Air Suspension

Greetings!!

What is Suspension?

A suspension is a mechanical (electro-mechanical in present days) device that was designed to, as the name says to suspend the wheels to ground. The soul purpose of designing it was to make the vehicle stay on ground (since it is a ground vehicle :P ), which was a serious problem in earlier days of motor sports.

The second major use of the Suspension is to provide comfort while riding/driving. This is called Ride Quality, which is an important factor in Pricing in Automotive Industry

Todays’ topic:

Air Suspension-

Unfortunately, This suspension is not available in 2 whellers (not yet) because of too many reasons.

This are very famous in heavy vehicles.

<Further topic will only be about 4 wheelers and above>

Traditionally, there are 2 types that are still used

i)                    Steel Coil Spring System.

ii)                   Leap Spring System.

But, Air Suspension consists of primary component called Air Springs made up of Rubberized Membrane, which stores the pressurized air.

Air Suspension System consists of

I)                    Air Supply Unit- Supplies Air from compressor to all springs via Reservoir.

II)                  Reservoir- it stores additional air pressure for control/emergency purpose.

III)                 Height Sensors- Present on all corners to sense and modulate air flow to springs.

IV)                Air springs- Pressurized air is supplied to maintain the height of the vehicle.

Types of Air Springs

a)       Convoluted Air Springs-  gives better packaging, distance between axle and frame is reduced.

b)      Rolling Lobe- Gives better tuning/control.

deflated/ de-presureized(For highways/ unloaded vehicle)

Pressurized(for off road/ loaded)

Types of Air Suspensions:

Open system and Closed system

Open System:

Air is given to ASU(Air Supply Unit), ASU sends air to Reservoir, and reservoir forwards the air to Air Springs.

Here air flows in only one direction ASU to Air Springs.

Older System, Noisier, Slower (like in city buses).

Closed System:

Air is given to ASU(Air Supply Unit), ASU sends air to Reservoir, and air moves back and forth between Reservoir and Air Springs.

                Air flows in one direction  from ASU to Reservoir, but air flows in both directions between Reservoir and Air Springs.

                Modern system, Faster response time, more efficient, generally quitter.

 Air Suspension Over Traditional Systems:

1)      Adjustable Ride Height

i)                    Ingress(Getting into the vehicle) and Egress(getting out of the vehicle)

ii)                   Off-road use:

a)       Higher Ground Clearance.

b)      Higher Approach angle.

c)       Higher Departure angle

d)      Higher Break-Over Angle

iii)                 Aerodynamics: Effectively lowers the height of the vehicle when crusing in highways providing less drag and higher fuel economy.

iv)                 Load leveling: As I mentioned earlier, this system is very popular in heavy vehicles and pick-ups’. When the vehicle is loaded in steel springs the height of the vehicle lowers due to the weight. But, in air suspension the height sensors measure the fall in height and increase the air pressure in the air spring rubber membrane to meet the targeted height. (Plz note: air will be same but air pressure in increased)

2)      Improved Ride Quality: due to setting of ride height, there is no additional drags or so and ride frequency is constant. Hence even if the vehicle is loaded the vehicle dynamics behaves the same and it feels the same even if it is loaded.

3)      Minimal heat generation compared to spring types

4)      Lower hystorsis

5)      Less shocks

Cons of Air Suspension :

1)      Expensive

2)      Temperature causes higher air pressure- so vehicle rise without the control of ASU(presently rectified to some extent by use of sophisticated height sensors, etc).