CHAPTER 7
SUSPENSIONS
Primary Function and types of Suspensions
General type
- Solid axle
- independent
Solid Axles Suspensions
Hotchkiss drive
Leaf springs
Simplest
Least expensive
Solid Axles Suspensions
Four Link De Dion
Independent Suspensions
Trailing Arm • Short-Long Arm SLA
Mostsimple and economic
Wheels remain parallel to the body
Room for front engine
Independent Suspensions
MacPherson Strut
Space for transverse engines
Upper ends fixed to body
Lower ends multi point linkage
Multi Link Rear Suspension
Trailing Arms
Highperformance car
Reduce Unsprung weight of differential body
Semi-Trailing Arms
Wheel camber based on pivot axis
Steer/camber combination
Anti Squat and Anti Pitch suspension
Load on rear axis
Trailing Arm Analysis
Trailing Arm Analysis
Diagram / equation for
Trailing arm
Rear Solid Drive Axle
Sum of the torque
Rear Solid Drive Axle
Pitch angle equation
Independent Rear Drive
Summary of equation for independent rear drive vehicles
Front Drive Axle
Four Wheel Drive
Assume independent suspension for both axle
Anti-Dive Suspension Geometry
- Full anti dive = accel lift on rear
- Flat stop undesirable
- Full anti-dive front caster increase
Steering effort
- Oversteer created by high pivot
Example problems
Example
Roll Center Analysis
Roll Center : point in the transverse vertical plane through the wheel centers.
Solid Axle Roll Centers
Positive Swing Arm Geometry
Roll center above arm
Negative geometry
Two independent suspension
Parallel / Incline Horizontal Links
MacPherson Strut
Virtual reaction point lies at
Intersection of axis of lower and
Strut perpendicular
Active Suspension
Actuator to generate
Desire force to the
Suspension geometry
CHAPTER 8
STEERING SYSTEM
Steering Linkage
Components:
joint
Isolator
Gearbox
Rack and Pinion
Vehiclewithout frame
Less complex
Gear box
Need reduction
Ackerman geometer
Ackerman geometry
Ackerman Geometry
Perfect turning about turn center
Steering geometry error
Toe change
Steering geometry error
Roll steer
Steering system Forces and Moments
Force / moment on wheels
Steering Forces and Moments
Vertical forces
Steering system forces and moments
Lateral forces
Steering system forces and moments
Steering system forces and moments
Tractive force
Steering system forces and moments
Aligning Torque
Steering system effects
Steering ratio Understeer
Steering effects
Understeer Braking Stability
Influence on FWD
Drive torque about steer axis
Tractive force on tire stiffness
Influence on FWD
