Mellde's grandfather August Johansson built one of the first cars in Stockholm and sold it to Lars Magnus Ericsson.
Mellde's father, Evald Johansson, taught car mechanics at a school in Stockholm.
Following his father, Mellde started drawing turbo compressors and diesel engines at the age of ten.
After finishing his basic education, Mellde studied thermodynamics for two years at the Stockholms Tekniska Institut (STI) under Folke Mannerstedt (race driver and engine designer) and Nils Gustafsson.
Mellde started working at SAAB in September 1946 and was put in charge of engine development.
40 workers volunteered and then Svante Holm explained that the real reason was that they would take the unsold cars and refit them with V4 engines.
Rolf quickly formed a group to work on the new 200-series, Jan Willsgård designed a new front and the V8 was changed to an inline 4.