then on, AS turbine engines were named after snakes. The Mamba and Double Mamba were turboprop engines, the latter being a complex piece of engineering with two side-by-side Mambas driving through a common gearbox, and could be found on the Fairey Gannet. The Python turboprop powered the Westland Wyvern strike aircraft. Further development of the Mamba removed the reduction gearbox to give the Adder turbojet. Another pioneer in the production of the RAE engine design was Metrovick, who started with a design known as the Metrovick F.2. This engine never entered production, and Metrovick turned to a larger design, the Beryl, and then to an even larger design, the Sapphire. Armstrong Siddeley later took over the Sapphire design, and it went on to be one of the most successful 2nd generation jet engines, competing with the better-known Rolls-Royce Avon. The company went on to develop an engine – originally for unmanned Jindivik target drones – called the Viper. This product was further developed by Bristol Siddeley and, later, Rolls-Royce and was sold in great numbers over many years. A range of rocket motors were also produced, including the Snarler and Stentor. The rocket development complemented that of Bristol, and Bristol Siddeley would become the leading British manufacturer of rocket engines for missiles. Diesel engines In 1946 Armstrong Siddeley produced their first diesel engines. They were medium-speed engines for industrial and agricultural use. Initially there was a single-cylinder engine producing at 900 rpm and a twin-cylinder version. Each cylinder had a capacity of 988 cm3 (60.2 cubic inches). The power output and speed was progressively increased. By the end of 1954 the single-cylinder engine was rated at at 1800 rpm and the twin-cylinder engine at the same speed. In 1955 the range was extended with the introduction of a 3-cylinder engine rated at . The engines were built at Armstrong Siddeley's factory at Walnut Street in Leicester until that factory closed in August 1957. Production was transferred to the factory of Armstrong Siddeley (Brockworth) Ltd in Gloucestershire and in 1958 to the factory of Petters Limited at Staines, Middlesex. The engines built by Petters were designated AS1, AS2 and AS3 to distinguish them from that company's other products. Production ended in 1962 when Petters introduced a replacement range of lightweight small high-speed air-cooled diesel engines. In April 1958 the company obtained a licence to build the Maybach MD series high-speed diesel