implementation in leaf spring suspension system for 2 wheeler

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CHAPTER   1
    INTRODUCTION
Suspension systems have been widely applied to vehicles, from the horse-drawn carriage with flexible leaf springs fixed in the four corners, to the modern automobile with complex control algorithms. The suspension of a road vehicle is usually designed with two objectives; to isolate the vehicle body from road irregularities and to maintain contact of the wheels with the roadway. Isolation is achieved by the use of springs and dampers and by rubber mountings at the connections of the individual suspension components. From a system design point of view, there are two main categories of disturbances on a vehicle, namely road and load disturbances. Road disturbances have the characteristics of large magnitude in low frequency such as hills and small magnitude in high frequency such as road roughness. Load disturbances include the variation of loads induced by accelerating, braking and cornering.
Therefore, suspension design is an art of compromise between these two goals (Wang 2001).Today, nearly all passenger cars and light trucks use independent front suspensions, because of the better resistance to vibrations. The main functions of a vehicle’s suspension systems are to isolate the structure and the occupants from shocks and vibrations generated by theroad surface. The suspension systems basically consist of all the elements that provide the connection between the tires and the vehicle body.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. 
For the suspension of carry-load vehicles many types of arrangements may be used depending on the type of the vehicle and the occurring operating loads. One advantageous type of suspension systems is the leaf-springs system, which needs less additional components than other suspension systems, thereby leading to lighter and lower-cost structures. Additionally, the leaf-spring’s performance determines both the suspension and the guidance of the vehicle due to the fact that the leaf-spring is connected with both the axle and the steering system.
The Leaf springs are mainly used in suspension systems to absorb shock loads in automobiles like light motor vehicles, heavy duty trucks and in rail systems. They carry lateral loads, brake torque, driving torque in addition to shock absorbing. Leaf springs are having an advantage that the ends of the spring may be guided along a definite path as it deflects. The use of composite materials for suspension leaf spring reduces the weight of conventional multi leaf steel leaf spring by nearly 75%.This achieves the vehicle with more fuel efficiency and improved riding qualities. For more compliant suspension system (i.e. energy storage capability), the leaf spring should absorb the vertical vibrations and impacts due to road irregularities by means of variations in the spring deflection so that the potential Energy is stored in spring as strain energy and then released slowly.

 In the present work comparative study is been carried out to understand the working principle of multi-leaf steel spring used in passenger cars. The multi-leaf steel spring is replaced with a composite single leaf spring made of E glass/ epoxy and Jute-Glass fiber composite. The stresses for both steel leaf spring and composite leaf springs are considered for the study. The primary objective is to compare their load carrying capacity, stiffness and weight savings of composite leaf spring. Finally, Natural frequencies and fatigue life of Natural Faber reinforced composite leaf spring is also predicted using life data.
CHAPTER 2
LITERATURE SURVEY

1. V.K. Aheret. al. “Fatigue Life Prediction of Multi Leaf Spring used in the Suspension System of Light Commercial Vehicle”, International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME), 2012.
2. Ravi Kumar V. et. al. “Analysis of Natural Fibre Composite Leaf Spring”, International Journal of Latest Trends in Engineering and Technology (IJL2TET) September 2013
The aim of present work is to compare the Glass-Fiber-Reinforced - Composite (GFRC) leaf spring with a Natural-Fiber-Reinforced Composite/Jute-Fiber – Reinforced – Composite (NFRC/JFRC) leaf spring. Fabrication is carried by hand lay-up technique and tested. The present work
3. T.N.V. Ashok Kumar at. al. “Design and Material Optimization of Heavy Vehicle Leaf Spring”, International Journal of Research in Mechanical Engineering & Technology, Nov 2013 - April 2014
The paper describes static and dynamic analysis of steel leaf spring and laminated composite Multi leaf spring. The objective is to compare displacement, frequencies, deflections and weight savings of composite leaf spring with that of steel leaf spring. Static and Dynamic Analysis of 3-D model of conventional leaf spring is performed using ANSYS 10.0. Same dimensions are used in composite multi leaf spring using S2 Glass/Epoxy and Kevlar/Epoxy unidirectional laminates. Analysis is done by layer stacking method for composites by changing reinforcement angles for 3 layers, 5 layers and 11 layers. The weight of composite leaf spring is compared with that of steel leaf spring. The design constraints are stresses and deflection. A weight reduction of 27.5 % is achieved by using composite leaf spring.
CHAPTER  3
SUSPENSION SYSTEM
3.1. Suspension System:
                             An early form of suspension on ox-drawn carts had the platform swing on iron chains attached to the wheeled frame of the carriage. This system remained the basis for all suspension systems until the turn of the 19th century, although the iron chains were replaced with the use of leather straps by the 17th century. No modern automobiles use the 'strap suspension' system.
Automobiles were initially developed as self-propelled versions of horse-drawn vehicles. However, horse-drawn vehicles had been designed for relatively slow speeds, and their suspension was not well suited to the higher speeds permitted by the internal combustion engine. The first workable spring-suspension required advanced metallurgical knowledge and skill, and only became possible with the advent of industrialization. Obadiah Elliott registered the first patent for a spring-suspension vehicle; - each wheel had two durable steel leaf springs on each side and the body of the carriage was fixed directly to the springs which were attached to the axles. Within a decade, most British horse carriages were equipped with springs; wooden springs in the case of light one-horse vehicles to avoid taxation, and steel springs in larger vehicles. These were often made of low-carbon steel and usually took the form of multiple layer leaf springs.
Leaf springs have been around since the early Egyptians. Ancient military engineers used leaf springs in the form of bows to power their siege engines, with little success at first. The use of leaf springs in catapults was later refined and made to work years later. Springs were not only made of metal, a sturdy tree branch could be used as a spring, such as with a bow.
 Horse-drawn carriages and the Ford Model T used this system, and it is still used today in larger vehicles, mainly mounted in the rear suspension.This was the first modern suspension system and, along with advances in the construction of roads, heralded the single greatest improvement in road transport until the advent of the automobile. The British steel springs were not well suited for use on America's rough roads of the time, so the Abbot-Downing Company of Concord, New Hampshire re-introduced leather strap suspension, which gave a swinging motion instead of the jolting up and down of a spring suspension.


Figure 3.0 plunger suspension
Henri Fournier on his uniquely damped and race winning 'Mors In 1901 Mors of Paris first fitted an automobile with shock absorbers. With the advantage of a damped suspension system on his 'Mors Machine', Henri Fournier won the prestigious Paris-to-Berlin race on 20 June 1901. Fournier's superior time was 11 hrs 46 min 10 sec, while the best competitor was LéonceGirardot in a Panhard with a time of 12 hrs 15 min 40 sec.
Coil springs first appeared on a production vehicle in 1906 in the Brush
Runabout made by the Brush Motor Company. Today, coil springs are used in most cars.  In 1920, Leyland Motors used torsion bars in a suspension system.In 1922, independent front suspension was pioneered on the Lancia Lambda and became more common in mass market cars from 1932. Today most cars have independent suspension on all four wheels.In 2002, a new passive suspension component was invented by Malcolm C. Smith, the inerter. This has the ability to increase the effective inertia of a wheel suspension using a geared flywheel, but without adding significant mass. It was initially employed in Formula 1 in secrecy but has since spread to other motorsport.





Figure 3.1 Shock absorber
          In addition, this suspension design uses single (mono) shock absorber bigger in size, with a stronger spring fitted on its outside. The monoshock is usually positioned near the center of the bike’s chassis of its ends attaches to the chassis and the other end to the rear swing-arm of the bike which attaches to the rear wheel. As the wheel moves up or down the monoshock absorber is either collapsed or extended further.



Figure3.2 Leaf spring

A leaf spring takes the form of a slender arc-shaped length of spring steel of rectangular cross-section. In the most common configuration, the center of the arc provides location for the axle, while loops formed at either end provide for attaching to the vehicle chassis. For very heavy vehicles, a leaf spring can be made from several leaves stacked on top of each other in several layers, often with progressively shorter leaves. Leaf springs can serve locating and to some extent damping as well as springing functions.
The stresses developed during the tests were compared with thestresses obtained from the FE analysis performed, simulating the test-rig configuration for two levels of developed stresses. As shown in Figure the agreement between calculated and measured stresses is satisfactory. The stress values are normalized by the maximum stress developed under the maximum applied force.

3.1.1. SPECIFICATION OF SPRING:

          The helical spring is designed in this project have the following design specifications:


1

Material

Mild steel

2

Number of coils

11

3

Outer diameter of  spring

55mm

4

Inner diameter of spring

50mm

5

Thickness of spring

5 mm

6

Width of bush

45 mm

7

Slot width

50 mm

8

Length of Slot

160 mm

9

Shaft diameter

58 mm


Table 3.1 Specification of leaf spring 

3.1.2. MANUFACTURING PROCESS:

Leaf spring:

          A leaf spring takes the form of a slender arc-shaped length of spring steel of rectangular cross-section. In the most common configuration, the center of the arc provides location for the axle, while loops formed at either end provide for attaching to the vehicle chassis. For very heavy vehicles, a leaf spring can be made from several leaves stacked on top of each other in several layers, often with progressively shorter leaves. Leaf springs can serve locating and to some extent damping as well as springing functions. While the interleaf friction provides a damping action, it is not well controlled and results in stilton in the motion of the suspension. For this reason, some manufacturers have used mono-leaf springs.


Figure 3.3 manufactured leaf spring



3.2. Shock absorber:
Pneumatic and hydraulic shock absorbers are used in conjunction with cushions and springs. An automobile shock absorber contains spring-loaded check valves and orifices to control the flow of oil through an internal piston.
One design consideration, when designing or choosing a shock absorber, is where that energy will go. In most shock absorbers, energy is converted to heat inside the viscous fluid. In hydraulic cylinders, the hydraulic fluid heats up, while in air cylinders, the hot air is usually exhausted to the atmosphere. In other types of shock absorbers, such as electromagnetic types, the dissipated energy can be stored and used later. In general terms, shock absorbers help cushion vehicles on uneven roads.Now, composite suspension system are used mainly in 2 wheelers and also leaf spring are made up of composite material in 4 wheelers.

Figure 3.4 mono tube and twin tube
Springs that are too hard or too soft cause the suspension to become ineffective because they fail to properly isolate the vehicle from the road. Vehicles that commonly experience suspension loads heavier than normal have heavy or hard springs with a spring rate close to the upper limit for that vehicle's weight. This allows the vehicle to perform properly under a heavy load when control is limited by the inertia of the load. Riding in an empty truck used forcarrying loads can be uncomfortable for passengers because of its high spring.                  However, even though we say they both have heavy springs, the actual spring rates for a 2,000 lb (910 kg) race car and a 10,000 lb (4,500 kg) truck are very different Vehicles with worn out or damaged springs ride lower to the ground which reduces the overall amount of compression available to the suspension and increases the amount of body lean. Performance vehicles can
sometimes have spring rate requirements other than vehicle weight and load


Figure.3.5 Shock Absorber

Figure 3.6 Shock Absorber (Side view)


Shock Absorber types:
Today's automotive suspension systems incorporate cylinder-type shock absorbers, most of which are of the double-acting type that generate damping forces in both the extending and contracting strokes.

·    Monotube shock absorbers

·    Twin-tube shock absorber

Monotube Shock Absorbers

Body mono-tube damper is divided into two chambers: the oil and gas. The piston and rod moves down and creates a balancing force. In the compression process, the oil displaced from the working stroke in the case. When working on a release, simtec controls the fluid flow. The gas in the chamber (most often nitrogen) is compressed and takes the whole hit and only then begins to pass the oil. Balancing power is determined by the shape, size and number of washers on the piston of the shock absorber piston diameter, diameter and gas pressure.

 










Figure.3.7Monotube shock absorber

Twin-tube Shock Absorbers:

As the name implies, shock absorbers of this type consist of two concentric cylinders. The inner cylinder is filled with oil and it also located a piston and rod. As in the single-tube shock absorbers inside the cavity moves the rod with piston, on which are mounted the valves that determine the effort, as rebound and compression. Additional bottom valve directs oil into the outer cylinder (tank) in the compression process, increasing the damping ratio. While working on lights out, the oil returns to the reservoir main chamber through a control valve. 




Figure.3.8.Twin-tube shock absorber
CHAPTER 4
COMPONENTS   AND   DESCRIPTION

4.1.   DAMPING:
Damping is the control of motion or oscillation, as seen with the use of hydraulic gates and valves in a vehicle's shock absorber. This may also vary, intentionally or unintentionally. Like spring rate, the optimal damping for comfort may be less than for control.



Figure.4.1 damping in suspension system


Figure. 4.2 Block diagram of damping
4.2.   LEAF SPRING:

4.2.1. Leaf spring:
Leaf springs also known as flat spring are made out of flat plates. Leaf springs are designed two ways: multi-leaf and mono-leaf. The leaf springs may carry loads, brake torque, driving torque, etc...
Characteristics:
1. Weight reduction,
2. High strength,
3. Corrosiveness,
4. Low specific gravity.


Figure 4.3 leaf spring

4.2.2 Types of leaf spring:
          Based on the number of plates, we have taken a brief look at the two different types of leaf spring out there and how they work.
·        Multi Leaf Springs
·        Mono Leaf Springs

Mono Leaf Springs:

Mono leaf springs are more suited to LCV’s than HGV’s as they are not designed for heavier vehicles. They are designed with a thicker center, gradually thinning out towards the ends, similar in structure to the multi leaf system, but without the added plates.
Once upon a time the single leaf spring system was popular but when they began breaking on heavier vehicles they started to go out of fashion a bit. They can still be seen and used, although not when the vehicle in question requires protection against a heavy load or the weight of the vehicle itself.


Figure.4.4. mono leaf spring
Multi Leaf Springs:
On a multi-leaf spring, the size of the plates gets smaller as you look downwards. The plates are laid lengthwise to layer them, with the longest piece on top manufactured with eyes or hooks to fix the springs in place. Multi leaf springs are recognized as the most common kind of leaf spring for light commercial vehicles and heavy good vehicles. The stacked format means that the springs are thicker in the middle, which is known as a semi elliptical look.



 



                






Figure4.5 Multi leaf spring

4.2.3 Different Leaf Spring Shapes:

·        Semi Elliptical – This is the normal shape for a multi-leaf spring, similar to the bow of a bow and arrow, but without the string.
·        Elliptical – Two leaf springs can be combined facing away from each other to create an oval shape. This is known as elliptical.
·        Quarter Elliptical – This is an older type of spring with a similar structure to that of a normal leaf spring, only different being that it is half.
·       
Three-Quarter Elliptic – Some larger vehicles can be seen sporting an extra half of a leaf spring to support the normal leaf spring, positioned over the top of the axle.

Figure 4.6 shapes

4.2.4.Manufacturing process:


Multi-leaf springs are made as follows:
1.     Shearing of flat bar
2.     Center hole punching / Drilling
3.     Heating process (hot & cold process)
·        Eye Forming / Wrapper Forming
·        Diamond cutting / end trimming / width cutting / end tapering
·        End punching / end grooving / end bending / end forging / eye grinding / end rolling
·        Center hole punching / Drilling / nibbing
4.     Heat Treatment
·        Heating
·        Hardening
·        Cambering
·        Quenching
·        Tempering
5.     Surface preparation
·        Shot peening / stress peening
·        Primary painting
6.     Eye bush preparation process
·        Eye reaming / eye boring
·        Bush insertion
·        Bush reaming
7.     Assemble
·        Presetting & load testing
·        Finish painting
Stress induced:
Figures show typical stress distributions along the tension surface of leaf 1and leaf 2, respectively, for three loading conditions. The stress values are normalized bythe maximum allowable stress that occurs at maximum vertical loading.


Figure 4.6.1 Stress induced

4.2.5 STANDARD SIZES OF SUSPENSION LEAF SPRING

·        Standard nominal widths are: 32,40,45,55,60,65,70,75,80,90,100 and   125 mm.
·        Standard nominal thickness are: 3.2,4.5,5,6,6.5,7,7.5,8,9,10,11,12,14 and 16 mm.
·        At the eye, the following bore diameter are recommended: 19,20,22,23,25,27,28,30,32,35,38,50,55 mm.
Model of the parabolic 2-leaf-spring and the additional components

Figure4.7 Parabolic leaf spring
The shackle at the rear eye and the bushings in the two eyes were modeled using rigid bars. All the components in the center clamped area were modeled. In contrast to Figure 2, in the case of the 2-leaf-spring in question only the elastomeric buffer, the so-called “S-buffer”, issued on the vehicle, positioned at distance 325mm measured from the center of the clamped area. Therefore only that one buffer was modeled using a non-linear spring element, whose force-deflection characteristic was provided by the vehicle manufacturer
The silencers prevent the friction contact between the two leaves. Their material behavior was simulated using the corresponding stress-strain curve provided by the vehicle manufacture
4.3 .1 Parabolic mono-leaf spring for rear axles with on-vehicle configuration

Figure.4.8 leaf spring in 4wheeler

For the design of serial leaf-springs, specific requirements regarding the dimensions of thevehicle configuration and the allowable developed stresses that occur under specific operating loading conditions are taken into account. In particularthe vehicle manufacturer sets the requirement of the fatigue life of the leaf-springs under specific operating loading conditions referring to the corresponding vehicle. On the other hand, the leaf-spring manufacturer having experimental


4.4 SPRING
The primary function of a spring is to deflect or distort under load and to recover its originalshape when the load is released. During deflection or distortion, it absorbs energy and release the same as and when required. Springs are used in many engineering applications such as automobiles and railway buffers in order to cushion, absorb or control energy due to shock and vibrations. Springs will suffer a sizeable change in form without being distorted
Permanently when the loads are applied. Springs are generally classified as leaf springs or helical springs. Leaf springs consist of a number of thin curved plates, each of same thickness and width but of different lengths, all bent to the same curvature.

4.4.1 CLASSIFICATION OF SPRINGS:
Based on the shape behavior obtained by some applied force, springs are classified into the following ways:
                                                    SPRINGS


                                    HELICAL SPRING    LEAF SPRINGS
 


                                                                                                                                     SPIRAL SPRINGS
                                                                                                          TORSION SPRING
TENSION HELICAL                                                 
           SPRING                COMPRESSION HELICAL
                                                        SPRING
I. HELICAL SPRINGS:
DEFINITON:
It is made of wire coiled in the form of helix.
CROSS-SECTION:
Circular, square or rectangular
CLASSIFICATION:
      1. Open coil springs (or) Compression helical springs
      2.Closed coil springs (or) Tension helical springs
4.4.2 HELICAL TENSION SPRINGS:
CHARACTERISTICS:
1.     Figure shows a helical tension spring. It has some means of transferring the load from the support to the body by means of some arrangement.
2.     It stretches apart to create load.
3.     The gap between the successive coils is small.
4.     The wire is coiled in a sequence that the turn is at right angles to the axis of the spring.
5.     The spring is loaded along the axis.
6.     By applying load the spring elongates in action as it mainly depends upon the end hooks as shown in Figureure2.
Figure.4.9 Closed coil helical spring

Figure 4.10 open coiled helical spring
APPLICATIONS:
1.Garage door assemblies
2.Vise-grip pilers
3.Carburetor
4.3 HELICAL COMPRESSION SPRINGS:
CHARACTERISTICS:
1.     The gap between the successive coils is larger.
2.     It is made of round wire and wrapped in cylindrical shape with a constant pitch between the coils.
3.     By applying the load the spring contracts in action.
4.     There are mainly four forms of compression springs as shown in Figure. They are as follows:
1) Plain end
2) Plain and ground end
3) Squared end
4) Squared and ground end
Among the four types, the plain end type is less expensive to manufacture. It tends to bow sideways when applying a compressive load.
APPLICATIONS:
1)    Ball point pens
2)    Pogo sticks
3)    Valve assemblies in engines



1). TORSION SPRINGS:
CHARACTERISTICS:
1.     It is also a form of helical spring, but it rotates about an axis to create load.
2.     It releases the load in an arc around the axis as shown in Figure.
3.     Mainly used for torque transmission
4.     The ends of the spring are attached to other application objects, so that if the object rotates around the center of the spring.
APPLICATIONS:
1.     Mouse tracks
2.     Rocker switches
3.     Door hinges
4.     Clipboards
2) SPIRAL SPRINGS:
CHARACTERISTICS:
1.     It is made of a band of steel wrapped around itself a number of times to create a geometric shape as shown in Figure.
2.     Its inner end is attached to an arbor and outer end is attached to a retaining drum.
3.     It has a few rotations and also contains a thicker band of steel.
4.     It releases power when it unwinds

APPLICATIONS:
1. Alarm timepiece
2. Watch
3. Automotive seat recliners
II. LEAF SPRING:
DEFINITION:
A Leaf spring is a simple form of spring commonly used in suspension
          Vehicles.
CHARACTERISTICS:
1.     Figureure6 shows a leaf spring.Sometimes it is also called as a semi-elliptical spring, as it takes the form of a slender arc shaped length of spring steel of rectangular cross section.
2.     The center of the arc provides the location for the axle,while the tie holes are provided at either end for attaching to the vehicle body.
3.     Heavy vehicles,leaves are stacked one upon the other to ensure rigidity and strength.
4.     It provides dampness and springing function.
5.     It can be attached directly to the frame at the both ends or attached directly to one end, usually at the front,with the other end attached through a shackle,a short swinging arm.
6.     The shackle takes up the tendency of the leaf spring to elongate when it gets compressed and by which the spring becomes softer.
7.     Thus depending upon the load bearing capacity of the vehicle the leaf spring is designed with graduated andungraduated leaves
8.     Because of the difference in the leaf length, different stress will be there at each leaf.To compensate the stress level,prestressing is to be done.Prestressing is achieved by bending the leaves to different radius of curvature before they are assembled with the center clip.
9.     The radius of curvature decreases with shorter leaves.
10.                  The extra initial gap found between the extra full length leaf and graduated length leaf is called as nip such prestressing achieved by a difference in the radius of curvature.
APPLICATIONS:
Mainly in automobiles suspension systems.
ADVANTAGES:
1.     It can carry lateral loads.
2.     It provides braking torque.
3.     It takes driving torque and withstand the shocks provided by the vehicles.
SPRING MATERIALS:
The mainly used material for manufacturing the springs are as follows:
1.     Hard drawn high carbon steel.
2.     Oil tempered high carbon steel.
3.     Stainless steel
4.     Copper or nickel based alloys.
5.     Phosphor bronze.
6.     Iconel.
7.     Monel
8.     Titanium.
9.     Chrome vanadium.
10.                        4.4.5. COIL SPRING:
            A coil spring, also known as a helical spring, is a mechanical device which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces. They are made of an elastic material formed into the shape of a helix which returns to its natural length when unloaded. Under tension or compression, the material (wire) of a coil spring undergoes torsion. The spring characteristics therefore depend on the shear modulus, not Young’s Modulus. A coil spring may also be used as a torsion spring: in this case the spring as a whole is subjected to torsion about its helical axis. The material of the spring is thereby subjected to a bending moment, either reducing or increasing the helical radius. In this mode, it is the Young’s Modulus of the material that determines the spring characteristics.


Figure.4.11 Helical spring

4.5 Design of coil springs:
        The design of a new spring involves the following considerations:-Space into which the spring must fit and operate. Values of workingforces and deflections.Accuracy   and reliability needed. The primary consideration in the design of the coil springs are that the induced stresses are below the  permissible  limits  while subjected to or  exerting  the  external  force F capable of providing the needed deflection or maintaining the spring rate desired.            
Figure.4.12 Design of spring


4.5.1 Stress distribution


In order to determine the stress distribution along the specimens, strain gages were used for the measurement of the occurring strains. The corresponding stresses were calculated taking into account the standardized Young’s modulus for steel E=2.1 GPa. The strain gages were positioned on the side of the specimens subjected under tension at various positions along the area between the loading-cylinders (±250 mm from the center of the specimen), because under the 4-points bending conditions the maximum stresses are
The stresses developed during the tests were compared with the stresses obtained from the FE analysis performed, simulating the test-rig configuration for two levels of developed stresses. As shown in Figure 8 the agreement between calculated and measured stresses is satisfactory. The stress values are normalized by the maximum stress developed under the maximum applied force.




Figure. 4.13stress induced
:. Stress distribution obtained from tests and FE analysis for two load level
4.6 SHAFT:
            A shaft is a rotating machine element which is used to transmit power from one place to another. This shaft form an integral part of the machine itself. The crank shaft is an example of machine shaft.A shaft is a rotating member, usually of circular cross section, used to transmit power or motion. It   provides the axis of rotation, or oscillation, of elements such as gears, pulleys, flywheels, cranks, sprockets, and the like and controls the geometry of their motion.An axle is a non-rotating member that carries no   torque and is used to support rotating wheels, pulleys, and the like.


Figure.4.14 Design of shaft
4.7 OIL GRADES:

Figure 4.17 Oil specification

CHAPTER 5
5.1 WORKING PRINCIPLE OF LEAF SPRING

The suspension system having main element termed as leaf spring is one of the potential and very critical term for weight reduction in automobile industries as its having a ten to twenty percent of the unspring weight. By introducing composites, it can helpful for design a better suspension system having a better ride quality but the condition is it must be achieved without much increase cost and also decrease quality and reliability.In the design of springs, strain energy becomes the major factor. The relationship of the specific strain energy can be expressed as
U=σ2/ρE
Where σ = strength,
ρ =density
E =Young’s Modulus of the spring material
It can be noted that material which is having a lower modulus and also having a lower density will have a greater specific strain energy capacity. So the introduction of composite materials can made it possible to reduce the weight of the leaf spring without any reduction into the load carrying capacity and stiffness.One of the advantages of composite is that two or more materials could be combined to take advantage of the good characteristics of each. Figure. 1.2 shows an Arrangement of leaf spring into a car Model a spring eye section is used to attach the front end of semi-elliptic shape leaf spring to the chasesframe and a free end having a bracket constraining vertical motion to attach the back end of semi-elliptic leaf spring to the chassis frame



5.2 WORKING PRINCIPLES OF SHOCK ABSORBER
Figure 5.1.1 Shock absorber
Mono tube shock absorbers

These shock absorbers are gas filled under high pressure, which consist only of a tube and have main valve, so no matter which way it would be installed. In the tube there are two pistons - separating piston and working piston. Working piston design is very similar to that of twin tube shock absorbers. This type of shock absorbers has a better prevention of aeration, allowing better performance. The tube of these shocks is wider than that of a twin tube and this makes difficulties of using this type of shock absorbers in cars whose OE shocks are twin tube type. Separation valve is moving freely and divide gas from oil at the bottom of the shock absorber. The area below the valve is filled with gas at a pressure of about 360 psi. This gas helps to absorb some of the weight of the car. The oil is placed over the separating piston.
CHAPTER 6

6.1 DESIGN   CALCULATION   FOR SHOCK ABSORBER:
            The design of a new spring involves the following considerations:-Space into which the spring   must    fit and operate.  -Values of working forces and deflections.  -Accuracy   and reliability needed. The primary consideration in the design of the coil springs are that the induced stresses are  below  the  permissible  limits  while  subjected  to  or  exerting  the  external  force  F capable of providing the needed deflection or maintaining the spring rate.
Figure 6.1 shock absorber

Data of shock absorber
Spring Steel (modulus of rigidity) G = 78600 N/mm2
Mean diameter of a coil, D=55mm (wire diameter + inner diameter)
Diameter of wire, d = 5mm
Total no of coils, n1= 12
 Height, h = 150mm

Step:1
 Outer diameter of spring coil, D0 = 2D +D
We know that:  D = Di+d
Therefore (Di) = 55 -5 = 55mm
Di=55mm

        D0=2D – Di = (2x55) – 50= 60mm 
D0= 60mm

Step: 2
No of active turns, n= 11
Weight of bike = 144kg
Spring index, C = D/d = 55/5=11mm  
C=11mm

Solid length, Ls=n1×d=12×5=60mm
Ls=60mm

Free length of spring,Lf = solid length + maximum compression
                                                    = 150+ 125 = 275mm
Lf=75mm

Step: 3
  Pitch of coil, P = Lf – Ls + d/n1= 275-60+5/12=11.7 mm
P=11.7mm


Step: 4
 Stresses in helical spring:
Maximum shear stress induced:
   τ = 0.5x σut = 0.5x 1050= 525 N/mm2.
τ =525 N/mm2

Result:

1. Outer diameter of spring coil, D0 = 60mm 
2. Spring index, C =11mm
3. Free length of spring,Lf= 275mm
            4. Pitch of coil, P=11.7 mm
5. Maximum shear stress induced, τ= 525 N/mm2






CHAPTER 7
ASSEMBLE DIAGRAM



Figure 7.1 leaf spring suspension system
Figure.7.23D view

Figure.7.3 Side view
CHAPTER 8
COMPONENTS SPECIFICATION

8.1 MATERIAL SELECTION:



SL.NO.

PART

MATERIAL

NO. OF

1
Shock absorber
Mild steel
1

2
Leaf soring

Tempered steel
2

3
Steel plate
mild steel
2

4
Rubber sheet
Steel
4

5
Bush
Mild steel
1

6
Spring
Steel alloy
2

7
Shaft
Mild steel
1

8
Frame and base
Mild steel
1



Table 8.1 Material selection


 

8.2 COST   ESTIMATION:






SI.NO


PART AND DESCRIPTION


COST

1

Shock absorber

400

2

Steel columns

750

3

Shaft

500

4

Leaf spring material

600

5

Lapping plates

450

6

Tempered plates

500

7

Rubber material

500

8

Frame, base and other materials

         600

9

Labor charge

1200
10
TOTAL
 5500/-

Table 8.2 Cost estimation

8.3 SPECIFICATION OF LEAF SPRING

Forces acting on leaf spring are as shown in Figure. Main forces acting on leaf spring are as follow but in this analysis only vertical loading condition is considered. Forces acting on leaf spring:
·         Vertical loading (Fv)
·        Side load (Fs)
·        Longitudinal load (Ft)
·        Twisting torque (Tt)
·        Windup torque (Tw)


:

Figure. 8.3 Load Acting on Leaf Spring

Assumptions for Analysis:
·         Automobile is assumed to be stationary.
·         There are 2Semi-elliptic leaf spring, one at front and one at rear axle. And for Only vertical loading.



CHAPTER 9

9.1 ADVANTAGES:
1.     The chassis roll can be controlled more efficiently
2.     They also controlled axle damping
3.     Leaf spring making the ideal for commercial vehicle
4.     Regains shape after bending till certain limit, useful for spring applications.
5.     Bikes will performs in high at mountain areas

9.2 LIMITATION:
1.     Only applicable for sports bikes
2.     weighter than normal suspension
9.3 APPLICATIONS:
1.     Applicable in dirt bike racing and requiring a high weight absorbing areas.
2.     To cushion, absorb or control energy due to either shock or vibration as in car springs,railway buffers, air-craft landing gears, shock absorbers and vibration dampers.
3.     To apply for high suspension system whenever failure in occurred.
4.     To store energy and releases in heavy vehicles like as cars,container vehicles,etc…

CHAPTER 10

CONCLUSION
From above results it is clearly seen that the objective was to obtain a spring with minimum weight and is capable of carrying given static external forces by constraints limiting stresses and displacements. For this the steel leaf spring is replaced by composite leaf spring. This is better than using steel leaf spring. After studying all the available literature it is found that weight reduction can be easily achieved by using composite materials instead of conventional steel, but there occurs a problem during the operation while using the composite leaf spring i.e. chip formation when the vehicle goes off road. Therefore there is an immense scope for the future work regarding use of composite materials in leaf springs to reduce the overall weight of the vehicle as well as the cost of the vehicle.












REFERENCE

1. M. Raghavedraet. al. “Modelling and Analysis of Laminated Composite Leaf under the Static Load Condition by using FEA”, International Journal of Modern Engineering Research (IJMER) Vol.2, Issue.4, July-Aug. 2012 pp-1875-1879

2. V.K. Aheret. al. “Fatigue Life Prediction of Multi Leaf Spring used in the Suspension System of Light Commercial Vehicle”, International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME), 2012.

3. Ravi Kumar V. et. al. “Analysis of Natural Fibre Composite Leaf Spring”, International Journal of Latest Trends in Engineering and Technology (IJL2TET) September 2013

4. T.N.V. Ashok Kumar at. al. “Design and Material Optimization of Heavy Vehicle Leaf Spring”, International Journal of Research in Mechanical Engineering & Technology, Nov 2013 - April 2014

5. PankajSainiet. al. “DESIGN AND ANALYSIS OF COMPOSITE LEAF SPRING FOR LIGHT VEHICLES”, International Journal of Innovative Research in Science, Engineering and Technology. Vol. 2, Issue 5, May 2013

6. Baviskar A. C. et. al. “Design and Analysis of a Leaf Spring for automobile suspension system: A Review”, International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 6, June 2013)






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