In the years after the First World War, engineer Hugo Rupp had been shopping the design for a small two-stroke industrial motor around various industrial concerns, without success. In 1919, Rupp met Jorge Rasmussen who instantly recognized the engine's commercial application. Rasmussen employed Rupp to develop the engine, initially as a 18cc "toy" engine as a demonstrator, but later as a general purpose industrial motor.
Rupp and Rasmussen could see an enormous market for a small clip-on motor for a bicycle, which would become the DKW Fahrad-Hilfsmotor (bicycle auxiliary motor). The 118cc single cylinder motor could be attached to the luggage rack of a standard bicycle with drive being delivered to the back wheel by a belt. The motor only generated a single horsepower, but it was better than pedaling! The Hilfsmotor was a hit and between 1919 and 1922 30,000 units were sold. The success of the motor led DKW to begin to manufacture their own bicycles with strengthened frames and connecting brackets for the engine. It was a small step from here to building true motorcycles.
DKW Fahrader: https://dkwautounionproject.blogspot.com/2018/09/dkw-fahrrader.html
1921 DKW Range: https://dkwautounionproject.blogspot.com/2019/10/1921-j-s-rasmussen-machinenfabrik.html
DKW's First Motorcycles: https://dkwautounionproject.blogspot.com/2025/08/dkws-first-motorcycles.html
