1. Principles and Springs
Suspension
Principles and Springs

2. Why To protect the passengers from bumps in the road.
To protect the vehicle from damage
To keep the wheel in contact with the road surface
Control pitch, roll and braking forces

3. How Fitting a spring between the road wheels and the chassis
Fitting a Pneumatic tyre to the wheel
Fitting Springs to seating

4. What Leaf Springs Coil Springs Rubber mountings Torsion Bars Pneumatic
Hydragas
Tyres

5. Tyres
Tyres are the first point of contact for the suspension system. The rubber tyre flexes when it comes into contact with a bump in the road and the air inside the tyre will compress to absorb some of the shock and travel

6. Laminated or Leaf Springs
The main leaf is rolled at each end to for eyes and has a number of leaves clamped to it.
Leaves are graduated in length to ensure a constant stress
Rebound clips transfer the load to some of the lower leaves to reduce the need to add too many springs
Rubber mountings absorb shock and noise
A swinging shackle is fitted to accommodate the alterations in spring length.

8. Stiffness rate The lower the rate the softer the ride
The force required to deflect the spring effects ride comfort and payload.
Length – the shorter the spring the higher the rate
Width – the wider the higher the rate
Thickness – the thicker the higher the rate
Number – more leaves the higher the rate
Force required, length, width, thickness , number

9. Friction
As the leaves flex they rub against each other causing friction. Although this does have a desirable damping effect it does create a hard ride, noise and wear. In older vehicles the leaves would be periodically sprayed with penetrating oil. These days special features have been added to prevent the need for servicing.
Various methods of reducing the friction

10. Friction reduction Synthetic rubber buttons
Reducing the number of leaves or using a single tapered leaf
Inter-leaf plates of low friction material

11. Transverse Leaf Spring
Triumph Herald used a transverse leaf spring which had the effect of drawing the wheels in wards when the weight was taken off them.

12. Coil Spring

13. Coil Spring
Usually used with independent suspension and some rear axle assemblies.
Although the coil is better at storing energy it does require more components to be fitted which can add to the weight.
Rate is governed by thickness and length of the spring.
The length is determined by the diameter and number of active coils.

14. McPherson Strut
Double Wishbone
Trailing Arm

15. Dampers Convert Kinetic energy to heat energy
When a spring is compressed it stores energy
When the energy is released the spring will extend beyond it’s normal length
This also stores energy which is released and compresses the spring
This characteristic is known as oscillation
A damper is fitted to reduce the oscillations and improve ride comfort and road holding.

17. 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 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.

18. Torsion bars Behaves like a coil spring
One end attached to the frame and the other to the control arm
The control arm rises and falls with the road wheel and the torsion bar twists and untwists to absorb the movement.
A damper is used to control the oscillations

19. assembly

20. Air Springs
A throwback again to the horse and carriage where leather bellows type airbags where used.
Changed to rubber air springs in the 1930’s
Not so much used at all today

21. Hydrolastic Suspension
The front and rear suspension units have Hydrolastic displacers
These are interconnected by a small bore pipe.
Each displacer incorporates a rubber spring
damping of the system is achieved by rubber valves
when a front wheel is deflected, fluid is displaced to the corresponding suspension unit.
That pressurises the interconnecting pipe which in turn stiffens the rear wheel damping and lowers it
The rubber springs are only slightly brought into play and the car is effectively kept level and freed from any tendency to pitch

22. Hydragas Suspension
With Hydragas, the rubber spring is removed completely. The fluid still exists but above the fluid there is now a separating membrane or diaphragm, and above that is a cylinder or sphere which is charged with nitrogen gas. The nitrogen section is what has become the spring and damping unit whilst the fluid is still free to run from the front to the rear units and back.

23. Beam Axle A dead Axle (non-driving)
Designed to reduce the sprung-weight of the rear axle in front wheel drive cars
A panhard rod is used to prevent lateral (side to side) movement of the assembly

24. Control Blade
Ford’s new suspension lowers centre of gravity and separates suspension components from handling components.

25. Conclusion
A suspension system separates the payload of a vehicle from the variations in road surface
It maintains maximum contact between the tyres and the road surface
Absorbs and controls pitch and roll from accelerating, cornering and braking forces.

26. Useful Websites http://www.mgfcar.de/hydragas
Homework research the following page hydropneumatic suspension.