Air suspension
Air suspension is used in place of conventional steel springs in heavy vehicle applications such as buses and trucks, and in some passenger cars.
Modern electronically controlled systems in automobiles and light trucks almost always feature self-leveling along with raising and lowering functions.
On 7 January 1901 the British engineer Archibald Sharp patented a method for making a seal allowing pneumatic or hydraulic apparatus described as a "rolling mitten seal",[1] and on 11 January 1901 he applied for a patent for the use of the device to provide air suspension on bicycles.
"[9] During World War II, the U.S. developed the air suspension for heavy aircraft in order to save weight with compact construction.
[13] Citroën replaced the conventional steel springs on the rear axle of their top-of-range model, the Traction Avant 15 Hydraulique.
In the U.S., General Motors built on its World War II experience with air suspension for trucks and airplanes.
[16] An "Air Dome" assembly at each wheel included sensors to compensate for uneven road surfaces and to automatically maintain the car's height.
[18][19] In 1958, Buick introduced an optional "Air-Poised Suspension" with four cylinders of air (instead of conventional coil springs) for automatic leveling, as well as a "Bootstrap" control on the dashboard to raise the car 5.5 inches (139.7 millimetres) for use on steep ramps or rutted country roads, as well as for facilitating tire changes or to clean the whitewall tires.
[21] An optional air suspension system was available on the 1958 and 1959 Rambler Ambassadors, as well as on all American Motors "Cross Country" station wagon models.
[22][23] The "Air-Coil Ride" utilized an engine-driven compressor, reservoir, air bags within the coil springs, and a ride-height control, but the $99 optional system was not popular among buyers and American Motors (AMC) discontinued it for 1960.
[22][24] Only Cadillac continued to offer air suspension through the 1960 model year, where it was standard equipment on the Eldorado Seville, Biarritz, and Brougham.
In 1984, Ford Motor Company incorporated a new design as a feature on the Lincoln Continental Mark VII.
Vehicle marques that have used air suspension on their models include: Audi, Acura,[27] Bentley, BMW, Cadillac, Citroën, Ford, Genesis, Hummer, Hyundai, Jaguar, Jeep, Land Rover, Lamborghini, Lexus, Lincoln, Mercedes-Benz, Mercedes--Maybach, Porsche, Ram, Rivian, Rolls-Royce, SsanYong, Subaru, Tesla, Volkswagen, Volvo, and more.
Since a car with lower ground clearance has different aerodynamic characteristics, automakers can use active suspension technology to improve efficiency or handling.
[28] In 2014 the new Mercedes S-Class Coupe introduced an update to Magic Body Control, called Active Curve Tilting.
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 on paved surfaces.
[32] 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.
When a pressure reservoir is present, the flow of air or gas is commonly controlled with pneumatic solenoid valves.
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.
In some cases, two of the link bars may be combined into a triangular shape which effectively constrains the vehicles axle laterally.
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.
[33] 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.
The air springs were designed to provide a smooth ride, with the additional ability to raise the body of the vehicle for off-road clearance and lower it for higher-speeds road driving.
With custom applications, improper installation may cause the air bags to rub against the vehicle's frame or other surrounding parts, damaging it.
Compressor burnout may also be caused by moisture from within the air system coming into contact with its electronic parts.
This causes moisture to build up in the system and can result in damaged air springs and/or a burned out compressor.
Many enthusiasts use diagnostic devices such as laptop and hand computers running specially developed software to clear spurious faults and avoid the need for repair.
Some manipulate the sensors to set the vehicle to a particular ride height at all times by adjusting the lever ratio on the height-sensing devices, or a supplementary ECU to "fool" the system.
Standard coaches also have a system called ferry lift, which raises the vehicle and increases its breakover angle.
