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A Kammback is a car body style that derives from the research of the German aerodynamicist Wunibald Kamm in the 1930s, this research itself deriving from that of another pioneer German aerodynamicist, Baron Reinhard Koenig-Fachsenfeld. "Kammback" is an American coinage. In Europe the design is generally known as a Kamm tail or K-tail.

Contents

[edit] History

Truncated concept car that AMC called a Kammback: AMC AMX-GT

Freiherr Reinhard Koenig-Fachsenfeld "developed a body style whose tail was cut off to form a flat rear surface"[1] while working on an aerodynamic design for a bus, and he patented the idea.[2]

The innovative tail treatment also minimized turbulence created by Paul Jaray's[3] aerodynamic designs on certain 1935 passenger cars. In 1936, "further research by the FKFS--Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart (Stuttgart Research Institute for Automotive and Automobile Engine Technology), under the direction of Wunibald Kamm, proved that vehicles with the so-called K- or Kamm tail, following Koenig-Faschsenfeld’s lead, offered a good compromise between everyday utility (e.g. vehicle length and interior dimensions) and an attractive drag coefficient."[1]

The earliest use of "Kamm" to describe an automobile body incorporating this design was the prototype 1940 'Kamm' Coupe based on a BMW 328 chassis. [4]

[edit] Aerodynamics

While the realities of fluid dynamics dictate that a teardrop shape is the ideal aerodynamic form, Kamm found that by cutting off / flattening the streamlined end of the tear at an intermediate point, and bringing that edge down towards the ground, he could gain most of the benefit of the teardrop shape without incurring such a large material, structural, and size problem. The airflow, once given the suggestion of the beginning of a turbulence-eliminating streamlined teardrop tail, tended to flow in an approximation of that manner regardless of the fact that the entire tail wasn't there. This is called the Kamm effect.

There is controversy about the proportions of a true Kamm tail. According to the classic definition the tail should be cut off where it has tapered to approximately 50% of the car’s maximum cross section, which Kamm found represented a good compromise - by that point the turbulence typical of flat-back vehicles had been mostly eliminated at typical speeds. Thus a minivan is not a Kammback, and neither are numerous cars that have truncated tails.

Automakers’ use of the term “Kammback” has diminished as Kamm's principles have become more generally assimilated into modern car design.

[edit] Kammback examples

[edit] High-performance cars

Kamm-tailed competition car: Ford GT40

The Kamm tail was used on many high-performance and competition cars, such as:

[edit] Mass-production cars

1972 Chevrolet Vega Kammback
Kamm-tailed 4-door: Citroën CX
Kamm-tailed Supermini: Audi A2

Kamm (and Kamm-like) tails can be seen on numerous mass-production cars, such as:

AMC and GM have publicized certain models with truncated tails as “Kammbacks” even though it is obvious to the eye that they do not meet the classic "50% cross-section" definition, i.e. the AMC AMX-GT and Pontiac Firebird-based "Type K" concept cars, [10] a Chevrolet Vega wagon, [11] and a version of the AMC Eagle. [12]

[edit] Hybrid mass-production cars

Kamm-tailed, first production hybrid: Honda Insight
Kamm-tailed modern hybrid:Toyota Prius

As the Kamm tail’s low drag helps improve fuel consumption, it features on hybrid cars designed for maximum economy, for example:

[edit] References

  1. ^ a b Eckermann, Erik, and Albrecht, Peter L. World History of the Automobile p. 117. SAE International, August 2001. ISBN 0-768-00800-X.
  2. ^ Montgomery, Bob. "Designing a spin for the tail end of things", The Irish Times, August 8, 2007. Retrieved on June 18, 2008.
  3. ^ "Paul Jaray", Coachbuilt.com. Retrieved on June 18, 2008.
  4. ^ Ihrig, Ron "Part 3: Production, Physics, Politics - Only the Strong Survive" German Design History in Car Design News, December 3, 2004, retrieved on 2008-05-25.
  5. ^ BMW Press Release dated 27 March 2007. "BMW AT TECHNO CLASSICA: HIGHLIGHTS FROM 90 YEARS OF HISTORY", “BMW Motorsport”: "Kamm was a key figure in the design of the body for this . . .car, which was built specially for the Mille Miglia 1940." Retrieved on July 10 2008.
  6. ^ Official BMW Motorsport Website "Victory in Italy": "(In the) 1940 Mille Miglia . . .Lurani and . . . Cortes retire(d) . . . their BMW 328 'Mille Miglia' Kamm coupe." Retrieved on 25 May 2008.
  7. ^ Consumer Guide, Editors of: '. . . tail chopped Kamm-style.' How Stuff Works, "Iso Grifo" Retrieved on 25 May 2008.
  8. ^ ". . .cut-off 'Kamm' tail", Ultimate Car Page, "Ford Mk IV". Retrieved on 25 May 2008.
  9. ^ Nye, Doug: ". . . a cut-off Kamm-theory tail . . ." Dino, The Little Ferrari, p. 110. Motorbooks 2004. ISBN 0760320101.
  10. ^ "Pontiac Type K Concept Cars" by the Auto Editors of Consumer Guide, undated, retrieved on 2008-05-25.
  11. ^ “Chevy’s New Car is Open for Business” Chevrolet Division of General Motors, 1970. Hosted by the Old Car Manual Project, retrieved on 2008-05-25.
  12. ^ History of the 1981 AMC Eagle, retrieved on 2008-05-25.

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