Coachwork

As a body of French carrosse for carriage, is referred to the complete structure of a motor vehicle. Self-supporting bodies are not only the structure itself but also the backbone of the vehicle in contrast.

Non- self-supporting body

In the classical sense, a motor vehicle from the Kompenenten chassis, powertrain and body is composed. The chassis, also known as chassis or frame, forming a framework, which supports the drive, the body and the load and stabilized against external forces. As a framework, several types of design were used. The body being mounted on the frame (usually screwed ) forms an outer skin for the protection of the occupant or of the transported goods.

Originally, cars usually an open- structure, but this soon changed. The American engineer and author HE Tarantous described in 1925 the trend from the open to the closed body. He demonstrated this with the statistics of the largest American coachbuilder this time, Fisher: Fisher 1919 83.500 put open bodies forth, in 1924 there were 239 502. The bodies were closed in 1919 at 31,318, in 1923 it overtook the open bodies and In 1924, Fisher 835 477 closed bodies forth.

The production of the bodies was sometimes carried out by external body shop. The factory supplied chassis with drive were built here following not rare individual customer requirements. The development of the effect took place in the 1920s. With the proliferation of the automobile, the outer appearance of the vehicles became more and more important. Specialized in sheet metal and woodworking enterprises made ​​bodies own way to the dealer and customer. The body was to Unterscheidungskritierium on the road, a sign of personal style and budget of the "Lord of the driver ". [Note 1] The first American cars came in late 1923 on the German market and changed the view of automobiles sustainable. They saw it not only as a commodity but as a piece of jewelry. The models of " Buick, Cadillac, Willys Knight, Studebaker, etc., [ ... ] it backwards broad sweeping cars, Tome, these locomotives " indeed were sometimes uncomfortable and unreliable, but they impressed from body forth the German automotive and bodywork manufacturers. The Berlin car journalist Hanns Steiner In 1924 states: " The old, boring, standard -like structure, the chassis each factory used in 1918, was no longer negotiable. Life, color, movement came into the bodies. Forms had to change. Our cityscape alive, joyful color patches ran through the gray. Until the grotesque it rose. "

At the beginning of the 1950s, the classic design has been replaced in the car construction of the monocoque body. When the truck frame construction has been retained, however, to this day. Even in small series vehicles produced, especially in the field of motor sports, often without a self-supporting body. For the construction of this aluminum or plastic ( often then GRP / CFRP) used often.

Self-supporting body

If the chassis and body of a motor vehicle are combined into one unit, it is called a self-supporting body, also called monocoque shell construction or. In this type of construction paneling, reinforcements, mounting plates and profiles with different joining techniques (gluing, spot welding, laser welding, soldering) are inextricably linked. But this structure takes over the supporting function. There is no separation between purely subjected to bending / torsion or shear components and parts which are used to seal / cladding ( such as in -wire or wire-frame ). All parts act as a static shells and take in their entirety, the forces introduced on. ( Subframe ) are used occasionally on the axles subframe.

The rigidity that guarantees normally the frame is achieved here by the compact skin sheet and hollow sheet metal sections with the largest possible cross-section and therefore section modulus (eg sills ). Beads increase the rigidity and the natural vibration frequency so as to prevent the boom. The attachment points for mounting components such as doors, fenders, doors and hinges are firmly integrated into the body, for example in the form of threaded plates and weld nuts. A high stiffness is important to keep elastic deformations at the joints of the attachments and to avoid creaking noises when driving. Small gaps are therefore only possible with very stiff bodies. Furthermore, the stiffness has an effect on the driving behavior, especially on bad roads or in extreme situations. In order to withstand vibration excitations by the engine and chassis, the natural frequency of the body must be adapted accordingly. In the body structure, a distinction between the static stiffness ( Nm per unit angle ) and the dynamic stiffness ( Hz). The latter is the upper middle class vehicles ( sedans such as the Ford Mondeo or Passat B6) 35-47 Hz In self-supporting bodies Cabriolet reinforcements in the subsoil and the sills are installed ( diagonal braces, etc.). Stiffeners on the underbody result in a downwardly open profile ( U-section ), while a sedan a rectangular cross -section corresponds to ( closed section ) and can be stiffer and stronger at lower mass so simultaneously. Suits have weger the missing back wall ( behind the rear seats ), which stiffens the car body diagonal, thus acts as a shear wall support without countermeasures a lower stiffness than sedans of the same type.

The Lancia Lambda 1922 was the first car with a unibody construction. The Citroen 11CV (1934 ) and the German Opel Olympia ( 1935) were the first production car with an all- steel body, the first self-supporting body made ​​of glass fiber reinforced resin had 1957 Lotus Elite. One of the first buses with selbesttragendem structure of the HS 160 counts by Henschel & Sohn.

The decisive advantages of the self-supporting body, the weight savings by eliminating the frame, as well as better ways of space utilization. Was made possible design for standard use by advances in sheet metal processing. At the beginning of the 1950s, the self-supporting body prevailed in car construction. Buses are built in both frame and monocoque construction. For trucks, the self-supporting body has not been able to establish.

In comparison to the frame construction, the unibody also some significant disadvantages. While suggest a framework different body styles fit without much effort, the possibilities are restricted to the extent in self-supporting bodies. The wide variety of bodies is, therefore, declined sharply in the 1950s compared to the pre-war period. Another problem of the self-supporting structure is its increased susceptibility to rust, which leads relatively quickly to the necessary scrapping the entire vehicle if certain body parts are rusted. Thus, the luxury car manufacturer Rolls Royce decided upon adoption of the Silver Cloud in 1955, deliberately bucking the trend for the frame construction, not losing the reputation of the long shelf life of the vehicles. Another argument for the frame construction was the avoidance of Dröhneffekten as they more or less pronounced occur with self-supporting bodies. In the GDR the frame construction was maintained at the Wartburg cars and vans Barkas. In addition to the variety of possible structures, that resulted in the advantage that worn vehicles could be relatively easily repaired.

Skeletal body (eg, " space frame " )

This body type has a skeleton of a closed hollow sections, which are connected directly or via nodes. Scale components such as the roof or the windshield are rigidly connected to the skeleton and take shear forces. Consequently, new materials, components and techniques used in the body. One expects this to weight savings, high torsional rigidity and new design possibilities. An example of this is the aluminum spaceframe or Audi Space Frame Audi A8 and Audi A2. Audi used since 1993 as aluminum bodywork material and uses nodes of cast aluminum alloys, deep-drawn parts and extrusions.

The first vehicle with a space frame (steel) was 1934, the Chrysler Airflow. Also in Berlin, built in the early 1970s AWS Shopper had a simple space frame made ​​of square tubes. The Fiat Multipla was the second generation of a vehicle with a steel space frame in series. Since the forming of closed steel profiles is problematic, you can see the vehicle, this construction also.

If ThyssenKrupp with the announced production technology for weight and cost- optimized tubular components quickly have success in the market, new possibilities are open here, because as a material steel is cheaper than aluminum. The steel manufacturer Salzgitter AG has developed a coordinated on production vehicles body structure together with the automotive supplier Karmann GmbH in response to the increasing use of aluminum in the body and tested on prototypes with new high-strength steels, the body weight with increased rigidity, same cost and same crash behavior is to reduce by 40 percent. Another example of a new concept of steel is the NSB of ThyssenKrupp.

Materials

Wood

The bodies of the first cars were made ​​entirely of wood. This design was common from the coach building. Wood was then used for the structure of the assembly. The body skin consisted of steel or aluminum sheet, rare leather or synthetic leather. A well-known example is the DKW F8. This design is rarely used today; The Morgan Motor Company is the most famous active manufacturer of cars with such a body.

A special, derived from early aircraft construction method allowed the French coachbuilder Charles Terres Weymann and businessman patented in all major states. Woods held as material for roof inserts with closed structures ( for example, Ford Model A) until the mid- 1930s, according to large presses for all steel roofs were available.

Steel

Sheet steel is currently (2014) with 90% market share, the most widely used material for the automotive industry. Budd developed at the end of the 1920s, the all-steel body. General Motors adapted it in 1934 in the United States ( " Turret Top" design). Very long but not strong enough presses were available to press complete auto roofs; therefore still vehicle roofs with impregnated materials have been produced up to the 1950s.

To prevent corrosion, steel is now mostly galvanized; Audi presented the most vehicles since the late 1970s to 2005 with fully galvanized ago. Very many manufacturers ( eg VW and Daimler -Benz) built bodies with zinc coating of the floor assembly. In all cases, to the factory, i.e., used in the rolling mill galvanized steel with a high quality cold-rolled surface.

Hot-dip galvanized sheet is always galvanized on both sides, the thickness of the zinc layer is 5 to 10 microns. Electrolytically galvanized sheet may comprise a single or double sided galvanized surface with a zinc layer thickness from 2.5 to 7.5 microns, with bilateral galvanizing different values ​​are possible side separately. Asian and American manufacturers often use plates with " galvannealed " surface produced by the thermal treatment of a hot-dip galvanized surface. Sheet with galvanically applied zinc -nickel layer is rarely used for body panel. In all cases the body ready built is intensively cleaned, phosphated and subjected to immersion in a cathodic dip painting. In addition, seams, joints and cavities are sealed with adhesives or sealants and subsequently preserved with wax. The galvanizing of sheet, of whatever kind, will always come to the role of a cathodic protection. This provides in synergy with the paint, preservatives and sealing measures the multiple term of protection of the individual measures. Thus, the corrosion of high-quality manufactured bodies no longer acts as a crucial factor in the effective usability duration.

The often rumored " fully galvanized " whole bodies in the car plant was never practiced, since this would not be completely coated at the complex geometry of a finished body with cavities, multiple Blechdopplungen, bonding and sealing seams.

Some producers have chosen for cost reasons, to limit the scope of the use of galvanized sheet metal to actually atmospheres. For the sake of weight saving many hybrid components made of aluminum and galvanized steel are also used in newer designs. In these there is usually a supporting structure made ​​of galvanized sheet steel and the visible external cladding made of aluminum sheet. For technical reasons and to avoid bimetallic corrosion such components are mechanically positively connected with each other and also bonded extensive.

Chance of vehicle bodies are also made of stainless steel. Testhalber did this Porsche in the 1970s; DeLorean put the bodies of his sports car completely forth in stainless steel.

To meet the current demands on the stability ( crashworthiness ), weight and appearance of the body, many new types of steel have been developed (eg, IF - steel) or with acceptable formability still are either very soft and very malleable much stronger (for example, DP steel).

Despite the higher density compared to the materials mentioned below can be produced by a proper combination of steel parts, a body that is not heavy, but make it cheaper than of light metals, which are less strong and stiff as steel.

Aluminum

Since the density of aluminum is lower than that of steel, there have been successful attempts to establish itself as the body material. In spite of the higher cost of aluminum can compete with steel because of its lower density, advantageous in many applications. In this case, however, which is also much lower modulus of elasticity of the material must be taken to obtain ( for example, about 40 % thicker plate thickness ) or more space is needed for the same stiffness either more material. A body made ​​entirely of aluminum is already mass produced (eg Audi A2 and A8, Jaguar XJ, Mercedes Benz SL or Opel Speedster ). Even individual vehicle components are made of aluminum in the middle class, such as the hood and tailgate consisted of the Subaru Legacy the fourth series of aluminum. The production of aluminum components and the joining of the individual components do not need it more time than for example in steel parts. The fuel consumption and emissions (weight savings in the vehicle) by aluminum lightweight is the role of energy -intensive production of the starting material. An Audi A8 for example, has saved only after a mileage of 170,000 km, the amount of CO2, which is additionally become vacant during the production of aluminum required for his body. A particularly elaborate aluminum construction operational Pierce -Arrow: Between 1904 and 1920 there were major components of the body such as torpedo plate, side panels or doors made ​​of cast aluminum.

Magnesium

The use of magnesium is the logical development of the aluminum body. So far, only items made ​​of magnesium are produced, no complete bodies.

The use of magnesium sheet is being accompanied by various problems. A fundamental difficulty is the limited deformability of the hexagonal lattice structure of magnesium at room temperature is only extended by hot working. Also, because of its high tendency to corrode the sheet metal as a fender or Seitwand little sense ( rockfall ). In order to continue to move the center of gravity of the vehicles down, also more applications in the Hood, but best in the roof area come into question.

Porsche has magnesium sheet successfully in the interior in the series - which is low in comparison numbers are likely to have influenced this decision is positive with certainty. The use of magnesium sheet in the interior is not critical because problems such as dirt, water or aggressive media there occur rarely.

Plastic

The first car with full plastic body, which was produced in series, was the Chevrolet Corvette. In 1955 the P70 from Zwickau with a cladding made of phenolic resin and cotton plastic ( thermoset ) and wood framework as a base. Later, when the Trabant wood framework was replaced by an all-steel skeleton and maintain the thermoset for planking. Today, plastic is used in many parts of the body. But there is no large series cars whose body is made entirely of plastic.

Plastic has the advantage not to corrode, and can be produced from renewable resources such as vegetable oil. The making of such a body is particularly suitable for small and medium series, since they can also produce handmade.

Nowadays, many solar cars and energy-saving cars are built with a plastic body to reduce weight. This takes place as a rule pure plastic fiberglass or carbon fiber are used, to increase the strength and stability compared to pure plastic again.

In a current project aims to develop together with Volvo and other organizations a new composite material made of carbon fibers (carbon fibers ) and polymer resins, which could also be used for the body, the Imperial College in London. The special feature is that it can save energy and thus to the body at the same time to the accumulator for future electric vehicles.