Great Bikes: 1923 BMW R32 – the birth of the boxer twin motorcycle
Story: Harry Fisher
If there is one defining element of the BMW motorcycle, it has to be the famous ‘boxer-twin’ engine layout that steadfastly refuses to be deleted from the model line-up. But what are the origins of this venerable motor?
The founding of BMW was in aircraft engine manufacture. Two companies – Otto and Rapp – were completely separate aircraft companies. By 1916, they had merged and, with the increasing emphasis on aerial warfare and the subsequent growth of the German Air Force, BFW (Bayerische Flugzeugwerke AG) as the new company was called, gained a reputation as engine builders of the highest order.
By 1917, they had gone public and taken the name of Bayerische Motoren Werke GmbH. The war helped the company to flourish, but with peace came understandable difficulties. In order to survive, the company was forced to divert materials originally intended for aero-engine production to other uses. In 1920, this included motorcycles.
Early motorcycles used proprietary engines and in 1921 a longitudinal flat-twin 494cc engine was produced, mainly for sale to other manufacturers. By 1923, however, the bedrock of 20thcentury BMW motorcycle production was laid when Max Friz, one of the original directors of the company, drew up plans for the R32. It was hailed as a masterpiece at the Paris Motorcycle Salon of 1923.
The engine was a flat twin and capacity remained at 494cc, but now the cylinders lay transversely in unit with a three-speed gearbox driving through a shaft to the rear wheel. Despite being rigid, the frame’s twin-triangle layout was way ahead of its time and the bike as a whole was a design concept that was modern enough to last for the rest of the 20thcentury.
But why a transverse boxer-twin? Well, it’s not rocket science, really. The cylinder layout gives good primary balance and also sticks them out into the airstream for super-efficient cooling (something that was not always possible with V-twins, which were very popular at that time). In addition, transmission of power to a shaft rear drive is relatively simple, without the need for chains or belts. Shaft drive was deemed the best method of power transmission and the boxer layout allowed easy installation of shaft drive.
3,090 R32’s were built between 1923 and 1926; its success launched BMW into the two-wheeled world and the modern BMW has a unique link back to the beginning of the line.