1935 Mercedes-Benz Sport Roadster 150 H (Heckmotor)
Part of the 130h, 150h and 170h Heckmotor (Rear Engine) series of the 1930s. 1.7-liter engine

When the 130 sedan appeared in 1934, it was the smallest production Mercedes in the company's history, as well as the first to carry its engine in the tail. The potential to build a sports car out of the innovative underpinnings of the humble sedan must have occurred to Mercedes' engineers from the beginning, because by the end of the year, they had produced a 150 Sports Saloon to compete in a 2,000-kilometer rally across Germany. One year later, the thinking behind the Sports Saloon gave birth to the 150 Sports Roadster.

While the 130 had a 1.3-liter, water-cooled four hung out behind the rear axle, the 150's 1.5-liter four was turned around 180 degrees, its midships location giving the chassis better balance and more stable handling. In place of the 1.3-liter's sidevalve arrangement, the 1.5 had overhead valves, and produced about 55 horsepower with a Solex two-barrel carburetor and a compression ratio of 7.1:1.

The chassis employed the tubular backbone developed for the 130, with independent suspension by transverse leaf spring in the front, and coil-sprung swing axles in the rear. Behind where the seats would be, the chassis forked to cradle the engine and transaxle. To provide adequate cooling, a squirrel-cage blower moved air through the rear-mounted radiator.

The rear-engine configuration allowed for wind-cheating bodywork. Unusual touches, such as the single high-beam headlamp and the twin spare tires mounted behind the rear-hinged doors, were blended with traditional sports-car elements like the swept vee windshield and the gently tapering boattail. Some called it beautiful, others called it ungainly, and all agreed it was distinctive. The car weighed in at 2,160 pounds, giving it a power-to-weight ratio of nearly 40 pounds per horsepower. Aerodynamics helped it to reach a top speed of 78 miles per hour.

Although Mercedes had been hoping for volume production, the Sports Roadster suffered some disadvantages in the marketplace. The mid-rear engine configuration and short wheelbase ruled out any possibility of a back seat, while the 16-gallon gas tank mounted in the car's nose ate into already scarce luggage space. And the price, at 6,600 deutschemarks, was nearly double that of a basic 130 sedan.

Despite the factory's best efforts to promote the 150 as "a spirited sports car" with acceleration that was nearly equal to that of larger, supercharged cars, buyers were not interested. The 150 Sports Roadster remained in the catalogue through 1936, but few were sold. Even Mercedes-Benz doesn't know how many were produced: One record says that 20 examples were built, while another puts the number at five. There is proof of the sale of just two cars, one of which was reacquired by Daimler AG in the 1950s.