Wunibald Kamm (April 26, 1893 in Basel – October 11, 1966 in Stuttgart) 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.
One goal of automotive aerodynamics is to reduce the air turbulence, or drag, caused by the shape of the automobile. Aerodynamic drag may be reduced either by reduction of frontal area or by reduction of drag coefficient. In bodies such as automobiles and airships, drag decreases after the rear of a car's cross-sectional area is reduced to fifty percent of the car's maximum cross section; "the best position is nearer 45 per cent of the length, and ... to have this maximum cross- section nearer the rear end than the front, and its drag has proved even less". There are other aspects of the car's design such as keeping the flow of air attached to the body far to the back of the car as possible to minimize pressure drag (the Bernoulli relationship). A design with less drag means higher efficiency and an increased maximum velocity, given the same powertrain.
German Professor, Wunibald Kamm worked with aerodynamics engineer Baron Reinhard von Koenig-Fachsenfeld. They developed a design with a smooth roofline and a taper in the automobile's body that is suddenly chopped off at the rear end. This design makes the air flow act as if a full tapered "tail" was present on the vehicle. A full size prototype was developed in 1938. It was a four-door sedan featuring a sharply truncated rear end. The test car represented a compromise between a low air resistance and practicality in the automobile's size and shape.
Established in 1930, the Research Institute of Automotive Engineering and Vehicle Engines located near Stuttgart (German: Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart - FKFS) was called the "Kamm-Institut" after its founder and long-time director.
The first "Kamm coupe"
In late summer of 1938, BMW tested a prototype of the so-called "Kamm-Coupe" based on their 328 chassis. It had a drag coefficient of only 0.25 compared to the great 1940 Mille Miglia winning BMW 328 Touring Coupe with drag coefficient 0.35. This automaker's naming of its coupé model appears to be the earliest use of "Kamm" to publicly describe an automobile body incorporating the Koenig-Fachsenfeld's design patent.
Kammback named production cars (USA)
- AMC Gremlin and AMC Eagle -- The design was not to improve streamlining, but to improve space efficiency.
- Chevrolet Vega -- The station wagon model had more taper than the Gremlin, but not enough to gain aero-effects.
The Kammback "cut off tail" design continues to be popular. Most often, however, it only insinuates streamlining when used in production cars. It is then only a design trick to make the vehicle look "fast".
Dr. Kamm's wind cheating principle is used in a variety of popular mass-market vehicles, supercars, highly efficient hybrid powered cars, as well as outright racecars.
- Institution of Mechanical Engineers (1970). Journal of Automotive Engineering, Volume 1. Institution of Mechanical Engineers (Great Britain). Automobile Division. p. 18.
- SAE transactions, Volume 27. Society of Automotive Engineers. 1932. p. 118.
- Barnard, R. H. (2001). Road vehicle aerodynamic design: an introduction. MechAero. p. 43. ISBN 978-0-9540734-0-4.
- Hirschel, Horst Prem, Gero Madelung, Ernst-Heinrich (2003). Aeronautical research in Germany: from Lilienthal until today, Volume 147. Springer-Verlag. p. 221. ISBN 978-3-540-40645-7. Retrieved 2 September 2010.
- "History (1930-1945)". Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart. Retrieved 3 September 2010.
- Ihrig, Ron "Part 3: Production, Physics, Politics - Only the Strong Survive" German Design History in Car Design News, Dec 3, 2004, retrieved on September 6, 2007.
- Article on the origins of Kammback design
- BMW Designers Wunibald Kamm on the website with overview of automotive designers working for BMW.