In 1906 June 26/7 the first French Grand Prix de l'ACF was held in Le Mans; Rene Hanriot driving a Darracq was joined by his longtime friend Jean Chassagne as a riding mechanic but had to retire due to engine trouble.
During this period, Chassagne was also working at Clément-Bayard, Senat workshops for airships and race-car engines on the development, assembly and testing of the experimental Demoiselles Santons-Dumont monoplanes.