When car designers start to work on a new project, they usually begin with sketches coming from their experience or their imagination. But when Mercedes-Benz engineers begin to think about a model for a bionic car, they went to the museum... to look at fish. In Mercedes and the boxfish, The Scientist describes why they settled on this particular fish, which lives in coral reefs, has great structural strength but low mass. After several years spent on the project, they unveiled the concept car in June 2005 in Washington, D.C. And as said one of member of the Mercedes team, this was "a complete transfer from nature to technology." But read more...
This fascinating lesson in car design has been both initiated and followed by Ronald Fricke, "head of the ichthyology department at the Rosenstein Museum in Stuttgart, with its huge collection of preserved fish." Here are some of his observations reported by The Scientist.
Fricke and his colleagues created a female Ostracion meleagris model, which they gave to DaimlerChrysler. "The female boxfish was chosen," according to Fricke, "because males have a protuberance on their head, not useful for a car, and besides, the females are stouter, which is good for a car shape." As the company began working on a prototype, "it became clear that the boxfish had an excellent aerodynamic shape, and even the car prototype was in the top range."
Fricke notes, "Cars obviously have some [aerodynamic] disadvantages compared to fish. For example, they have to have windshield wipers and wheels. Also, the snout was reduced for aesthetic reasons and on the surface of the car, it wasn't possible to take advantage, for now, of the star-like structure of the scales, which add to aerodynamics and stability. No such surface structures are possible in the car."
You'll find tons of information about this car on the DaimlerChrysler web site. Here is a link to this concept car home page, which contains many details about this bionic car which is 4.24 meters long, 1.82 meters wide and 1.59 meters high, and can seat four people.
And here are two other links to Gone fishin' (PDF format, 6 pages, 585 KB) and to The Mercedes-Benz bionic car as a concept vehicle (PDF format, 16 pages, 187 KB), from which the five images below have been extracted. (Credit for all images: DaimlerChrysler).
Below is a photograph of a boxfish (ostracion cubicus)). "It has its home in the coral reefs, lagoons and seaweed of the tropical seas, where it has a great deal in common with cars in many respects. It needs to conserve its strength and move with the least possible consumption of energy, which requires powerful muscles and a streamlined shape. It must withstand high pressures and protect its body during collisions, which requires a rigid outer skin. And it needs to move in confined spaces in its search for food, which requires good manoeuvrability."
Here is a visualization of an aerodynamic calculation of the boxfish model: Cd value 0.06. "Despite its angular structure, the boxfish has almost as good streamlining qualities as the water drop shape which specialists consider to be the standard for the ideal aerodynamic form. When exposed to an open flow, this streamlined shape has a Cd value of 0.04."
Now, let's move to a wind tunnel model of a boxfish. "Using computer calculations and wind tunnel tests with an accurate model of the boxfish, the Mercedes engineers achieved a value which came very close to this ideal, namely 0.06."
And here is a wind tunnel model of a car with the contours of a boxfish. "To make use of the aerodynamic potential the specialists in Stuttgart first created a 1:4 scale model car whose shape substantially corresponded to the boxfish. The angular outside contours of the living model were adapted in the area of the roof and side skirts, as was the prominent, descending rear end with its heavily scalloped sides and pronounced wedge shape." And they were surprised by the results: the Cd value for the car was 0.095.
Finally, here is a picture of the Mercedes-Benz bionic concept car. "The concept car still retains outstanding aerodynamic characteristics: with a Cd value of 0.19 the fully-functioning and driveable Mercedes-Benz bionic car is among the aerodynamically most efficient in this size category."
With such a low Cd value, it's quite normal that this car doesn't use much gasoline. In fact, this concept car consumes 4.3 liters of fuel per 100 kilometers (or 70 miles per US gallon), making it 20 percent more economical than a comparable standard-production model. Still it has a maximum speed of 190 km/h.
Would you like to drive such a car? Please let me know.
Sources: Bill Sharfman, The Scientist, Volume 20, Issue 9, Page 17, September 2006; and DaimlerChrysler web site
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