During the Occupation, he refused to work for the Germans and converted immediately his workshops toward civilian fabrications. This permitted to maintain conserver jobs for the whole staff.
It was then that he decided to make an auxiliary gasoline engine that could be fitted on any bicycle, since cars were relegated to garages, due to the scarcity of fuel. He did this in partnership with Pierre ANDRIOT (1885-1945), the husband of his first cousin Elise VEROTS. Pierre ANDRIOT was himself an engineer specialised in carburetors for aviation automobiles.
Carburation was at the time one of the major problems of thermal engines, especially for such small engines that had not been made yet : 0.5 CV that was designed to burn as little gasoline as possible, a gasoline that was also of poor quality, containing various proportions of alcohol.
Thus was conceived the VAP engine, an acronym based on Vérots-Andriot-Pierre, Pierre being their common first name. A few years later appeared, after the war, Vélosolex, who based their bike on a similar idea but avoided breaching the patent law.
Let us recall that the VAP engine was set on the rear wheel geared on a toothed wheel fixed on the rays of the bike wheel. Vélosolex had to content itself with the front wheel, at the top of that wheel which heightened the gravity center thus decreasing the stability of the bike. Moreover the Vélosolex engine transmitted power to the front wheel through friction on the tyre, which caused premature wear, and rejected the exhaust fumes in the face of the driver instead of rejecting them behind him.