- Gears are pairs of toothed wheels that interlock and so transmit power from one shaft to another.
- The first gears were wooden, with wooden teeth. By the 6th century AD, wooden gears were used in windmills, watermills and winches.
- Metal gears appeared in 87 BC and were later used for clocks. Today, all gears are metal and made on a `gear-bobbing’ machine.
- Simple gears are wheels with straight-cut teeth.
- Helical gears have slanting rather than straight teeth, and run smoother. The gears in cars are helical.
- Bevel or mitre gears are cone-shaped, allowing the gear shafts to interlock at right angles.
- In worm gears one big helical gear interlocks with a long spiral gear on a shaft at right angles.
- Planetary gears have a number of gear wheels known as spurs or planets that rotate around a central ‘sun’ gear.
- In a planetary gear the planet and sun gear all rotate within a ring called an annulus.
- Automatic gearboxes in cars use planetary or epicyclic gears.
Gear Facts
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