Rex was a Catalan brand of auxiliary engines for bicycles, manufactured between 1953 and 1959 in Barcelona by the company Construcciones Mecánicas Rex, SA. They were designed by the automobile and aircraft engineer, Wilfredo Ricart (May 1897 – August 1974).
Rex, as a company, were founded in Barcelona in 1913 and was one of the oldest Spanish patent holders and manufacturers of ICE (Internal Combustion Engines). It was also where the engineer Wilfredo Ricart, first started to learn and create his designs. Ricart went on to have an important design and engineering career both in and out of Spain including as Chief Engineer at Alfa Romeo. However, in Spain, he is probably best known as the designer of the Spanish Pegaso Z-102 – the fastest car in the world at the time of its introduction.
The Rex auxiliary motor incorporated a 63cc engine that developed 1.2 CV at just under 3,000 RPM. It was very popular, particularly in the Barcelona area where it was manufactured and had a reputation for reliability and frugality as it could cover 100 kilometres on less than 2 litres of fuel.
The Rex auxiliary motor was a very compact unit and incorporated an integral fuel tank. The unit was attached to a bicycle frame at the rear, and it had a roller type final drive that was in contact with the rear tyre.
Rex went on to offer a complete Ciclomotor (moped), manufactured from pressed steel.
Spanish Motorcycles 