Engineer Marcel Leyat designed the Hélica, the only propeller-driven automobile that ever really worked, as a wingless airplane. The steering mechanism commanded the rear axle and a throttle controlled the speed. The Hélica's aerodynamic shape, light weight (225 kilograms), two-cylinder engine and four-blade propeller enabled it to travel up to 105 km/h. It consumed eight to nine litres per 100 kilometres. The vehicle in the museum, the first in the 1921 series, also had a commercial purpose: signs on the sides advertised "Gellycine, for your hands and face". But for financial and legal reasons, Leyat could not fill the 600 orders he received for his invention, including one from Spain's King Alphonse XIII.