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Nicolas-Joseph Cugnot (26 February 1725 – 2 October 1804) was a French inventor. He built two self-propelled steam carriages, one of which is preserved at the Musée des arts et Métiers in Paris. He was almost certainly the first to construct a full-size working steam-powered vehicle.
It has been recorded that Ferdinand Verbiest, a member of a Jesuit mission in China, built a 'steam car', c.1672. It was probably a model. An account by the Abbé Huc described the vehicle as being equipped with an aeolipile whose steam jet was directed 'upon a wheel to which four wings were attached; the motion thus produced was communicated by gearing to the wheel of the car.'.
As described, Verbiest's steam turbine-powered vehicle would have been an interesting experiment, with no prospect of practical utility. In contrast, Cugnot's surviving machine was designed and constructed with serious intent. Its engine was remarkably ingenious and of advanced design and construction, but the boiler design left much to be desired. For the time, Cugnot's machine was truly remarkable.
Cugnot was born in Void, Lorraine, (now department of Meuse), France. He trained as a military engineer. He experimented with working models of steam-engine-powered vehicles for the French Army, intended for transporting cannon, starting in 1765.
Cugnot ingeniously converted the reciprocating motion of steam pistons into rotary motion, using a ratchet arrangement. A small version of his three-wheeled 'fardier à vapeur' ran in 1769. (A fardier was a strongly-built two-wheeled horse-drawn cart for transporting very heavy equipment such as cannon barrels).
The following year, a full-size version of the 'fardier à vapeur' was built, specified to be able to carry 4 tons and cover 2 lieues (7.8 km or 4.8 miles) in one hour, a performance it never achieved in practice. The vehicle, which weighed about 2.5 tonnes tare, had two wheels at the rear and a single driving wheel at the front; this front wheel supported the steam boiler and driving mechanism. The power unit was articulated to the "trailer".
The vehicle was reported to have been very unstable due to poor weight distribution - which would have been a serious disadvantage seeing that it was intended that the fardier should be able to traverse rough terrain and climb steep hills.
In 1771, the second vehicle is said to have gone out of control and knocked down part of the Arsenal wall, possibly the first known automobile accident. According to Georges Ageon, the earliest mention of this occurrence dates from 1801 and it does not feature in contemporary accounts. Boiler performance was also particularly poor, even by the standards of the day, with the fire needing to be re-lit and steam raised again every quarter of an hour or so, considerably reducing overall speed.
After running a small number of trials variously described as being between Paris and Vincennes and at Meudon, the project was abandoned and the French Army's experiment with mechanical vehicles came to an end.
In 1772, King Louis XV granted Cugnot a pension of 600 livres a year for his innovative work and the experiment was judged interesting enough for the fardier to be kept at the Arsenal until transferred to the Conservatoire National des Arts et Métiers in 1800, where it can still be seen today.
With the French Revolution, Cugnot's pension was withdrawn in 1789, and the inventor went into exile in Brussels, where he lived in poverty. Shortly before his death, he was invited back to France by Napoleon Bonaparte and Nicolas-Joseph Cugnot returned to Paris, where he died on October 2, 1804.
Cugnot's achievement deserves wider recognition. Prior to the construction of his machines, steam engines were large, immobile, and produced only reciprocating motion. They worked on the atmospheric principle, requiring a condenser. Cugnot boldly embarked on the development of a machine which produced rotary motion, worked with direct steam pressure, needed no condenser, and at the same time was sufficiently compact to propel itself and its burden. This required the introduction of a number of ingenious and novel mechanisms, demanding a degree of precision in their manufacture. It is true that the design of the boiler was seriously flawed with respect to feeding and firing, but no doubt Cugnot would have addressed these problems in time. Presumably Cugnot was also the first to introduce the tyre tread!
The reciprocating motion of the pistons was converted to rotary motion at the driving wheel by means of ratchets and pawls. Two cylinders were needed to make the engine self-acting. Steam to and from the cylinders was admitted and exhausted through a single four-way valve (a semi-rotary cock with four ports). The valve was rotated by pitch chains, activated by tappets on the piston rods.
The action of the pawls and ratchets could be reversed, effectively at the flick of a switch, by an ingenious mechanism. The motive power for the ratchet on one side would then be provided by the piston on the opposite side. The pawl is symmetrical, and a spring acts through linkage to apply a small force to bias it to rotate either clockwise or anti-clockwise. Photo here. The pawl and the leaf spring can just be seen in photo 4.
The cylinders and pistons have the appearance of being machined to high standards of accuracy. Photo 8 shows that there is some form of iron or steel piston ring. The cylinders are made from a copper alloy, possibly bronze.
This YouTube animation shows how the pistons drive the wheel and how the steam admission/exhaust valve is operated.
See here for Musée des arts et Métiers photos of details of the engine.