Petrol–electric transmission
Petrol–electric transmission (UK English) or gasoline–electric transmission or gas–electric transmission (US English) is a transmission system for vehicles powered by petrol engines. Petrol-electric transmission was used for a variety of applications in road, rail, and marine transport, in the early 20th century. After World War I, it was largely superseded by diesel-electric transmission, a similar transmission system used for diesel engines; but petrol-electric has become popular again in the 21st century in hybrid electric vehicles. Petrol–electric transmission was used in certain niche markets in the early 20th century, such as  in the petrol–electric railway locomotives produced in Britain for use on the War Department Light Railways during World War I or for privately owned Arad & Csanad United Railways. In France, the Crochat petrol–electric transmission system was used for standard gauge locomotives (up to 240kW of electrical power). Description. Petrol-electric transmission works by converting the mechanical force of the petrol engine into electrical energy (through a dynamo), and using the electrical energy to drive traction motors, which propel the vehicle mechanically. The traction motors may be driven directly or via a rechargeable battery; if the latter method is  used, the vehicle is classed as a hybrid vehicle. Advantages and disadvantages. Petrol–electric transmission allows smooth, stepless, acceleration without gear changes. The disadvantages are increased cost and weight. Historical applications. Road. Examples of road vehicles using petrol–electric transmission include the Tilling-Stevens bus (UK) and the Owen Magnetic touring car (USA). Rail. Examples of petrol–electric rail vehicles include the North Eastern Railway 1903 Petrol Electric Autocar, Doodlebug (rail car), GE 57-ton gas-electric boxcab, Weitzer railmotor and the petrol–electric locomotives built for the War Department Light Railways by Dick, Kerr & Co. and British Westinghouse. In  France, the "Crochat-Colardeau" system of Henry Crochat and Emmanuel Colardeau was used in some petrol–electric railcars. Marine. Most submarines that served in World War I were diesel–electric. However, some petrol–electric submarines had been built before the war. Examples include: Plunger-class submarine (USA), A-class submarine (1903) (UK), SM U-1 (Austria-Hungary), Russian submarine Krab (1912). Military vehicles. Petrol–electric systems were tested on the British Mark II tank, American Holt gas electric tank and French Saint Chamont in 1917. The latter used the Crochat-Colardeau system of Henry Crochat and Emmanuel Colardeau. This allowed the  left and right traction motors to run at different speeds for steering and is detailed in patent US1416611. The 1936 prototype Char G1P was also designed with a petrol–electric drive. Ferdinand Porsche was the main developer of these drive trains for military vehicles in Nazi Germany. He created the VK 3001 (P) prototype and VK 4501, of which 91 units were produced as the Porsche Tiger. They were later converted into Ferdinand, and subsequently Elefant, tank destroyers. Another noteworthy design was the 188-tonne Porsche type 205 prototypes, commonly known as the Maus super-heavy tank. Modern applications. In  the 21st century, petrol–electric transmission has gained a new lease of life in hybrid electric vehicles. Examples include: Ford Fusion Hybrid; Honda Civic Hybrid; Toyota Prius.