Automotive design is the process of developing the appearance, to some extent the ergonomics, of motor vehicles, including automobiles, trucks, buses and vans. The functional design and development of a modern motor vehicle is done by a large team from many different disciplines included within automotive engineering, design roles are not associated with requirements for Professional or Chartered-Engineer qualifications. Automotive design in this context is concerned with developing the visual appearance or aesthetics of the vehicle, though it is involved in the creation of the product concept. Automotive design as a professional vocation is practiced by designers who may have an art background and a degree in industrial design or transportation design. Terminology used in the field is found in the glossary of automotive design; the task of the design team is split into three main aspects: exterior design, interior design, color and trim design. Graphic design is an aspect of automotive design.
Design focuses not only on the isolated outer shape of automobile parts, but concentrates on the combination of form and function, starting from the vehicle package. The aesthetic value will need to correspond to ergonomic utility features as well. In particular, vehicular electronic components and parts will give more challenges to automotive designers who are required to update on the latest information and knowledge associated with emerging vehicular gadgetry dashtop mobile devices, like GPS navigation, satellite radio, HD radio, mobile TV, MP3 players, video playback, smartphone interfaces. Though not all the new vehicular gadgets are to be designated as factory standard items, some of them may be integral to determining the future course of any specific vehicular models; the designer responsible for the exterior of the vehicle develops the proportions and surfaces of the vehicle. Exterior design is first done by a series of manual drawings. Progressively, drawings that are more detailed are executed and approved by appropriate layers of management.
Industrial plasticine and or digital models are developed from, along with the drawings. The data from these models are used to create a full-sized mock-up of the final design. With three- and five-axis CNC milling machines, the clay model is first designed in a computer program and "carved" using the machine and large amounts of clay. In times of high-class 3d software and virtual models on power walls, the clay model is still the most important tool to evaluate the design of a car and, therefore, is used throughout the industry; the designer responsible for the vehicles' interior develops the proportions, shape and surfaces for the instrument panel, door trim panels, pillar trims, etc. Here the emphasis is on the comfort of the passengers; the procedure here is the same as with exterior design. The color and trim designer is responsible for the research and development of all interior and exterior colors and materials used on a vehicle; these include paints, fabric designs, grains, headliner, wood trim, so on.
Color, contrast and pattern must be combined to give the vehicle a unique interior environment experience. Designers work with the exterior and interior designers. Designers draw inspiration from other design disciplines such as: industrial design, home furnishing and sometimes product design. Specific research is done into global trends to design for projects two to three model years in the future. Trend boards are created from this research in order to keep track of design influences as they relate to the automotive industry; the designer uses this information to develop themes and concepts that are further refined and tested on the vehicle models. The design team develops graphics for items such as: badges, dials, kick or tread strips, liveries; the sketches and rendering are transformed into 3D Digital surface modelling and rendering for real-time evaluation with Math data in initial stages. During the development process succeeding phases will require the 3D model developed to meet the aesthetic requirements of a designer and well as all engineering and manufacturing requirements.
The developed CAS digital model will be re-developed for manufacturing meeting the Class-A surface standards that involves both technical as well as aesthetics. This data will be further developed by Product Engineering team; these modelers have a background in Industrial design or sometimes tooling engineering in case of some Class-A modelers. Autodesk Alias and ICEM Surf are the two most used software tools for Class-A development. Several manufacturers have varied development cycles for designing an Automobile, but in practice these are the following. Design and User Research Concept Development sketching CAS Clay modeling Interior Buck Model Vehicle ergonomics Class-A Surface Development Colour and Trim Vehicle GraphicsThe design process occurs concurrently with other product Engineers who will be engineering the styling data for meeting performance and safety regulations. From mid-phase and forth interactions between the designers and product engineers culminates into a finished product be manufacturing ready.
Apart from this the Engineering team parallelly works in the following areas. Product Engineering, NVH Development team, Prototype
From 1931 to 1939, Daimler-Benz AG produced three cars with rear engine as well as a few prototypes. The production numbers remained quite low for each of these models compared to the production of classical front-engine Mercedes cars. At the beginning of the 1930s, inspired by modern streamlined shapes, there were attempts to move car engines from the forward compartment to the rear of the car; such a move allows a reduction in the volume of the front compartment. At the same time, the voluminous rear provides a lot of space behind the rear axle. Moreover, when engines are rear mounted, the drive shaft is eliminated; the most famous such development was with the 1930s Tatra cars under the leadership of Hans Ledwinka. In 1930, Daimler-Benz entrusted Hans Nibel with the development of a small rear-engined car, starting from the same principles. In 1931, working with Max Wagner, the type W17 or 120 was created, a two-door, equipped with four seats, vertical front and rear wheel arches, a four-cylinder boxer engine in the rear with a displacement of 1200 cc and a power of 25 hp.
There were attempts with transverse four-cylinder inline engines. In 1932/1933 Mercedes built a prototype with a front similar to the VW Beetle, a longer tail; the front wheel of the type W25 D or 175 is slanted or tilted backwards, the tail fin attached to the middle of the hood divides the oval rear window, so it anticipated the small oval two piece rear window of the Beetle known as "pretzel form". The "D" referred to the three-cylinder diesel engine OM 134 with an output of 30 hp, but due to high noise level, this vehicle was again rejected. From this type, 12 test cars were assembled The Mercedes-Benz 130H was a low-production automobile built in Germany in the 1930s, it was presented in February 1934 at the Berlin Car Show. Conceived by Hans Nibel, chief engineer of Mercedes Benz, the 130H was inspired by Edmund Rumpler's Tropfenwagen, it followed on the Rumpler-chassis Tropfenwagen racers, which ran between 1923 and 1926. Created in 1931 by Nibel, it had the 1.3 liter sidevalve four-cylinder engine mounted at the back, hence the "H", from German heck, With the fan between the rear coil springs, it drove a transmission with three forward speeds, plus a semi-automatic overdrive which did not require the use of a clutch.
The backbone chassis owed something to Hans Ledwinka, suspension was independent at all four corners. Daimler-Benz put the 130H in production in 1934. Due to its suspension, handling proved poor, although adequate on German roads at the time, while its ride quality was superior to anything in Germany; the motor had a power of 26 PS and was able to propel the small two-door sedan at a speed of 92 km/h. The synchronised four-speed gearbox is accommodated in front of the rear axle, the balance being provided by coil springs; the front axle was equipped with two transverse leaf springs. The car was sold as an open-top sedan or a convertible, each being fitted with two doors. Due to its extreme unbalance, the car had awkward handling; because of the low sales volume, the model was discontinued in 1936. Nibel followed the 130H with a more powerful 150H, with chassis designed by Daimler's Max Wagner; the Mercedes-Benz 150H was a prototype sports racing automobile built in Germany in the 1930s. It was derived in 1935 from the 130 with only two seats and a more powerful engine, with 1498 cc and a power of 55 PS.
The top speed of the car was 125 km/h. Conceived by Hans Nibel, chief engineer of Mercedes-Benz, the 150H was inspired by Edmund Rumpler's Tropfen-Auto, it followed on the Rumpler-chassis Tropfenwagen racers, which ran between 1923 and 1926, was based on the backbone chassis of earlier 130H. Created in 1934 by Nibel and chassis engineer Max Wagner; the 150H was a two-seat sports roadster. It featured coil-sprung swing axle rear suspension. A water-cooled 1,498 cc OHC four-cylinder engine, producing 55 hp, was mounted in back, hence the "H", from German heck; the radiator was behind that, above the transaxle, with a squirrel-cage blower feeding both radiator and carburetor. The roadster featured disc wheels, DuVal-style windshield, side-mounted spare, three headlights, the third mounted at the lip of the hood above the bumper; the car was only offered as a Sport Roadster. The gas tank, which in the case of the Mercedes-Benz 130 was installed over the engine, was transferred to the front compartment, therefore there was no room for luggage there.
The practicality of the 150 was therefore limited, the price of the car was quite high at 6600 RM. The car was discontinued in 1936 due to poor sales. Six 150Hs were built as coupes, "with low-drag lines that eerily presaged the VW Beetle", they were raced in several rallies, demonstrating much better handling than the 130H, before Nibel and Wagner turned to Grand Prix cars. Only twenty were produced before the 150H was abandoned in 1936; the last remaining 150 Sport Roadster has been restored mechanically by the Mercedes-Benz Classic Center USA in Irvine, California in 2010. In 1936, in parallel to the classical front-engine Mercedes-Benz 170 V, Daimler-Benz AG introduced the Mercedes-Benz 170 H which had the same engine as the 170 V, with an architecture derived from the one of the 130, its predecessor; the 170 H was powered by a four-cylinder 1697 cc engine with a power of 38 PS. The "H" stood for "Heckmo
The layout of a car is defined by the location of the engine and drive wheels. Layouts can be divided into three categories: front-wheel drive, rear-wheel drive and four-wheel drive. Many different combinations of engine location and driven wheels are found in practice, the location of each is dependent on the application for which the car will be used; the front-engine, front-wheel-drive layout places both the internal combustion engine and driven wheels at the front of the vehicle. This is the most common layout for cars since the late 20th century; some early front-wheel drive cars from the 1930s had the engine located in the middle of the car. A rear-engine, front-wheel-drive layout is one in which the engine is between or behind the rear wheels, drives the front wheels via a driveshaft, the complete reverse of a conventional front-engine, rear-wheel-drive vehicle layout; this layout has only been used on concept cars. The front-engine, rear-wheel drive layout is one where the engine is located at the front of the vehicle and driven wheels are located at the rear.
This was the traditional automobile layout for most of the 20th century, remains the most common layout for rear-wheel drive cars. The mid-engine, rear-wheel drive layout is one where the rear wheels are driven by an engine placed just in front of them, behind the passenger compartment. In contrast to the rear-engined RR layout, the center of mass of the engine is in front of the rear axle; this layout is chosen for its low moment of inertia and favorable weight distribution. The rear-engine, rear-wheel drive layout places both the engine and drive wheels at the rear of the vehicle. In contrast to the MR layout, the center of mass of the engine is between the rear axle and the rear bumper. Although common in transit buses and coaches due to the elimination of the drive shaft with low-floor bus, this layout has become rare in passenger cars; the Porsche 911 is notable for its continuous use of the RR layout since 1963. Car drivetrains where power can be sent to all four wheels are referred to as either four-wheel drive or all-wheel drive.
The front-engine, four-wheel drive layout places the engine at the front of the vehicle and drives all four roadwheels. This layout is chosen for better control on many surfaces, is an important part of rally racing as well as off-road driving. Most four-wheel-drive layouts are front-engined and are derivatives of earlier front-engine, rear-wheel-drive designs; the mid-engine, four-wheel drive layout places the engine in the middle of the vehicle, between both axles and drives all four road wheels. Although the term "mid-engine" can mean the engine is placed anywhere in the car such that the centre of gravity of the engine lies between the front and rear axles, it is used for sports cars and racing cars where the engine is behind the passenger compartment; the motive output is sent down a shaft to a differential in the centre of the car, which in the case of an M4 layout, distributes power to both front and rear axles. The rear-engine, four-wheel drive layout places the engine at the rear of the vehicle, drives all four wheels.
This layout is chosen to improve the traction or the handling of existing vehicle designs using the rear-engine, rear-wheel-drive layout. For example, the Porsche 911 added all-wheel drive to the existing line-up of rear-wheel drive models in 1989. Automobile handling Car classification Drivetrain layout
Auto Union AG, was an amalgamation of four German automobile manufacturers, founded in 1932 and established in 1936 in Chemnitz, Saxony. It is the immediate predecessor of Audi; as well as acting as an umbrella firm for its four constituent brands, Auto Union is known for its racing team. The Silver Arrows of the two German teams dominated not only GP car racing from 1934 onwards but set records that would take decades to beat, such as the fastest speed attained on a public road. After being reduced to near ruin in the aftermath of World War II, Auto Union was re-founded in Ingolstadt, Bavaria in 1949 evolving into the modern day Audi company following its takeover by Volkswagen in 1964 and merger with NSU Motorenwerke in 1969; the current corporate entity which bears the Auto Union name – Auto Union GmbH – was founded in 1985 and is a wholly owned subsidiary of Audi AG. The company's distinctive logo, of four interlocking rings to represent the original four members of the Auto Union, survives as the logo of Audi.
Auto Union was formed in Germany in 1932 merging: Zschopauer Motorenwerke J. S. Rasmussen founded by Danish engineer Jørgen Skafte Rasmussen in 1916, it branched out into motorcycles, front-drive two-stroke cars built at Audi works in Zwickau since 1931. Horch – founded 1904 by August Horch in Zwickau, it built cars starting from straight-twin engines to luxury models with V8- and V12 engines. Audi – because of disputes with the CFO, August Horch in 1909 left his namesake enterprise and founded Audi across town, building inline-four-, six- and eight-cylinder-engined cars. In 1928 Audi became a subsidiary of Zschopauer Motorenwerke. Wanderer – founded in 1911, with small four-cylinder cars and a more luxurious straight-6 built in Siegmar In August 1928, the owner of DKW, acquired a majority ownership of Audiwerke AG. In the same year, Rasmussen bought the remains of the US automobile manufacturer Rickenbacker, including the manufacturing equipment for eight- and six-cylinder engines; these engines were used in Audi Audi Imperator and Audi Dresden models.
At the same time, six-cylinder and four-cylinder models were manufactured. In 1930 the Saxony Regional Bank, which had financed Rasmussen's business expansion in the 1920s, installed Richard Bruhn on the board of Audiwerke AG, there followed a brutal pruning and rationalization of the various auto-businesses that Rasmussen had accumulated; the outcome was the founding in Summer 1932 of Auto Union AG with just four component businesses, being Zschopauer Motorenwerke with its brand DKW, Audi and the car producing piece of Wanderer, brought together under the umbrella of single shareholder company Auto Union. Although all four brands continued to sell cars under their own names and brands, the technological development became more centralized, with some Audi models employing engines by Horch or Wanderer. Auto Union chairman, Baron von Oertzen, wanted a showpiece project to announce the new brand. At the 1933 Berlin Motor Show, German Chancellor Adolf Hitler announced two new programs: The people's car: a project that became the KdF car A state-sponsored motor racing programme: to develop a "high speed German automotive industry," the foundation of which would be an annual sum of 500,000 Reichsmark At fellow director's Adolf Rosenberger insistence, von Oertzen met with Dr. Ferdinand Porsche, who had done work for him before, developed his own P-Wagen project racing car based on the new 750 kg formula.
German racing driver Hans Stuck Sr. had met Hitler before he became Chancellor, not being able to gain a seat at Mercedes, accepted the invitation of Rosenberger to join him, von Oertzen, Porsche in approaching the Chancellor. In a meeting in the Reich Chancellory, Hitler agreed with Porsche that for the glory of Germany, it would be better for two companies to develop the project, resulting in Hitler agreeing to pay ₤40,000 for the country's best racing car of 1934, as well as an annual stipend of 250,000 RM each for Mercedes and Auto Union; this annoyed Mercedes, who had developed their Mercedes-Benz W25, gratified, its racing program having financial difficulties since 1931. It resulted in a heated exchange both on and off the racing track between the two companies until World War II. Having garnered state funds, Auto Union bought Porsches Hochleistungsfahrzeugbau GmbH and hence the P-Wagen Project for 75,000 RM, relocating the company to Auto Unions Horch plant at Zwickau; the Auto Union racing cars types A to D were built as Grand Prix racing cars from 1934 to 1939.
They resembled the earlier Benz Tropfenwagen built in part by Rumpler engineers, The only Grand Prix racers to wear Auto Union's four-ringed logo, they were dominant in 1936. From 1935 to 1937, Auto Union cars car won 25 races, driven by Ernst von Delius, Bernd Rosemeyer, Hans Stuck Sr. and Achille Varzi. Much has been written about the difficult handling characteristics of this car, but its tremendous power and acceleration were undeniable – a driver could induce wheelspin at over 100 mph; the cars used supercharged piston engines. Rosemeyer would drive one arou
A sedan — saloon — is a passenger car in a three-box configuration with separate compartments for engine and cargo. Sedan's first recorded use as a name for a car body was in 1912; the name comes from a 17th century development of a litter, the sedan chair, a one-person enclosed box with windows and carried by porters. Variations of the sedan style of body include: close-coupled sedan, club sedan, convertible sedan, fastback sedan, hardtop sedan, notchback sedan and sedanet/sedanette; the current definition of a sedan is a car with a closed body with the engine and cargo in separate compartments. This broad definition does not differentiate sedans from various other car body styles, but in practice the typical characteristics of sedans are: a B-pillar that supports the roof two rows of seats a three-box design with the engine at the front and the cargo area at the rear a less steeply sloping roofline than a coupé, which results in increased headroom for rear passenger and a less sporting appearance.
A rear interior volume of at least 33 cu ft It is sometimes suggested that sedans must have four doors. However, several sources state that a sedan can have four doors. In addition, terms such as sedan and coupé have been more loosely interpreted by car manufacturers since 2010; when a manufacturer produces two-door sedan and four-door sedan versions of the same model, the shape and position of the greenhouse on both versions may be identical, with only the B-pillar positioned further back to accommodate the longer doors on the two-door versions. A sedan chair, a sophisticated litter, was an enclosed box with windows used to transport one seated person. Porters at the front and rear carried the chair with horizontal poles. Litters date back to long before ancient Egypt and China. Sedan chairs were developed in the 1630s. Reputable etymologists suggest the name of the chair probably came through Italian dialects from the Latin sedere meaning to sit; the same experts report that the first recorded use of sedan for an automobile body occurred in 1912 when a new Studebaker model was described by its manufacturers as a sedan.
The same American dictionary provides this description: "Sedan an enclosed automobile for four or more people, having two or four doors". There were enclosed automobile bodies before 1912. Long before that time the same enclosed but horse-drawn carriages were known as broughams in the United Kingdom, they were berlinas in France and Italy. Both names are still used there for sedans. There is an unsubstantiated claim that the body of a particular 1899 Renault Voiturette Type B was the first motor vehicle, a sedan, it was a two-door two-seater vehicle with an extra external seat for a footman/mechanic. Georgano claims the earliest usage matching a modern definition of a sedan was a 1911 Speedwell sedan manufactured in the United States. In American English and Latin American Spanish, the term sedan is used. In British English, a car of this configuration is called a saloon. Hatchback sedans are known as hatchbacks. Super saloon is used to describe a high performance saloon car where sports saloon would have been used in the past.
Saloon has been used by British car manufacturers in the United States, for example, the Rolls-Royce Park Ward. In Australia and New Zealand sedan is now predominantly used, they were simply cars. In the 21st century saloon is still found in the long-established names of particular motor races. In other languages, sedans are known as berlina though they may include hatchbacks; these names, like sedan, all come from forms of passenger transport used before the advent of automobiles. In German sedans are berlines or limousines and limousines are stretch-limousines. In the United States notchback sedan distinguishes models with a horizontal trunklid; the term is only referred to in the marketing when it is necessary to distinguish between two sedan body styles of the same model range. Several sedans have a fastback profile, but instead of a trunk lid, the entire back of the vehicle lifts up. Examples include the Chevrolet Malibu Maxx, Audi A5 Sportback and Tesla Model S; the names "hatchback" and "sedan" are used to differentiate between body styles of the same model.
Therefore the term "hatchback sedan" is not used, to avoid confusion. There have been many sedans with a fastback style. Hardtop sedans were a popular body style in the United States from the 1950s to the 1970s. Hardtops are manufactured without a B-pillar leaving uninterrupted open space or, when closed, glass along the side of the car; the top was intended to look like a convertible's top but it was fixed and made of hard material that did not fold. All manufacturers in the United States from the early 1950s into the 1970s provided at least a 2-door hardtop model in their range and, if their engineers could manage it, a 4-door hardtop as well; the lack of side-bracing demanded a strong and heavy chassis frame to combat unavoidable flexing. The fashion may have delayed the introduction of unibody construction. In 1973 the US government passed Federal Motor Vehicle Safety Standard 216 creating a standard roof strength test to measure the integrity of roof structure in motor vehicles to come into effect some years later.
Edmund Rumpler was an Austrian automobile and aircraft designer. Born in Vienna Austro-Hungarian Empire, he worked in Germany. An automotive engineer by training, he collaborated with Hans Ledwinka on the first Tatra car, the Präsident, in 1897. By age 30, in 1902, he had quit Daimler to become technical director of Adler, he designed the first German engine to have gearbox as a unit at Adler. The next year, he patented; the Wright brothers turned Rumpler's attention to aviation. He quit Adler in 1907, in 1910, copying countryman Igo Etrich's Taube, Rumpler became the first aircraft manufacturer in Germany. Rumpler continued to be interested in automobiles, after the First World War, he applied aircraft streamlining to a car, building the Tropfenwagen in Berlin. A production model proved a sensation at the 1921 Berlin Auto Show. Rumpler's efforts produced a car with an astoundingly low Cw of only 0.28. The Rumpler design inspired the 1923 Benz Auto Union Grand Prix racers. Rumpler's Tropfenwagen was not a commercial success, only 100 Tropfenwagen were built, just two of which survive.
Rumpler returned to aircraft. Because Rumpler was Jewish, he was imprisoned after Adolf Hitler took power in 1933, his career was ruined though he was soon released, he died in 1940, the Nazis destroyed his records. Notable owners of Tatra 77 Lyons, Pete. "10 Best Ahead-of-Their-Time Machines". Car and Driver, 1/88, pp. 73–4. Setright, L. J. K. "Aerodynamics: Finding the Right Shape for the Car Body", in Northey, Tom, ed. World of Automobiles, Vol. 1, p. 38. Wise, David Burgess. "Rumpler: One Aeroplane which Never Flew", in Northey, Tom, ed. World of Automobiles, Vol. 17, p. 1964
In both road and rail vehicles, the wheelbase is the distance between the centers of the front and rear wheels. For road vehicles with more than two axles, the wheelbase is the distance between the steering axle and the centerpoint of the driving axle group. In the case of a tri-axle truck, the wheelbase would be the distance between the steering axle and a point midway between the two rear axles; the wheelbase of a vehicle equals the distance between its rear wheels. At equilibrium, the total torque of the forces acting on a vehicle is zero. Therefore, the wheelbase is related to the force on each pair of tires by the following formula: F f = d r L m g F r = d f L m g where F f is the force on the front tires, F r is the force on the rear tires, L is the wheelbase, d r is the distance from the center of mass to the rear wheels, d f is the distance from the center of gravity to the front wheels, m is the mass of the vehicle, g is the gravity constant. So, for example, when a truck is loaded, its center of gravity shifts rearward and the force on the rear tires increases.
The vehicle will ride lower. The amount the vehicle sinks will depend on counter acting forces, like the size of the tires, tire pressure, the spring rate of the suspension. If the vehicle is accelerating or decelerating, extra torque is placed on the rear or front tire respectively; the equation relating the wheelbase, height above the ground of the CM, the force on each pair of tires becomes: F f = d r L m g − h c m L m a F r = d f L m g + h c m L m a where F f is the force on the front tires, F r is the force on the rear tires, d r is the distance from the CM to the rear wheels, d f is the distance from the CM to the front wheels, L is the wheelbase, m is the mass of the vehicle, g is the acceleration of gravity, h c m is the height of the CM above the ground, a is the acceleration. So, as is common experience, when the vehicle accelerates, the rear sinks and the front rises depending on the suspension; when braking the front noses down and the rear rises.:Because of the effect the wheelbase has on the weight distribution of the vehicle, wheelbase dimensions are crucial to the balance and steering.
For example, a car with a much greater weight load on the rear tends to understeer due to the lack of the load on the front tires and therefore the grip from them. This is why it is crucial, when towing a single-axle caravan, to distribute the caravan's weight so that down-thrust on the tow-hook is about 100 pounds force. A car may oversteer or "spin out" if there is too much force on the front tires and not enough on the rear tires; when turning there is lateral torque placed upon the tires which imparts a turning force that depends upon the length of the tire distances from the CM. Thus, in a car with a short wheelbase, the short lever arm from the CM to the rear wheel will result in a greater lateral force on the rear tire which means greater acceleration and less time for the driver to adjust and prevent a spin out or worse. Wheelbases provide the basis for one of the most common vehicle size class systems; some luxury vehicles are offered with long-wheelbase variants to increase the spaciousness and therefore the luxury of the vehicle.
This practice can be found on full-size cars like the Mercedes-Benz S-Class, but ultra-luxury vehicles such as the Rolls-Royce Phantom and large family cars like the Rover 75 came with'limousine' versions. Prime Minister of the United Kingdom Tony Blair was given a long-wheelbase version of the Rover 75 for official use, and some SUVs like the VW Tiguan and Jeep Wrangler come in LWB models In contrast, coupé varieties of some vehicles such as the Honda Accord are built on shorter wheelbases than the sedans they are derived from. The wheelbase on many commercially available bicycles and motorcycles is so short, relative to the height of their centers of mass, that they are able to perform stoppies and wheelies. In skateboarding the word'wheelbase' is used for the distance between the two inner pairs of mounting holes on the deck; this is different from the distance between the rotational centers