The tail of Kamm (also kambbek , from the English Kammback , in honor of the Swiss Wunibald Kamm , also the English K-tail, Kamm tail ) is the name of the car body shape with a rear part, the roof of which is at first smoothly sloping, but then ends with an almost vertical trim.
Content
Benefits
The tail of Kamm is one of the solutions to the practical problem of creating a streamlined car body: a well streamlined body is too long, and attempts to shorten it with a steeper back bevel lead to the separation of the boundary layer and a sharp increase in resistance [1] . Kamm suggested making the rear bevel smooth to tighten the gap and thereby reduce the size of the turbulent flow behind the body. The experiments showed that the resistance is approximately proportional to the cross section of the turbulence zone and does not depend on the shape of the body after the point of separation of the flow, which allows you to sharply cut the body in this place and thus use a relatively large part of the length of the car to accommodate a high passenger compartment.
Cumback is far from the aerodynamic ideal. For example, a drop-shaped body, gradually thinning in the back, may not have a turbulence zone behind it at all and therefore have very little resistance; according to urban legend [2] , hulls constructed according to the kambek scheme are more streamlined, being deployed “back to front”. The tail of Kamm is a practical compromise between the drag coefficient , length restrictions and the need to place passengers and baggage inside the body.
History
Research Institute of Vehicles and Automotive Engines in Stuttgart ( German. FKFS ) under the leadership of Kamm in 1938 built a prototype “ K-1 »With a low coefficient of drag (0.23). However, Kamm's ideas went into the series, and even then not for long, only starting with the English. Nash Airflyte (USA, 1949-1951) and Borgward Hanza 2400 S (Germany, 1952-1959).
Due to its good aerodynamic properties, the form was used in sports cars, but for a long time it was used only occasionally for mass cars (for example, in the Chevrolet Vega , AMC Hornet , Citroen CX ).
Due to its use in Vega and Hornet, the name “cumback” is often used as a synonym for wagon or hatchback , although it formally defines specific aerodynamics in the rear, which has become the de facto standard for modern small cars (including Toyota Prius coefficient of resistance 0.25 [3] ).
Notes
- ↑ Tony Foale. Motorcycle Handling and Chassis Design: The Art and Science . Tony Foale, 2006. (English)
- ↑ Popular Mechanics and the MythBusters Unveil A Backwards Porsche . Popular Mechanics .
- ↑ Toyota Prius: Eco-mobility's poster car . // Autotech review, vol. 1, No. 3. March 2012.P. 55.
Literature
- Erik Eckermann. World History of the Automobile . SAE, 2001.S. 117.