The biggest (only?) fringe benefit of my job is what I learn. Decades of perusing old books and magazines don’t begin to add up to the collective knowledge and perspective that TTAC’s commentators provide. Case in point: I wrote the Illustrated History of Automotive Aerodynamics because I’ve always been smitten by streamlined cars ever since I saw a Tatra as a young child. And I thought I had all the slippery bases pretty well covered. But thanks to a late comment by NeilBlanchard, I’ve been introduced to what is undoubtedly one of the most remarkable aerodynamic cars ever, the 1938 Schlörwagen. It was originally tested at Cd 0.186, but a later test by VW in the seventies of a model resulted in a Cd of 0.15. Either of these values put the “pillbug” at or near the top of the list of the most aerodynamic concept cars ever built, like the Ford Probe V of 1985, with a Cd of .137.
Built on the chassis of the rear-engine Mercedes 170H, it was substantially faster as well as 20% to 40% more fuel efficient than its donor car. The Russians took the Schlörwagen as war booty and conducted tests as a propeller driven vehicle (below). It represents a state of aerodynamic efficiency in league with the most aerodynamic cars being considered today, such as the Aptera. Thanks Neil; and the article has been duly updated as well as my knowledge.