Friday 30th January 1807
Isaac de Rivaz was issued with a French patent for his explosion motor, an important ancestor of the modern internal combustion engine. The de Rivaz engine had no timing mechanism and the introduction of the fuel mixture and ignition were all under manual control. The compressed hydrogen gas fuel was stored in a balloon connected by a pipe to the cylinder. Oxygen was supplied from the air by a separate air inlet. Manually operated valves allowed introduction of the gas and air at the correct point in the cycle. A lever worked by hand moved a secondary, opposed, piston. This evacuated the exhaust gases, sucked in a fresh mixture and closed the inlet and exhaust valves. A Volta cell was used to ignite the gas within the cylinder by pressing an external button that created an electric spark inside the cylinder.
The explosion drove the piston freely up the vertically mounted cylinder, storing the energy by lifting the heavy piston to an elevated position. The piston returned under its own weight and engaged a ratchet that connected the piston rod to a pulley. This pulley was in turn attached to a drum around which a rope was wound. The rope’s other end was attached to a second drum on the charette’s front wheels. The weight of the piston during its return down the cylinder was enough to turn the drums and move the charette. When the return stroke was over, the ratchet allowed the top drum to disconnect from the piston rod ready for the next powered lift of the piston.
Around 1985 the Giannada Automobile Museum produced two reconstructions of the charette, a model about 50 cm long and a larger working one about 2 meters long. The working model used air pressure to simulate the gas/chemical explosion. On one occasion this car moved about 100 meters in front of the museum as part of a demonstration.