Model of a worm gear

Models of gears by Théodore Olivier. A gear transmits movement and can also change its direction (angular and bevel gears). When two gearwheels do not have the same number of teeth, the rotation speed is reduced. Some gears can transform rotary movement into rectilinear movement (rack and pinion). Known since ancient times, the first gears were wooden, bulky, and their teeth laboured under the strain. With the birth of mechanical clockmaking in the Middle Ages, the transmission of movement had to be more regular. Gear wheels were now metallic, but their components were worn by their torque and noisy abrasion. Scientists in the late 16th century, including Leonardo da Vinci, studied the geometry of gears and their teeth to reduce friction. Well aware of the crucial role of gear mechanisms in industrial development, teachers at the Conservatoire, including Charles Dupin, began constructing teaching models in the late 1820s. Charged with teaching descriptive geometry, Théodore Olivier designed some thirty wooden models in the 1840s, and had them made by one of the Conservatoire’s most skilful craftsmen.