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Wednesday, June 17, 2020

An extraordinary aerodynamic performance of the Schlörwagen

In the automotive world, there are a lot of coefficient numbers that are needed when the manufacturer or whoever is engineering a vehicle. One of them is the drag coefficient, which is a measure of how efficiently a vehicle moves through the air. When viewed from this drag coefficient number, it turns out that the cars that exist today can not beat the drag coefficient numbers of a 1938 experimental vehicle named Schlörwagen, or known as the nickname "Göttinger Egg" or "Pillbug". 
The Schlörwagen was nearly 7 feet wide, mostly due to its body panels that covered the front wheels. (Picture from: https://bit.ly/30LTW56)
This is a hybrid vehicle designed by Karl Schlör. This car was made as an experimental vehicle, which was designed very aerodynamically with a unique shape that rounded in front and then tapers to the back. Seem like, it is intentionally done so that the car gets a minimum coefficient of drag.

This car's story started, when Karl Schlör, a German engineer who worked for Munich-based Krauss Maffei, proposed a very low drag coefficient body in early 1936. Under his supervision at the Aerodynamic Research Institute (Aerodynamischen Versuchsanstalt, or AVA) in German-occupied Riga, a model was later built. The model has then carried out a test in a wind tunnel and produced a very low drag coefficient of 0.113.
The car was designed by German engineer Karl Schlör, who worked at the Aerodynamic Research Institute (Aerodynamischen Versuchsanstalt, or AVA) in German-occupied Riga. (Picture from: https://bit.ly/30LTW56)
The next car model was made in full scale built on the Mercedes-Benz 170H chassis using a rear-mounted 38-horsepower engine. The car's body is made of aluminum which was built by Ludewig Brothers of Essen. Subsequent tests of this full-scale car model showed a slightly higher drag coefficient but still in an impressive number of 0.186.
1942, engineers took a 130-horsepower Russian aircraft motor and bolted it to the back of the car for some test runs. (Picture from: https://bit.ly/30LTW56)
The teardrop-shaped car had flush-fitting windows with curved windows and a closed-floor. Furthermore, the car has a length of about 4.33 meters, 1.48 meters high, 2.10 meters wide, and a wheelbase of 2.60 meters. Although the body was built using aluminum, it was about 250 kg heavier than that of the Mercedes 170H. It was also mentioned due to the aerodynamic shape and its rear-mounted engine far back center of gravity affected the driving safety of the Schlörwagens and made them very vulnerable to crosswinds.
The Schlörwagen, like other aerodynamically-designed cars of the era, took the shape of an airplane wing or teardrop. (Picture from: https://bit.ly/30LTW56)
In a test drive with a production vehicle Mercedes 170H as a comparison, the Schlörwagen was able to run up to a top speed of 135 kph or 20 kph faster than the Mercedes; while the fuel consumption is 8 liters per 100 kilometers or 20 and 40 percent less than the reference vehicles. According to Karl Schlör, the vehicle could reach speeds of 146 kph.
The DLR made a 1:5 scaled model using the original plans and ran it through a wind tunnel to celebrate its 75th anniversary. (Picture from: https://bit.ly/30LTW56)
The experimental car was first introduced to the public at the 1939 Berlin Auto Show and was never mass-produced. Although this experimental car is capable of carrying 7 people in the cabin that is less comfortable, maybe this is one of the reasons why the car was never mass-produced despite being hampered the onset of World War 2.
The Schlörwagen could fit up to seven passengers in its less-comfortable cabin. (Picture from: https://bit.ly/30LTW56)
During the war, the experimental activities of the car were unpublished and almost forgotten. And in 1942, engineers conducted an experiment by attaching a Soviet-captured aircraft engine to the car body. If initially, they expect a result that can provide a breakthrough performance from this awkward and strange creation. However, after several rounds of test tracks in Göttingen. But a 130 horsepower additional power from aircraft engines did not work.
The Schlörwagen was first introduced to the public at the 1939 Berlin Auto Show. (Picture from: https://bit.ly/30LTW56)
After that, the only example of Schlörwagen was kept in a run-down building near Göttingen, in the condition that the chair and wheels were removed. Once, the British Military Administration eventually towed it away somewhere, and it hasn't been seen since. One theory says the car was sent to England, but there is also a mention of the possibility because the body was badly damaged and then scrapped.
And in 2014, the German Aerospace Center (DLR) conducted a retest in a wind tunnel of a model on a scale of 1: 5 based on original images of the Schlörwagen, to see how it performed. The results were amazing, they found that air clung tightly to the vehicle, without causing stalls or turbulence that would slow it down. One of the original drawings kept in the DLR archives in the scale 1:5 is on display in the PS Speicher transport museum in Einbeck. *** [EKA | FROM VARIOUS SOURCES | WIKIPEDIA | WIRED]
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