An electric boost function helps in instances where maximum acceleration is desired, when the electric motor works in tandem with the combustion engine during acceleration.
Given a free hand in the design, his team developed a continuously variable transmission system that allows the petrol engine and electric motor to work separately or in tandem.
The radical minimalism of these machines, built mostly in Europe in the 1950s and early '60s, reflected the region's postwar scarcity. (One resourceful builder beat old cooking pots into fender panels.) They typically measure 10 feet long or less, with less than 700-cc engine displacement and one or two seats arranged side by side or in tandem, scooter style.