To meet Louis Renault's demands for maximum lightness of all elements of the tank, the driver's seat back was reduced to a single strap. Louis Renault took the controls and began to climb a pile of wood chips in front of a workshop.
FT tank
During the climb, he leaned back and the seat back - which was too fragile - broke, tipping Renault backward, while the tank continued its ascent before descending the other side. Getting out, Renault said to the engineer: "Well, my friend, you'll have to make me something more solid - make me a pivoting seat back using sheet steel." This anecdote reveals the empiricism behind the design of this tank, produced within a few months.
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Video : https://www.youtube.com/watch?v=Yr1vJWjRQ5Y&feature=youtu.be
Source : BNF