A two-stroke diesel engine is a diesel engine that works in two strokes. A diesel engine is an internal combustion engine that operates using the Diesel cycle. Invented in 1892 by German engineer Rudolf Diesel, it was based on the hot-bulb engine design and patented on February 23, 1893. During the period of 1900 to 1930, four-stroke diesel engines enjoyed a relative dominance in practical diesel applications. Charles F. Kettering and colleagues, working at the various incarnations of Electro-Motive and at the General Motors Research Corporation during the 1930s, advanced the art and science of two-stroke diesel technology to yield engines with much higher power-to-weight ratios than the two-stroke diesels of old. This work was instrumental in bringing about the dieselisation of railroads in the 1940s and 1950s.