When the Germans were building Kettenrads, the French were building... this.
World War II saw a great deal of technological innovation, including the world of motorcycles. Germany, for instance, crossed a motorcycle and a tank and got the Kettenrad, which we've written about before. Not all such innovations were breakthroughs, however. Some of these studies were nothing more than evolutionary dead ends. Such was the case with the Mercier Motor Chenille.
Adrien Mercier was a Swiss inventor who was building small mopeds in France. During the 1930s, as war seemed more and more inevitable, Mercier began work on his own version of a motorcycle with a tank tread. The result of his tinkering was called the Chenille, the French word for "caterpillar."
Mercier took an unusual approach in the design of the Chenille by making it front wheel... er, tread, drive. The front steering section of the bike contained entire powerplant and drivetrain, attached to a 150mm (about six-inch) wide tread. A 350cc JAP engine powered this contraption, with an engine-driven fan providing extra cooling for low speeds. It made 10 horsepower at 3,000 RPM and transferred its power to the tread through a three-speed transmission. The back of the Chenille was extremely simple, consisting of nothing more than a back wheel, a fuel tank, a seat, and a few tubes holding them together.
In 1937, the French military put the Chenille through its paces to see what it could do. It could achieve a top speed of 65 km/h (about 40 mph), almost as fast as the Kettenrad. Even better, it was able to climb a 45-percent grade. It wasn't all sunshine and rainbows, though. During the first test, the Chenille had a large armored shield that prevented it from riding through dirt effectively, which is the fundamental purpose of any treaded vehicle. This shield was removed for all future testing. The video above also shows that it was somewhat awkward to ride and maneuver at lower speeds.
While the French military found Mercier's design interesting, they decided not to order any—likely because France had more pressing matters to worry about, like getting invaded by Germany. Only about five Chenilles were ever built. A friend of mine is fond of saying that there are no bad ideas. There are good ideas, and then there are awesome ideas. The Mercier Motor Chenille was certainly one of those awesome ideas.