MINI PROJECT REPORT ON SUSPENSION SYSTEM OF AN ICF BOGIE At South central railway, carriage workshop Lallaguda, Secunderabad.
Dissertation work submitted to Jawaharlal Nehru Technology University.
In partial fulfillment of the requirements of the award of
BACHELOR OF TECHNOLOGY IN MECHANICAL ENGINEERING BY T.KIRAN KUMAR 097Z1A0345
S.SREEDHAR REDDY 097Z1A0343
P.PRANAY KUMAR 097Z1A0339
B.CHARITHA 097Z1A0309
NALLA NARASIMHA REDDY EDUCATION SOCIETY’S GROUP OF INSTITUTIONS Chowdhariguda, Korremula ‘X’ Road via Narapally, Ghatkesar Ghatkesar (mandal), Ranga Reddy (DIST)- 500088
1
ACKNOWLEDGEMENT
With deep sense of gratitude, I acknowledge the guidance, help and active cooperation render by the following people whose guidance has sustained the effort which lead to the successful completion of the project. I express my deep sense of gratitude to Mr .T. PAVAN KUMAR, HOD, MECHANICAL BRANCH and Mr.SURESH KUMAR(instructor)
Of
NALLA NARASIMHA REDDY
EDUCATION SOCIETY‟S GROUP OF INSTITUTIONS. For giving valuable guidance through out the project. We are grateful to Shri.S.VASUDEVAIAH, Dy.CME, lallaguda carriage workshop, for providing us an opportunity to do this project in SCR. We would like to thank Mr.G. SATYA KUMAR, CI, BTC, for guiding us through our project. He helped us at every stage in understanding and solving many problems encountered during the course of project. We sincerely thank Mr.T.N.RAMANA RAO, Junior Instructors of BTC, who directed us to successful completion of project. We would like to thank Mr. CHANDHRA SHEKAR, SSE, SMITHY SHOP and MR.K. ANJANAILU, SSE, BOGIE SHOP, who in spite of their hectic schedule helped us in
carrying out our work and helped us in a great way by co-operating at every stage. All together, working in SCR was a great learning experience. We would cherish our experience in this organization for out life time
2
ABSTRACT
Every vehicle has suspension system which provides comfort to driver and passengers. Suspension system maintains traction between tyres and road which is compulsory for every vehicle. It also protects the vehicle body from damages during pitches and downs. In suspension system, springs play major role because it takes load of vehicle and transfer it to wheels. As every vehicle is equippe d with “suspension system” we have selected this project and explained about suspension system of a railway bogie including its process of over hauling. Hope this is useful for every mechanical student.
.
3
INDEX
ACKNOWLEDGEMENT
ABSTRACT
INTRODUCTION
INDIAN RAILWAYS
SOUTH CENTRAL RAILWAY
LALLAGUDA WORKSHOP
SUSPENSION SYSTEM
INTRODUCTION
COMPONENTS
IMPROTANCE
PRINCIPLE
CONCEPT OF RIDE QUALITY
SUSPENSION SYSTEM OF ICF BOGIE
TYPES OF BOGIES
INTRODUCTION TO ICF(ALL COILED) BOGIE
PRIMARY SUSPENSION SYSTEM
SECONDARY SUSPENSION SYSTEM
PROCEDURE OF OVER HAULING OF SUSPENSION SYSTEMS OF ICF BOGIE
OVER HAULING OF PRIMARY SUSPENSIONSYSTEM
OVER HAULIG OF SECONDARY SUSPENSIONSYSTEM
ADVANTAGES OF SUSPENSION SYSTEM
SUGGESTIONS
CONCLUSION
4
INTRODUCTION TO SUSPENSION SYSTEM
Suspension system is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. It is basically cushion for passengers, protects the luggage or any cargo and also itself from damage and wear.
Sir William Brush is the father of suspension system in automobiles. It is located between the wheel axles and the vehicle body, also call frame.
5
COMPONENTS OF SUSPENSION SYSTEM
SPRINGS DAMPERS ANTI SWAY BARS OR LINKAGES
SPRINGS
DEFINITION FOR SPRING:
Springs are elastic bodies (generally metal) that canbe twisted, pulled, or stretched by some force. They canreturn to their original shape when the force is released. In other words it is also termed as a resilient member.
CLASSIFICATION OF SPRINGS:
Based on the shape behavior obtained by some applied force, springs are classified into the following ways: SPRINGS
HELICAL SPRINGS
LEAF SPRINGS
SPIRAL SPRINGS TORSION SPRING TENSION HELICAL SPRING
COMPRESSION HELICAL SPRIGS
6
HELICAL SPRINGS:DEFINITON:
It is made of wire coiled in the form of helix. CROSS-SECTION:
Circular, square or rectangular CLASSIFICATION :
1.Closed coil springs (or) Tension helical springs 2. Open coil springs (or) Compression helical springs 3. TORSION SPRINGS 4. SPIRAL SPRING 1)HELICAL TENSION SPRINGS:CHARACTERISTICS :
•
Figure1 shows a helical tension spring. It has some means of transferring the load from the support to the body by means of some arrangement.
•
It stretches apart to create load.
•
The gap between the successive coils is small.
•
The wire is coiled in a sequence that the turn is at right angles to the axis of the spring.
•
The spring is loaded along the axis.
•
By applying load the spring elongates in action as it mainly depends upon the end hooks as shown in figure2.
7
FIGURE1.TENSION HELICAL SPRING
FIGURE2.TYPES OF END HOOKS OF A HELICAL EXTENSION SPRING
APPLICATIONS:
•
Garage door assemblies
•
Vise-grip pilers
•
Carburetors
8
2) HELICAL COMPRESSION SPRINGS:-
CHARACTERISTICS :
•
The gap between the successive coils is larger.
•
It is made of round wire and wrapped in cylindrical shape with a constant pitch between the coils.
•
By applying the load the spring contracts in action.
•
There are mainly four forms of compression co mpression springs as shown in figure3.. They are as follows:
Plain end
Plain and ground end
Squared end
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. FIGURE3.COMPRESSION HELICAL SPRING
9
APPLICATIONS:
•
Ball point pens
•
Pogo sticks
•
Valve assemblies in engines
•
Suspension system of automobile s
3) TORSION SPRINGS:-
CHARACTERISTICS :
It is also a form of helical spring, but it rotates about an axis to create load.
It releases the load in an arc around the axis as shown in figure4.
Mainly used for torque transmission
The ends of the spring are attached to other application objects, so that if the object rotates around the center of the spring, it tends to push the spring to retrieve its normal position.
FIGURE4.TORSION SPRING
APPLICATIONS:
•
Mouse tracks
•
Rocker switches
•
Door hinges
10
•
Clipboards
•
Automobile starters
4) SPIRAL SPRINGS:-
CHARACTERISTICS:
It is made of a band of steel wrapped around itself a number of times to create a geometric shape, as shown in figure5.
Its inner end is attached to an arbor and outer end is attached to a retaining drum.
It has a few rotations and also contains a thicker band of steel.
It releases power when it unwinds.
APPLICATIONS :
•
Alarm timepiece
•
Watch
•
Automotive seat recliners
FIGURE5. SPIRAL SPRING
11
LEAF SPRING:DEFINITION:
A Leaf spring is a simple form of spring commonly used in the suspension vehicles. .LEAF SPRING
CHARACTERISTICS:
Figure shows a leaf spring. Sometimes it is also called as a semielliptical spring, as it takes the form of a slender arc shaped length of spring steel of rectangular cross section.
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.
Heavy vehicles,leaves are stacked one upon the other to ensure rigidity and strength.
It provides dampness and springing function.
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.
The shackle takes up the tendency of the leaf spring to elongate when it gets compressed and by which the spring becomes softer.
Thus depending upon the load bearing capacity of the vehicle the leaf spring is designed with graduated and Un-graduated Un -graduated leaves as shown in figure7.
12
FIGURE7.LEAF SPRINGS-FABRICATION STAGES
Because of the difference in the leaf length,different stress will be there at each leaf.To compensate the stress level,pre-stressing is to be done.Pre-stressing is achieved by bending the leaves to different radius of curvature before they are assembled with the center clip.
The radius of curvature decreases with shorter leaves.
The extra in-tail gap found between the extra full length leaf and graduated length leaf is called as nip.Such pre-stressing achieved by a difference in the radius of curvature is known as nipping which is shown in figure8. FIGURE8.NIPPING IN LEAF SPRINGS
APPLICATIONS:
•
Mainly in automobiles suspension systems.
13
ADVANTAGES:
It can carry lateral loads.
It provides braking torque.
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:
•
Hard drawn high carbon steel.
•
Oil tempered high carbon steel.
•
Stainless steel.
•
Copper or nickel based alloys.
•
Phosphor bronze.
•
Iconel.
•
Monel.
•
Titanium.
•
Chrome vanadium.
•
Chrome silicon.
Depending upon the strength of the material,the material is slected for the design of the spring as shown in figure9.
14
15
NOMENCLATURE OF SPRING Active Coils
Those coils which are free to deflect under load . Angular Relationship of ends
The relative position of the plane of the hooks or loops of extension spring to each other. Buckling
Bowing or lateral deflection of compression springs when compressed, related to the slenderness ration (L/D). Closed Ends
End of compression springs where the pitch of the end coils is reduced so that the end coils touch. Closed and Ground Ends
As with closed ends, except that the end is ground to provide a flat plane. Close-Wound
Coiled with adjacent coils touching . Deflection
Motion of the spring ends or arms under the application or removal of an external load. Elastic Limit
Maximum stress to which a material may be subjected without permanent set.
16
Endurance Limit
Maximum stress at which any given material may operate indefinitely without failure for a given minimum stress. Free Angle
Angel between the arms of a torsion spring when the spring is not loaded . Free Length
The overall length of a spring in the unloaded position. Frequency (natural)
The lowest inherent rate of free vibration of a spring itself (usually in cycles per second) with ends restrained. Hysteresis
The mechanical energy loss that always occurs under cyclical loading and unloading of a spring, proportional to the arc between the loading and unloading load-deflection curves within the elastic range of a spring. Initial Tension
The force that tends to keep the coils of an extension spring closed and which must be overcome before the coil starts to open . Loops
Coil-like wire shapes at the ends of extension springs that provide for attachment and force application. Mean Coil Diameter
Outside wire diameter minus one wire diameter.
17
Modulus in shear or torsion
Coefficient of stiffness for extension and compression springs. Modulus in tension or bending
Coefficient of stiffness used for torsion and flat springs. (Young's modulus). Open ends, not ground
End of a compression spring with a constant pitch for each coil. Open ends ground
g rinding operation . "Opens ends, not ground" followed by an end grinding Permanent Set
A material that is deflected so far that its elastic properties have been exceeded and it does not return to its original condition upon release of load is said to have taken a "permanent set ". Pitch
The distance from center to center of the wire in adjacent active coils. Spring Rate (or) Stiffness (or) Spring Constant
Changes in load per unit of deflection, generally given in Kilo Newton per meter. (KN/m). Remove Set
The process of closing to a solid height a compression spring which has been coiled longer than the desired finished length, so as to increase the elastic limit. Set
Permanent distortion which occurs when a spring is stressed beyond the elastic limit of the material.
18
Slenderness Ratio
Ratio of spring length to mean coil diameter . Solid Height
Length of a compression spring when under sufficient load to bring all coils into contact with adjacent coils. Spring Index
Ratio of mean coil diameter to wire diameter . Stress Range
The difference in operating stresses at minimum and maximum loads . Squareness of ends
Angular deviation between the axis o a compression spring and a normal to the plane of the other ends. Squareness under load
As in squarenessof ends except with the spring under load. ,
Torque
A twisting action in torsion springs which tends to produce rotation, equal to the load multiplied by the distance (or moment arm) from the load to the axis of the spring body. Usually expressed in inch-oz, inch-pounds i nch-pounds or in foot-pounds. Total number of coils
Number of active coils plus the coils forming the ends. Spring Index
The ratio between Mean dia of coil to the diameter of the wire.
19
Solid length
It is the product of total number of coils and the diameter of the wire when the spring is in the compressed state. It is otherwise ot herwise called as Solid height also .
FIGURE10.NOMENCLATURE OF SPRING
20
FIGURE11.HELICAL SPRING IN LOADED END CONDITION
Depending upon the type of the compression helical spring the numbers of coils are decided as shown in figure12.The Pitch angle is calculated as shown in figure13.
FIGURE12.RELATION BETWEEN ENDS AND NOMENCLATURE OF A COMPRESSION HELICAL SPRING
FIGURE13.RELATION BETWEEN PITCH AND MEAN DIAMETER OF COIL
21
DAMPERS
Shock absorbers, linear dampers, and dashpots are devices used as dampers in suspension system of a vehicle. They may be mechanical (e.g., elastomeric) or rely on a fluid (gas, air, hydraulic), which absorbs shock by allowing controlled flow from outer to inner chamber of a cylinder during piston actuation. The piston rod is typically returned returned to the unloaded position position with a spring. Shock absorbers typically contain both a fluid or mechanical dampening system and a return mechanism to the unengaged position. position. They generally used in automobiles. automobiles. Linear dampers is an inclusive term that can be applied to many forms of dashpots and shock absorbers; typically used for devices designed primarily for reciprocating motion attenuation attenuation rather than absorption absorption of large shock loads. Dashpots are typically distinct in that while they use controlled fluid flow to dampen and decelerate motion, they do not necessarily incorporate an integral return mechanism such as a spring. Dashpots are often relatively small, precise devices used for applications such as instrumentation instrumentation and precision manufacturing.
IMPORTANCE AND WORKING OF DAMPERS
22
Unless a dampening structure is present, a vehicle spring will extend and release the energy it absorbs from a bump at an uncontrolled rate. The spring will continue to bounce at its natural frequency until all of the energy originally put into it is used up. A suspension built on springs alone would make for an extremely bouncy ride and, depending on the terrain, an uncontrollable car. Enter the dampers, or snubber, a device that controls unwanted spring motion through a process known as dampening. Shock absorbers slow down and reduce the magnitude of vibratory motions by turning the kinetic energy of suspension movement into heat energy that can be dissipated through hydraulic fluid. To understand how this works, it's best to look inside a shock absorber to see its structure and function. A shock absorber is basically an oil pump placed between the frame of the car and the wheels. The upper mount of the shock connects to the frame (i.e., the sprung weight), while the lower mount connects to the axle, near the wheel (i.e., the un-sprung un -sprung weight). In a twin-tube design, one of the most common types of shock absorbers, the upper mount is connected to a piston rod, which in turn is connected to a piston, which in turn sits in a tube filled with hydraulic fluid. The inner tube is known as the pressure tube, and the outer tube is known as the reserve tube. The reserve tube stores excess hydraulic fluid. When the car wheel encounters a bump in the road and causes the spring to coil and uncoil, the energy of the spring is transferred to the shock absorber through the upper mount, down through the piston rod and into the piston. Orifices perforate the piston and allow fluid to leak through as the piston moves up and down in the pressure tube. Because the orifices are relatively tiny, only a small amount of fluid, under great pressure, passes through. This slows down the piston, which in turn slows down the spring. Shock absorbers work in two cycles -- the compression cycle and the extension cycle. The compression cycle occurs as the piston moves downward, compressing the hydraulic
23
fluid in the chamber below the piston. The extension cycle occurs as the piston moves toward the top of the pressure tube, compressing the fluid in the chamber above the piston. A typical car or light truck will have more resistance during its extension cycle than its compression cycle. With that in mind, the compression cycle controls the motion of the vehicle's un-sprung weight, while extension controls the heavier, sprung weight. All modern shock absorbers are velocity-sensitive -- the faster the suspension moves, the more resistance the shock absorber provides. This enables shocks to adjust to road conditions and to control all of the unwanted motions that can occur in a moving vehicle, including bounce, sway, brake dive and acceleration squat.
ANTI SWAY BARS OR LINKAGES
An
anti-sway
bar or anti-roll
bar or stabilizer
bar is
a
part
of
an automobilesuspension, that helps reduce the body roll of a vehicle during fast cornering or over road irregularities. It connects opposite (left/right) wheels together through short lever arms linked by a torsion spring. A sway bar increases the suspension's roll stiffness — its its resistance to roll in turns, independent of its spring ratein the vertical direction. The first stabilizer bar patent was awarded to the Canadian S. L. C. Coleman of Fredericton, New Brunswick on April 22, 1919.
PURPOSE AND OPERATION
An anti-sway or anti-roll bar is intended to force each side of the vehicle to lower, or rise, to similar heights, to reduce the sideways tilting (roll) of the vehicle on curves, sharp corners, or large bumps. With the bar removed, a vehicle's wheels
24
can tilt away by much larger distances (as shown by the SUV image at right). Although there are many variations in design, a common function is to force the opposite wheel's shock absorber, spring or suspension rod to lower, or rise, to a similar level as the other wheel. In a fast turn, a vehicle tends to drop closer onto the outer wheels, and the sway bar will soon force the opposite wheel to also get closer to the vehicle. As a result, the vehicle tends to "hug" the road, closer in a fast turn, where all wheels are closer to the body. After the fast turn, then the downward pressure is reduced, and the paired wheels can return to their normal height against the vehicle, kept at similar levels by the connecting sway bar. Because each pair of wheels is cross-connected by a bar, then the combined operation causes all wheels to generally offset the separate tilting of the others, and the vehicle tends to remain level against the general slope of the terrain. A negative side-effect, of connecting pairs of wheels, is that a jarring or bump to one wheel tends to also jar the opposite wheel, causing a larger impact applied across the whole width of the vehicle. If there are several potholes scattered in the road, then a vehicle will tend to rock, side-to-side, or waddle, due to the action of the bar at each pair of wheels. Other suspension techniques can be used to delay, or dampen, the effect of the connecting bar, as when hitting small holes which momentarily jolt just a single wheel, whereas larger holes or longer tilting would then tug the bar with the opposite wheel.
PRINCIPLE
A sway bar is usually a torsion spring that resists body roll motions. It is usually constructed out of a wide, U-shaped steel bar that connects to the body at two points, and at the left and right sides of the suspension. If the left and right wheels move together, the bar rotates about its mounting points. If the wheels move
25
relative to each other, the bar is subjected to torsion and forced to twist. Each end of the bar is connected to an end linkthrough a flexible joint. The sway bar end link in turn connects to a spot near a wheel or axle, permitting forces to be transferred from a heavily-loaded axle to the opposite side . Forces are therefore transferred:
•
from the heavily-loaded axle
•
to the connected end link via a bushing
•
to the anti-sway (torsion) bar via a flexible joint
•
to the connected end link on the opposite side of the vehicle
•
to the opposite axle .
The bar resists the torsion through its stiffness. The stiffness of an anti-roll bar is proportional to the stiffness of the material, the fourth power of its radius, and the inverse of the length of the lever arms (i.e., the shorter the lever arm, the stiffer the bar). Stiffness is also related to the geometry of the mounting points and the rigidity of the bar's mounting points. The stiffer the bar, the more force required to move the left and right wheels relative to each other. This increases the amount of force required to make the body roll. In a turn the sprung mass of the vehicle's body produces a lateral force at the center of gravity (CG), proportional to lateral acceleration. Because the CG is usually not on the roll axis, the lateral force creates a moment about the roll axis that tends to roll the body. (The roll axis is a line that joins the front and rear roll centers (SAEJ670e)). The moment is called the roll couple. Roll couple is resisted by the suspension roll stiffness, which is a function of the spring rate of the vehicle's springs and of the anti-roll bars, if any. The use of anti-
26
roll bars allows designers to reduce roll without making the suspension's springs stiffer in the vertical plane, which allows improved body control with less compromise of ride quality One effect of body (frame) lean, for typical suspension geometry, is positive camber of the wheels on the outside of the turn and negative on the inside, which reduces their cornering grip (especially with cross ply tires).
27
IMPORTANCE OF SUSPENSION SYSTEM
Suspension system allows the vehicle to travel over rough surfaces with a minimum of up and down body movements. It also allows the vehicle to corner with minimum roll or tendency to loose traction between the tires and road surface. The suspension provides a cu-shioning cu-shioning effect action, therefore, the passengers passengers or move up and down they meets bumps and holes in the road.
THE MAIN IMPORTANCE OF SUSPENSION SYSTEM ARE :
•
Support the weight of vehicle
•
Maintain traction between the tires and the road
•
It supports the weight of vehicle
•
Provides smoother ride for the driver and passengers i.e. acts as cushion.
•
Protects your vehicle from damage and wear .
•
It also plays a critical role in maintaining self- driving conditions.
•
It also keeps the wheels pressed firmly to the ground for traction
•
It isolates the body from road shocks and vibrations which would otherwise be transferred to the passengers and load.
•
Good handling
•
Shields the vehicle from damage
•
Increases life of vehicle keeps the th e tires pressed firmly to ground
28
PRINCIPLE OF SUSPENSION
PRINCIPLE
When a tire hits an obstruction, there is a reaction force. The size of this reaction force depends on the un-sprung mass at each wheel assembly.
In general, the larger the ratio of sprung weight to un-sprung weight, the less the body and vehicle occupants are affected by bumps, dips, and other surface imperfections such as small bridges. A large sprung weight to un-sprung weight ratio can also impact vehicle control. DEFINITIONS OF SPRUNG &UNSPRUNG MASS Sprung mass:-Sprung mass (weight) refers to vehicle parts supported s upported on the
suspension system, such as the body, frame, engine, the internal components, passengers, and cargo . Un-sprung mass:- Un-sprung mass refers to the components that follow the road
contours, such as wheels, tires, brake assemblies, and any part of the steering and suspension not supported by the springs. WORKING OF SUSPENSION SYSTEM
No road is perfectly flat i.e. without irregularities. Even a freshly paved highways have subtle forces on wheels. According to Newton law of motion all forces have both magnitude and direction. A bump in the road causes the wheel to move up and down perpendicular to the road surface. The magnitude of course, depends on whether the wheel is striking a giant bump or a tiny speck. Thus, either the wheel experiences a vertical acceleration as it passes over an imperfection.
29
CONCEPT OF RIDE QUALITY
DEFINITION
Ride quality refers to the degree of protection offered vehicle occupants from uneven elements in the road surface, or the terrain if driving off-road. A car with very good ride quality is also a comfortable car to ride in. Cars which disturb vehicle occupants with major or minor road irregularities would be judged to have low ride quality. Key factors for ride quality are Whole body vibrationand vibration and noise. IMPORTANCE
While pleasant, the comfort of the vehicle driver is also important for car safety, both because of driver fatigue on long journeys in uncomfortable vehicles, and also because road disruption can impact the driver's ability to control the vehicle. Early vehicles with its live axle suspension design, were both uncomfortable and handled poorly. Automakers often perceive providing an adequate degree of ride quality as a compromise with car handling, because cars with firm suspension offer more roll stiffness, keeping the tires more perpendicular to the road. Similarly, a lower center of gravity is more ideal for handling, but low bodywork forces the driver's and passengers' legs more forward and less down, and low ground clearance limits suspension travel, requiring stiffer springs. Ride quality is also related to good braking and acceleration on poor surfaces. It protects the car itself, as well as its passengers and cargo, from vibration that might eventually damage or loosen components of the car.
30
On the other hand "poor" ride quality improves blood circulation, helps to keep the driver awake, helps the driver sense speed and road condition and is enjoyed by small children and traditional sportscar enthusiasts.
Ride quality is depend on ride index, ride index is the ratio of sprung mass to un sprung mass. The quality of ride low in two conditions i.e. 1.When ride index value is low 2. When ride index value is high. The quality of ride is high when ride index value is in b/w 15 to 35. Ride quality is also dependson type of suspension system used.
31
INTRODUCTUION TO ICF BOGIE
Bogie or trolley is a main part of a train where it takes load from coach and transfer it to wheel axel through through suspension suspension systems. CHARACTERSITICS OF ICF BOGIE
•
It is an independent unit used under a long vehicle.
•
It is usually mounted on two pairs of wheels.
(In exceptional cases, such as special purpose stocks or high capacity vehicles of well Wagons
or crocodile trucks, inspection carriages etc.. the bogie may be
mounted on three or more pairs of
Wheels)
•
Normally two bogies are used under a Vehicle.
•
Each bogie carries half the load of the vehicle body and it‟s loading.
•
Each bogie is provided with a pivot on its central transom or bolster for engagement with its male counterpart provided underneath the vehicle under frame.
:
TYPES OF BOGIES USED IN INDIAN RAILWAYS
•
IRS Bogie
•
SCHLIEREN Bogie (ICF Laminated Bogie)
•
MAN-HAL Bogie (BEML Bogie)
•
ICF All Coiled Bogie
•
IR-20 Bogie
•
Fiat Bogie (Similar to IR-20 Bogie)
32
INTRODUCTION TO ICF (ALL COILED) BOGIE
ICF Bogie is a conventional railway bogie used on the majority of Indian Railway main line passenger coaches. The design of the bogie was developed by ICF (Integral Coach Factory), Perumbur, India in collaboration with the Swiss Car & Elevator Manufacturing Co., Schlieren, Switzerland in the 1950s. The design is also called the Schlieren design based on the location of the Swiss company.
BOGIE FRAME
The frame of the ICF bogie is a fabricated structure made up of mild steel channels and angles welded to form the main frame of the bogie. The frame is divided into three main sections. The first and the third section are mirror images of each other. Various types of brackets are welded to the frame for supporting bogie components.
33
BOGIE BOLSTER
The body bolster is a box type fabricated member made up of channels and welded to the body of the coach. It is a free-floating member. The body bolster transfers the dead weight of the coach body to the bogie frame. There are two type of bolsters in an ICF bogie: body bolster and the bogie bolster. The body bolster is welded to the coach body whereas the bogie bolster is a free floating member which takes the entire load of the coach through the body bolster.In body bolster there are 2 side bearers and a center pivot pin are joined by excellent quality welding. These three parts acts as a male part and matches with the female part welded to bogie bolster. These are very vital parts for smooth running of a train.
34
CENTER PIVOT PIN
A center pivot pin is bolted to the body bolster. The center pivot pin runs down vertically through the center of the bogie bolster through the center pivot. It allows for rotation of the bogie when the coach is moving on the curves. A silent block, which is cylindrical metal rubber bonded structure, is placed in the central hole of the bogie bolster through which the center pivot pin passes. It provides the cushioning effect.
Centre Pivot
35
WHEEL SET ASSEMBLY:
Wheel arrangement is of Bo-Bo type as per the UIC classification. The wheel set assembly consists of two pairs of wheels and axle. The wheels may be cast wheels or forged wheels. The wheels are manufactured at Durgapur Steel Plant of SAIL( Steel authority of India Ltd.) or at Wheel and Axle Plant of Indian Railways bases at Yelahanka near Banglore in the state of Karnataka. At times, imported wheels are also used. These wheels and axles are machined in the various railway workshops in the wheels shops and pressed together.
ROLLER BEARING ASSEMBLY:
Roller bearings are used on the ICF bogies. These bearings are press fitted on the axle journal by heating the bearings at a temperature of 80 to 100 °C in an induction furnace. Before fitting the roller bearing , an axle collar is press fitted. The collar ensures that the bearing does not move towards the center of the axle. After pressing the collar, a rear cover for the axle box is fitted. The rear cover has two main grooves. In one of the grooves, a nitrile rubber sealing ring is placed. The sealing ring ensures that the grease in the axle box housing does not seep out during the running of the wheels. A woolen felt ring is placed in another groove.
36
After the rear cover, a retaining ring is placed. The retaining ring is made of steel and is a press fit. The retaining ring ensures that the rear cover assembly is secured tightly between the axle collar and the retaining ring and stays at one place. The roller bearing is pressed after the retraining ring. Earlier, the collar and the bearings were heated in an oil bath. But now the practices has been discontinuedand an induction furnace is used to heat them before fitting on the axle. The axle box housing, which is a steel casting, is then placed on the axle. The bearing is housed in the axle box housing. Axle box grease is filled in the axle box housing. Each axle box housing is filled with approximately 2.5 kg. of grease. The front cover for the axle box is placed on a housing which closes the axle box. The front cover is bolted by using torque wrench.
BRAKE BEAM ASSEMBLY
ICF bogie uses two types of brake beams. 13 ton and 16 ton. Both of the brake beams are fabricated structures. The brake beam is made from steel pipes and welded at the ends. The brake beam has a typical isosceles triangle shape. The two ends of the brake beam have a provision for fixing a brake head. The brake head in turn receives the brake block. The material of the brake block is non-asbestos, and non-metallic in nature.
37
BRAKE HEAD
Two types of brake heads are used. ICF brake head and the IGP brake head. A brake head is a fabricated structure made up of steel plates welded together . BREAK BLOCKS
Brake blocks are also of two types. ICF brake head uses the "L" type brake block and the "K" type brake block is used on the IGP type brake head. "L" & "K" types are so called since the shape of the brake blocks resembles the corresponding English alphabet letter. The third end of the brake beam has a bracket for connecting the "Z" & the floating lever. These levers are connected to the main frame of the bogie with the help of steel brackets. These brackets are welded to the bogie frame . BRAKE LEVERS
Various type of levers are used on the ICF Bogie .The typical levers being the "Z" lever, floating lever and the connecting lever. Theses levers are used to connect the brake beam with the piston of the brake cylinder. The location of the brake cylinders decides whether the bogie shall be a BMBC Bogie or a non BMBC Bogie. Conventional bogies are those ICF bogies in which the brake cylinder is mounted on the body of the coach and not placed on the bogie frame itself. BRAKE CYLINDER
In a ICF Bogie, the brake cylinder is mounted on the bogie frame itself. Traditionally, the ICF Bogies were conventional type i.e. the brake cylinder was mounted on the body of the coach. However, in the later modification, the new bogies are being manufactured with the BMBC designs only. Even the old type bogies are being converted into BMBC Bogies. The BMBC bogie has many advantages over the conventional ICF bogie. The foremost being that, since the
38
brake cylinder is mounted on the bogie frame itself and is nearer to the brake beam, the brake application time is reduced. Moreover, a small brake cylinder is adequate for braking purpose. This also reduces the overall weight of the ICF bogie apart from the advantage of quick brake application. PRIMARY SUSPENSION
The primary suspension in a ICF Bogie is through a dashpot arrangement. The dashpot arrangement consists of a cylinder (lower spring seat) and the piston (axle box guide). Axle box springs are placed on the lower spring seat placed on the axle box wing of the axle box housing assembly. A rubber or a Hytrel washer is placed below the lower spring seat for cushioning effect. The axle box guide is welded to the bogie frame. The axle box guide acts as a piston. A homopolymer acetyle washer is placed on the lower end of the axle box guide. The end portion of the axle box guide is covered with a guide cap, which has holes in it. A sealing ring is placed near the washer and performs the function of a piston ring. The axle box guide moves in the lower spring seat filled with dashpot oil. This arrangement provides the dampening effect during the running of the coach.
39
SECONDARY SUSPENSION
The secondary suspension arrangement of the ICF bogies is through bolster springs. The bogie bolster is not bolted or welded anywhere to the bogie frame. It is attached to the bogie frame through the anchor link. The anchor link is a tubular structure with cylindrical housing on both the ends. The cylindrical housings have silent blocks placed in them. The anchor link is fixed to the bogie bolster and the bogie frame with the help of steel brackets welded to the bogie bolster and the bogie frame. Both the ends of the anchor link act as a hinge and allow movement of the bogie bolster when the coach is moving on a curved track.
LOWER SPRING BEAM
The bolster springs are supported on a lower spring beam. The lower spring beam is a fabricated structure made of steel plates. It is trapezoidal in shape with small steel tubes on each end. The location of the bolster spring seating seati ng is marked by two circular grooves in the center. A rubber washer is placed at the grooved section. The bolster spring sits on the rubber washer. The lower spring beam is also a freefloating structure. It is not bolted or welded either to the bogie frame or the bogie bolster. It is attached to the bogie frame on the outside with the help of a steel hanger. They are traditionally called the BSS Hangers (Bogie Secondary Suspension Hangers). A BSS pin is placed in the tubular section in the end portion of the lower spring beam. A hanger block is placed below the BSS pin. The BSS hanger in turn supports the hanger. This arrangement is done on all the four corners of the lower spring beam. The top end of the hanger also has a similar
40
arrangement. However, instead of the BSS pin, steel brackets are welded on the lower side of the bogie frame of which the BSS hanger hangs with the help of hanger block. This arrangement is same for all the four top corners of the hangers. Hence, the lower spring beam also become a floating member hinged to the bogie frame with the help of hangers on the top and the bottom. This allows for the longitudinal movement of the lower spring beam.
EQUALIZING STAY ROD
The inner section of the lower spring beam is connected to the bogie bolster with the help of an equalizing stay rod. It is a double Y -shaped member fabricated fabricated using steel tubes and sheets. The equalizing stay rod is also hinged on both the ends with the lower spring beam as well as the bogie bolster with the help of brackets welded to the bogie bolster. They are connected through a pin making it a hinged arrangement.
41
SUSPENSION OF ICF (ALL COILED) BOGIE
An ICF Bogie consist consist of two types of suspension system they are :
Primary Suspension System or Axel Box Suspension System. S ystem.
Secondary Suspension System or Bolster Suspension System.
PRIMAR SUSPENSION SYSTEM Since every suspension system consists of springs and dampers , so in this system we use helical compression springs as suspension suspension spring spring an dashpot arrangement as dampers. Primary suspension suspension system of ICF bogie consist of following components: components:
Axle box guide with dashpot arrangement.
Axle box helical compression spring
Derling washers & Hydral washer
Packing rings
AXLE BOX GUIDE DASHPOT ARRANGEMENT
Axle box guide with dashpot arrangement is mainly a cylinder piston arrangement used on the primary suspension of Indian Railway coaches of ICF design. The lower spring seat acts as a cylinder and the axle box guide acts as a piston. The dashpot guide arrangement has the following main components:
Lower Spring Seat, Lower Rubber Washer, Compensating Ring, Guide G uide Bush, Dust Shield ring,Circlip, Dust Shield Spring, Protective Tube with Upper Rubber Washer, Axle Box Guide Screw with sealing washer.
42
The axle box guide (piston) is welded to the bottom flange of the bogie side frame. Similarly, the lower Spring seat(cylinder) is placed on the axle box housing wings forms a complete dashpot guide arrangement of the ICF design coaches. Axle box guides traditionally had a guide cap with 9 holes of 5mm diameter each; however, in the latest design, the guide cap is made an integral part of the guide. Approximately 1.5 liters of dashpot oil is required per guide arrangement. Air vent screws are fitted on the dashpot for topping of oil so that the minimum oil level is maintained at 40mm. Traditionally, rubber washers have been used at the seating arrangement of the primary springs of the axle box housing in the ICF design passenger coaches on the Indian Railways. The rubber washer is used directly on the axle box seating area. the lower spring seat sits on the washers. The lower spring seat is a tubular structure and 3/4 section is partitioned by using a circular ring which is welded at the 3/4 section. On the top of spring seat, a polymer ring called NFTC ring sits. The primary spring sits on the NFTC ring. The lower spring seat plays the role of a cylinder in the dashpot arrangement and is filled with oil. In the dashpot arrangement, the top portion is called the axle box guide. The axle box guide is welded to the bogie frame. The axle box guide works as a piston in the Lower spring seat filled with oil. This helps in damping the vibrations caused during running train operation. The axle box guide, which is welded to the bogie frame has a polymer washer (homo-polymer acetal guide) bush fixed at the head. A polymer packing ring and a guide ring is attached with the Acetal guide bush. These two components act as piston rings for the axle box guide. In order to ensure that the packing ring and the
43
guide ring retain their respective place, a dashpot spring is fixed which applies continuous pressure on the piston ring. The bottom of the axle box guide has a guide cap with perforations so that during the downward movement of the axle guide in the lower spring seat, the oil in the dashpot rushes in the axle box guide. This provides the dampening of vibration in a running coach. The guide cap is fixed with the help of a steel circlip. However in the new design of Axle box guide, the guide cap is welded with the guide assembly and hence the need of a guide cap has been eliminated. The complete guide and lower spring arrangement is covered with a dashpot cover also known as protective tube. The protective tube has a circular ring over it called the dust shield which prevents the ingress of the dust in the cylinder piston arrangement of the dashpot.
44
1 2 1. SPECIALSEREWWITH
3
SEALINGWASHER
4
2. GUIDE 3. PROTECTIVETUBECO MPLETE
5
4. UPPERRUBBERWASHER
6
5. TOP SPRING SEAT 6. DUSTSHIELDSPRING
7
7. DUSTSHIELD 8. HELICALSPRING
8
9. GUIDERING
OIL LEVEL UNDERTARE
9
10. RUBBERPACKING RING 0 4
11. GUIDEBUSH
OILLEVELBEF ORE ASSEMBLING
12. CIRCLIP L E V E L L I A R O T X
10 5 . 2 4 1
4 0 1
5 . 2 9
11
13. C OMPENSATING RING 14. LOWERRUBBERWASHER 15. SAFETYSTRAP 16. LOWERSPRING SEAT
12 13 XTO RAILLEVEL-
14
686 FORALLAC & NON-AC COACHES EXCEPTPOWERCARS POWERCAR-
15
670 FORBOGIEON LUGGAGESIDE
16
672 FORBOGIEON GENERATORSIDE
MODIFIED AXLE BOX GUIDE ARRANGEMENT Figure 3.2a
AXLE BOX HELICAL COMPRESSION SPRING Here helical compression compression springs are used in primary suspension system which are made up of chrome vanadium/chrome vanadium/chrome molybdenum steel. The diameter of coil approximately 245mm. 245mm. Dimensions and working load of some axle box springs are given below.
45
Axle box compression springs with dash pot arrangement (primary suspension system)
DERLING AND HYDRAL WASHERS
They are used in primary suspension system in order to isolate the migrations caused by wheel and it gives perfect seating for axle box compression. They are made up of high density molecular poly utherane.
DERLING WASHER
HYDRAL WASHER
46
PACKING RINGS
These are used in primary suspension system to get equal buffer head. Since all wheels have have different different diameters(due diameters(due to unequal unequal wear wear of wheels) in order order to get same buffer head the packing rings of different dimensions are to be used in primary suspension system.
PACKING RINGS
SECONDARY SUSPENSION SYSTEM
The main function of Secondary suspension system of icf bogie is to transfer the coach load from bloster to bogie frame through BSS hangers . The main components of secondary system are:
Bolster
Lower spring beam
Bolster compression springs
BSS hangers
BSS block
BSS pin
Equalizing stay rod
Anchor link
Shock absorber
47
BOLSTER
The body bolster is a box type fabricated member made up of channels and welded to the body of the coach. It is a free-floating member. The body bolster transfers the dead weight of the coach body to the bogie frame. There are two type of bolsters in an ICF bogie: body bolster and the bogie bolster. The body bolster is welded to the coach body whereas the bogie bolster is a free floating member which takes the entire load of the coach through the body bolster.In body bolster there are 2 side bearers and a center pivot pin are joined by excellent quality welding. These three parts acts as a male part and matches with the female part welded to bogie bolster. These are very vital parts for smooth running of a train.
Bogie Bolster
LOWER SPRING BEAM
The bolster springs are supported on a lower spring beam. The lower spring beam is a fabricated structure made of steel plates. It is trapezoidal in shape with small steel tubes on each end. The location of the bolster spring seating is marked by two
48
circular grooves in the center. A rubber washer is placed at the grooved section. The bolster spring sits on the rubber washer. The lower spring beam is also a freefloating structure. It is not bolted or welded either to the bogie frame or the bogie bolster. It is attached to the bogie frame on the outside with the help of a steel hanger. They are traditionally called the BSS Hangers (Bogie Secondary Suspension Hangers). A BSS pin is placed in the tubular section in the end portion of the lower spring beam. A hanger block is placed below the BSS pin. The BSS hanger in turn supports the hanger. This arrangement is done on all the four corners of the lower spring beam. The top end of the hanger also has a similar arrangement. However, instead of the BSS pin, steel brackets are welded on the lower side of the bogie frame of which the BSS hanger hangs with the help of hanger block. This arrangement is same for all the four top corners of the hangers. Hence, the lower spring beam also become a floating member hinged to the bogie frame with the help of hangers on the top and the bottom. This allows for the longitudinal movement of the lower spring beam .
LOWER SPRING BEAM
49
BOLSTER COMPRESSION SPRINGS
Since it is a ICF all coiled bogie, helical compression springs are used in secondary suspension
system.
They
are
made
up
of
chrome
vanadium/
chrome
molybdenumsteel. The mean diameter of bolster springs are approximately 324mm. Dimensions and safe working load of some bolster springs are given below.
Load deflection testing and grouping of Bolster spring (B.G Main line coaches) Code
Wir Wire dia
Free height
Test Load
Acceptable Groups as per loaded spring height height under test load A
B
C
Yello ellow w
Oxfo Oxford rd Blue Blue #
Green
B 01
42
385
3300
301-317
301-305
306-311
312-317
B 03
42
400
4800
291-308
291-296
297-303
304-308
B 04
47
400
6100
286-304
286-291
292-297
298-304
B 06
36
416
4200
280-299
280-286
287-292
293-299
B11
47
B 13
34
386
6700
306-322
306-311
312-317
318-322
B 15
40
393
B 16
32.5
286
6000
256-272
256-261
262-267
268-272
50
BSS HANGERS, BSS BLOCKS, BSS PINS
In secondary suspension system, the bolster is supported on helical coiled springs which are placed on lower spring beam. The lower spring beam is suspended from bogie side frame through BSS hangers on BSS hanger blocks. This BSS hanger blocks are supported on BSS hanger pins which are attached in bogie frame .
BSS HANGERS
BSS BLOCK
BSS PIN
51
The figure shows assemble parts of BSS Hanger, BSS Block, BSS Pin
EQUALIZING STAY RO-
The inner section of the lower spring beam is connected to the bogie bolster with the help of an equalizing stay rod. It is a double Y -shaped member fabricated fabricated using steel tubes and sheets. The equalizing stay rod is also hinged on both the ends with the lower spring beam as well as the bogie bolster with the help of brackets welded to the bogie bolster. They are connected through a pin making it a hinged arrangement.
Equalizing Stay Rod & Anchor Link
52
ANCHOR LINK
It is a pin connection to the Bolster sides and the Bogie Transoms. The main function of anchor link is to transfer braking/tractive force from bogie frame to bolster and it restricts the rolling motion of bolster. It It can swivel universally universally to permit the bolster to rise and fall and sway side wards. One anchor link isprovided on each side of the bolster diagonally across. Fitted with silent block bushes in order to isolate vibrations vibrations from bogie frame. frame. It holds in position longitudinally longitudinally the floating bogie bolster.
SHOCK ABSORBER
In order to decrease the unwanted oscillations during pitching, shock absorbers are used as damper. Since secondary suspension of ICF Bogie has helical coil springs, to isolate unwanted oscillations of this spring a gabrieal or escort shock absorbers are used.
53
Figure shows a gabrieal hydraulic shock absorber with capacity capacity of ±600kg (i.e.,in (i.e.,in tensile and in compression) at a speed of 10cm/sec is fitted to work in parallel with the bolster springs to provide damping for vertical oscillations.
54
PROCEDURE OF OVER HAULING OF SUSPENSIONSYSTEMS OF ICF BOGIE
Over hauling of primary suspension system
Over hauling of secondary suspension system
OVER HAULING OF PRIMARY SUSPENSION SYSTEM
The main components in primary suspension system to be over haul are:1) Axle box compression springs 2) Dash pot 3) Guide bush 4) Dearling and hydral washers or rubber pads
OVER HAULING OF SECONDARY SUSPENSION SYSTEM
The main compents in secondary suspension system to be over haul are:1) Bolster springs 2) BSS hangers 3) BSS block and BSS pin 4) Shock absorbers 5) Lower spring beam
55
POH OFPRIMARY SUSPENSION SYSTEM
OVER HAULING OF AXLE BOX COMPRESSION SPRINGS:Steps to follow over hauling of axle box compression springs:Step 1:- After dismantling the bogie parts, the axle box compression springs are sent
to sand blasting chamber where these springs are cleaned with a blast of sand . Step 2:- Now these springs are sent to Spring Sectio n. Step 3:- In spring section, these springs are cleaned completely from oil, grease,
scale etc. by putting them in a Bosch tank containing degreasing agents (soda ash: 2%, caustic soda: 1% and tri sodium phosphate:1% in 5000 liters of water) for a period of 8 hours and then then followed followed by rinsing with hot water/steam water/steam to clean off any residual chemicals.
Step 4:- Now inspect the spring visually under proper illumination for broken,
cracks, dents, tool marks, welding marks or corrosion pits. Springs having cracks/dent/tool/welding cracks/dent/tool/welding marks or corrosion pitting should be rejected .
56
Step 5:- Now accepted springs are sent in to shot blasting/ pining machine, where
springs are hit by a group of cast steel balls at a force of 25kg/sq.cm to improve fatigue strength and this process also clean the surface of the spring from paints,
scales etc…which are not perfectly cleaned in Bosch tank .
Shot blasting/pining machine
Step 6:- After shot blasting springs are subjected to Load Test on Hydraulic Load
Testing Machine. In this process the springs are tested for deflection on the application of working loads for ½ minute, if springs deflect beyond its range it is rejected. The table shows the range of acceptable deflection limits of different springs under specified working load and it also indicates grouping of springs with respect to their deflection limits. Tie a single loop of sealing wire on one of the
coils of category „A‟ springs, springs, two loops for „B‟ „B‟ and three loops for „C‟ „C‟ group.
57
Load Testing Machine
Step 7:- After this process, springs are sent to Magna Flux Crack Detection Test in
order to identify cracks which are not visible by naked eye. In this Magna Flux Crack Detection Test springs are first magnetized with the help of electric current, after magnetization a fluorescent liquid containing small iron particles suspended in water. Now the cracked spring is detected under ultra violet rays if spring
58
contains any cracks which are not visible to naked eye. By this way cracked spring is rejected in this process.
Magna flux crack detecting machine
Cracked detected under ultra violet rays
Step 8:- After crack detecting test, the accepted springs should be given one coat of
Red Oxide Zinc Chromate and followed by a coat of Black Japan in order to get better abrasion resistance and corrosion resistance.
Step 9:- The springs have to be painted with colour codes which are grouped with
respective to their deflection ranges . Spring group
Color code
A
Yellow
B
Oxford Blue
C
Green
59
Step 10:- Then similar colour code springs are kept in a bin, which are used in a
same bogie.
OVER HAULING OF DASHPOTS Steps to follow over hauling of Dash Pots:Step 1:- After dismantling the bogie parts, the dash pots are sent to sand blasting
chamber, where it is cleaned by blast of sand. Step 2:- Then it is sent to Bogie section, where it is visually checked for cracks,
dents, deformation etc..If they are detected, the dash pot is rejected . Step 3:- Acceptable dash pots are sent to assemble section for reuse .
Over hauling of Dash Pots
60
OVER HAULING OF GUIDE BUSH Steps to follow over hauling of Guide bush:Step 1:- Since guide is permanently attached to bogie frame hence it is cleaned
along with bogie frame. visually checked for damages. damages. If Step 2:- After tramling of bogie frame the guide is visually any damages are detected the guide is separated from bogie frame with the help of gas cutter. Step 3:- The guide bush of a guide is replaced in every POH.
Over hauling of Guide bush
OVER HAULING OF DEARLING AND HYDRAL WASHERS Steps to follow over hauling of Dearling and hydral washers:Step 1:- After dismantling dearling and hydral washers from bogie, they are sent to
bearing chamber where they are cleaned with the help of saw dust. Step 2:- Check the washers for wear, cracks, dents etc.. if any of them is found the
washers are rejected and replaced with new one .
61
Dearling washer
Hydral washers
POH OF SECONDARY SUSPENSION SYSTEM
OVR HAULING OF BOLSTER HELICAL COMPRESSION SPRINGS:Steps to follow over hauling of bolster helical compression springs:Step 1:- After dismantling the bogie parts, the bolster helical compression springs
are sent to sand blasting chamber where these springs are cleaned with a blast of sand. Step 2:-Now these springs are sent to Spring Section . Step 3:- In spring section, these springs are cleaned completely from oil, grease,
scale etc. by putting them in a Bosch tank containing degreasing agents (soda ash: 2%, caustic soda: 1% and tri sodium phosphate:1% in 5000 liters of water) for a period of 8 hours and and then followed by rinsing with hot water/steam water/steam to clean off off any residual chemicals.
62
Step 4:- Now inspect the spring visually under proper illumination for broken,
cracks, dents, tool marks, welding marks or corrosion pits. Springs having cracks/dent/tool/welding cracks/dent/tool/welding marks or corrosion pitting should be rejected .
Step 5:- Now accepted springs are sent in to shot blasting/ pining machine, where
springs are hit by a group of cast steel balls at a force of 25kg/sq.cm to improve fatigue strength and this process also clean the surface of the spring from paints,
scales etc…which are not perfectly cleaned in Bosch tank.
Shot blasting/pining machine
63
Step 6:-After shot blasting springs are subjected to Load Test on Hydraulic Load
Testing Machine. In this process the springs are tested for deflection on the application of working loads for ½ minute, if springs deflect beyond its range it is rejected. The table shows the range of acceptable deflection limits of different springs under specified working load and it also indicates grouping of springs with respect to their deflection limits. Tie a single loop of sealing wire on one of the
coils of category „A‟ springs, two loops for „B‟ and three loops for „C‟ group .
Load Testing Machine
64
Step 7:-After this process, springs are sent to Magna Flux Crack Detection Test in
order to identify cracks which are not visible by naked eye. In this Magna Flux Crack Detection Test springs are first magnetized with the help of electric current, after magnetization a fluorescent liquid containing small iron particles suspended in water. Now the cracked spring is detected under ultra violet rays if spring contains any cracks which are not visible to naked eye. By this way cracked spring is rejected in this process.
Magna flux crack detecting machine
Cracked detected under ultra violet rays
Step 8:- After crack detecting test, the accepted springs should be given one coat of
Red Oxide Zinc Chromate and followed by a coat of Black Japan in order to get better abrasion resistance and corrosion resistance.
65
Step 9:- The springs have to be painted with colour codes which are grouped with
respective to their deflection ranges. Spring group
Color code
A
Yellow
B
Oxford Blue
C
Green
Step 10:- Then similar colour code springs are kept in a bin, which are used in a
same bogie.
OVER HAULING OF BSS HANGERS:Steps to follow over hauling of BSS Hangers:Step 1:-Check the cleaned hangers for cracks and wear. Replace the hangers if
cracked or wear exceeds 1mm. Magna flux crack detection equipment shall be used for checking.
66
Step 2:-The horizontal wearing surface may be built up using 2B electrodes, filed
and ground to size. Then hard powder coating may be applied. Hardness value should be 55-60 RH. Step 3:-The vertical gap should be within the permissible limit i.e., 384-386 mm.
All the hangers should be tested to tensile load of 8 tones and replaced if any permanent set is observed in the hangers. Step 4:-After repair and testing all the BSS hangers should be painted with one coat
of anti corrosive back paint. Write the actual length between the wearing arms on the BSS hanger with paint.
BSS HANGERS
REJECTED BSS HANGER
OVER HAULING OF BSS BLOCK AND BSS PIN Steps to follow over hauling of BSS block and BSS pin:Step 1:- Check the cleaned BSS block and BSS pin for dimensions, cracks and
wear. Step 2:- Reject them if any change in dimensions beyond its limits, cracks or wears
are appeared .
67
Step 3:- Acceptable blocks and pins are sent to assemble section to reuse. Step 4:- Apply colour code as yellow for acceptable pins and red for rejected pins.
OVER HAULING OF SHOCK ABSORBERS Steps to follow over hauling of Shock Absorbers:Step 1:-Periodicity overhaul
a) Schedule overhaul:- shock absorbers should be given a schedule overhaul:
When their capacities vary beyond ± 20% of o f their specified values, or
After 4 lakh kilometers or alternate POH, whichever is earlier.
b) Non schedule overhaul:- shock absorbers should also be overhauled whenever suspected to be defective. Which is indicated primarily by oil lekage or when they are physically damaged. Step 2:-Testing
a) The shock absorber is tested on the special purpose machine (RDSO sketch mos. 69.2.04.00 to 69.2.04.08) which can measure its capacity in both tension and compression by developing the resisting force at a
68
velocity of 10cm/sec. the length of shock absorber and its stroke should be within the limits specified. b) The shock absorber must be tested at every POH and reused if overhauling is not due and its capacity is within ±20%. A register should be maintained in the shock absorber section wherein the test results of each shock absorber should be recorded before the shock absorber is certified fit for use on coaches. Step 3:- After the testing and certification, the protection cover of the shock
absorber should be pressed into position on the piston rod disc and spot welding at six points around the periphery. Step 4:- The shock absorber should then be extended on the mounting fixture and
painted. When the paint dries, it should be compressed and then removed from the fixture. Step 5:- The dare of testing, the date of overhauling and the name of the shop where
overhauled should invariably be stamped on the name plate o shock absorber before it is sent for fitment.
OVER HAULING OF LOWER SPRING BEAM Steps to follow over hauling of Lower spring beam:Step 1:-Check :-Check the lower spring beam (plank) for cracks, corrosion, etc. and repair
or replace as required.
69
Step 2:- The following parts of the lower spring plank should be inspected and
repaired or replaced as required:
Bolster suspension straps if bent or damaged
Stay rod brackets if worm, bent or corroded
Shock absorber fixing bosses if damaged
Spring guide rings If required
Lug if damaged
Step 3:- Replace the following parts:
Bushes of BSS brackets of worm beyond permissible limits
Equalizing stay brackets bushes
BSS pins If worm beyond permissible limits.
Step 4:- The locations where the repairs have been carried out or found corroded out
or found corroded should be cleaned to bare metal and painted with two coats of primer to IS:2074 to a minimum minimum Dry Dry Film Thickness
(DFT) of 50 microns microns
followed by one coat of anti-corrosive Black Japan Type-B to IS:341 to a DFT of 35 microns, after which entire lower spring beam is to be given one coat of Black Japan Type-B to IS:341 to a minimum DFT of 35 microns.
Lower spring beam
70
ADVANTAGES
Comfort to the passengers
Good handling
Shields the vehicle from damage
Increases the life of the vehicle
Keep the tires pressed firmly to the ground
71
SUGGESTION
Suspension system of a ICF bogie mainly fails due to failure of springs and improper assembly. Since failure of springs is mainly due to improper hardness, we would suggest that to involve a heat treatment process of springs during over hauling in order to get desire hardness. A special care should be taken during assembly of suspension system in order to avoid failure due to improper assembly
72
CONCLUSION
From the whole discussion in suspension system, I observe that suspension system is like a white blood cell .As white blood cell provides energy to our body to fight against diseases or viruses which try to destroy or try to decrease our life ,in the similar way suspension system provides the energy to a vehicle to protect itself from damaging, increasing life of the vehicle ,increases the handing, increases comfort of passengers and many more. So, according to me if you remove the suspension system, then you feel like in bull- cart in Audi, Mercedes types luxurious cars. The only difference is speed. So, the scope of Suspension System is Too Bright.
73
