Kammback

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Kammback on a 1969 Fiat 850 Coupe '69 Fiat 850 Coupe, example of Kammback.jpg
Kammback on a 1969 Fiat 850 Coupe

A Kammback—also known as "Kamm tail" or "K-tail"—is an automotive styling feature. The rear of the car slopes downwards before abruptly cutting off with a vertical surface. A Kammback minimizes aerodynamic drag while maintaining a practical shape for a vehicle.

Contents

The Kammback is named after German aero-dynamicist Wunibald Kamm for his work developing the design in the 1930s.

An efficient aerodynamic body shape of a vehicle improves its efficiency and fuel consumption. [1]

Some vehicles incorporate the kammback design based on aerodynamic principles, while some use a cut-off tail as a design or marketing feature.

Origins

1950 Nash Airflyte 1950 Nash Airflyte Ambassador Super (9351640857).jpg
1950 Nash Airflyte
1952 Borgward Hansa 2400 2007-09-08 02 Borgward Hansa 2400 (Ausschn, ret).jpg
1952 Borgward Hansa 2400

As the speed of cars increased during the 1920s and 1930s, designers observed and began to apply the principles of automotive aerodynamics. [2] As aerodynamic drag increases, more energy, and thus more fuel, are required to advance a vehicle. [3]

In 1922, Paul Jaray patented a car based on a tear-drop profile (i.e. a rounded nose and long tapering tail) to minimize the aerodynamic drag that is created at higher speeds. [4] [5] The streamliner vehicles of the mid 1930s—such as the Tatra 77, Chrysler Airflow and Lincoln-Zephyr—were designed according to these discoveries.

However, the long tail was not a practical shape for a car, so automotive designers sought other solutions. In 1935, German aircraft designer Georg Hans Madelung showed alternatives to minimize drag without a long tail. [6] In 1936, a similar theory was applied to cars after Baron Reinhard Koenig-Fachsenfeld developed a smooth roofline but with an abrupt end at a vertical surface, effective in achieving low amounts of drag similar to a streamlined body. [5] [7] [8] He worked on an aerodynamic design for a bus, and Koenig-Fachsenfeld patented the idea. [9] Koenig-Fachsenfeld worked with Wunibald Kamm at Stuttgart University, investigating vehicle shapes "provide a good compromise between everyday utility (e.g. vehicle length and interior dimensions) and an attractive drag coefficient". [5] [7] In addition to aerodynamic efficiency, Wunibald Kamm emphasized vehicle stability in his design. [7] He proved mathematically and empirically the effectiveness of the design. [10]

In 1938, Kamm produced a prototype using a Kammback, based on a BMW 328. [11] The Kammback, along with other aerodynamic modifications, gave the prototype a drag coefficient of 0.25. [12]

The earliest mass-produced cars using Kammback principles were the 1949–1951 Nash Airflyte in the United States and the 1952–1955 Borgward Hansa 2400 in Europe. [7]

Aerodynamic theory

The ideal shape to minimize drag is a "teardrop," a smooth airfoil-like shape, but it is not practical for road vehicles because of size constraints. [1] However, researchers including Kamm found that abruptly cutting off the tail resulted in a minimal increase in drag. [5] The reason for this is that a turbulent wake region forms behind the vertical surface at the rear of the car. This wake region mimics the effect of the tapered tail in that air in the free stream does not enter this region (avoiding boundary layer separation), therefore smooth airflow is maintained, minimizing drag. [11]

Kamm's design is based on the tail being truncated at the point where the cross section area is 50% of the car's maximum cross-section, [5] [13] which Kamm found represented a good compromise, as by that point the turbulence typical of flat-back vehicles had been mostly eliminated at typical speeds.

The Kamm tail presented a partial solution to the problem of aerodynamic lift, which was becoming severe as sports car racing speeds increased during the 1950s. The design paradigm of sloping the tail to reduce drag was carried to an extreme on cars such as the Cunningham C-5R, [14] resulting in an airfoil effect lifting the rear of the car at speed and so running the risk of instability or loss of control. The Kamm tail decreased the area of the lifting surface while creating a low-pressure zone underneath the tail.

Some studies showed the addition of a rear spoiler to a kammback design was not beneficial because the overall drag increased with the angles that were studied. [1]

Usage

1964-1969 Ford GT40 Ford GT40 (rear).jpg
1964-1969 Ford GT40
1974-1985 Citroen CX Citroen CX rear.jpg
1974-1985 Citroën CX
2000-2006 Honda Insight Honda-Insight-Rear.jpg
2000-2006 Honda Insight
2009-2015 Toyota Prius 2009 Toyota Prius (ZVW30R) liftback (2011-12-06) 02.jpg
2009-2015 Toyota Prius
2011 Audi A7 2011 Audi A7 (4G) 3.0 TFSI quattro hatchback (2016-01-07) 02.jpg
2011 Audi A7

In 1959, the Kamm tail came into use on full-body racing cars as an anti-lift measure, and within a few years would be used on virtually all such vehicles. The design had a resurgence in the early 2000s as a method to reduce fuel consumption in hybrid electric vehicles.

Several cars have been marketed as Kammbacks, despite the profile not adhering to aerodynamic philosophy of a Kammback. These models include the 1971–1977 Chevrolet Vega Kammback wagon, [15] the 1981–1982 AMC Eagle Kammback, [16] [17] [18] [19] the AMC AMX-GT and the Pontiac Firebird–based "Type K" concept cars. [20] [21] [22] [23] [24]

Some models that are marketed as "coupes"—such as BMW and Mercedes SUVs—"use a sort-of Kammback shape, though their tail ends have a few more lumps and bumps than a proper Kammback ought to have." [25]

Cars that have had a Kammback include:

Related Research Articles

Automotive aerodynamics

Automotive aerodynamics is the study of the aerodynamics of road vehicles. Its main goals are reducing drag and wind noise, minimizing noise emission, and preventing undesired lift forces and other causes of aerodynamic instability at high speeds. Air is also considered a fluid in this case. For some classes of racing vehicles, it may also be important to produce downforce to improve traction and thus cornering abilities.

Coupe Closed two-door car body style with a permanently attached fixed roof which is shorter than a sedan

A coupe or coupé is a passenger car with a sloping or truncated rear roofline and two doors.

Grand tourer High-performance luxury car

A grand tourer (GT) is a type of sports car that is designed for high speed and long-distance driving, due to a combination of performance and luxury attributes. The most common format is a front-engine, rear-wheel-drive two-door coupé with either a two-seat or a 2+2 arrangement. Grand tourers are most often the coupé derivative of luxury saloons.

Zagato

Zagato is an independent coachbuilding company and total design centre located northwest of Milan in Terrazzano, a small village near Rho, Lombardy, Italy. The company's premises occupy an area of 23,000 square metres, 11,000 of which are covered.

Fastback Type of styling to rear car bodywork

A fastback is an automotive styling feature, defined by the rear of the car having a single slope from the roof to the tail. The kammback is a type of fastback style.

Grille (car)

In automotive engineering, a grille covers an opening in the body of a vehicle to allow air to enter or exit. Most vehicles feature a grille at the front of the vehicle to protect the radiator and engine. Merriam-Webster describes grilles as "a grating forming a barrier or screen; especially: an ornamental one at the front end of an automobile." Other common grille locations include below the front bumper, in front of the wheels, in the cowl for cabin ventilation, or on the rear deck lid. Grilles evolved from previously installed gravel shields that were designed to protect exposed radiators typically used on cars until the early 1930s.

<i>Automobile</i> (magazine) American automotive magazine

Automobile was an American automobile magazine published by the Motor Trend Group. A group of former employees of Car and Driver led by David E. Davis founded Automobile in 1986 with support from Rupert Murdoch's News Corporation—using the credo No Boring Cars.Automobile distinguished itself as more of a lifestyle magazine than the other automotive publications, an editorial theme that Davis greatly expanded upon from his tenure as the editor of Car and Driver, though it was a sister publication to Motor Trend.

Geneva Motor Show Annual Swiss auto show

The Geneva International Motor Show is an annual auto show held in March in the Swiss city of Geneva. The show is hosted at the Palexpo, a convention centre located next to the Geneva Cointrin International Airport. The Salon is organised by the Organisation Internationale des Constructeurs d'Automobiles, and is considered an important major international auto show.

Giotto Bizzarrini

Giotto Bizzarrini is an Italian automobile engineer who was active from the 1950s through the 1970s.

Pininfarina Italian car design firm and coachbuilder.

Pininfarina S.p.A. is an Italian car design firm and coachbuilder, with headquarters in Cambiano, Turin, Italy. It was founded by Battista "Pinin" Farina in 1930. On 14 December 2015, Mahindra Group acquired Pininfarina S.p.A. for about €168 million.

Wunibald Kamm was an automobile designer, engineer, and aerodynamicist. He is best known for his breakthrough in reducing car turbulence at high speeds; the style of car bodywork based on his research has come to be known as a Kammback or a Kamm-tail.

Alfa Romeo Giulietta (750/101) Motor vehicle

The Alfa Romeo Giulietta was a family of automobiles made by Italian car manufacturer Alfa Romeo from 1954 to 1965 which included a 2+2 coupé, four-door saloon, estate, spider, Sprint, and Sprint Speciale. The 2+2 was Alfa Romeo's first successful foray into the 1.3-litre class. From 1954 to 1965 a total of 177,690 Giuliettas were made, the great majority in saloon (Berlina), Sprint coupé, or Spider body styles, but also as Sprint Speciale and Sprint Zagato coupés, and the rare Promiscua estate.

Alfa Romeo Giulia TZ Italian sports car

The Alfa Romeo Giulia TZ was a sports car and racing car manufactured by Alfa Romeo from 1963 to 1967. It replaced the Giulietta SZ. In 2011, the name was reduced from Giulia TZ to TZ in the new TZ3 model.

Automobile drag coefficient The resistance of a car to moving through air

The drag coefficient is a common measure in automotive design as it pertains to aerodynamics. Drag is a force that acts parallel to and in the same direction as the airflow. The drag coefficient of an automobile measures the way the automobile passes through the surrounding air. When automobile companies design a new vehicle they take into consideration the automobile drag coefficient in addition to the other performance characteristics. Aerodynamic drag increases with the square of speed; therefore it becomes critically important at higher speeds. Reducing the drag coefficient in an automobile improves the performance of the vehicle as it pertains to speed and fuel efficiency. There are many different ways to reduce the drag of a vehicle. A common way to measure the drag of the vehicle is through the drag area.

The Turin Motor Show was an auto show held annually in Turin, Italy. The first official show took place between 21 and 24 April 1900, at the Castle of Valentino, becoming a permanent fixture in Turin from 1938 having shared it with Milan and Rome until that time. From 1972, the show was held biannually and in 1984, it moved into Fiat's shuttered Lingotto factory.

Alfa Romeo Spider Motor vehicle

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References

  1. 1 2 3 Santos, Rodrigo de Oliveira; Lyra, Paulo Roberto Maciel; Souza, Márcio Rodrigo de Araújo; Souza Júnior, Marcelo Alexandre de (2012). "Aerodynamic Design of Super Efficient Vehicle". SAE International. 36–0352. Retrieved 16 January 2021.
  2. Hucho, Wolf-Heinrich (1987). Aerodynamics of Road Vehicles: from fluid mechanics to vehicle engineering. Butterworths. pp. 19–20. ISBN   978-0-408-01422-9.
  3. "The Effect of Aerodynamic Drag on Fuel Economy". Auto Research Center. Retrieved 16 January 2021.
  4. "Paul Jaray 1889-1974". Coachbuilt.com. Retrieved 9 June 2014.
  5. 1 2 3 4 5 Ziemnowicz, Christopher (2004). "The Origin of the Kammback Design". Archived from the original on 15 April 2012. Retrieved 9 June 2014.
  6. Gowans, Alan (1981). Learning To See: Historical perspective on modern popular/commercial arts. Popular Press 1. p. 360. ISBN   978-0-87972-182-4.
  7. 1 2 3 4 Eckermann, Erik; Albrecht, Peter L. (2001). World History of the Automobile. SAE International. pp. 115–117. ISBN   978-0-7680-0800-5 . Retrieved 9 June 2014.
  8. Ludvigsen, Karl (Fall 1967). "Automobile Aerodynamics: Form and Fashion". Automobile Quarterly. 6 (2).
  9. Montgomery, Bob (8 August 2007). "Designing a spin for the tail end of things" (fee required). The Irish Times . Retrieved 8 December 2011.
  10. Bush, Donald J. (1975). The streamlined decade . George Braziller. p.  109. ISBN   978-0-8076-0793-0.
  11. Ihrig, Ron (3 December 2004). "Part 3: Production, Physics, Politics - Only the Strong Survive - German Design History". Car Design News . Archived from the original on 22 July 2012. Retrieved 9 June 2014.
  12. "Kamm Back". Auto Repair About. Retrieved 9 June 2014.
  13. "Cunningham C5-R, 1953". auta5p.eu. Retrieved 16 January 2021.
  14. Stevenson, eon (2008). American automobile advertising, 1930-1980: an illustrated history. McFarland. p. 221. ISBN   9780786452316 . Retrieved 9 June 2014.
  15. "History of the 1981 AMC Eagle". AMC Eagle Den. Retrieved 9 June 2014.
  16. Ernst, Kurt (10 March 2014). "Lost Cars of the 1980s – 1981-1982 AMC Eagle Series 50 Kammback" . Retrieved 9 June 2014.
  17. Witzenburg, Gary; Miller, Moss (September 1980). "Driving the new AMC Eagles". Popular Mechanics. 154 (4): 100.
  18. Stevenson, eon (2008). American automobile advertising, 1930-1980: an illustrated history. McFarland. p. 221. ISBN   9780786452316 . Retrieved 5 January 2014.
  19. "Kamm Tail AMX". Car and Driver . 14: 99. 1968. Retrieved 9 June 2014.
  20. Mitchell, Larry G. (2000). AMC Muscle Cars. Motorbooks. p. 23. ISBN   9780760307618 . Retrieved 9 June 2014. ...with a chopped-off rear end that was known as a Kamm-back.
  21. Editors of Consumer Guide (15 November 2007). "Chevrolet Camaro and Pontiac Firebird Concept Cars". auto.howstuffworks.com. Retrieved 9 June 2014.CS1 maint: extra text: authors list (link)
  22. Wilson, Bill (26 March 2014). "The Pontiac Kammback: Innovation vs. Convention". Boldride. Retrieved 9 June 2014.
  23. Stone, Matt (August 2009). "Pontiac Trans Am Greats: We Shall Never Pass This Way Again". Motor Trend . Retrieved 9 June 2014.
  24. Gold, Aaron (8 July 2020). "What Is a Kammback Car?". Automobile Magazine. Retrieved 16 January 2021.
  25. "BMW Press Release dated 27 March 2007. "BMW at Techno Classica". Archived from the original on 27 May 2007. Retrieved 9 June 2014. Kamm was a key figure in the design of the body for this . . .car, which was built specially for the Mille Miglia 1940."
  26. "Victory in Italy". bmw-motorsport. 9 June 2014. Archived from the original on 20 March 2007. Giovanni Lurani and Franco Cortes have to retire on lap seven with their BMW 328 'Mille Miglia' Kamm coupe.
  27. Editors of Consumer Guide (17 May 2007). "Iso Grifo". auto.howstuffworks.com. Retrieved 9 June 2014.CS1 maint: extra text: authors list (link)
  28. "Ford Mk IV". Ultimate Car Page. 9 June 2014. ...cut-off 'Kamm' tail
  29. Krebs, Michelle (7 March 2011). "Saab Tells the World: 'We're Still Here'". Edmunds . Retrieved 25 February 2016. ...Kamm-back tail, both reminiscent of the original Saab Sonett.
  30. Nye, Doug (2004). Dino, The Little Ferrari. Motorbooks. p. 110. ISBN   0-7603-2010-1. ...a cut-off Kamm-theory tail...
  31. 1 2 Robinson, Peter; LOCI Ltd (2002). "The Pininfarina 1800". LOCI Ltd. Retrieved 9 June 2014.
  32. Leffingwell, Randy (2002). Mustang: The Original Muscle Car. MBI Publishing. p. 126. ISBN   978-0-7603-1349-7 . Retrieved 9 June 2014.
  33. Larminie, James; Lowry, John (2004). Electric Vehicle Technology Explained. Wiley. pp. 8–32. ISBN   9780470090695 . Retrieved 27 February 2016. At the back of the Insight the teardrop shape is abruptly cut off in what is called the Kamm effect.
  34. Zenlea, David (8 February 2012). "First Drive: 2012 Toyota Prius C". Automobile. Retrieved 27 February 2016. ...featuring the same Kammback profile as the Prius and Prius V hatchbacks...
  35. Peters, Eric (22 May 2014). "2014 Honda Insight Review". National Motorists Association. Retrieved 27 February 2016. ...a Kammback layout, meaning the roof slopes gradually backward where it meets up with a fairly tall/vertical tail section.
  36. Halvorson, Bengt (20 February 2017). "2017 Hyundai Ioniq Hybrid". Car and Driver. Retrieved 19 June 2019. Despite the Ioniq’s wind-cheating Kamm-back profile, the styling is far more conservative than that of the polarizing Prius.
  37. Express, Auto (19 April 2021). "Ford Mustang Mach-E review - Practicality, comfort and boot space" . Retrieved 3 June 2021. ...Mach-E’s sloping coupe-style roof line...
  38. Turkus, Brandon (15 December 2020). "2021 Ford Mustang Mach-E First Drive Review: A Faster Horse" . Retrieved 3 June 2021. ...he black roof hides some of the mass from the front and sides, but viewed from behind, design sorcery can't obscure the height of the rear glass, the Kammback tail, or the rear fenders' girth...