Gear
part · 300 BC · Ancient world
A toothed wheel that transmits rotation and changes speed and torque.
Principles and materials it uses
- Torque — uses. The gear ratio changes torque and speed.
- Bronze — is made of. Ancient gears were bronze.
- Wood — is made of. In mills — wooden ones.
- Cast iron — is made of. Large gears of machines and mills were cast in iron: it fills a mould well and wears slowly.
- Plastic — is made of. Small gears in toys, clocks and printers are plastic: light and quiet.
Where it is used
- Transmission (gearbox) — is part of. A gearbox is a set of gears.
- Mechanical clock — is part of. A gear train counts seconds, minutes and hours.
- Pocket watch — is part of. The wheel train carries energy to the hands.
- Babbage’s Analytical Engine — is part of. Gears performed the calculations.
- Babbage’s Difference Engine — is part of. Numbers were stored in the positions of gear wheels.
- Antikythera mechanism — is part of. The mechanism contains at least 30 bronze gears.
- Watermill — is part of. Gears carry rotation from the horizontal shaft to the millstone.
- Windmill — is part of. A gear turns the rotation towards the millstones.
- Screw-cutting lathe — is part of. Change gears set the pitch of the thread.
- Mechanical calculator — is part of. Numbers are positions of gear wheels.
- Leibniz’s stepped reckoner — is part of. A stepped drum and gears.
- Cash register — is part of. A counting mechanism of gears.
- Pendulum clock — is part of. A wheel train.
- Lawn mower — is part of. The wheels turn the blade cylinder through gears.
- Electric drill — is part of. A reduction gear.
- Enigma — is part of. The rotors were stepped by a gear mechanism.
- Mixer — is part of. A gear train turns the beaters.
- Can opener — is part of. Roller openers.
- Arkwright’s water frame — is part of. Drafting rollers running at different speeds.
- Seed drill — is part of. The seeding mechanism is driven from the wheel.
- Reaper — is part of. The knife is driven from the wheel.
- Sakia — is part of. A gear drive from the animal to the wheel.
- Manual gearbox — is part of. Gears.
- Odometer — is part of. Gear counters.
- Taximeter — is part of. A mechanical counter driven from the wheel.
- Egg beater — is part of. A bevel gear.
- Mangle — is part of. Rollers on gears.
- Carpet sweeper — is part of. The brush is turned by the wheels.
- Concrete mixer — is part of. The drum’s ring gear.
- Differential analyser — is part of. Mechanics.
What it is a kind of
- Reduction gear — includes. A reduction gear is built from gears.
- Planetary gear — includes. A kind of gear train.
- Worm gear — includes. A kind of gear train.
- Rack and pinion — includes. A gear and a rack.
- Geneva drive — includes. A kind of gear mechanism.
- Ratchet — includes. A toothed wheel with a pawl.
- Wheel — is a kind of. A gear is a wheel with teeth around its rim: the teeth mesh and pass rotation along.
Things built in a similar way
- Chain drive — works like. Like a gear train, a chain drive transmits rotation at a set ratio, but between distant shafts.
- Sprocket — works like. A sprocket resembles a gear, but its teeth engage a chain rather than another wheel.