand-copying of drawings and
inconsistency between
o Drawings
CAD/CAM Software
Software allows the human user to turn a
hardware configuration into a powerful design and
Manufacturing system. CAD/CAM software falls
into two broad categories, 2D and 3D,Based on the
number of dimensions are called 2-D
representations of 3-D objects is inherently
confusing. Equally problem has been the inability
of manufacturing personnel to properly read and
interpret complicated 2-D representations of
objects. 3-D software permits the parts to be
viewed with the 3-D planes-height, width, and
depth-visible. The trend in CAD/CAM is toward3-D
representation of graphic images. Such
representation approximate the actual shape and
appearance of the object to be produced; therefore,
they are easier to read and understand.
Applications of CAD/CAM
The emergence of CAD/CAM has had a major
impact on manufacturing, by standardizing
product development and by reducing design
effort, tryout, and prototype work; it has made
possible significantly reduced costs and improved
productivity. AutoCAD is a computer-aided
drafting and design system implemented on a
personal computer. It supports a large number of
devices. Device drivers come with the system and
include most of the digitizers, printer/plotters,
video display boards, and plotters available on the
market.
AutoCAD supports 2-D drafting and 3-D
wire-frame models. The system is designed as a
single-user CAD package. The drawing elements
are lines, poly lines of any width, arcs, circles,
faces, and solids. There are many ways to define a
drawing element. For example, a circle can be
defined by center and its radius, three points, and
two end points of its diameter. The system always
prompts the user for all options.

Of course, the prompt can be turned off by
advanced users. Annotation and dimensioning are
also supported. Text and dimension symbols can
be placed on anywhere on the drawing, at any
angle, and at any size.
V. INTRODUCTION TO CATIA V5
CATIA (Computer Aided Three-dimensional
Interactive Application) is a multi-platform
CAD/CAM/CAE commercial software suite
developed by the French company Dassault
Systems. Written in the C++ programming
language, CATIA is the cornerstone of the Dassault
Systems product lifecycle management software
suite.
Commonly referred to as a 3D Product Lifecycle
Management software suite, CATIA supports
multiple stages of product development, including
conceptualization, design (CAD), manufacturing
(CAM), and engineering (CAE). CATIA facilitates
collaborative engineering across disciplines,
including surfacing & shape design, mechanical
engineering, and equipment and systems
engineering. CATIA provides a suite of surfacing,
reverse engineering, and visualization solutions to
create, modify, and validate complex innovative
shapes, from subdivision, styling, and Class A
surfaces to mechanical functional surfaces.
CATIA enables the creation of 3D parts, from 3D
sketches, sheet metal, composites, molded, forged
or tooling parts up to the definition of mechanical
assemblies. It provides tools to complete product
definition, including functional tolerances as well
as kinematics definition. CATIA facilitates the
design of electronic, electrical, and distributed
systems such as fluid and HVAC systems, all the
way to the production of documentation for
manufacturing.
Industries
CATIA can be applied to a wide variety of
industries, from aerospace and defense,
automotive, and industrial equipment, to high
tech, shipbuilding, consumer goods, plant design,
consumer packaged goods, life sciences,
architecture and construction, process power and
petroleum, and services. CATIA V4, CATIA V5,
Pro/ENGINEER, NX (formerly Unigraphics), and
SolidWorks are the dominant systems.
Aerospace
The Boeing Company used CATIA V4 to develop its
777 airlines and used CATIA V5 for the 787 series
aircraft. They have employed the full range of
Dassault Systems 3D PLM products – CATIA,
DELMIA, and ENOVIA LCA – supplemented by
Boeing-developed applications.
 The development of the Indian Light Combat
Aircraft has used CATIA V5.
 European aerospace Airbus has used CATIA
since 2001.
 The Anglo/Italian Helicopter Company
AgustaWestland uses CATIA V4 and V5 to
design their full range of aircraft.

VI. INTRODUCTION TO ANSYS
ANSYS is general-purpose finite element analysis
(FEA) software package. Finite Element Analysis is
a numerical method of deconstructing a complex
system into very small pieces (of user-designated
size) called elements. The software implements
equations that govern the behaviour of these
elements and solves them all; creating a
comprehensive explanation of how the system acts
as a whole. These results then can be presented in
tabulated, or graphical forms. This type of analysis
is typically used for the design and optimization of
a system far too complex to analyse by
hand. Systems that may fit into this category are
too complex due to their geometry, scale, or
governing equations.
With virtual prototyping techniques, users can
iterate various scenarios to optimize the product
long before the manufacturing is started. This
enables a reduction in the level of risk, and in the
cost of ineffective designs. The multifaceted nature
of ANSYS also provides a means to ensure that
users are able to see the effect of a design on the
whole behavior of the product, be it
electromagnetic, thermal, mechanical etc.
Generic Steps to Solving any Problem in ANSYS
Like solving any problem analytically, you need
to define (1) your solution domain, (2) the physical
model, (3) boundary conditions and (4) the physical
properties. You then solve the problem and present
the results. In numerical methods, the main
difference is an extra step called mesh generation.
This is the step that divides the complex model into
small elements that become solvable in an
otherwise too complex situation. Below describe
the processes in terminology slightly more attune
to the software.
Build Geometry
Construct a two or three-dimensional
representation of the object to be modeled and
tested using the work plane coordinate system
within ANSYS.
Define Material Properties
Now that the part exists, define a library of the
necessary materials that compose the object (or
project) being modeled. This includes thermal and
mechanical properties.
Generate Mesh
At this point ANSYS understands the makeup of
the part. Now define how the modeled system
should be broken down into finite pieces.
Apply Loads
Once the system is fully designed, the last task is
to burden the system with constraints, such as
physical loadings or boundary conditions.
Obtain Solution
This is actually a step, because ANSYS needs to
understand within what state (steady state,
transient… etc.) the problem must be solved.
Present the Results
After the solution has been obtained, there are
many ways to present ANSYS’ results, choose from
many options such as tables, graphs, and contour
plots.
Specific Capabilities of ANSYS
Structural
Structural analysis is probably the most
common application of the finite element method
as it implies bridges and buildings, naval,

aeronautical, and mechanical structures such as
ship hulls, aircraft bodies, and machine housings,
as well as mechanical components such as pistons,
machine parts, and tools.
Buckling Analysis – Used to calculate the buckling
loads and determine the buckling mode shape.
Both linear (eigenvalue) buckling and nonlinear
buckling analyses are possible.In addition to the
above analysis types, several special-purpose
features are available such as Fracture
mechanics, Composite material analysis,
Fatigue, and both p-Method and Beam analyses.
Modal Analysis - A modal analysis is typically
used to determine the vibration characteristics
(natural frequencies and mode shapes) of a
structure or a machine component while it is being
designed. It can also serve as a starting point for
another, more detailed, dynamic analysis, such as
a harmonic response or full transient dynamic
analysis. Modal analyses, while being one of the
most basic dynamic analysis types available in
ANSYS, can also be more computationally time
consuming than a typical static analysis. A
reduced solver, utilizing automatically or manually
selected master degrees of freedom is used to
drastically reduce the problem size and solution
time.
Harmonic Analysis- Used extensively by
companies who produce rotating machinery,
ANSYS Harmonic analysis is used to predict the
sustained dynamic behavior of structures to
consistent cyclic loading. Examples of rotating
machines which produced or are subjected to
harmonic loading are:
 Turbines
o Gas Turbines for Aircraft and Power
Generation
o Steam Turbines
o Wind Turbine
o Water Turbines
o Turbopump
 Internal Combustion engines
 Electric motors and generators
 Gas and fluid pumps
 Disc drives
A harmonic analysis can be used to verify
whether or not a machine design will successfully
overcome resonance, fatigue, and other harmful
effects of forced vibrations..
Fluid Flow
The ANSYS/FLOTRAN CFD (Computational
Fluid Dynamics) offers comprehensive tools for
analyzing two-dimensional and three-dimensional
fluid flow fields. ANSYS is capable of modeling a
vast range of analysis types such as: airfoils for
pressure analysis of airplane wings (lift and drag),
flow in supersonic nozzles, and complex,
three-dimensional flow patterns in a pipe bend. In
addition, ANSYS/FLOTRAN could be used to
perform tasks including:
 Calculating the gas pressure and temperature
distributions in an engine exhaust manifold
 Studying the thermal stratification and
breakup in piping systems
 Using flow mixing studies to evaluate potential
for thermal shock
 Doing natural convection analyses to evaluate
the thermal performance of chips in electronic
enclosures
 Conducting heat exchanger studies involving
different fluids separated by solid regions
Preparing the analysis part
VII. CONCLUSION
In our project we have designed a shock absorber
used in a 150cc bike. We have modeled the shock
absorber by using 3D parametric software
Pro/Engineer. To validate the strength of our
design, we have done structural analysis and
modal analysis on the shock absorber. We have
done analysis by varying spring material Spring
Steel and Beryllium Copper. By observing the

analysis results, the analyzed stress values are less
than their respective yield stress values. So our
design is safe. By comparing the results for both
materials, the stress value is less for Spring Steel
than Beryllium Copper. Also the shock absorber
design is modified by reducing the diameter of
spring by 2mm and structural, modal analysis is
done on the shock absorber. By reducing the
diameter, the weight of the spring reduces. By
comparing the results for both materials, the stress
value is less for Spring Steel than Beryllium
Copper. By comparing the results for present
design and modified design, the stress and
displacement values are less for modified design.
So we can conclude that as per our analysis using
material Spring steel for spring is best and also our
modified design is safe.
REFERENCES
[1] Pinjarla.Poormohan and Lakshmana Kishore T,
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pp.578-592, December 2012
[2] Kommalapati. Rameshbabu, TippaBhimasankar Rao,
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system for variable load conditions” International
Journal of Computational Engineering Research, Vol
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[3] Gajendra Singh Rathore and Upendra Kumar Joshi,
“Fatigue Stress analysis of helical Compression
Spring: A Review”, International Journal of Emerging
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2013
[4] B. Pyttel, I. Brunner, B. Kaiser, C. Berger, M.
Mahendran, “Fatigue behaviour of helical
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[6] Mehdi Bakhshesh and Majid Bakhshesh.,
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[7] B. Kaiser , B. Pyttel, C. Berger, “VHCF-behavior of
helical compression springs made of different
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[8] YuujiShimatani, Kazuaki Shiozawa, TakehiroNakada
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