Airride
Air suspension systems are commonly referred to as Airride chassis , which are used for subsequent, i.e. non-factory installation for vehicle tuning , especially in sports cars or bikes . Often there is talk of an "Airride" as such, without the additional designation "chassis".
definition
In contrast to the conventional concept of air suspension , Airride chassis (air = air; to ride = drive) are developed, manufactured and sold by specialized companies for retrofitting vehicles. The range of equippable series vehicles is growing steadily. This means that vehicles for which no air suspension is available ex works can be retrofitted with it. This mostly happens during vehicle tuning due to the infinitely variable height adjustment from inside the vehicle (optionally via remote control). The comfort aspect, which plays the main role in factory air suspension systems, takes a back seat.
Sense and purpose
The vehicle-specific manufactured pneumatic air suspension units consist of specially adapted shock absorbers and an air bellows, which replaces the otherwise common steel spring.
The control loops, which play an important role in luxury-class vehicles, did not initially exist. The focus was on the ability to continuously adjust the height of the vehicle. The adjustment range could be larger: beyond the standard height, up to partially stored on the stop buffers. Due to the appearance achieved in this way and the possibility of avoiding damage to the lowered vehicle in certain situations (for example high curbs at a driveway), Airride chassis are becoming increasingly popular in the vehicle tuning scene. All-wheel drive vehicles that are also street legal can use the Airride to raise the body and drive on unpaved roads without the vehicle floor or spoilers touching the ground or crossing watercourses without the driver getting wet feet.
Due to the increasing interest, more and more regulating systems with complex sensors and control valves are offered.
Layout and function
Numerous components are required for operation, and they must be housed in the interior (and in some cases in the engine compartment) of the vehicle. Compressors, air tanks, solenoid valves and air hoses are installed to generate the air pressure. In order to maintain the trunk with a view to suitability for everyday use, these components are often installed in the spare wheel recess in a manner similar to gas tanks in petrol vehicles that have been converted to LPG operation. The actual height adjustment takes place on the suspension struts and air bellows themselves. Depending on the version of the standard chassis, the standard coil springs are replaced by air bellows. In addition, shock absorbers specially designed for the vehicle and the air bellows are used. The function of the shock absorbers in the basic Airride models is the same as that of conventional sports shock absorbers. More complex variants also have electronically adjustable damper hardness. The air bellows inflate when pressure is applied and thus raise the vehicle and lower it when the air pressure is reduced (by releasing it into the atmosphere). The air flows are controlled by switches in the interior via solenoid valves that distribute the air from the air tank into the corresponding air bellows. To lower the vehicle, the air (overpressure) in the bellows is blown off into the environment by pressure compensation (not the vehicle's own weight) when the drain valves are opened. This creates the exhaust noise typical of Airride vehicles. The air in front of the solenoid valves in the air tank is generated by an electric compressor that sucks in air from the environment and compresses it into the tank. So that there is always enough pressure (air) to operate the height adjustment, the compressor switches on automatically when the pressure in the air tank falls below a minimum. When a set maximum pressure is reached, it switches off again automatically.
As already mentioned, common solenoid directional control valves are used for control . These can be designed as 5/3 (with two dummy plugs, these become 3/3-way valves) or as 2/2-way valves.
Use of 5/3-way valves: These combine the control for opening and lowering in one valve. The three switch positions:
- all lines shut off
- Air supply from the tank to the air bellows
- Air discharge from the bellows into the environment
For the axle-by-axle control, a 5/3-way valve is required for the front and rear axles. The two connections that are not required are sealed airtight with blind plugs.
Use of 2/2-way valves: These are less complex and therefore cheaper to replace than the 5/3-way valves. However, twice as many 2/2 valves are required as for control with 5/3 valves. The 2/2-way valves only have two switching positions:
- All lines shut off
- Air supply from the tank into the air bellows or air discharge into the environment
So two 2/2-way valves are required for opening and lowering an axle (one for raising it, one for lowering it). A total of four 2/2-way valves are required for axis-by-axis control.
To control each individual air bellows, twice the number of valves is required, i.e. four for 5/3-way valves and eight for 2/2-way valves. This so-called single wheel control is only allowed for show purposes and not in the StVZO , since any unfavorable loss of air can considerably impair the maneuverability of the vehicle when driving due to the enormous articulation of the axles. From a driving dynamics perspective, however, the individual wheel control prevents the air from the bellows on the outside of the bend from being pushed into the inside of the bend when cornering. The respective bellows are separated from one another and there is significantly less rolling motion.
Directives and legal situation according to the StVZO
With regard to the entry of the system in the vehicle registration document, there are already TÜV reports for many vehicle models with which it is possible to legally drive an Airride vehicle on public roads. Additional requirements must be taken into account:
- The system must have an optical or acoustic warning device that sounds when the pressure falls below a preset value
- If the system is completely pressureless, the wheels must be free to move and the vehicle must be able to move safely
- Adjusting the vehicle height may only be possible when the vehicle is stationary. A corresponding connection to the vehicle's ignition or handbrake should therefore exist
- Installation must be carried out by a specialist workshop
- As with other sports suspensions, the general freedom of movement of the wheels must be guaranteed for unhindered driving
Situation in Austria
In 2015, Christian Müller from the Lowrider company, in collaboration with legal experts, car technicians and the help of TÜV Austria, was able to achieve the first legal registration of an air suspension gear. What used to apply only to special vehicles such as ambulance vehicles or special police vehicles can now be installed and approved in every type of vehicle from classic cars to sports cars. Basically, the regulation in Austria is very similar to the regulation in Germany. Chassis that are delivered by the dealer with a certificate (e.g. TA Technix) can be standardized in Austria since the beginning of 2015. With considerable additional effort, chassis from various other manufacturers - z. B. AIR LIFT, AIR FORCE etc. - can be entered. For this purpose, an expert opinion from a civil engineer must be prepared. He must approve the components used with the help of data sheets and technical information from the manufacturer. Additional requirements must be taken into account:
- In principle, the same rules apply as when registering other sports suspensions. (ad / tire combination, 8cm or 11cm ground clearance when driving, distances to neighboring parts)
- The lowest legal position is emergency operation. This depends on the wheel, tire, attachments, etc. The vehicle must remain fully drivable and steerable in emergency mode (0 bar) up to 50 km / h.
- Adjustment of the vehicle height may only be possible when the vehicle is stationary - mostly in conjunction with the handbrake on. The height adjustment may only be carried out on an axle-by-axle basis (front and rear axles separated). Individual driving of bikes is not permitted.
- The system must have a warning lamp and / or warning buzzer that sounds when the pressure falls below and exceeds the pressure specified in the report and cannot be switched off.
- As soon as the vehicle comes to a standstill on public roads, it can be parked in a depressurized state (0 bar).
- The ride height can be set to 11 cm fixed, or 8 cm with full axle load. For this purpose, the bellows pressure is determined in the respective ride height and the corresponding dimensions (wheel center - wheel house edge or lane wheel house edge) entered in the type certificate. In some cases, the maximum and minimum permissible pressure is to be indicated by a sticker in the vehicle.
Situation in the USA
Such systems are well known in the United States. In Europe, pneumatic airride systems are often confused with hydraulic systems. While both systems are very common in the USA, in Europe, and especially in Germany, this is the case with pneumatic airride systems. The reason for this is that the hydraulic, so-called " lowrider " chassis, which work with oil pressure, oil pumps and hydraulic cylinders, are not approved for use on public roads in Germany. For show purposes, trade fairs and similar purposes, however, there are some companies that equip vehicles with it.
literature
- Karl-Heinz Dietsche, Thomas Jäger, Robert Bosch GmbH: Automotive pocket book. 25th edition, Friedr. Vieweg & Sohn Verlag, Wiesbaden, 2003, ISBN 3-528-23876-3
- Max Bohner, Richard Fischer, Rolf Gscheidle: Expertise in automotive technology. 27th edition, Verlag Europa-Lehrmittel, Haan-Gruiten, 2001, ISBN 3-8085-2067-1
- Peter Gerigk, Detlev Bruhn, Dietmar Danner: Automotive engineering. 3rd edition, Westermann Schulbuchverlag GmbH, Braunschweig, 2000, ISBN 3-14-221500-X
- Peter A. Wellers, Hermann Strobel, Erich Auch-Schwelk: Vehicle technology expertise. 5th edition, Holland + Josenhans Verlag, Stuttgart, 1997, ISBN 3-7782-3520-6
Individual evidence
- ↑ This is how lowriders become legal in Austria. In: DiePresse.com. April 7, 2017. Retrieved January 26, 2018 .
- ↑ - ( Memento of the original from October 13, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
