137028787 Air Suspension Syatem Docx

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Air SuspensionAir suspension is a type of vehicle suspension powered by an engine drivenor electric air pump or compressor. This pump pressurizes the air, using

compressed air as a spring. Air suspension replaces conventional steel

springs. If the engine is left off for an extended period, the car will settle to

the ground. The purpose of air suspension is to provide a smooth ride

quality and in some cases self-leveling.While not using high pressure mineral oil, the system aims to achieve a

result similar to thehydropneumatic suspension arrangement introduced in

1954 by Citron.

With a leg up on other companies, GM used its experience with commercial

busses air suspension to introduce systems for its car lines, beginning with

the 1958 model year. Air bags at each wheel replaced the standard coil

springs, and had sensors to keep the car level under load and in turns. It was

too slow to react in sudden maneuvers, however.

Period reviews rated the air suspension somewhat superior in ride quality,

but not dramatically. Some reliability issues plagued these systems, as well.

Thus, as an option, air suspension was short lived in that era.

Vehicles that use air suspension today include models from Maybach, Rolls-

Royce, Lexus,Mercedes-Benz, Land Rover/Range

Rover, SsangYong, Audi, Subaru, Volkswagen, and Lincolnand Ford, among

others.

The air suspension designs from Land Rover, SsangYong, Subaru and some

Audi, VW, and Lexus models, feature height adjustable suspension

controlled by the driver, suitable for clearing rough terrain. The Lincoln

Continental and Mark VIII also featured an air suspension system in which

the driver could choose how sporty or comfortable they wanted the

suspension to feel. These suspension settings were also linked to the

memory seat system, meaning that the car would automatically adjust the

suspension to the individual driver. The control system in the Mark VIII also

lowered the suspension by about 25 mm (1 inch) at speeds exceeding about

100 km/h (60 mph) for improved aerodynamic performance. Unfortunately,


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however, these systems turned out to be unreliable and in many cases ended

up being retrofitted with aftermarket replacements or conventional steel coil

springs.

In addition to passenger cars, air suspension is broadly used on semi trailers

and buses, which are both transportation sectors that helped pioneer the use

and design of air suspension. An unusual application was on EMDs

experimental Aerotrain

Air Suspension System ComponentsEarly versions of air suspension systems were relatively simple. Air bagsreplaced the coil

springs. The bag was inflated to the correct pressure or height with an outside compressor

through a valve on the bag. Changes in technology and use added more components, and

control, to the system. But today's air suspension systems all have a basic stock of similar

components that vary little from maker to maker. The differences come mainly in controls and

ease of installation.

Air bag material has changed little over time. The bag is a composite of rubber and polyurethane,

which provides structural integrity, air-tight construction, toughness against light abrasion from

road debris and sand, and resistance to salt and chemical corrosion.

The bags come in three basic shapes:

Double-convoluted bag. This bag is shaped like an hourglass. The design allows for a little morelateral flexibility than the other designs.

Tapered sleeve. This air bag performs the same as any other but is designed to fit in a tighterarea and offers a little more adjustability on ride height.
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Rolling sleeve. This is also a specific-application air bag. The pertinent differences between thetwo sleeves are really about ride height and spring control, and what's best for the vehicle and

the application.

Most air suspension systems now come with an on-board compressor. The compressor is anelectric pump feeding air to the bags through a series of compressed air lines. The compressor isgenerally mounted on the vehicle's frame, or in the trunk. The vast majority of compressors come

with an attached drier. The compressor works by drawing outside air into the pump,

compressing it and moving it to the bags. Outside air is often laden with moisture, and moisture

can wreak havoc in a closed system. The drier uses a substance known as a desiccant to absorbas much moisture from the air as possible before the air is sent through the system.

Simpler compressor systems rely on the compressor itself to maintain, increase or decrease

pressure. More advanced systems add an air tank to maintain pressure and provide an even

transition between pressures.Compressorscan be activated manually or automatically, and

controlled solely by the driver, automatically through an electronic system, or a combination of

both.

CUSTOM APPLICATIONS

Over the last decade or so air suspension has become extremely popular in the custom

automobile culture: street rods, trucks, cars, and even motorcycles may have air springs. They

are used in these applications to provide an adjustable suspension which allows vehicles to sit

extremely low, yet be able rise to a level high enough to maneuver over obstacles and

inconsistencies in the roadways (and parking lots). These systems generally employ small,

electric or engine-driven air compressors which sometimes fill an on-board air receiver tank

which stores compressed air for use in the future without delay. High-pressured industrial gas

bottles (such as nitrogen or carbon dioxide tanks used to store shielding gases for welding) are

sometimes used in more radical air suspension setups. Either of these reservoir systems may be

fully adjustable, being able to adjust each wheels air pressure individually. This allows the user

to tilt the vehicle side to side, front to back, in some instances hit a 3-wheel (contort the

vehicle so one wheel lifts up from the ground) o r even hop the entire vehicle into the air. When

a pressure reservoir is present, the flow of air or gas is commonly controlled with pneumaticsolenoid valves. This allows the user to make adjustments by simply pressing a momentary-

contact electric button or switch.

The installation and configuration of these systems varies for different makes and models but the

underlying principle remains the same. The metal spring (coil or leaf) is removed, and an air bag,

also referred to as an air spring, is inserted or fabricated to fit in the place of the factory spring.

When air pressure is supplied to the air bag, the suspension can be adjusted either up or down

(lifted or lowered).

For vehicles with leaf spring suspension such as pickup trucks, the leaf spring is sometimeseliminated and replaced with a multiple-bar linkage. These bars are typically in a trailing arm
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configuration and the air spring may be situated vertically between a link bar or the axle housing

and a point on the vehicles frame. In other cases, the air bag is situated on the opposite side of

the axle from the main link bars on an additional cantilever member. If the main linkage bars are

oriented parallel to the longitudinal (driving) axis of the car, the axle housing may be constrained

laterally with either a Panhard rod or Watts linkage. In some cases, two of the link bars may be

combined into a triangular shape which effectively constrains the vehicles axle laterally.

Often, owners may desire to lower their vehicle to such an extent that they must cut away

portions of the frame for more clearance. A reinforcement member commonly referred to as a C-

notch is then bolted or welded to the vehicle frame in order to maintain structural integrity.

Specifically on pickup trucks, this process is termed notching because a portion (notch) of the

cargo bed may also be removed, along with the wheel wells, to provide maximum axle clearance.

For some, it is desirable to have the vehicle so low that the frame rests on the ground when the

air bags are fully deflated.

Common air suspension problems

Air line failure is a failure of the tubing which connects the air bags or struts to the rest of the airsystem, and is typically DOT-approved nylon air brake line. This usually occurs when the air

lines, which must be routed to the air bags through the chassis of the vehicle, rub against a

sharp edge of a chassis member or a moving suspension component, causing a hole to be

formed. This mode of failure will typically take some time to occur after the initial installation of

the system as the integrity of a section of air line is compromised to the point of failure due to

the rubbing and resultant abrasion of the material. An air line failure may also occur if a piece of

road debris hits an air line and punctures or tears it.

Compressor failure is primarily due to leaking air springs or air struts. The compressor will burnout trying to maintain the correct air pressure in a leaking air system. Compressor burnout may

also be caused by moisture from within the air system coming into contact with its electronic

parts.

In Dryer failure the dryer, which functions to remove moisture from the air system, eventuallybecomes saturated and unable to perform that function. This causes moisture to build up in the

system and can result in damaged air springs and/or a burned out compressor.


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The Disadvantages of Having Air SuspensionAir (pneumatic) suspensions are one of three basic types of suspensions, the other two being spring

and hydraulic. While air suspensions do offer ride-height adjustability, the air-bag springs that they

utilize to suspend the vehicle are slow to respond and dynamically inferior in almost every other way.

Handling

The standard air suspension's primary problem is that the user must reduce pressure in the air bag todrop the car and increase pressure to raise it. This results in a car that handles like a barge when it's


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lowered and bucks like a concrete bronco when its set higher -- exactly the opposite of what you'd

want.

Heavy and Complicated

Air suspensions require a network of air hoses, junction regulators and control valves to function andan air compressor to fill the bags. While lighter than an equivalent hydraulic setup, these parts can add

over 100 lbs. to the car, depending on compressor size. Moreover, every junction is an opportunity for

leaks.

Slow Response

Air is elastic, meaning that it has mass and doesn't like to change direction. Air suspensions cannot

respond to changes in road conditions with anything approaching the speed of an equivalent

magneto-rheological (MR) dampener. An MR dampener uses a magnet to thicken the metallic fluid

inside its body, allowing the car's computer to change ride firmness at the speed of electricity.

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137028787 Air Suspension Syatem Docx