Wunibald Kamm
Encyclopedia
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.
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
.
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
was called the "Kamm-Institut" after its founder and long-time director.
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.
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, supercar
s, highly efficient hybrid powered cars, as well as outright racecars.
Automotive design
Automotive design is the profession involved in the development of the appearance, and to some extent the ergonomics, of motor vehicles or more specifically road vehicles. This most commonly refers to automobiles but also refers to motorcycles, trucks, buses, coaches, and vans...
, engineer
Engineer
An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems. Engineers design materials, structures, machines and systems while considering the limitations imposed by practicality,...
, and aerodynamicist
Aerodynamics
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...
. 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
Kammback
A Kammback is a car body style that derives from the research of the German aerodynamicist Wunibald Kamm in the 1930s. The design calls for a body with smooth contours that continues to a tail that is abruptly cut off. This shape reduces the drag of the vehicle."Kammback" is an American term...
or a Kamm-tail.
Design
One goal of automotive aerodynamicsAutomotive aerodynamics
Automotive aerodynamics is the study of the aerodynamics of road vehicles. The main concerns of automotive aerodynamics are reducing drag , reducing wind noise, minimizing noise emission, and preventing undesired lift forces and other causes of aerodynamic instability at high speeds...
is to reduce the air turbulence
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...
, or drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
, 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
Bernoulli's principle
In fluid dynamics, Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy...
). A design with less drag means higher efficiency and an increased maximum velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
, given the same powertrain
Powertrain
In a motor vehicle, the term powertrain or powerplant refers to the group of components that generate power and deliver it to the road surface, water, or air. This includes the engine, transmission, drive shafts, differentials, and the final drive...
.
Career
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 prototypePrototype
A prototype is an early sample or model built to test a concept or process or to act as a thing to be replicated or learned from.The word prototype derives from the Greek πρωτότυπον , "primitive form", neutral of πρωτότυπος , "original, primitive", from πρῶτος , "first" and τύπος ,...
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
Stuttgart
Stuttgart is the capital of the state of Baden-Württemberg in southern Germany. The sixth-largest city in Germany, Stuttgart has a population of 600,038 while the metropolitan area has a population of 5.3 million ....
was called the "Kamm-Institut" after its founder and long-time director.
The first "Kamm coupe"
In late summer of 1938, BMWBMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...
tested a prototype of the so-called "Kamm-Coupe" based on their 328 chassis
BMW 328
The BMW 328 is a sports car made by BMW between 1936 and 1940, with the body design credited to Peter Szymanowski, who became BMW chief of design after World War II ....
. It had a drag coefficient
Drag coefficient
In fluid dynamics, the drag coefficient is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment such as air or water. It is used in the drag equation, where a lower drag coefficient indicates the object will have less aerodynamic or...
of only 0.25 compared to the great 1940 Mille Miglia
Mille Miglia
The Mille Miglia was an open-road endurance race which took place in Italy twenty-four times from 1927 to 1957 ....
winning BMW 328
BMW 328
The BMW 328 is a sports car made by BMW between 1936 and 1940, with the body design credited to Peter Szymanowski, who became BMW chief of design after World War II ....
Touring Coupe with drag coefficient 0.35. This automaker's naming of its coupé
Coupé
A coupé or coupe is a closed car body style , the precise definition of which varies from manufacturer to manufacturer, and over time...
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 GremlinAMC GremlinThe AMC Gremlin is a two-door subcompact car produced in the United States and Canada by the American Motors Corporation between 1970 and 1978. AMC reduced its development and manufacturing costs by adapting a shortened Hornet platform with a Kammback-type tail...
and AMC EagleAMC EagleThe AMC Eagle is a compact-sized four-wheel drive passenger vehicle that was produced by American Motors Corporation . The AMC Eagle line of vehicles inaugurated a new product category of "sport-utility" or crossover SUV....
-- The design was not to improve streamlining, but to improve space efficiency. - Chevrolet VegaChevrolet VegaThe Chevrolet Vega is a subcompact, two-door automobile that was produced by the Chevrolet division of General Motors for the 1971-1977 model years. Named after the star Vega, the car was powered by a lightweight aluminum-block inline four-cylinder engine...
-- The station wagonStation wagonA station wagon is a body style variant of a sedan/saloon with its roof extended rearward over a shared passenger/cargo volume with access at the back via a third or fifth door , instead of a trunk lid...
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
Production vehicle
A production vehicle is one that is put into mass production, as a model produced in large numbers and offered for sale to the public. It is the vehicle you can actually go out and buy ....
. 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, supercar
Supercar
Supercar is a term used most often to describe an expensive high end car. It has been defined specifically as "a very expensive, fast or powerful car"...
s, highly efficient hybrid powered cars, as well as outright racecars.
External links
- Article on the origins of Kammback design
- BMW Designers Wunibald Kamm on the website with overview of automotive designers working for BMW.