The document discusses suspension systems and components. It outlines the objectives of suspension systems which include providing good ride and handling performance, ensuring steering control is maintained during maneuvering, and providing isolation from high frequency vibrations. It describes types of independent and dependent suspensions and components such as springs, dampers, wishbones. It covers analyses like mobility, kinematics and forces in suspension members for different load conditions. Different suspension configurations are discussed including MacPherson strut, double wishbone, solid axle leaf spring systems.

1. Suspension Systems & Components
Submitted by Vinay Tiwari
1
Suspension Systems & Components
Submitted by Vinay Tiwari

2. Suspension Systems & Components
ObjectivesObjectives
To provide good ride and handling performance
Vertical compliance providing chassis isolation
Ensuring that the wheels follow the road profile
Very little tire load fluctuation
To ensure that steering control is maintained during maneuvering
Wheels to be maintained in the proper position with respect to
road surface
To provide isolation from high frequency vibration from tire
excitation
Requires appropriate isolation in the suspension joints
Prevent transmission of ‘road noise’ to the vehicle body
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To provide good ride and handling performance
Vertical compliance providing chassis isolation
Ensuring that the wheels follow the road profile
Very little tire load fluctuation
To ensure that steering control is maintained during maneuvering
Wheels to be maintained in the proper position with respect to
road surface
To provide isolation from high frequency vibration from tire
excitation
Requires appropriate isolation in the suspension joints
Prevent transmission of ‘road noise’ to the vehicle body

3. Suspension Systems & Components
To ensure that the vehicle responds favorably to control forces
produced by the tires during
Longitudinal braking
Accelerating forces,
Lateral cornering forces and
Braking and accelerating torques
This requires the suspension geometry to be designed to resist
squat, dive and roll of the vehicle body
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To ensure that the vehicle responds favorably to control forces
produced by the tires during
Longitudinal braking
Accelerating forces,
Lateral cornering forces and
Braking and accelerating torques
This requires the suspension geometry to be designed to resist
squat, dive and roll of the vehicle body

4. Suspension Systems & Components
Wheel - Degrees of FreedomWheel - Degrees of Freedom
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5. Suspension Systems & Components
The Mobility Of Suspension MechanismsThe Mobility Of Suspension Mechanisms
Guide motion of each wheel along (unique)
vertical path relative to the vehicle body without
significant change in camber.
Mobility (DOF) analysis is useful for checking
for the appropriate number of degrees of
freedom,
Does not help in synthesis to provide the
desired motion
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Guide motion of each wheel along (unique)
vertical path relative to the vehicle body without
significant change in camber.
Mobility (DOF) analysis is useful for checking
for the appropriate number of degrees of
freedom,
Does not help in synthesis to provide the
desired motion

6. Suspension Systems & Components
Suspension Types - IndependentSuspension Types - Independent
Motion of wheel pairs is
independent, so that a
disturbance at one wheel is
not directly transmitted to its
partner
Better ride and handling
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Motion of wheel pairs is
independent, so that a
disturbance at one wheel is
not directly transmitted to its
partner
Better ride and handling

7. Suspension Systems & Components
MacPherson StrutMacPherson Strut
Combines a shock absorber and a coil spring into a single
unit.
Provides a more compact and lighter suspension system used
for front-wheel drive vehicles
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8. Suspension Systems & Components
Elements of Independent SuspensionElements of Independent Suspension
Spring
Coil springs
Leaf springs
Damper shock absorber
Need for damper
Suspension System – Damper Working principleSuspension System – Damper Working principle
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Suspension System – Damper Working principleSuspension System – Damper Working principle
Hydraulic dampers are prevalent
During bumps or compression, rod & piston move into the Shock
Absorber
In rebound, or extension, they move out
For dampening to be effective, resistance is needed in both directions
– provided by oil and valves

9. Suspension Systems & Components
Suspension System – Hydraulic DamperSuspension System – Hydraulic Damper
Without a damper structure a car
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
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Without a damper structure a car
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

10. Suspension Systems & Components
Kinematic Analysis -GraphicalKinematic Analysis -Graphical
Graphical Analysis
•Objective
The suspension ratio R
(the rate of change of
vertical movement at D
as a function of spring
compression)
The bump to scrub
rate for the given
position of the
mechanism.
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Graphical Analysis
•Objective
The suspension ratio R
(the rate of change of
vertical movement at D
as a function of spring
compression)
The bump to scrub
rate for the given
position of the
mechanism.

11. Suspension Systems & Components
Kinematic Analysis -GraphicalKinematic Analysis -Graphical
Draw suspension
mechanism to scale,
assume chassis is fixed
Construct the velocity
diagram
VB = ωBArBA
The suspension ratio R
(the rate of change of
vertical movement at D as
a function of spring
compression)
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Draw suspension
mechanism to scale,
assume chassis is fixed
Construct the velocity
diagram
VB = ωBArBA
The suspension ratio R
(the rate of change of
vertical movement at D as
a function of spring
compression)

12. Suspension Systems & Components
Double-wishbone suspension A-arm
Suspension/Parallelogram system
Double-wishbone suspension A-arm
Suspension/Parallelogram system
Each wishbone, which has two mounting positions to the frame
and one at the wheel, bears a shock absorber and a coil spring to
absorb vibrations.
Double-wishbone suspensions allow for more control over the
camber angle of the wheel, which describes the degree to which
the wheels tilt in and out.
They also help minimize roll or sway and provide for a more
consistent steering feel.
Allows the spindles to travel vertically up and down. When they
do this, they also have a slight side-to-side motion caused by the
arc that the wishbones describe around their pivot points. This
side-to-side motion is known as scrub.
Common on the front wheels of larger cars.
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Each wishbone, which has two mounting positions to the frame
and one at the wheel, bears a shock absorber and a coil spring to
absorb vibrations.
Double-wishbone suspensions allow for more control over the
camber angle of the wheel, which describes the degree to which
the wheels tilt in and out.
They also help minimize roll or sway and provide for a more
consistent steering feel.
Allows the spindles to travel vertically up and down. When they
do this, they also have a slight side-to-side motion caused by the
arc that the wishbones describe around their pivot points. This
side-to-side motion is known as scrub.
Common on the front wheels of larger cars.

13. Suspension Systems & Components
Double-wishbone suspension A-arm
Suspension/Parallelogram system
Double-wishbone suspension A-arm
Suspension/Parallelogram system
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14. Suspension Systems & Components
Kinematic Analysis – Sample calculationKinematic Analysis – Sample calculation
Double wish bone
•The objectives are
Determine camber angle
α, and suspension ratio R
(as defined in the previous
example slide)
For suspension
movement described by “q”
varying from 80° to 100°
Given that in the static
laden position “q” = 90°.
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Double wish bone
•The objectives are
Determine camber angle
α, and suspension ratio R
(as defined in the previous
example slide)
For suspension
movement described by “q”
varying from 80° to 100°
Given that in the static
laden position “q” = 90°.

15. Suspension Systems & Components
Kinematic Analysis – Sample calculationKinematic Analysis – Sample calculation
Positions are provided
Two non-linear equations solved for positions described interval 1°
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16. Suspension Systems & Components
Kinematic AnalysisKinematic Analysis
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17. Suspension Systems & Components
Kinematic AnalysisKinematic Analysis
The second part of the solution begins by expressing the length
of the suspension spring in terms of the primary variable and then
proceeds to determine the velocity coefficients
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18. Suspension Systems & Components
Kinematic Analysis-ResultsKinematic Analysis-Results
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19. Suspension Systems & Components
Forces in suspension members - BasicsForces in suspension members - Basics
Mass of the members is
negligible compared to that
of the applied loading.
Friction and compliance at
the joints assumed negligible
and the spring or wheel rate
needs to be known
Familiar with the use of
free-body diagrams for
determining internal forces in
structures
Conditions for equilibrium
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Mass of the members is
negligible compared to that
of the applied loading.
Friction and compliance at
the joints assumed negligible
and the spring or wheel rate
needs to be known
Familiar with the use of
free-body diagrams for
determining internal forces in
structures
Conditions for equilibrium
Equilibrium of two and three force
members, (a) Requirements for
equilibrium of a two force member (b)
Requirements for equilibrium of a
three-force member

20. Suspension Systems & Components
Vertical loadingVertical loading
Force
analysis of a
double
wishbone
suspension
(a) Diagram
showing applied
forces
(b)FBD of wheel
and triangle of
forces
(c) FBD of link
CD and triangle
of forces
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Force
analysis of a
double
wishbone
suspension
(a) Diagram
showing applied
forces
(b)FBD of wheel
and triangle of
forces
(c) FBD of link
CD and triangle
of forces

21. Suspension Systems & Components
Vertical loadingVertical loading
Assume FW is the wheel load and FS the force exerted by the spring on
the suspension mechanism
AB and CD are respectively two-force and three force members
FB and FC can be determined from concurrent forces
Similar analysis possible for other types also.
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Assume FW is the wheel load and FS the force exerted by the spring on
the suspension mechanism
AB and CD are respectively two-force and three force members
FB and FC can be determined from concurrent forces
Similar analysis possible for other types also.

22. Suspension Systems & Components
Vertical loading-MacPhersonVertical loading-MacPherson
Force
analysis of a
MacPherson
strut,
(a) Wheel
loading,
(b) Forces
acting on
the strut
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Force
analysis of a
MacPherson
strut,
(a) Wheel
loading,
(b) Forces
acting on
the strut

23. Suspension Systems & Components
Other loadingsOther loadings
Lateral Loadings due to cornering effects
Longitudinal loadings arise from
Braking,
Drag forces on the vehicle and
Shock loading due to the wheels striking bumps and pot-holes.
Same method as before used to analyze these loading conditions
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Lateral Loadings due to cornering effects
Longitudinal loadings arise from
Braking,
Drag forces on the vehicle and
Shock loading due to the wheels striking bumps and pot-holes.
Same method as before used to analyze these loading conditions

24. Suspension Systems & Components
Forces in suspension members
Dynamic factors for Shock loading
Forces in suspension members
Dynamic factors for Shock loading
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25. Suspension Systems & Components
Suspension Types - DependentSuspension Types - Dependent
Motion of a wheel on one side of the vehicle is dependent on the
motion of its partner on the other side
Rarely used in modern passenger cars
Can not give good ride
Can not control high braking and accelerating torques
Used in commercial and off-highway vehicles
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Motion of a wheel on one side of the vehicle is dependent on the
motion of its partner on the other side
Rarely used in modern passenger cars
Can not give good ride
Can not control high braking and accelerating torques
Used in commercial and off-highway vehicles

26. Suspension Systems & Components
Hotchkiss DriveHotchkiss Drive
Axle is mounted on longitudinal leaf
springs, which are compliant vertically
and stiff horizontally
The springs are pin-connected to the
chassis at one end and to a pivoted
link at the other.
This enables the change of length of
the spring to be accommodated due
to loading
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Axle is mounted on longitudinal leaf
springs, which are compliant vertically
and stiff horizontally
The springs are pin-connected to the
chassis at one end and to a pivoted
link at the other.
This enables the change of length of
the spring to be accommodated due
to loading

27. Suspension Systems & Components
Semi-dependent SuspensionSemi-dependent Suspension
The rigid connection between pairs of wheels is replaced by a
compliant link.
A beam which can bend and flex providing both positional control of
the wheels as well as compliance.
Tend to be simple in construction but lack scope for design flexibility
Additional compliance can be provided by rubber or hydro-elastic
springs.
Wheel camber is, in this case, the same as body roll
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The rigid connection between pairs of wheels is replaced by a
compliant link.
A beam which can bend and flex providing both positional control of
the wheels as well as compliance.
Tend to be simple in construction but lack scope for design flexibility
Additional compliance can be provided by rubber or hydro-elastic
springs.
Wheel camber is, in this case, the same as body roll
Trailing twist axle
suspension

28. Suspension Systems & Components
Solid Axle Leaf Spring Suspension/Coil Spring
Rear Dependent Suspension
•Bus/Truck Suspension
Leaf Spring/Progressive Spring
Tandem Axle Suspension
Air Bellow Suspension
Some Other Suspension TypesSome Other Suspension Types
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Solid Axle Leaf Spring Suspension/Coil Spring
Rear Dependent Suspension
•Bus/Truck Suspension
Leaf Spring/Progressive Spring
Tandem Axle Suspension
Air Bellow Suspension

29. Suspension Systems & Components
END
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