The Compte Albert de Dion and Georges Bouton began designing petrol engines in 1893 and soon discovered that the accepted standard of engines by Carl Benz and Gottlieb Daimler were essentially unreliable because, at their running speed of 500-750 rpm they knocked badly and suffered constant big-end failures, but if the speed was increased to 1500 rpm and adequate lubrication supplied, the knock disappeared and the engines became considerably more reliable. In 1895 the first De Dion Bouton tricycles left the factory with 3/4 hp engines, and by 1896 this had grown to 1 3/4 hp or more than twice the specific output of the Daimler and Benz engines. The tricyclists constantly wanted more power and ways to carry passengers, so De Dion Bouton decided it was time to join the profusion of voiturettes or light cars that were now appearing on the market. Development was not rushed and by autumn of 1899 their prototype rear engined voiturette had been thoroughly tested and production started. The first models had 2 3/4 hp engines which increased to 3 1/2 hp within a year, and eventually to 4 1/2 hp. The engine was water cooled and drove through an elegant and practical arrangement of final drive and rear suspension now known as the "De Dion axle". Although the exact number is not known, it is believed that over 1500 voiturettes were sold by April 1901, and after that production was running at 200 per month. The most popular body style was "vis-a-vis", where passengers in the forward seat faced backwards and the driver and other passenger faced forwards, but other styles were available.