Seminar Report
Transcript of Seminar Report
KANPUR INSTITUTE OF TECHNOLOGY
A Seminar report on
Nitro Shock Absorber
Year 2010-11
Guided By- Submitted By-Mr. Ritesh Dixit Harsh Krishnan SrivastavaLecturer ME Pre Final YearME Department 0816540019
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CERTIFICATE
This is to certify that Harsh Krishnan Srivastava has worked under our supervision and guidance for the senior titled Nitro Shock Absorber in partial fulfillment of the requirements for the award of degree of BACHELOR OF TECHNOLOGY in Mechanical Engineering of UTTAR PRADESH TECHNICAL UNIVERSITY, LUCKNOW during academic year 2010-2011. It is further seen that to the best of our knowledge .This work has not be submitted to any university in fulfillment of requirement of any degree and has not be published elsewhere .His submission of the above mentioned course is here by approved.
Mr.Ritesh Dixit(Lecturer)Mechanical Engg. DepartmentKanpur Institute of Technology
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ACKNOWLEDGEMENT
The writing of the acknowledgement after completion of report is pleasure for me. It signals the completion of text, but more important if provides an opportunity to express my indepthness of those to contribute on so much to me and to this report. I feel honoured to express my heart fold and sincere gratitude to Mr.RiteshDixit, Kanpur Institute of Technology for his constant and generous help and able guidence throughout .I wish to convey my deep sense of gratitude to my teachers for their able guidance throughout the study.I would also like to thank my valuable friends for their excellent cooperation during this period. With great pride, I would like to thank my correspondents as without their help bringing out this seminar project would have been impossible.
Harsh Krishnan SrivastavaMechanical - Pre Final Year
0816540019
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PREFACE
It is required to take a seminar project report for the partial fulfillment of the B.Tech programme so as to practical experience now in the mechanism world each company tries to launch new technologies in the market. Their main aim is to develop our system which is efficiency and also eco-friendly and is accepted at large by focusing on various attitudes like price, quantity and other special unique features.
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CONTENTS Page No.
INTRODUCTION 6
NEED FOR SHOCK ABSORBERS 14
SHOCK ABSORBER ACTION 17
GAS FILED SHOCK ABSORBERS 21
TYPES 24
WORKING 25
ADVANTAGES 28
MOUNTING TIPS 34
CONCLUSION 35
REFERENCES 36
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SYNOPSIS
In the present scenario of automobile industry manufacturers are trying to produce
comfortable and safe vehicles which the consumers are looking for. A shock absorber is a
damping element of the vehicle suspension, and its performance directly affects the
comfortability, dynamic load of the wheel and dynamic stroke of the suspension. The
conventional type of shock absorbers has got the main drawback that it causes foaming of
the fluid at high speeds of operation. This results in a decrease of the damping forces and
a loss of spring control. The gas filled shock absorbers are designed to reduce foaming of
the oil and provide a smooth ride for a long period.
INTRODUCTION
For a smooth and comfortable ride the disturbing forces should be eliminated or reduced
considerably by using some devices. Shock absorbers are such devices which isolate the
vibrations by absorbing some disturbing energy themselves. Of the many types telescopic
shocks are widely used which has got the draw back that the flow of oil in the cylinder
can cause foam of oil and air to form. These limit the optimum throughout of the flow in
the valves. Gas shocks represent an advance over traditional shocks. Nitrogen filled gas
shock absorbers are the results of years of extensive research and development with top
flight shock design engineers. They are designed for both lowered and stock vehicles to
provide shock absorbers that would out perform anything on the market today. Nitro
shock absorbers are high quality, nitrogen filled shocks designed and gas charged
specifically for each vehicle application. The addition of nitrogen under pressure limits
the foaming effect and increases efficiency.
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A BRIEF HISTORY
In the early 1900's, cars still rode on carriage springs. After all, early drivers had bigger things to worry about than the quality of their ride - like keeping their cars rolling over the rocks and ruts that often passed for roads.Pioneering vehicle manufacturers were faced early on with the challenges of enhancing driver control and passenger comfort. These early suspension designs found the front wheels attached to the axle using steering spindles and kingpins. This allowed the wheels to pivot while the axle remained stationary. Additionally, the up and down oscillation of the leaf spring was damped by device called a shock absorber.
These first shock absorbers were simply two arms connected by a bolt with a friction disk between them. Resistance was adjusted by tightening or loosening the bolt.As might be expected, the shocks were not very durable, and the performance left much to be desired. Over the years, shock absorbers have evolved into more sophisticated designs.
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WHAT SHOCKS DO
Let's start our discussion of shock absorbers with one of very important point: despite what many people think, conventional shock absorbers do not support vehicle weight. Instead, the primary purpose of the shock absorber is to control spring and suspension movement. This is accomplished by turning the kinetic energy of suspension movement into thermal energy, or heat energy, to be dissipated through the hydraulic fluid.Shock absorbers are basically oil pumps. A piston is attached to the end of the piston rod and works against hydraulic fluid in the pressure tube. As the suspension travels up and down, the hydraulic fluid is forced through tiny holes, called orifices, inside the piston. However, these orifices let only a small amount of fluid through the piston. This slows down the piston, which in turn slows down spring and suspension movement.The amount of resistance a shock absorber develops depends on the speed of the suspension and the number and size of the orifices in the piston. All modern shock absorbers are velocity sensitive hydraulic damping devices - meaning the faster the suspension moves, the more resistance the shock absorber provides. Because of this feature, shock absorbers adjust to road conditions. As a result, shock absorbers reduce the rate of:
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Bounce
Roll or sway
Brake dive and Acceleration squat
Shock absorbers work on the principle of fluid displacement on both the compression and extension cycle. A typical car or light truck will have more resistance during its extension cycle then its compression cycle. The compression cycle controls the motion of a vehicle's unsprung weight, while extension controls the heavier sprung weight.
Compression cycle
During the compression stroke or downward movement, some fluid flows through the piston from chamber B to chamber A and some through the compression valve into the reserve tube. To control the flow, there are three valving stages each in the piston and in the compression valve.At the piston, oil flows through the oil ports, and at slow piston speeds, the first stage bleeds come into play and restrict the amount of oil flow. This allows a controlled flow of fluid from chamber B to chamber A.At faster piston speeds, the increase in fluid pressure below the piston in chamber B causes the discs to open up away from the valve seat.At high speeds, the limit of the second stage discs phases into the third stage orifice restrictions. Compression control, then, is the force that results from a higher pressure present in chamber B, which acts on the bottom of the piston and the piston rod area.
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Extension cycle
As the piston and rod move upward toward the top of the pressure tube, the volume of chamber A is reduced and thus is at a higher pressure than chamber B. Because of this higher pressure, fluid flows down through the piston's 3-stage extension valve into chamber B.However, the piston rod volume has been withdrawn from chamber B greatly increasing its volume. Thus the volume of fluid from chamber A is insufficient to fill chamber B. The pressure in the reserve tube is now greater than that in chamber B, forcing the compression intake valve to unseat. Fluid then flows from the reserve tube into chamber B, keeping the pressure tube full.Extension control is a force present as a result of the higher pressure in chamber A, acting on the topside of the piston area.
SHOCK ABSORBER DESIGN
There are several shock absorber designs in use today:o Twin Tube Designs
o Gas Charged
o PSD
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o ASD
Mono-Tube
Basic Twin Tube Design
The twin tube design has an inner tube known as the working or pressure tube and an outer tube known as the reserve tube. The outer tube is used to store excess hydraulic fluid.There are many types of shock absorber mounts used today. Most of these use rubber bushings between the shock absorber and the frame or suspension to reduce transmitted road noise and suspension vibration. The rubber bushings are flexible to allow movement during suspension travel. The upper mount of the shock absorber connects to the vehicle frame.Notice that the piston rod passes through a rod guide and a seal at the upper end of the pressure tube. The rod guide keeps the rod in line with the pressure tube and allows the piston to move freely inside. The seal keeps the hydraulic oil inside and contamination out.The base valve located at the bottom of the pressure tube is called a compression valve. It controls fluid movement during the compression cycle.
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Bore size is the diameter of the piston and the inside of the pressure tube. Generally, the larger the unit, the higher the potential control levels because of the larger piston displacement and pressure areas. The larger the piston area, the lower the internal operating pressure and temperatures. This provides higher damping capabilities.Ride engineers select valving values for a particular vehicle to achieve optimal ride characteristics of balance and stability under a wide variety of driving conditions. Their selection of valve springs and orifices control fluid flow within the unit, which determines the feel and handling of the vehicle.
Twin Tube - Gas Charged Design
The development of gas charged shock absorbers was a major advance in ride control technology. This advance solved many ride control problems which occurred due to an
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increasing number of vehicles using uni-body construction, shorter wheelbases and increased use of higher tire pressures.The design of twin tube gas charged shock absorbers solves many of today's ride control problems by adding a low pressure charge of nitrogen gas in the reserve tube. The pressure of the nitrogen in the reserve tube varies from 100 to 150 psi, depending on the amount of fluid in the reserve tube. The gas serves several important functions to improve the ride control characteristics of a shock.The prime function of gas charging is to minimize aeration of the hydraulic fluid. The pressure of the nitrogen gas compresses air bubbles in the hydraulic fluid. This prevents the oil and air from mixing and creating foam. Foam affects performance because it can be compressed - fluid can not. With aeration reduced, the shock is able to react faster and more predictably, allowing for quicker response time and helping keep the tire firmly planted on the road surface.
An additional benefit of gas charging is that it creates a mild boost in spring rate to the vehicle. This does not mean that a gas charged shock would raise the vehicle up to correct ride height if the springs were sagging. It does help reduce body roll, sway, brake dive, and acceleration squat.This mild boost in spring rate is also caused by the difference in the surface area above and below the piston. With greater surface area below the piston than above, more pressurized fluid is in contact with this surface. This is why a gas charged shock absorber will extend on its own.
The final important function of the gas charge is to allow engineers greater
flexibility in valving design. In the past such factors as damping and aeration forced
compromises in design.
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NEED FOR SHOCK ABSORBERS
Springs alone cannot provide a satisfactorily smooth ride. Therefore an additional
device called a “shock absorber” is used with each spring. Consider the action of a coil
spring. The spring is under an initial load provided by the weight of the vehicle. This
gives the spring an original amount of compression. When the wheel passes over a bump,
the spring becomes further compressed. After the bump is passed the spring attempts to
return to its original position. However it over rides its original position and expands too
much. This behaviour causes the vehicle frame to be thrown upward. Having expanded
too much, the spring attempts to compress that it will return to its original position; but in
compressing it again overrides. In doing this the wheel may be raised clear of the road
and the frame consequently drops. The result is an oscillating motion of the spring that
causes the wheel to rebound or bounce up and down several times, after a bump is
encountered. If, in the mean time, another bump is encountered, a second series of
rebounding will be started. On a bumpy road, and particularly in rounding a curve, the
oscillations might be so serious as to cause the driver to lose control of the vehicle.
A shock absorber is basically a hydraulic damping mechanism for controlling
spring vibrations. It controls spring movements in both directions: when the spring is
compressed and when it is extended, the amount of resistance needed in each direction is
determined by the type of vehicle, the type of suspension, the location of the shock
absorber in the suspension system and the position in which it is mounted. Shock
absorbers are a critical product that determines an automobile’s character not only by
improving ride quality but also by functioning to control the attitude and stability of the
automobile body.
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PRINCIPLE OF OPERATION
The damping mechanism of a shock absorber is viscous damping. Viscosity is the
property of a fluid by virtue of which it offers resistance to the motion of one layer over
the adjacent on. The main components of a viscous damper are cylinder, piston and
viscous fluid. There is a clearance between the cylinder walls and the piston. More the
clearance more will be the velocity of the piston in the viscous fluid and it will offer less
value of viscous damping coefficient. The basic system is shown below. The damping
force is opposite to the direction of velocity.
I-CLEARNCE, II-PISTON, III-VISCOUS FLUID
The damping resistance depends on the pressure difference on the both sides of
the piston in the viscous medium. The figure shown below shows the example of free
vibrations with viscous damping.
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The equation of motion for the system can be written as mx + cx +kx = 0
Energy dissipation in viscous damping :
For a vibratory body some amount of energy is dissipated because of damping.
This energy dissipation can be per cycle. Rate of change of work W is called energy. For
a viscously damped system the force F is expressed as
F= cx = cdx/dt, where x = dx/dt
Work done W = Fx = (cdx/dt) x
The rate of change of work per cycle
i.e. Energy dissipated
Let us assume the simple harmonic motion of the type x = Asinωt
(dx/dt) ² = ω²A²cos²ωt
The equation for
This shows that the energy dissipation per cycle is proportional to the square of the
amplitude of motion.
The total energy of a vibrating system can be either maximum of its potential or kinetic
energy. The maximum kinetic energy of the system can be written as E = (KE) max =
1/2mx²max
= 1/2mω²A²
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SHOK ABSORBER ACTION
Shock absorbers develop control or resistance by forcing fluid through restricted
passages. A cross-sectional view of a typical shock absorber is shown below. Its main
components and working is also given below.
The inside parts of a shock absorber
The upper mounting is attached to a piston rod. The piston rod is attached to a
piston and rebound valve assembly. A rebound chamber is located above the piston and a
compression chamber below the piston. These chambers are full of hydraulic fluid. A
compression intake valve is positioned in the bottom of the cylinder and connected
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hydraulically to a reserve chamber also full of hydraulic fluid. The lower mounting is
attached to the cylinder tube in which the piston operates.
During compression, the movement of the shock absorber causes the piston to move
downward with respect to the cylinder tube, transferring fluid from the compression
chamber to the rebound chamber. This is accomplished by fluid moving through the outer
piston hole and unseating the piston intake valve.
During rebound, the pressure in the compression chamber falls below that of the
reserve chamber. As a result, the compression valve will unseat and allow fluid to flow
from the reserve chamber into the compression chamber. At the same time, fluid in the
rebound chamber will be transferred into the compression chamber through the inner
piston holes and the rebound valve.
Spring Schematic Diagram of the Interior of a Shock Absorber
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FORMS OF SUSPENSIONS AND TYPES OF SHOCK
ABSORBERS
Various types of shock absorbers are available in the market. Out of that the
widely used types and their characteristics are given below.
Type Product Characteristics
Double-wishbone(Multilink)
Double-tube
The outer part of the double tube is used as a gas chamber, which is filled with low- pressure nitrogen gas. This type can provide stable damping force.
Single-tube
Separation between oil and nitrogen gas by a free piston provides stable damping force, as well as high performance.
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Strut
Double-tube
This type consists of double tubes that comprise part of the support structure of the suspension. Filled with low-pressure nitrogen gas, it provides stable damping force.
Inverted type
Structurally, this is a single-tube type placed upside down. Its large-diameter pipe provides sufficient rigidity to bear the heavy load from the car body, characteristic of a strut.
With a steering arm
When connected to the power steering system at a point higher than normal, this type allows the cabin space to be expanded and the maneuvering stability improved.
Type with separately mounted spring (rigid axle, etc.)
Unit damper
Because the spring is mounted separately, this type features a simple structure comprised of a damping mechanism
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WHY GAS FILLED SHOCK ABSORBERS?
The rapid movement of the fluid between the chambers during the rebound and
compression strokes can cause foaming of the fluid. Foaming is the mixing of free air and
the shock fluid. When foaming occurs, the shock develops a lag because the piston is
moving through an air pocket that offers up resistance. The foaming results in a decrease
of the damping forces and a loss of spring control.
During the movement of the piston rod, the fluid id forced through the valuing of
the piston. When the piston rod is moving quickly, the shock absorbers oil cannot get
through the valuing fast enough, which causes pressure increases in front of the piston
and pressure decreases behind the piston. The result is foaming and a loss of shock
absorber control. The need for a gas filled shock absorber arises here.
GAS FILLED SHOCK ABSORBER
The gas filed shock absorbers is designed to reduce the foaming of the oil. It uses
a piston and oil chamber similar to other shock absorbers. The difference is that instead
of a double tube with a reserve chamber, a dividing piston separates the oil chamber from
the gas chamber. The oil chamber contains a special hydraulic oil and the gas chamber
contains nitrogen at 25 times atmospheric pressure. The schematic diagram showing the
inside parts of a gas filled shock absorber is shown below.
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The inside parts of a gas-filled shock absorber.
When the piston rod is moved into the shock absorber, oil is displaced as in
double tube principle. This oil displacement causes the dividing piston to press in the gas
chamber, thus reducing it in size. With the return of the piston rod the gas pressure
returns the dividing piston to its starting position.
Whenever the oil column is held at a static pressure of approximately 25 times
atmospheric pressure, the pressure decreases behind, the working piston cannot be high
enough for the gas to exit from the oil column. Consequently, the gas filled shock
absorber operates without foaming.
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Gas Shock Absorbers
Gas shock absorbers represent an advance over traditional shocks. At high speeds, the flow of oil in the cylinder can cause a foam of oil and air to form. This limits the optimum throughput of the flow in the valves. The addition of nitrogen under pressure limits this phenomenon and increases efficiency. There are two types of gas shock absorbers:
Single tube with high pressure
Twin-tube with low pressure gas.
1. High pressure single tube shock absorbers.
Gas shock absorbers operate on the same basic principle of movement of the piston in an oil filled tube but they contain, at one end, a small quantity of nitrogen under high pressure (25 bars). The gas is prevented from mixing with the oil by a floating piston. When the piston rod passes into the body and displaces oil, the oil compresses the nitrogen even further. The volume of gas changes, playing the same role as an equalization tube. The permanent pressure exerted on the oil by the gas guarantees an instantaneous response and quieter piston valve operation. At the same time, this constant pressure eliminates cavitation and foaming which could momentarily degrade the effectiveness of the shock absorber.
2. Low Pressure gas twin-tube shock absorbers
The Monroe Original twin-tube Gas-Technology design retains the classical twin-tube while adding, at the top of the reserve tube, nitrogen under relatively low pressure 2,5-5 bars instead of the 25-30 bars used in high pressure shock absorbers.This pressure is sufficient to to radically improve the efficiency of the shock absorber. The Monroe Original low-pressure design presents two main innovations:
in the upper part of the reserve tube, air at atmospheric pressure is replaced by nitrogen ( an inert gas) at pressure of 2,5 to 5 bars.This is introduced once and for all during manufacture.
The oil seal surrounding the piston rod in the upper body of the shock absorber has been especially designed with one lip to prevent the entry of dust and with a further two sealing lips to prevent oil escaping.The base of the seal is in the form of a circular strip which functions as a non-return valve.The flexibility of the strip allows the oil to flow back into the reserve tubes and keeps the gas pressure solely on the oil in the reserve.
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The low pressure shock absorber design has enabled Monroe to solve certain problems
associated with the MacPersonsystem.These shock absobers produce a very comfortable
ride and very precise steering.
TYPES OF GAS FILLED SHOCK ABSORBERS
Twin– tube with low pressure gas.
Single- tube with high pressure gas.
LOW PRESSURE TWIN- TUBE SHOCKS
Twin- tube gas technology design retains the classical twin-tube while adding at
the top of the reserve tube nitrogen under relatively low pressure 2.5- 5 bars instead of
25- 30 bars used in high pressure shock absorbers. This pressure is sufficient to radically
improve the efficiency of the shock absorbers.
HIGH PRESSURE SINGLE- TUBE SHOCKS
Gas shock absorbers operate in the same principle of movement of the piston in
an oil filled tube but they contain at one end a small quantity of nitrogen under high
pressure (25 bars). The gas is prevented from mixing with the oil by a floating piston.
When the piston rod passes into the body and displaces oil, the oil compresses the
nitrogen even further. The volume of gas changes playing the role as an equalization
tube. The permanent pressure exerted on the oil by the gas guarantees an instantaneous
response and the quieter piston valve operation. At the same time this constant pressure
eliminates cavitations and foaming which could momentarily degrade the effectiveness of
the shock absorber.
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WORKING
Bump Stroke:
When the piston rod is pushed in oil flows without resistance from below the
piston through the orifices and the non-return valve to the enlarged volume above the
piston. Simultaneously, a quantity of oil is displaced by the volume of the rod entering
the cylinder. This volume of oil is forced to flow through the bottom valve into the
reservoir tube (filled with air (1 bar) or nitrogen gas (4-8 bar)). The resistance,
encountered by the oil passing through the footvalve, generates the bump damping.
Rebound Stroke:
When the piston rod is pulled out, the oil above the piston is pressurized and forced to
flow through the piston. The resistance, encountered by the oil on passing through the
piston, generates the rebound damping. Simultaneously, some oil flows back, without
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resistance, from the reservoir tube through the footvalve to the lower part of the cylinder
to compensate for the volume of the piston rod emerging from the cylinder.
Twin Tube Shock Absorber
A twin tube shock or the Twin tube shock absorber is a low pressure shock having tube inside the outer shock body which contains the piston assembly. In order to create damping force, different coil springs inside the shock body are used. The inner tube is known as pressure tube whereas the outer tube is known as the reserve tube. The reserve tube is used for storing different types of hydraulic fluid. The mounts used for the shock absorber are many but the most popularly used rubber mount is rubber bushings between the shock absorber and the suspension for minimizing suspension vibration.
The piston rod passes to the upper end of the pressure tube through rod guide and the seal. The rod guide assist the piston to move freely inside whereas the oil is kept inside by the seal. The movement of the fluid is controlled by the base valve which is located at the bottom of the pressure tube.
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Working of a Twin Tube Shock Absorber
The pushing of the piston results in the flow of the oil without resistance from below the piston through different outlets to the area above the piston. The oil displaced the rod flows into the reservoir tube filled with air. The oil encounters the resistance while passing through the foot valve thereby generating the bump damping.
The oil above the piston is pressurized when the piston rod is pulled out which the flows through the piston. The oil when encounters an resistance while passing through the piston, generates the rebound damping.
Types of Twin Tube Shock Absorber
Twin tube shock absorber can be of different types depending on the mechanism used. Some of the popular types are as follows:
Gas Charged Twin Tube Shock Absorber Gas charged shock absorber solved many problems associated with driving. The design uses low pressure charge of nitrogen gas in the reserve tube. The pressure of the gas may vary and depends upon the amount of fluid in the reserve tube.
The gas helps in minimizing the aeration of the hydraulic fluid. The creation of foam is prevented because the gas compresses air bubbles in the hydraulic fluid. Reduction of aeration enhances the working capacity of the shocks. This shock absorber gives more flexibility to the engineers to design valve. The additional advantage of the shock absorber is that it creates a mild boost in spring rate to the vehicle.
Benefits of Gas Charged Twin Shock Absorber
The handling is improved through roll reduction and the reduction of sway and dive.
It reduces aeration and give smooth control in different types of road conditions.
The heat may lead to the reduction of damping capability in the shock absorber however in gas charged shocks this is reduced to a considerable extent.
Position Sensitive Damping (PSD) Twin Tube Shock Absorber
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Twin tube shock PSD design is a new technology in the field of shock absorber. In this twin shock absorber, the position of the valve within the pressure tube is taken into account. The pressure tube contains the tapered grooves which enables optimal ride comfort and added control. The grooves in effect creates two zones within the pressure tube.
In the first zone, the tapered grooves allow hydraulic fluid to pass freely around and through the piston thereby reducing the resistance on the piston and ensuring a smooth, comfortable ride. The first zone is utilized in case of normal ride. In case of demanding situations, second zone called as control zone is utilized. The fluid flow towards the piston valving for more control of the vehicle's suspension which gives better control.
Advantages
Give fine and smooth ride.
It can adapt itself quickly to different road and weight conditions.
It has two shocks in itself that is-comfort and control
Acceleration Sensitive Damping (ASD) Twin Tube Shocker
Twin tube ASD shocker brings the benefits of both the comfort and the control. Twin
tube ASD design shocker uses the compression valve which provides a bypass to fluid
flow around the compression valve. The compression valve is designed in such a way
that it senses a bump in the road and adjust the shock automatically to absorb the impact
thereby giving greater control to the shock.
MONO- TUBE SHOCK ABSORBERS :
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The main components are:
Pressure cylinder, also called housing
Piston rod connected to a piston rod
Floating piston, also called separating piston
Piston rod guide
Upper and lower attachment
Mono Tube Shock Absorber
Mono tube shock absorber or monotube shock regulates the flow of the oil between the compression and compensation chambers by using mechanically fixed base valve. The shock also utilizes compressible bladder in the compensation chamber for allowing volume compensation. The use of base valve and the compressible bladder together eliminate the need for pressurized gas and a floating piston which were the important features of the traditional monotube dampers.
How It Works
In mono tube design, the damping force is created by deflective discs which are heat treated stainless spring steel. The discs are generally stacked in a pyramid pattern. The shim with the largest diameter faces the piston. The disc which is in close proximity to piston open first and allows the flow of the oil. The rate of the shock both on compression and rebound can be changed by increasing thickness and sometimes diameters.
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Monotube shock absorber consists of two chambers which are stacked on each other and are separated by a "floating piston". Both the piston are filled with oil and gas respectively. In the oil filled chamber damping forces are created. The gas chamber is separated by a floating piston. The compression of shock results in the compression of the air chamber by the floating piston which displaces the volume of the shaft. This type of pressure creates the rod-pressure.
The pushing of piston rod also forces the floating piston towards downwards thereby increasing pressure in both gas and oil section. This also results in the flow of the oil through the piston. This type of resistance generates the bump damping.
Rebound damping is produced when the oil between piston and guide is forced to flow through the piston. This happens when the piston is pulled out
Benefits
Gives good control and smooth ride.
Monotube Shocks Can be mounted at any angle.
It is lighter as compared to equivalent twin tube designs.
Has high severity life.
Adjusts to road conditions automatically.
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Features The features of the mono tube shock absorber include:
It has distinctive mono disc design.
The vehicle can be assembled easily.
Weight is light.
Element of lag and fade is absent.
Reliable and durable.
It also comes in controlled ride application.
How does it work?
Bump Stroke:
Unlike the bi-tube damper, the mono-tube has no reservoir tube. Still, a possibility
is needed to store the oil that is displaced by the rod when entering the cylinder. This is
achieved by making the oil capacity of the cylinder adaptable. Therefore the cylinder is
not completely filled with oil; the lower part contains (nitrogen) gas under 20-30 bar. Gas
and oil are separated by the floating piston. When the piston rod is pushed in, the floating
piston is also forced down the displacement of the piston rod, thus slightly increasing
pressure in both gas and oil section. Also, the oil below the piston is forced to flow
through the piston. The resistance encountered in this manner generates the bump
damping.
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Rebound Stroke:
When the piston rod is pulled out, the oil between piston and guide is forced to
flow through the piston. The resistance encountered in this manner generates the rebound
damping. At the same time, part of the piston rod will emerge from the cylinder and the
free (floating) piston will move upwards.
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ADVANTAGES OF NITRO SHOCKS
Instantaneous response :
Because the high pressure eliminates aeration (foaming), action is always is
immediate.
The low mass of gas and the single tube further improves response time.
Better fade resistance :
Since there is no outer tube, cooling is much better which gives a drastic
reduction in fade. Thus more consistent handling and control.
Better durability :
Single-tube construction also allows for a larger internal working area, reducing
stress and fatigue for better durability.
De Carbon’s monodisc valving system features a single moving part that
drastically reduces inertia and friction, to improve durability and performance.
Better cooling of the mono tube design results in lower operating temperatures
and thus longer life.
No need for re-adjustment:
The viscosity of hydraulic fluid changes as temperature changes. This may
because of climate, season (summer/winter) or heavy duty (motorway cruising).
The high pressure gas compensates immediately and automatically for changes in
viscosity.
TIPS BEFORE MOUNTING
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A stiff suspension does not necessarily mean good handling. Often the contrary. If
still a stiff suspension is needed it should come from the springs. The function of the
shock absorber is to dampen oscillations of the spring by converting energy to heat. Do
not use shock absorbers to obtain a stiff suspension. Shock absorbers and springs each
have their own function. Respect those functions.
Do not use new shocks to compensate for old and tired springs. The shocks will
soon fail when the springs are bad. Worn shocks do not only reduce safety and handling,
they also increase the risk of having a broken spring as the spring is allowed to oscillate.
When to buy shocks?
Shock absorbers last a long time, but they tend to degrade slowly throughout their life. So
when is it time to replace them?
In some cases, a seal will rupture. A shock covered in oil is a good indication that
it has failed. The age-old test of bouncing on a fender is really only a rough guide as to
whether the vehicle needs new shocks. Usually the slow degradation in shock absorber's
performance won't be noticed until it affects handling fairly dramatically. Depending on
how rough the roads are, modern shocks can last 80-100,000 miles, but remember that a
shock with 60,000 miles on it won't perform as well as a new one.
Which ones are right?
Choosing which shocks to buy largely depends upon what kind of vehicle and the
kind of driving. As with most automotive components, it is important the specific vehicle,
since mismatched shocks can drastically affect handling and could even be dangerous.
The best advice will probably come from a mechanic who is familiar with the vehicle.
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CONCLUSION
In the current scenario of automobile industry the need for vehicles which provides
smooth and comfort ride is growing. Nitro shock absorbers are designed to be ultimate in
performance and comfort. In a country like ours whose roads are not up to world
standards the need for automotive components like nitro shocks are necessary. It goes
without saying that if the right choice is made the improvements in vehicles ride and
handling can be shocking.
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REFERENCES
1. “In For A Shock”, S.B.L Beohar; Mechanical Systems and Signal Processing.
2. Automotive Encyclopedia; Tobolt, Johnson.
3. Auto Mechanical Fundamentals; Stockel.
4. http://belltech.net
5. http://monroeshocks.com
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