BODYWORK. Frame: steel tube bicycle frame. Front suspension: rigid. Rear suspension: rigid.

MECHANICALS. Engine: single-cylinder, two-stroke. Displacement: 63 cc.Transmission: by friction roller. Gearbox: 2-speed. Engine number: 4307298.

DOCUMENTS: No documentation.

HISTORY: Despite its modest power output, the auxiliary engine that powers this bicycle represents an intriguing chapter in the history of theSpanish motor industry. Produced between 1953 and 1960, it had limited commercial success, as the advent of the Seat 600 overshadowed theentire two-wheeled sector. Its manufacturer, Construcciones Mecánicas Rex, was one of the oldest in the country, having begun operations in 1913 under a different corporate name, originally dedicated to producing industrial engines.

Two years later, the company hired a young and promising engineer named Wifredo Ricart, who would later go on to enjoy a distinguished career, particularly at Pegaso. In 1953, long after his departure from the firm, Ricart designed for Rex this small engine with an inverted cylinder, wherethe fuel tank and exhaust silencer formed a single unit. Mounted over the rear wheel, it transmitted power to the tyre via a friction roller. Withmagneto ignition and a proprietary carburettor, it produced 1.2 hp, allowing a top speed of 45 km/h with a fuel consumption of 1.8 litres per 100 km.

The example offered here corresponds to the first version of the model, mounted on a conventional bicycle frame. It was carefully restored by itsprevious owner, who had begun his professional career at Construcciones Mecánicas Rex as a trainee mechanic.