From the 1940s onward, various steam cars were constructed, usually by enthusiasts. Among those mentioned were Charles Keen, Cal Williams' 1950 Ford Conversion, Forrest R Detrick's 1957 Detrick S-101 prototype, and Harry Peterson's Stanley powered Peterson.[9] The Detrick was constructed by Detrick, William H Mehrling, and Lee Gaeke who designed the engine based on a Stanley.[10][11]