Gear Facts



  • 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.