Automotive Suspension System Configurations Engineering Essay

This paper presents an probe and research in to assorted automotive suspension system constellations and their working, methodological analysiss used in planing, analyzing and proving them physically. This paper besides includes the treatment on the typical values for the features of suspension based on the geometry and conformity in relation to the interaction with the Surs and the kineticss of the complete vehicle.

This paper includes the computations of suspension system at assorted conditions using different tonss. The physical research lab trials such as K & A ; C rig trial and shaker rig trial are done to happen out the suspension features.

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This journal paper besides includes the relationship between the Surs, suspension system and the vehicle dynamic public presentation.


By and large all the four stroke internal burning engines produce high power and acceleration. But all the generated power will non be wholly utile if the driver can non command the car. This is where the function of suspension system comes in to play. The chief intent of the suspension system is to increase the frictional force between the route and the car Sur. There will be no demand of suspension system if the roads are absolutely level and with no abnormalities. As the roads are non absolutely level, the abnormalities on the route surface will interact with the Surs of the car. Forces will be applied on the wheels due to these imperfectnesss.

Fig.1 Layout of a Suspension System in a auto

When the Sur of the car comes in contact with the bump on the route, it will do the wheel to travel up and down perpendicular to the surface of the route. The type of bump with which the Sur comes in contact will make up one’s mind the magnitude of the force. Due to this force a perpendicular acceleration is gained by the Surs and is transferred from the wheels to the frame of the car in the same perpendicular way.

Fig.2 Accelerations moving on a Sur due to a bump

In this instance the contact between the Sur and the route can be wholly lost as the wheel tends to travel in the perpendicular way due to the perpendicular acceleration. After that the wheel can bang back down in to the route due to the gravitation consequence. This causes more uncomfortableness to the riders. In order to avoid this job the suspension system is introduced which will absorb the perpendicular forces on the wheel and let the frame and organic structure to sit undisturbed even during the drive on the bumpy roads. So, the suspension supports the vehicle and provides the padding of the drive while keeping the Sur and wheel right positioned in relation to the route.


The human body is the portion which comprises of all the parts beneath the autos organic structure. The suspension system is besides installed on the human body merely. The suspension system of a auto consists of assorted constituents such as springs, dampers or daze absorbers, control weaponries, ball articulations, maneuvering metacarpophalangeal joint and axle.


Springs are the constituents which will back up the weight of the vehicle and absorbs the tonss and the forces exerted by the route. It keeps the wheels of the vehicle resiling up and down while go throughing a bump on the route. There are assorted types of springs used for assorted types of suspension systems depending on the functionality of the spring.

Coil Springs:

These are the most normally used springs in a suspension system. These are made by injuring unit of ammunition a heavy responsibility torsional saloon about an axis. The springs compress and expand to in order to absorb the route dazes.

Fig.3 Coil springs

Leaf Springs:

Leaf springs are made by jumping together several beds of metals in signifier of foliages. These are initial used in Equus caballus drawn passenger cars and subsequently used in many autos. But now these are by and large used in heavy burden vehicles and trucks.

Fig.4 Leaf springs

Tortuosity bars:

Torsion saloon plants on the writhing belongings of a steel saloon. One terminal of the tortuosity saloon is attached to the vehicle frame and the other terminal is attached to a wish bone. This makes the saloon to move like a lever which moves sheer. When the vehicle comes across a bump, the perpendicular action is transferred to the wish bone and so to the tortuosity saloon due to the prying action. This makes the tortuosity saloon to writhe about its axis which in bend provides the spring force. These are largely used in European autos.

Fig.5 Suspension system with Torsion saloon

Air springs:

Air springs are the air filled cylindrical Chamberss which are placed in between the wheel and the organic structure of the auto. The wheel quivers are absorbed by doing usage of the compressive qualities of air.

Fig.6 Air springs

Damper or Shock Absorber:

A auto spring will widen and let go of the energy it absorbs from a bump at a uncontrolled rate if there is no moistening construction. Until all the energy put in to the spring is used up, it will go on to resile at its natural frequence. So, the suspension system holding merely spring will do the drive bumpier which in bend makes the auto unsteady.

Fig.7 Shock absorber

The daze absorber is the device which controls the unwanted spring gesture through stifling procedure. The magnitude of vibratory gestures is reduced by the Shock absorbers by change overing the kinetic energy of suspension motion into heat energy which can be dissipated through hydraulic fluid. The daze absorber is an oil pump which is placed in between the wheels and the auto frame. The spring is placed over the daze absorber as shown in the figure. When the auto encounters a bump the spring will gyrate and uncoil and the energy of the spring is transferred to the daze absorber. The gesture of the spring is controlled by the to and fro gesture of the Piston inside the daze absorber.


The suspension system is chiefly classified in to two types. They are

Dependent suspension system

Independent suspension system

Dependent suspension system:

In this suspension system the two wheels are interlinked by linking to the axle. So, when any one of the wheel get over a bump, so the warp on this wheel will be transmitted to the other wheel on the opposite side of the axle. This will impact the drive quality.

If one of the wheels gets struck, so the opposite wheel does non set to the terrain and sits flat on the surface of the route. This will ensue in the loss grip. The dependent suspension system is used in the rear of many autos and trucks and on the forepart of four wheel thrust vehicles. The major disadvantage of the dependent suspension system is its susceptibleness to tramp shimmy maneuvering quivers and the ability to polish the dynamic response of the vehicle is besides limited for the dependent suspension system.

Fig.8 Dependent suspension system

Independent suspension system:

When the vehicle with stiff axle comes across a bump, the axle jousts doing the full vehicle to lean on one side. This type of phenomenon is non desirable for a proper drive and can be overcome by utilizing the independent suspension system.

In independent suspension system, each wheel can travel up and down independently without impacting the wheel on the antonym of the axle. The wheels in this suspension system are connected to a swing axle by utilizing cosmopolitan articulations. Each wheel is mounted on separate suspension system such that the perpendicular motion of one wheel does non impact the other wheel on the opposite side of the axle.

Fig.9 Independent suspension system

Most of the rider autos are now utilizing independent suspension system. The compact design of it provides optimal drive quality, vehicle handling and more room for the larger bole.

Some of the common suspension systems which come under the dependant and the independent suspension systems are:

McPherson prance

Short-Long Arm or double- wishing bone system

Hotchkiss suspension system

Twin I-Beam

Four links

Draging nexus

McPherson-Strut Suspension System:

The McPherson prance suspension was invented in the 1940s by Earl S. McPherson of Ford. It has since become one of the dominating suspensions systems of the universe because of its concentration and low cost. Unlike other suspension designs, in McPherson prance suspension, the telescopic daze absorber serves as a nexus to command the place of the wheel.

Therefore it saves the upper control arm. Besides, since the prance is vertically positioned, the whole suspension is really compact. To front-wheel thrust autos, whose engine and transmittal are all located inside the front compartment, they need front suspensions which engage really small breadth of the auto. Undoubtedly, McPherson strut suspension is the most suited 1. However, this simple design does non offer really good handling. Body axial rotation and wheel ‘s motion lead to fluctuation in camber, although non every bit terrible as swing axle suspension.

Fig.10 McPherson Strut Suspension System

Double-wishbone suspension system:

The double-wishbone suspension system is normally used for the forepart axle. A spiral spring which uses the upper and lower control weaponries of unequal length is called a short-arm/long-arm or double-wishbone system.

Fig.11 Double wishing bone suspension system

The control arms pivot on the vehicle organic structure or frame. The upper terminal of the spiral spring remainders in a pocket in the frame. The lower terminal remainders on the lower control arm. As the wheel moves up and down, the control arms pivot and the spring shortens or lengthens. Thus the suspension system absorbs the route dazes and provides vehicle an undisturbed drive.

Hotchkiss suspension system:

The Hotchkiss is a type of dependent suspension system used in rear wheels of many visible radiation and heavy trucks. This system has a solid axle which is located by semi egg-shaped foliage spring. The spring is mounted longitudinally and is connected to the human body at their terminal. This type of suspension is inexpensive and simple in building.

Fig.12 Hotchkiss suspension system

A Hotchkiss suspension is a live-axle rear suspension in which leaf springs handle both the axle ‘s springing and its location.

Duplicate I-beam:

This system is largely used by Ford F-series trucks. Twin I-beam suspension was introduced in 1965. This is a combination of draging arm suspension and solid beam axle suspension. In this instance the beam is split into two and mounted offset from the Centre of the human body, one subdivision for each side of the suspension. The tracking weaponries are really prima weaponries and the guidance cogwheel is mounted in forepart of the suspension apparatus. The Ford claims this makes for a heavy responsibility independent front suspension apparatus capable of managing the tonss associated with their trucks.

Fig.13 I-Beam Suspension system

Four links:

In this system the lower control arm gives support from the longitudinal forces and the upper control arm gives support from sidelong forces which occur from the braking and driving torsions. A four-link suspension system provides an infinite sum of accommodations to counterbalance for altering conditions and route conditions. Because of this ground they are preferred over other types of rear dependent suspension system.

Fig.14 Four-link suspension system

Draging nexus suspension system:

In this type of suspension system a coils spring is attached to the tracking nexus which itself is attached to the shaft transporting the wheel hub. When the wheel moves up and down, it winds and unwinds the spring.

Fig.15 Trailing nexus suspension system

Hydrolastic suspension:

In this type of suspension the forepart and the rear suspension system are connected together in order to better level the auto when drive. The forepart and the rear suspension units have the hydrolastic displacers, one per side. These are interconnected by a little dullard pipe. Each displacer incorporates a gum elastic spring and damping of the system is achieved by gum elastic valves. So when a forepart wheel is deflected, fluid is displaced to the corresponding suspension unit. That pressurizes the interconnecting pipe which in bend stiffens the rear wheel damping and lowers it.

Hydragas suspension:

Hydragas is an development of hydrolastic and basically the design and installing of the system is same. The difference is in the displacer unit itself.

Hydragas suspension was famously used in the 1986 Porsche 959 mass meeting auto that entered the Paris- Dakar mass meeting and now we can happen it in a MGF runabout.

Fig.16 ( a ) Hydrolastic suspension system Fig.16 ( B ) Hydrolastic suspension system


In a suspension system, the wheel is connected to the frame through assorted links. The perpendicular gesture of the wheels relative to the organic structure is controlled by the spring and the damper of the suspension system. The suspension system of a general route vehicle consists of gum elastic shrubs which reduces the transmittal of noise, quiver and abrasiveness in to the rider ‘s compartment. The conformity in the links, shrubs will ensue in the dependance of faux pas angle and the camber angle of the wheel on the forces moving. By analyzing the suspensions through links, the operation and behavior of the suspension system can be easy known. In order to analyze the suspension system the followers should be considered

The geometry of the idealized suspension system is analysed by look intoing the possible agreements of the links and the wheel gesture relation to the human body which is implicated by the links.

The constituents of the suspension system which control the wheel gestures are checked for any conformity. These constituents include springs and anti axial rotation bars. The conformities of links and gum elastic shrubs are besides checked.

Clash introduced by dampers and the residuary clash in the articulations

Inactiveness of the constituents due to their gesture relevant to the suspension action.


The features of a suspension system is a complete system where it presents the analysis of human body heaving and axial rotation, the axial rotation Centre and axial rotation axis, burden transportation and the distribution of the perpendicular forces, and the influence of fliping in response to acceleration and breakage. This can be done by looking at the geometry of maneuvering systems, at the maneuvering effects of wheel bump and human body axial rotation, and at the maneuvering effects of wheel forces because of system conformity. These factors are of considerable importance in commanding the behavior and the feel of the vehicle, and every one of them must be carefully controlled if the vehicle is to manage good. Therefore the computations of suspension features involves assorted parametric quantities such as

Bump motion, wheel recession and half path alteration:

The bump is an upward supplanting of a wheel relation to the auto organic structure, sometimes applied more loosely to intend up or down supplanting. It is besides known as compaction or jolt. When the auto is in combined breakage and cornering, the longitudinal and sidelong burden transportations result in a different combination of heaving and bump on each wheel.

Bump motion ( BM ) is the independent variable and is taken every bit positive as the wheel moves in the upward omega way relation to the vehicle organic structure. Similarly wheel recession ( WR ) and halftrack alteration ( HTC ) are taken as positive ten and y waies severally.

Fig.17 Calculation of Bump motion, wheel recession and halftrack alteration

Half path alteration is a step of how much the contact spot moves in and out comparative to the vehicle organic structure as the vehicle axial rotations.

Camber and maneuver angle:

Camber angle is defined as the angle measured in the front lift between the wheel plane and the perpendicular. Camber angle is measured in grades and taken every bit positive if the top of the wheel leans towards comparative to the vehicle organic structure.

The tip or toe angle is defined as the angle measured in the top lift between the longitudinal axis of the vehicle and the line of intersection of the wheel plane and route surface. Steer angle is taken here every bit positive if the forepart of the wheel toes towards the vehicle. Both camber and maneuver angle can be calculated utilizing two markers located on the wheel spindle axis.

Fig.18 Calculation of camber angle and tip angle

Castor angle and suspension trail:

Castor angle is defined as the angle measured in the side lift between the guidance ( top banana ) axis and the perpendicular. Castor angle is measured in grades and taken every bit positive if the top of the maneuvering axis tilts towards the rear.

Suspension trail ( TR ) is the longitudinal distance in the ten way between the wheel base and the intersection between the maneuvering axis and the land. The suspension trail generates a step of stableness supplying a minute arm for sidelong Sur forces that will do the route wheels to ‘centre ‘ . The suspension trail combines with tyre pneumatic trail and contributes to the maneuvering ‘feel ‘ .

Fig.19 Calculation of Castor angle and suspension trail

Steering axis disposition and land degree beginning:

The maneuvering axis disposition is defined as the angle measured in the front lift between the guidance ( top banana ) axis and the perpendicular. The angle is measured in grades and taken every bit positive if the top of the maneuvering axis tilts inwards.

Ground degree beginning ( GO ) is the sidelong distance in the y way between the wheel base and the intersection between the maneuvering axis and the land. The land degree beginning is frequently referred to as the chaparral radius as the sum of ‘scrub ‘ in the Sur as it steers will depend on the magnitude of the land degree beginning. The computation of the maneuvering axis disposition and land degree beginning is shown below

Fig.20 Calculation of maneuvering axis disposition and land degree beginning

Roll Centre:

The point where the sidelong forces developed by the wheels are transmitted to the vehicle is known as axial rotation Centre. If the axial rotation Centre of the forepart and rear suspension is joined, Roll axis can be produced. It is the axis about which the vehicle rolls over cornering. The distance of the axial rotation Centre from land is known as Roll Centre tallness. It is of import to observe that the axial rotation axis is present merely when the vehicle is following a consecutive way. As the vehicle axial rotations, the geometry of the suspension alterations doing the axial rotation Centre to travel. Roll axis helps in finding the axial rotation angle and burden transportation on forepart and rear axle.

The axial rotation Centre is found by projecting a line between the wheel base and the instant Centre. The point at which this line intersects the centre line of the vehicle is taken to be the axial rotation Centre. The axial rotation Centre for a dual wishing bone is shown in building below

Fig.21 Positions of instant Centre and axial rotation Centre for a dual wishing bone suspension

The Roll Centre for dual Wishbone suspension system is found by widening the upper and lower weaponries of suspension system. An fanciful line is drawn from the Sur contact spot to that point. The point where the contact spot line cuts the centre line of the vehicle is considered as axial rotation Centre and the tallness from the land is known as axial rotation Centre tallness.

The axial rotation Centre for a McPherson prance type suspension is formed the same manner as Double wishing bone type suspension system. The point where the lower arm when extended meets the perpendicular line from the prance is the instant Centre. The line from the Sur contact spot is joined to that instant Centre. The point where this centre line cuts the centre line of the vehicle is called axial rotation Centre and the tallness from the land is known as axial rotation Centre tallness and the building is as follows

Fig.22 Positions of instant Centre and axial rotation Centre for a McPherson prance suspension


Suspension constituents and Surs have a enormous influence on drive and managing qualities of autos. Therefore the testing for these constituents is more of import. In laboratory many theoretical and practical vehicle kineticss probes takes topographic point. These trial rigs are equipped with extremely sophisticated measuring informations acquisition systems and they provide a new quality of proving.

Kinematicss and Compliance Rig:

Kinematicss and conformity belongingss of vehicle suspensions have a major impact on drive and handling belongingss. The K & A ; C trial rig is designed to look into both full vehicles and stand-alone suspension systems.

Fig.23Vehicle on the K & A ; C trial rig

Design of the K & A ; C Test Rig:

The rig chiefly consists of four stations equipped with hydraulic cylinders that allow any coveted perpendicular warp of the autos wheels. Additionally, there are two more little cylinders in every station to imitate sidelong and longitudinal force application. A auto can either be tested with its wheels mounted or with particular kinematic devices mounted that simulate the kinematics of a rolled wheel. These devices can be adjusted to fit the Sur semi diameter and pneumatic trail value. With the devices being mounted, sidelong and longitudinal force application is no longer limited to the maximal clash force in the Sur contact spot ; this increases the rig ‘s field of operation and it makes proving less complicated.

In both instances there are air shock absorbers mounted between suspension and rig to cut down clash to a minimal value of about 20 N even at maximal wheel burden. This allows the suspension to debar in sidelong and longitudinal way as it does in world if horizontal forces are applied.

The maximal force scope in sidelong and longitudinal way is 10 KN. The rig is adjustable to any wheel base between 2000 millimeter and 3250 millimeter ; the path breadth forepart and rear is independently adjustable between 1180 millimeter and 1650mm.

Fig.24 Twist beam Axle on the K & A ; C trial rig in operation

Test Rig Operation System:

The rig consists of 12 electro-hydraulic control loops that may be operated either in supplanting control or in force control manner. The basic maps of the rig such as run-up, creaky or exigency modus operandis are provided by an highly dependable microcontroller unit. Every control loops are continuously monitored itself. If, for case, one cylinder exceeds its antecedently adjusted force bound, all cylinders will be locked up automatically. Thereafter the rig will slowly run down to the impersonal place. These safety modus operandis guarantee that the suspension will non be damaged by the rig due to overload. Additionally there are two operation manners available for the whole rig. Forces and supplantings can either be adjusted manually or automatically. In the automatic operation mode a Personal computer system generates the values of forces and supplantings in the class of clip. Consequently, full driving tactics such as a steady-state round tally can be simulated on the rig. Apart from the standard probes there are other probes which are automatically performed such as

Seven station shaker rig trial:

The other type of trials involved in the research lab is the shaker rig trial. These trials are done chiefly for the racing autos because the path trial are by and large expensive and clip consuming and in some instances it is impossible to implement. In those instances physical research lab trials come into a major consideration.

The seven stations are hydraulic cylinders in which four of them have level pans on which the Surs sit on and back up the auto. The other three are called the aero stevedores and are attached to the sprung mass. The auto is placed on the pans and the trial is carried as shown in figure.

Fig.25 Racing auto undergoing a shaker rig trial


When the Sur of a vehicle passes over the bump so there would be some alterations in the geometry of the suspension which in bend affects the assorted parametric quantities that are related to the suspension. This in bend affects the whole vehicle kineticss. The alteration in these parametric quantities occurs during cornering of the vehicle and affects the drive quality and Surs every bit good. Thus the parametric quantities involved in keeping the relationship between the Sur, suspension system and the vehicle kineticss are given below. The assorted parametric quantities involved are listed and described in brief above. The alteration in these parametric quantities is shown below with regard to the bump motion. The assorted parametric quantities involved are

Front wheel bump tip:

As the forepart wheels travel through jolt the toe angle becomes more negative and the wheels point off from the Centre of the auto.

Fig.26 Graph demoing the affect of toe angle on forepart wheel bump tip

Similarly, as the wheels travel through bounciness, the toe-angles become more positive and the wheels increasingly point towards the Centre of the auto.

Rear wheel bump tip:

On the rear wheels the bump-steer features are in the opposing way to that seen at the forepart. The graph besides shows how the conformity washer absorbs a important sum of the bump-steer toe-angle alterations – but it is loosely in the same way as the standard suspension.

Fig.27 Graph demoing the affect of toe angle on rear wheel bump tip

Bump-steer is the least desirable characteristic in suspension geometry as the wheel rides over a bump, the steered wheel is deflected outward – so that there is a little guidance motion towards the side that wheel is mounted on the auto. Then, as the suspension rebounds, the maneuvering motion is directed in the opposite way. Thus directional stableness is affected.

Steering axis disposition:

Steering axis disposition defines the angle of inward thin upwards or towards the Centre of the auto of the guidance. This angle promotes some maneuvering self-centring and besides modifies some of the camber alteration induced by increasing maneuvering angle in association with caster.

It lessens the negative camber alteration on the outer wheel, whilst increasing the positive camber on the interior wheel. Wheel offset defines the relationship between the copulating face of the hub and wheel and the wheel centre line.

Fig.28 Steering axis disposition beginnings

If a wheel has zero beginning, so the wheel and hub coupling surfaces would be on the same line. A positive beginning would see the climb faces mate towards the outer border of the wheel whilst a negative beginning would be in the opposite way.

Ideally, the male monarch pin should cross the land at the same point as the wheel ‘s centre line. When the King Pin intersect to the wheel ‘s centre line towards the Centre of the auto when the wheel has excessively much positive beginning, the heavier the guidance becomes, the less predictable the guidance responses and the less predictable the directional stableness. The distance between the wheel Centre and the King Pin land intersect is besides known as the chaparral radius.

On rear wheel thrust with positive chaparral radius, the vehicle forward gesture and the route opposition on the contact spot produces a turning minute which causes the wheel to toe out and negative chaparral radius causes wheel to toe in. But in front wheel drive the above instance gets wholly opposite. The positive chaparral radius causes wheel to toe in and the negative causes toe out.

Half path alteration:

It is a step of how much the contact spot moves in and out comparative to the vehicle organic structure as the vehicle axial rotations. When the wheel moves over a bump the half path besides changes.

Over bumps the half path angle is positive and negative over recoil.

Fig.29 Graph demoing the affect of bump on half path alteration

Caster angle:

The Castor angle is the angle measured in grades formed between the axis of the top banana and the perpendicular to the land looking at the vehicle from the side. The stableness phenomenon is created on the footing of the distance between the point at which the top banana axis extension falls in relation to the way of travel and the point of contact between the Sur and the land.

Fig.30 Caster angle of a Sur

In the instance of positive caster angle where the top banana extension falls in front of the point of contact between the Surs and the land the wheel is pulled, as it is the line of application of the force applied to the axis that passes in forepart of wheels center without taking the way of travel into history, and each effort made by the wheel to divert from consecutive line travel will be counteracted by the unbending twosome generated by the force and by the turn overing opposition of the wheel. With negative Castor the wheel is pushed as it is the line of application of the force applied to the axis passes behind the center of the wheel.

Fig.31 Graph demoing the affect of bump on Castor angle

When the vehicle wheel move over the bump and recoil, the Castor angle value alterations but remain positive throughout. Consequently the best stableness status for consecutive line travel is obtained with a positive Castor angle. In this instance the phenomenon of “ wheel wobble ” and the attendant effects on maneuvering are avoided.

Camber angle:

Camber angle is measured in grades and taken every bit positive if the top of the wheel leans towards comparative to the vehicle organic structure. It is used in the design of maneuvering and suspension.

Fig.32 Camber angle of a suspension system

Camber angle alters the managing qualities of a peculiar suspension design and in peculiar negative camber improves grip when cornering. This is because it places the Sur at a more optimum angle to the route conveying the forces through the perpendicular plane of the Sur instead than through a shear force across it. Another ground for negative camber is that a gum elastic Sur tends to turn over on itself while cornering. If the Sur had zero camber, the interior border of the contact spot would get down to raise off of the land, thereby cut downing the country of the contact spot. By using negative camber this consequence is reduced, thereby maximizes the contact spot country.

Fig.33 Graph demoing the affect of bump on camber angle

When the vehicle moves over a bump and bounce camber angle alterations. To keep a proper camber angle of the wheel with regard to the route, the camber angle of the wheel with regard to the vehicle goes negative over the bump and positive over recoil.


The vehicles are used for going from one topographic point to another. While making so safety, comfort and drive quality are besides desired. The suspension system plays an of import function in safety, comfort and the drive quality. The parametric quantities and features involved in the suspension have their consequence on vehicle kineticss. Even the little fluctuation in the features of suspension will impact the drive.

The journal paper explained the different features of the suspension which plays an of import function in obtaining the drive comfort. Different types of suspension systems are explained. The physical proving done on the suspension systems are explained. The fluctuation of assorted suspension features in relation to knock and heave are discussed and are represented in graphs. This helps in happening the defects in the suspensions which enables the interior decorators to rectify the jobs and helps them in developing new suspension systems for the modern autos.



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