Staff Writer (Updated: 9/16/2015):
BMW motorcycle frames of the 1920s, at least those equipped with the popular "touring" sidecars, proved prone to fracture from their simple connection welds. As such, research began on a new frame that eventually led to an all-new motorcycle design - the R11 series. The revised frame was constructed as two separate channels from stamped sheet metal with rivets connecting the two halves during assembly. The new formation helped the frame accept the weight and inherent stress imposed by the carrying of a sidecar. To power the R11, BMW devised an all-powerful line up of 750cc engines consisting of a 16-horsepower version as well as a 28-horsepower overhead valve (OHV) version. From these two engines were born the R11 "touring" and R16 "sports" models. New telescopic "forks" were devised during the early part of the 1930s and helped to revamped the R11 and R16 models in 1935. A new 4-speed, hand-shifted gearbox was also fitted and gave birth to the respective model designations R12 and R17.
That same year, the R12 was selected for production by the German Army to staff its reconnaissance and security ranks. By 1936, electric arc welding was gaining steam and BMW utilized the technology to address their joint stress problems to make for a more robust machine when employing a sidecar, helping to make the R12 series (and its R17 sister) a commercial success.
The German Army R12 was fitted with a BMW 2-cylinder, 4-stroke engine of 745cc, delivering 18 to 20 horsepower at 3,400 to 4,000rpm. Despite the weak output, the engine delivered the needed power to haul the motorcycle frame and its optional unpowered sidecar as required. She measured in at 2.10 meters, held a width of 0.90 meters (sans sidecar) and stood at 0.94 meters. Her weight was listed at 413lbs. Maximum road speed was listed at 62mph while range was out to 158 miles with its 14 liter internal fuel capacity. A passenger could be carried over the rear wheel fender on an optional seat positioned directly behind and slightly above the driver. Otherwise this position could be reserved for carrying supplies on a simple optional rack system. Saddlebags could be hitched to the sides of the rear fender. A rounded headlamp illuminated the area ahead for dawn/dusk operations. Characteristic of the brand was its wheel mud covers, straight horizontal handle bars, multi-spoke wheels and its broad, flat sprung driver's seat.
When in service with the Wehrmacht, the R12 was called upon to relay messages from point to point while also utilized as a fast reconnaissance element. She proved a solid, speedy and relatively reliable battlefield instrument. However, heavy mud and snow were quick to wreak havoc on the critical working components of the motorcycle, forcing the German Army to continue its search for a dedicated replacement system. The addition of a sidecar increased ridership to three persons (the typical operating number for German motorized sidecar elements during the war) and could offer light battlefield support by mounting either a MG34 or MG42 series 7.92mm general purpose machine gun on a special mount along the sidecar front facing. Motorcycles formed specialized motorized infantry regiments for the Wehrmacht and provided a critical punch in the early phases of the blitzkrieg where speed and coordinated overwhelming force was essential to any victory. The R12 series, therefore, went on to see service with the German Army along ever major front to that point in the war - from fighting in the deserts of Africa to the frigid cold of the East Front.
The R12 was eventually superseded in the German ranks by the BMW R75 series. The R75 was a purpose-built military motorcycle with fully-powered sidecar (including heating) that improved upon the frame, function and scope of the original R12. The R75 began replacing R12s during 1942 but she would never reach the production figures of the legendary R12.
The R12 remains a rare collector's piece today with very few in circulation around the world.